XFA: Upgrade libpng to 1.6.20.

third_party/libpng/pngrutil.c

+
 /* pngrutil.c - utilities to read a PNG file
  *
- * Last changed in libpng 1.6.3 [July 18, 2013]
- * Copyright (c) 1998-2013 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.20 [December 3, 2015]
+ * Copyright (c) 1998-2015 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
  * and license in png.h
  *
  * This file contains routines that are only called from within
  * libpng itself during the course of reading an image.
  */
@@ skipping 66 matching lines @@
  * the following code does a two's complement to native conversion.
  */
 png_int_32 (PNGAPI
 png_get_int_32)(png_const_bytep buf)
 {
    png_uint_32 uval = png_get_uint_32(buf);
    if ((uval & 0x80000000) == 0) /* non-negative */
       return uval;
 
    uval = (uval ^ 0xffffffff) + 1;  /* 2's complement: -x = ~x+1 */
-   return -(png_int_32)uval;
+   if ((uval & 0x80000000) == 0) /* no overflow */
+       return -(png_int_32)uval;
+   /* The following has to be safe; this function only gets called on PNG data
+    * and if we get here that data is invalid.  0 is the most safe value and
+    * if not then an attacker would surely just generate a PNG with 0 instead.
+    */
+   return 0;
 }
 
 /* Grab an unsigned 16-bit integer from a buffer in big-endian format. */
 png_uint_16 (PNGAPI
 png_get_uint_16)(png_const_bytep buf)
 {
    /* ANSI-C requires an int value to accomodate at least 16 bits so this
     * works and allows the compiler not to worry about possible narrowing
-    * on 32 bit systems.  (Pre-ANSI systems did not make integers smaller
+    * on 32-bit systems.  (Pre-ANSI systems did not make integers smaller
     * than 16 bits either.)
     */
    unsigned int val =
        ((unsigned int)(*buf) << 8) +
        ((unsigned int)(*(buf + 1)));
 
    return (png_uint_16)val;
 }
 
-#endif /* PNG_READ_INT_FUNCTIONS_SUPPORTED */
+#endif /* READ_INT_FUNCTIONS */
 
 /* Read and check the PNG file signature */
 void /* PRIVATE */
 png_read_sig(png_structrp png_ptr, png_inforp info_ptr)
 {
    png_size_t num_checked, num_to_check;
 
    /* Exit if the user application does not expect a signature. */
    if (png_ptr->sig_bytes >= 8)
       return;
 
    num_checked = png_ptr->sig_bytes;
    num_to_check = 8 - num_checked;
 
 #ifdef PNG_IO_STATE_SUPPORTED
    png_ptr->io_state = PNG_IO_READING | PNG_IO_SIGNATURE;
 #endif
 
    /* The signature must be serialized in a single I/O call. */
    png_read_data(png_ptr, &(info_ptr->signature[num_checked]), num_to_check);
    png_ptr->sig_bytes = 8;
 
-   if (png_sig_cmp(info_ptr->signature, num_checked, num_to_check))
+   if (png_sig_cmp(info_ptr->signature, num_checked, num_to_check) != 0)
    {
       if (num_checked < 4 &&
           png_sig_cmp(info_ptr->signature, num_checked, num_to_check - 4))
          png_error(png_ptr, "Not a PNG file");
       else
          png_error(png_ptr, "PNG file corrupted by ASCII conversion");
    }
    if (num_checked < 3)
       png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
 }
@@ skipping 65 matching lines @@
       png_byte tmpbuf[PNG_INFLATE_BUF_SIZE];
 
       len = (sizeof tmpbuf);
       if (len > skip)
          len = skip;
       skip -= len;
 
       png_crc_read(png_ptr, tmpbuf, len);
    }
 
-   if (png_crc_error(png_ptr))
-   {
-      if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) ?
-          !(png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN) :
-          (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_USE))
+   if (png_crc_error(png_ptr) != 0)
+   {
+      if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) != 0 ?
+          (png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN) == 0 :
+          (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_USE) != 0)
       {
          png_chunk_warning(png_ptr, "CRC error");
       }
 
       else
-      {
-         png_chunk_benign_error(png_ptr, "CRC error");
-         return (0);
-      }
+         png_chunk_error(png_ptr, "CRC error");
 
       return (1);
    }
 
    return (0);
 }
 
 /* Compare the CRC stored in the PNG file with that calculated by libpng from
  * the data it has read thus far.
  */
 int /* PRIVATE */
 png_crc_error(png_structrp png_ptr)
 {
    png_byte crc_bytes[4];
    png_uint_32 crc;
    int need_crc = 1;
 
-   if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name))
+   if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) != 0)
    {
       if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==
           (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))
          need_crc = 0;
    }
 
    else /* critical */
    {
-      if (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE)
+      if ((png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE) != 0)
          need_crc = 0;
    }
 
 #ifdef PNG_IO_STATE_SUPPORTED
    png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_CRC;
 #endif
 
    /* The chunk CRC must be serialized in a single I/O call. */
    png_read_data(png_ptr, crc_bytes, 4);
 
-   if (need_crc)
+   if (need_crc != 0)
    {
       crc = png_get_uint_32(crc_bytes);
       return ((int)(crc != png_ptr->crc));
    }
 
    else
       return (0);
 }
 
+#if defined(PNG_READ_iCCP_SUPPORTED) || defined(PNG_READ_iTXt_SUPPORTED) ||\
+    defined(PNG_READ_pCAL_SUPPORTED) || defined(PNG_READ_sCAL_SUPPORTED) ||\
+    defined(PNG_READ_sPLT_SUPPORTED) || defined(PNG_READ_tEXt_SUPPORTED) ||\
+    defined(PNG_READ_zTXt_SUPPORTED) || defined(PNG_SEQUENTIAL_READ_SUPPORTED)
 /* Manage the read buffer; this simply reallocates the buffer if it is not small
  * enough (or if it is not allocated).  The routine returns a pointer to the
  * buffer; if an error occurs and 'warn' is set the routine returns NULL, else
  * it will call png_error (via png_malloc) on failure.  (warn == 2 means
  * 'silent').
  */
 static png_bytep
 png_read_buffer(png_structrp png_ptr, png_alloc_size_t new_size, int warn)
 {
    png_bytep buffer = png_ptr->read_buffer;
@@ skipping 12 matching lines @@
       buffer = png_voidcast(png_bytep, png_malloc_base(png_ptr, new_size));
 
       if (buffer != NULL)
       {
          png_ptr->read_buffer = buffer;
          png_ptr->read_buffer_size = new_size;
       }
 
       else if (warn < 2) /* else silent */
       {
-#ifdef PNG_WARNINGS_SUPPORTED
-         if (warn)
+         if (warn != 0)
              png_chunk_warning(png_ptr, "insufficient memory to read chunk");
+
          else
-#endif
-         {
-#ifdef PNG_ERROR_TEXT_SUPPORTED
              png_chunk_error(png_ptr, "insufficient memory to read chunk");
-#endif
-         }
       }
    }
 
    return buffer;
 }
+#endif /* READ_iCCP|iTXt|pCAL|sCAL|sPLT|tEXt|zTXt|SEQUENTIAL_READ */
 
 /* png_inflate_claim: claim the zstream for some nefarious purpose that involves
  * decompression.  Returns Z_OK on success, else a zlib error code.  It checks
  * the owner but, in final release builds, just issues a warning if some other
  * chunk apparently owns the stream.  Prior to release it does a png_error.
  */
 static int
 png_inflate_claim(png_structrp png_ptr, png_uint_32 owner)
 {
    if (png_ptr->zowner != 0)
    {
       char msg[64];
 
       PNG_STRING_FROM_CHUNK(msg, png_ptr->zowner);
       /* So the message that results is "<chunk> using zstream"; this is an
        * internal error, but is very useful for debugging.  i18n requirements
        * are minimal.
        */
       (void)png_safecat(msg, (sizeof msg), 4, " using zstream");
-#     if PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC
-         png_chunk_warning(png_ptr, msg);
-         png_ptr->zowner = 0;
-#     else
-         png_chunk_error(png_ptr, msg);
-#     endif
+#if PNG_RELEASE_BUILD
+      png_chunk_warning(png_ptr, msg);
+      png_ptr->zowner = 0;
+#else
+      png_chunk_error(png_ptr, msg);
+#endif
    }
 
    /* Implementation note: unlike 'png_deflate_claim' this internal function
     * does not take the size of the data as an argument.  Some efficiency could
     * be gained by using this when it is known *if* the zlib stream itself does
     * not record the number; however, this is an illusion: the original writer
     * of the PNG may have selected a lower window size, and we really must
     * follow that because, for systems with with limited capabilities, we
     * would otherwise reject the application's attempts to use a smaller window
     * size (zlib doesn't have an interface to say "this or lower"!).
     *
     * inflateReset2 was added to zlib 1.2.4; before this the window could not be
     * reset, therefore it is necessary to always allocate the maximum window
     * size with earlier zlibs just in case later compressed chunks need it.
     */
    {
       int ret; /* zlib return code */
-#     if PNG_ZLIB_VERNUM >= 0x1240
-
-#        if defined(PNG_SET_OPTION_SUPPORTED) && \
-            defined(PNG_MAXIMUM_INFLATE_WINDOW)
-            int window_bits;
-
-            if (((png_ptr->options >> PNG_MAXIMUM_INFLATE_WINDOW) & 3) ==
-               PNG_OPTION_ON)
-               window_bits = 15;
-
-            else
-               window_bits = 0;
-#        else
-#           define window_bits 0
-#        endif
-#     endif
+#if PNG_ZLIB_VERNUM >= 0x1240
+
+# if defined(PNG_SET_OPTION_SUPPORTED) && defined(PNG_MAXIMUM_INFLATE_WINDOW)
+      int window_bits;
+
+      if (((png_ptr->options >> PNG_MAXIMUM_INFLATE_WINDOW) & 3) ==
+          PNG_OPTION_ON)
+      {
+         window_bits = 15;
+         png_ptr->zstream_start = 0; /* fixed window size */
+      }
+
+      else
+      {
+         window_bits = 0;
+         png_ptr->zstream_start = 1;
+      }
+# else
+#   define window_bits 0
+# endif
+#endif
 
       /* Set this for safety, just in case the previous owner left pointers to
        * memory allocations.
        */
       png_ptr->zstream.next_in = NULL;
       png_ptr->zstream.avail_in = 0;
       png_ptr->zstream.next_out = NULL;
       png_ptr->zstream.avail_out = 0;
 
-      if (png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED)
-      {
-#        if PNG_ZLIB_VERNUM < 0x1240
-            ret = inflateReset(&png_ptr->zstream);
-#        else
-            ret = inflateReset2(&png_ptr->zstream, window_bits);
-#        endif
+      if ((png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED) != 0)
+      {
+#if PNG_ZLIB_VERNUM < 0x1240
+         ret = inflateReset(&png_ptr->zstream);
+#else
+         ret = inflateReset2(&png_ptr->zstream, window_bits);
+#endif
       }
 
       else
       {
-#        if PNG_ZLIB_VERNUM < 0x1240
-            ret = inflateInit(&png_ptr->zstream);
-#        else
-            ret = inflateInit2(&png_ptr->zstream, window_bits);
-#        endif
+#if PNG_ZLIB_VERNUM < 0x1240
+         ret = inflateInit(&png_ptr->zstream);
+#else
+         ret = inflateInit2(&png_ptr->zstream, window_bits);
+#endif
 
          if (ret == Z_OK)
             png_ptr->flags |= PNG_FLAG_ZSTREAM_INITIALIZED;
       }
 
       if (ret == Z_OK)
          png_ptr->zowner = owner;
 
       else
          png_zstream_error(png_ptr, ret);
 
       return ret;
    }
 
-#  ifdef window_bits
-#     undef window_bits
-#  endif
-}
+#ifdef window_bits
+# undef window_bits
+#endif
+}
+
+#if PNG_ZLIB_VERNUM >= 0x1240
+/* Handle the start of the inflate stream if we called inflateInit2(strm,0);
+ * in this case some zlib versions skip validation of the CINFO field and, in
+ * certain circumstances, libpng may end up displaying an invalid image, in
+ * contrast to implementations that call zlib in the normal way (e.g. libpng
+ * 1.5).
+ */
+int /* PRIVATE */
+png_zlib_inflate(png_structrp png_ptr, int flush)
+{
+   if (png_ptr->zstream_start && png_ptr->zstream.avail_in > 0)
+   {
+      if ((*png_ptr->zstream.next_in >> 4) > 7)
+      {
+         png_ptr->zstream.msg = "invalid window size (libpng)";
+         return Z_DATA_ERROR;
+      }
+
+      png_ptr->zstream_start = 0;
+   }
+
+   return inflate(&png_ptr->zstream, flush);
+}
+#endif /* Zlib >= 1.2.4 */
 
 #ifdef PNG_READ_COMPRESSED_TEXT_SUPPORTED
 /* png_inflate now returns zlib error codes including Z_OK and Z_STREAM_END to
  * allow the caller to do multiple calls if required.  If the 'finish' flag is
  * set Z_FINISH will be passed to the final inflate() call and Z_STREAM_END must
  * be returned or there has been a problem, otherwise Z_SYNC_FLUSH is used and
  * Z_OK or Z_STREAM_END will be returned on success.
  *
  * The input and output sizes are updated to the actual amounts of data consumed
  * or written, not the amount available (as in a z_stream).  The data pointers
@@ skipping 74 matching lines @@
 
          png_ptr->zstream.avail_out = avail;
          avail_out -= avail;
 
          /* zlib inflate call */
          /* In fact 'avail_out' may be 0 at this point, that happens at the end
           * of the read when the final LZ end code was not passed at the end of
           * the previous chunk of input data.  Tell zlib if we have reached the
           * end of the output buffer.
           */
-         ret = inflate(&png_ptr->zstream, avail_out > 0 ? Z_NO_FLUSH :
-            (finish ? Z_FINISH : Z_SYNC_FLUSH));
+         ret = PNG_INFLATE(png_ptr, avail_out > 0 ? Z_NO_FLUSH :
+             (finish ? Z_FINISH : Z_SYNC_FLUSH));
       } while (ret == Z_OK);
 
       /* For safety kill the local buffer pointer now */
       if (output == NULL)
          png_ptr->zstream.next_out = NULL;
 
       /* Claw back the 'size' and 'remaining_space' byte counts. */
       avail_in += png_ptr->zstream.avail_in;
       avail_out += png_ptr->zstream.avail_out;
 
@@ skipping 37 matching lines @@
 {
    /* TODO: implement different limits for different types of chunk.
     *
     * The caller supplies *newlength set to the maximum length of the
     * uncompressed data, but this routine allocates space for the prefix and
     * maybe a '\0' terminator too.  We have to assume that 'prefix_size' is
     * limited only by the maximum chunk size.
     */
    png_alloc_size_t limit = PNG_SIZE_MAX;
 
-#  ifdef PNG_SET_CHUNK_MALLOC_LIMIT_SUPPORTED
-      if (png_ptr->user_chunk_malloc_max > 0 &&
-         png_ptr->user_chunk_malloc_max < limit)
-         limit = png_ptr->user_chunk_malloc_max;
-#  elif PNG_USER_CHUNK_MALLOC_MAX > 0
-      if (PNG_USER_CHUNK_MALLOC_MAX < limit)
-         limit = PNG_USER_CHUNK_MALLOC_MAX;
-#  endif
+# ifdef PNG_SET_USER_LIMITS_SUPPORTED
+   if (png_ptr->user_chunk_malloc_max > 0 &&
+       png_ptr->user_chunk_malloc_max < limit)
+      limit = png_ptr->user_chunk_malloc_max;
+# elif PNG_USER_CHUNK_MALLOC_MAX > 0
+   if (PNG_USER_CHUNK_MALLOC_MAX < limit)
+      limit = PNG_USER_CHUNK_MALLOC_MAX;
+# endif
 
    if (limit >= prefix_size + (terminate != 0))
    {
       int ret;
 
       limit -= prefix_size + (terminate != 0);
 
       if (limit < *newlength)
          *newlength = limit;
 
@@ skipping 33 matching lines @@
                if (text != NULL)
                {
                   ret = png_inflate(png_ptr, png_ptr->chunk_name, 1/*finish*/,
                      png_ptr->read_buffer + prefix_size, &lzsize,
                      text + prefix_size, newlength);
 
                   if (ret == Z_STREAM_END)
                   {
                      if (new_size == *newlength)
                      {
-                        if (terminate)
+                        if (terminate != 0)
                            text[prefix_size + *newlength] = 0;
 
                         if (prefix_size > 0)
                            memcpy(text, png_ptr->read_buffer, prefix_size);
 
                         {
                            png_bytep old_ptr = png_ptr->read_buffer;
 
                            png_ptr->read_buffer = text;
                            png_ptr->read_buffer_size = buffer_size;
@@ skipping 60 matching lines @@
       return ret;
    }
 
    else
    {
       /* Application/configuration limits exceeded */
       png_zstream_error(png_ptr, Z_MEM_ERROR);
       return Z_MEM_ERROR;
    }
 }
-#endif /* PNG_READ_COMPRESSED_TEXT_SUPPORTED */
+#endif /* READ_COMPRESSED_TEXT */
 
 #ifdef PNG_READ_iCCP_SUPPORTED
 /* Perform a partial read and decompress, producing 'avail_out' bytes and
  * reading from the current chunk as required.
  */
 static int
 png_inflate_read(png_structrp png_ptr, png_bytep read_buffer, uInt read_size,
    png_uint_32p chunk_bytes, png_bytep next_out, png_alloc_size_t *out_size,
    int finish)
 {
@@ skipping 27 matching lines @@
                avail = (uInt)*out_size;
             *out_size -= avail;
 
             png_ptr->zstream.avail_out = avail;
          }
 
          /* Use Z_SYNC_FLUSH when there is no more chunk data to ensure that all
           * the available output is produced; this allows reading of truncated
           * streams.
           */
-         ret = inflate(&png_ptr->zstream,
+         ret = PNG_INFLATE(png_ptr,
             *chunk_bytes > 0 ? Z_NO_FLUSH : (finish ? Z_FINISH : Z_SYNC_FLUSH));
       }
       while (ret == Z_OK && (*out_size > 0 || png_ptr->zstream.avail_out > 0));
 
       *out_size += png_ptr->zstream.avail_out;
       png_ptr->zstream.avail_out = 0; /* Should not be required, but is safe */
 
       /* Ensure the error message pointer is always set: */
       png_zstream_error(png_ptr, ret);
       return ret;
    }
 
    else
    {
       png_ptr->zstream.msg = PNGZ_MSG_CAST("zstream unclaimed");
       return Z_STREAM_ERROR;
    }
 }
 #endif
 
 /* Read and check the IDHR chunk */
+
 void /* PRIVATE */
 png_handle_IHDR(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
    png_byte buf[13];
    png_uint_32 width, height;
    int bit_depth, color_type, compression_type, filter_type;
    int interlace_type;
 
    png_debug(1, "in png_handle_IHDR");
 
-   if (png_ptr->mode & PNG_HAVE_IHDR)
+   if ((png_ptr->mode & PNG_HAVE_IHDR) != 0)
       png_chunk_error(png_ptr, "out of place");
 
    /* Check the length */
    if (length != 13)
       png_chunk_error(png_ptr, "invalid");
 
    png_ptr->mode |= PNG_HAVE_IHDR;
 
    png_crc_read(png_ptr, buf, 13);
    png_crc_finish(png_ptr, 0);
@@ skipping 33 matching lines @@
       case PNG_COLOR_TYPE_GRAY_ALPHA:
          png_ptr->channels = 2;
          break;
 
       case PNG_COLOR_TYPE_RGB_ALPHA:
          png_ptr->channels = 4;
          break;
    }
 
    /* Set up other useful info */
-   png_ptr->pixel_depth = (png_byte)(png_ptr->bit_depth *
-   png_ptr->channels);
+   png_ptr->pixel_depth = (png_byte)(png_ptr->bit_depth * png_ptr->channels);
    png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth, png_ptr->width);
    png_debug1(3, "bit_depth = %d", png_ptr->bit_depth);
    png_debug1(3, "channels = %d", png_ptr->channels);
    png_debug1(3, "rowbytes = %lu", (unsigned long)png_ptr->rowbytes);
    png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth,
        color_type, interlace_type, compression_type, filter_type);
 }
 
 /* Read and check the palette */
 void /* PRIVATE */
 png_handle_PLTE(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
    png_color palette[PNG_MAX_PALETTE_LENGTH];
-   int num, i;
+   int max_palette_length, num, i;
 #ifdef PNG_POINTER_INDEXING_SUPPORTED
    png_colorp pal_ptr;
 #endif
 
    png_debug(1, "in png_handle_PLTE");
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
    /* Moved to before the 'after IDAT' check below because otherwise duplicate
     * PLTE chunks are potentially ignored (the spec says there shall not be more
     * than one PLTE, the error is not treated as benign, so this check trumps
     * the requirement that PLTE appears before IDAT.)
     */
-   else if (png_ptr->mode & PNG_HAVE_PLTE)
+   else if ((png_ptr->mode & PNG_HAVE_PLTE) != 0)
       png_chunk_error(png_ptr, "duplicate");
 
-   else if (png_ptr->mode & PNG_HAVE_IDAT)
+   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
    {
       /* This is benign because the non-benign error happened before, when an
        * IDAT was encountered in a color-mapped image with no PLTE.
        */
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of place");
       return;
    }
 
    png_ptr->mode |= PNG_HAVE_PLTE;
 
-   if (!(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
+   if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) == 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "ignored in grayscale PNG");
       return;
    }
 
 #ifndef PNG_READ_OPT_PLTE_SUPPORTED
    if (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
    {
       png_crc_finish(png_ptr, length);
@@ skipping 10 matching lines @@
 
       else
          png_chunk_error(png_ptr, "invalid");
 
       return;
    }
 
    /* The cast is safe because 'length' is less than 3*PNG_MAX_PALETTE_LENGTH */
    num = (int)length / 3;
 
+   /* If the palette has 256 or fewer entries but is too large for the bit
+    * depth, we don't issue an error, to preserve the behavior of previous
+    * libpng versions. We silently truncate the unused extra palette entries
+    * here.
+    */
+   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+      max_palette_length = (1 << png_ptr->bit_depth);
+   else
+      max_palette_length = PNG_MAX_PALETTE_LENGTH;
+
+   if (num > max_palette_length)
+      num = max_palette_length;
+
 #ifdef PNG_POINTER_INDEXING_SUPPORTED
    for (i = 0, pal_ptr = palette; i < num; i++, pal_ptr++)
    {
       png_byte buf[3];
 
       png_crc_read(png_ptr, buf, 3);
       pal_ptr->red = buf[0];
       pal_ptr->green = buf[1];
       pal_ptr->blue = buf[2];
    }
@@ skipping 12 matching lines @@
 
    /* If we actually need the PLTE chunk (ie for a paletted image), we do
     * whatever the normal CRC configuration tells us.  However, if we
     * have an RGB image, the PLTE can be considered ancillary, so
     * we will act as though it is.
     */
 #ifndef PNG_READ_OPT_PLTE_SUPPORTED
    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
 #endif
    {
-      png_crc_finish(png_ptr, 0);
+      png_crc_finish(png_ptr, (int) length - num * 3);
    }
 
 #ifndef PNG_READ_OPT_PLTE_SUPPORTED
-   else if (png_crc_error(png_ptr))  /* Only if we have a CRC error */
+   else if (png_crc_error(png_ptr) != 0)  /* Only if we have a CRC error */
    {
       /* If we don't want to use the data from an ancillary chunk,
        * we have two options: an error abort, or a warning and we
        * ignore the data in this chunk (which should be OK, since
        * it's considered ancillary for a RGB or RGBA image).
        *
        * IMPLEMENTATION NOTE: this is only here because png_crc_finish uses the
        * chunk type to determine whether to check the ancillary or the critical
        * flags.
        */
-      if (!(png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_USE))
-      {
-         if (png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN)
-         {
-            png_chunk_benign_error(png_ptr, "CRC error");
-         }
+      if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_USE) == 0)
+      {
+         if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN) != 0)
+            return;
 
          else
-         {
-            png_chunk_warning(png_ptr, "CRC error");
-            return;
-         }
+            png_chunk_error(png_ptr, "CRC error");
       }
 
       /* Otherwise, we (optionally) emit a warning and use the chunk. */
-      else if (!(png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN))
-      {
+      else if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN) == 0)
          png_chunk_warning(png_ptr, "CRC error");
-      }
    }
 #endif
 
    /* TODO: png_set_PLTE has the side effect of setting png_ptr->palette to its
     * own copy of the palette.  This has the side effect that when png_start_row
     * is called (this happens after any call to png_read_update_info) the
     * info_ptr palette gets changed.  This is extremely unexpected and
     * confusing.
     *
     * Fix this by not sharing the palette in this way.
     */
    png_set_PLTE(png_ptr, info_ptr, palette, num);
 
    /* The three chunks, bKGD, hIST and tRNS *must* appear after PLTE and before
     * IDAT.  Prior to 1.6.0 this was not checked; instead the code merely
     * checked the apparent validity of a tRNS chunk inserted before PLTE on a
     * palette PNG.  1.6.0 attempts to rigorously follow the standard and
     * therefore does a benign error if the erroneous condition is detected *and*
     * cancels the tRNS if the benign error returns.  The alternative is to
     * amend the standard since it would be rather hypocritical of the standards
     * maintainers to ignore it.
     */
 #ifdef PNG_READ_tRNS_SUPPORTED
    if (png_ptr->num_trans > 0 ||
-      (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tRNS) != 0))
+       (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tRNS) != 0))
    {
       /* Cancel this because otherwise it would be used if the transforms
        * require it.  Don't cancel the 'valid' flag because this would prevent
        * detection of duplicate chunks.
        */
       png_ptr->num_trans = 0;
 
       if (info_ptr != NULL)
          info_ptr->num_trans = 0;
 
@@ skipping 10 matching lines @@
    if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_bKGD) != 0)
       png_chunk_benign_error(png_ptr, "bKGD must be after");
 #endif
 }
 
 void /* PRIVATE */
 png_handle_IEND(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
    png_debug(1, "in png_handle_IEND");
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR) || !(png_ptr->mode & PNG_HAVE_IDAT))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0 ||
+       (png_ptr->mode & PNG_HAVE_IDAT) == 0)
       png_chunk_error(png_ptr, "out of place");
 
    png_ptr->mode |= (PNG_AFTER_IDAT | PNG_HAVE_IEND);
 
    png_crc_finish(png_ptr, length);
 
    if (length != 0)
       png_chunk_benign_error(png_ptr, "invalid");
 
    PNG_UNUSED(info_ptr)
 }
 
 #ifdef PNG_READ_gAMA_SUPPORTED
 void /* PRIVATE */
 png_handle_gAMA(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
    png_fixed_point igamma;
    png_byte buf[4];
 
    png_debug(1, "in png_handle_gAMA");
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   else if (png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE))
+   else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of place");
       return;
    }
 
    if (length != 4)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "invalid");
       return;
    }
 
    png_crc_read(png_ptr, buf, 4);
 
-   if (png_crc_finish(png_ptr, 0))
+   if (png_crc_finish(png_ptr, 0) != 0)
       return;
 
    igamma = png_get_fixed_point(NULL, buf);
 
    png_colorspace_set_gamma(png_ptr, &png_ptr->colorspace, igamma);
    png_colorspace_sync(png_ptr, info_ptr);
 }
 #endif
 
 #ifdef PNG_READ_sBIT_SUPPORTED
 void /* PRIVATE */
 png_handle_sBIT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
-   unsigned int truelen;
+   unsigned int truelen, i;
+   png_byte sample_depth;
    png_byte buf[4];
 
    png_debug(1, "in png_handle_sBIT");
 
-   buf[0] = buf[1] = buf[2] = buf[3] = 0;
-
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   else if (png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE))
+   else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of place");
       return;
    }
 
-   if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_sBIT))
+   if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_sBIT) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "duplicate");
       return;
    }
 
    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+   {
       truelen = 3;
+      sample_depth = 8;
+   }
 
    else
+   {
       truelen = png_ptr->channels;
+      sample_depth = png_ptr->bit_depth;
+   }
 
    if (length != truelen || length > 4)
    {
       png_chunk_benign_error(png_ptr, "invalid");
       png_crc_finish(png_ptr, length);
       return;
    }
 
+   buf[0] = buf[1] = buf[2] = buf[3] = sample_depth;
    png_crc_read(png_ptr, buf, truelen);
 
-   if (png_crc_finish(png_ptr, 0))
-      return;
-
-   if (png_ptr->color_type & PNG_COLOR_MASK_COLOR)
+   if (png_crc_finish(png_ptr, 0) != 0)
+      return;
+
+   for (i=0; i<truelen; ++i)
+   {
+      if (buf[i] == 0 || buf[i] > sample_depth)
+      {
+         png_chunk_benign_error(png_ptr, "invalid");
+         return;
+      }
+   }
+
+   if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
    {
       png_ptr->sig_bit.red = buf[0];
       png_ptr->sig_bit.green = buf[1];
       png_ptr->sig_bit.blue = buf[2];
       png_ptr->sig_bit.alpha = buf[3];
    }
 
    else
    {
       png_ptr->sig_bit.gray = buf[0];
       png_ptr->sig_bit.red = buf[0];
       png_ptr->sig_bit.green = buf[0];
       png_ptr->sig_bit.blue = buf[0];
       png_ptr->sig_bit.alpha = buf[1];
    }
 
    png_set_sBIT(png_ptr, info_ptr, &(png_ptr->sig_bit));
 }
 #endif
 
 #ifdef PNG_READ_cHRM_SUPPORTED
 void /* PRIVATE */
 png_handle_cHRM(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
    png_byte buf[32];
    png_xy xy;
 
    png_debug(1, "in png_handle_cHRM");
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   else if (png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE))
+   else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of place");
       return;
    }
 
    if (length != 32)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "invalid");
       return;
    }
 
    png_crc_read(png_ptr, buf, 32);
 
-   if (png_crc_finish(png_ptr, 0))
+   if (png_crc_finish(png_ptr, 0) != 0)
       return;
 
    xy.whitex = png_get_fixed_point(NULL, buf);
    xy.whitey = png_get_fixed_point(NULL, buf + 4);
    xy.redx   = png_get_fixed_point(NULL, buf + 8);
    xy.redy   = png_get_fixed_point(NULL, buf + 12);
    xy.greenx = png_get_fixed_point(NULL, buf + 16);
    xy.greeny = png_get_fixed_point(NULL, buf + 20);
    xy.bluex  = png_get_fixed_point(NULL, buf + 24);
    xy.bluey  = png_get_fixed_point(NULL, buf + 28);
 
    if (xy.whitex == PNG_FIXED_ERROR ||
        xy.whitey == PNG_FIXED_ERROR ||
        xy.redx   == PNG_FIXED_ERROR ||
        xy.redy   == PNG_FIXED_ERROR ||
        xy.greenx == PNG_FIXED_ERROR ||
        xy.greeny == PNG_FIXED_ERROR ||
        xy.bluex  == PNG_FIXED_ERROR ||
        xy.bluey  == PNG_FIXED_ERROR)
    {
       png_chunk_benign_error(png_ptr, "invalid values");
       return;
    }
 
    /* If a colorspace error has already been output skip this chunk */
-   if (png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID)
-      return;
-
-   if (png_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM)
+   if ((png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0)
+      return;
+
+   if ((png_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM) != 0)
    {
       png_ptr->colorspace.flags |= PNG_COLORSPACE_INVALID;
       png_colorspace_sync(png_ptr, info_ptr);
       png_chunk_benign_error(png_ptr, "duplicate");
       return;
    }
 
    png_ptr->colorspace.flags |= PNG_COLORSPACE_FROM_cHRM;
    (void)png_colorspace_set_chromaticities(png_ptr, &png_ptr->colorspace, &xy,
       1/*prefer cHRM values*/);
    png_colorspace_sync(png_ptr, info_ptr);
 }
 #endif
 
 #ifdef PNG_READ_sRGB_SUPPORTED
 void /* PRIVATE */
 png_handle_sRGB(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
    png_byte intent;
 
    png_debug(1, "in png_handle_sRGB");
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   else if (png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE))
+   else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of place");
       return;
    }
 
    if (length != 1)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "invalid");
       return;
    }
 
    png_crc_read(png_ptr, &intent, 1);
 
-   if (png_crc_finish(png_ptr, 0))
+   if (png_crc_finish(png_ptr, 0) != 0)
       return;
 
    /* If a colorspace error has already been output skip this chunk */
-   if (png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID)
+   if ((png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0)
       return;
 
    /* Only one sRGB or iCCP chunk is allowed, use the HAVE_INTENT flag to detect
     * this.
     */
-   if (png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_INTENT)
+   if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_INTENT) != 0)
    {
       png_ptr->colorspace.flags |= PNG_COLORSPACE_INVALID;
       png_colorspace_sync(png_ptr, info_ptr);
       png_chunk_benign_error(png_ptr, "too many profiles");
       return;
    }
 
    (void)png_colorspace_set_sRGB(png_ptr, &png_ptr->colorspace, intent);
    png_colorspace_sync(png_ptr, info_ptr);
 }
-#endif /* PNG_READ_sRGB_SUPPORTED */
+#endif /* READ_sRGB */
 
 #ifdef PNG_READ_iCCP_SUPPORTED
 void /* PRIVATE */
 png_handle_iCCP(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 /* Note: this does not properly handle profiles that are > 64K under DOS */
 {
    png_const_charp errmsg = NULL; /* error message output, or no error */
    int finished = 0; /* crc checked */
 
    png_debug(1, "in png_handle_iCCP");
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   else if (png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE))
+   else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of place");
       return;
    }
 
    /* Consistent with all the above colorspace handling an obviously *invalid*
     * chunk is just ignored, so does not invalidate the color space.  An
     * alternative is to set the 'invalid' flags at the start of this routine
     * and only clear them in they were not set before and all the tests pass.
-    * The minimum 'deflate' stream is assumed to be just the 2 byte header and 4
-    * byte checksum.  The keyword must be one character and there is a
-    * terminator (0) byte and the compression method.
+    * The minimum 'deflate' stream is assumed to be just the 2 byte header and
+    * 4 byte checksum.  The keyword must be at least one character and there is
+    * a terminator (0) byte and the compression method.
     */
    if (length < 9)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "too short");
       return;
    }
 
    /* If a colorspace error has already been output skip this chunk */
-   if (png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID)
+   if ((png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0)
    {
       png_crc_finish(png_ptr, length);
       return;
    }
 
    /* Only one sRGB or iCCP chunk is allowed, use the HAVE_INTENT flag to detect
     * this.
     */
    if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_INTENT) == 0)
    {
@@ skipping 39 matching lines @@
                   0/*finish: don't, because the output is too small*/);
 
                if (size == 0)
                {
                   /* We have the ICC profile header; do the basic header checks.
                    */
                   const png_uint_32 profile_length =
                      png_get_uint_32(profile_header);
 
                   if (png_icc_check_length(png_ptr, &png_ptr->colorspace,
-                     keyword, profile_length))
+                     keyword, profile_length) != 0)
                   {
                      /* The length is apparently ok, so we can check the 132
                       * byte header.
                       */
                      if (png_icc_check_header(png_ptr, &png_ptr->colorspace,
                         keyword, profile_length, profile_header,
-                        png_ptr->color_type))
+                        png_ptr->color_type) != 0)
                      {
                         /* Now read the tag table; a variable size buffer is
                          * needed at this point, allocate one for the whole
                          * profile.  The header check has already validated
                          * that none of these stuff will overflow.
                          */
                         const png_uint_32 tag_count = png_get_uint_32(
                            profile_header+128);
                         png_bytep profile = png_read_buffer(png_ptr,
                            profile_length, 2/*silent*/);
 
                         if (profile != NULL)
                         {
                            memcpy(profile, profile_header,
                               (sizeof profile_header));
 
                            size = 12 * tag_count;
 
                            (void)png_inflate_read(png_ptr, local_buffer,
                               (sizeof local_buffer), &length,
                               profile + (sizeof profile_header), &size, 0);
 
-                           /* Still expect a a buffer error because we expect
+                           /* Still expect a buffer error because we expect
                             * there to be some tag data!
                             */
                            if (size == 0)
                            {
                               if (png_icc_check_tag_table(png_ptr,
                                  &png_ptr->colorspace, keyword, profile_length,
-                                 profile))
+                                 profile) != 0)
                               {
                                  /* The profile has been validated for basic
                                   * security issues, so read the whole thing in.
                                   */
                                  size = profile_length - (sizeof profile_header)
                                     - 12 * tag_count;
 
                                  (void)png_inflate_read(png_ptr, local_buffer,
                                     (sizeof local_buffer), &length,
                                     profile + (sizeof profile_header) +
@@ skipping 12 matching lines @@
                                         * keep going.
                                         */
                                        png_chunk_warning(png_ptr,
                                           "extra compressed data");
                                     }
 
                                     png_crc_finish(png_ptr, length);
                                     finished = 1;
 
 #                                   ifdef PNG_sRGB_SUPPORTED
-                                       /* Check for a match against sRGB */
-                                       png_icc_set_sRGB(png_ptr,
-                                          &png_ptr->colorspace, profile,
-                                          png_ptr->zstream.adler);
+                                    /* Check for a match against sRGB */
+                                    png_icc_set_sRGB(png_ptr,
+                                       &png_ptr->colorspace, profile,
+                                       png_ptr->zstream.adler);
 #                                   endif
 
                                     /* Steal the profile for info_ptr. */
                                     if (info_ptr != NULL)
                                     {
                                        png_free_data(png_ptr, info_ptr,
                                           PNG_FREE_ICCP, 0);
 
                                        info_ptr->iccp_name = png_voidcast(char*,
                                           png_malloc_base(png_ptr,
@@ skipping 29 matching lines @@
                                     if (errmsg == NULL)
                                     {
                                        png_ptr->zowner = 0;
                                        return;
                                     }
                                  }
 
                                  else if (size > 0)
                                     errmsg = "truncated";
 
+#ifndef __COVERITY__
                                  else
                                     errmsg = png_ptr->zstream.msg;
+#endif
                               }
 
                               /* else png_icc_check_tag_table output an error */
                            }
 
                            else /* profile truncated */
                               errmsg = png_ptr->zstream.msg;
                         }
 
                         else
@@ skipping 22 matching lines @@
       }
 
       else
          errmsg = "bad keyword";
    }
 
    else
       errmsg = "too many profiles";
 
    /* Failure: the reason is in 'errmsg' */
-   if (!finished)
+   if (finished == 0)
       png_crc_finish(png_ptr, length);
 
    png_ptr->colorspace.flags |= PNG_COLORSPACE_INVALID;
    png_colorspace_sync(png_ptr, info_ptr);
    if (errmsg != NULL) /* else already output */
       png_chunk_benign_error(png_ptr, errmsg);
 }
-#endif /* PNG_READ_iCCP_SUPPORTED */
+#endif /* READ_iCCP */
 
 #ifdef PNG_READ_sPLT_SUPPORTED
 void /* PRIVATE */
 png_handle_sPLT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 /* Note: this does not properly handle chunks that are > 64K under DOS */
 {
    png_bytep entry_start, buffer;
    png_sPLT_t new_palette;
    png_sPLT_entryp pp;
    png_uint_32 data_length;
@@ skipping 15 matching lines @@
 
       if (--png_ptr->user_chunk_cache_max == 1)
       {
          png_warning(png_ptr, "No space in chunk cache for sPLT");
          png_crc_finish(png_ptr, length);
          return;
       }
    }
 #endif
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   else if (png_ptr->mode & PNG_HAVE_IDAT)
+   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of place");
       return;
    }
 
 #ifdef PNG_MAX_MALLOC_64K
    if (length > 65535U)
    {
       png_crc_finish(png_ptr, length);
@@ skipping 10 matching lines @@
       return;
    }
 
 
    /* WARNING: this may break if size_t is less than 32 bits; it is assumed
     * that the PNG_MAX_MALLOC_64K test is enabled in this case, but this is a
     * potential breakage point if the types in pngconf.h aren't exactly right.
     */
    png_crc_read(png_ptr, buffer, length);
 
-   if (png_crc_finish(png_ptr, skip))
+   if (png_crc_finish(png_ptr, skip) != 0)
       return;
 
    buffer[length] = 0;
 
    for (entry_start = buffer; *entry_start; entry_start++)
       /* Empty loop to find end of name */ ;
 
    ++entry_start;
 
    /* A sample depth should follow the separator, and we should be on it  */
-   if (entry_start > buffer + length - 2)
+   if (length < 2U || entry_start > buffer + (length - 2U))
    {
       png_warning(png_ptr, "malformed sPLT chunk");
       return;
    }
 
    new_palette.depth = *entry_start++;
    entry_size = (new_palette.depth == 8 ? 6 : 10);
    /* This must fit in a png_uint_32 because it is derived from the original
     * chunk data length.
     */
    data_length = length - (png_uint_32)(entry_start - buffer);
 
    /* Integrity-check the data length */
-   if (data_length % entry_size)
+   if ((data_length % entry_size) != 0)
    {
       png_warning(png_ptr, "sPLT chunk has bad length");
       return;
    }
 
    dl = (png_int_32)(data_length / entry_size);
    max_dl = PNG_SIZE_MAX / (sizeof (png_sPLT_entry));
 
    if (dl > max_dl)
    {
-       png_warning(png_ptr, "sPLT chunk too long");
-       return;
+      png_warning(png_ptr, "sPLT chunk too long");
+      return;
    }
 
    new_palette.nentries = (png_int_32)(data_length / entry_size);
 
    new_palette.entries = (png_sPLT_entryp)png_malloc_warn(
        png_ptr, new_palette.nentries * (sizeof (png_sPLT_entry)));
 
    if (new_palette.entries == NULL)
    {
-       png_warning(png_ptr, "sPLT chunk requires too much memory");
-       return;
+      png_warning(png_ptr, "sPLT chunk requires too much memory");
+      return;
    }
 
 #ifdef PNG_POINTER_INDEXING_SUPPORTED
    for (i = 0; i < new_palette.nentries; i++)
    {
       pp = new_palette.entries + i;
 
       if (new_palette.depth == 8)
       {
          pp->red = *entry_start++;
@@ skipping 38 matching lines @@
    }
 #endif
 
    /* Discard all chunk data except the name and stash that */
    new_palette.name = (png_charp)buffer;
 
    png_set_sPLT(png_ptr, info_ptr, &new_palette, 1);
 
    png_free(png_ptr, new_palette.entries);
 }
-#endif /* PNG_READ_sPLT_SUPPORTED */
+#endif /* READ_sPLT */
 
 #ifdef PNG_READ_tRNS_SUPPORTED
 void /* PRIVATE */
 png_handle_tRNS(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
    png_byte readbuf[PNG_MAX_PALETTE_LENGTH];
 
    png_debug(1, "in png_handle_tRNS");
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   else if (png_ptr->mode & PNG_HAVE_IDAT)
+   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of place");
       return;
    }
 
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tRNS))
+   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tRNS) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "duplicate");
       return;
    }
 
    if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
    {
       png_byte buf[2];
 
@@ skipping 22 matching lines @@
 
       png_crc_read(png_ptr, buf, length);
       png_ptr->num_trans = 1;
       png_ptr->trans_color.red = png_get_uint_16(buf);
       png_ptr->trans_color.green = png_get_uint_16(buf + 2);
       png_ptr->trans_color.blue = png_get_uint_16(buf + 4);
    }
 
    else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
    {
-      if (!(png_ptr->mode & PNG_HAVE_PLTE))
+      if ((png_ptr->mode & PNG_HAVE_PLTE) == 0)
       {
          /* TODO: is this actually an error in the ISO spec? */
          png_crc_finish(png_ptr, length);
          png_chunk_benign_error(png_ptr, "out of place");
          return;
       }
 
-      if (length > png_ptr->num_palette || length > PNG_MAX_PALETTE_LENGTH ||
+      if (length > (unsigned int) png_ptr->num_palette ||
+         length > (unsigned int) PNG_MAX_PALETTE_LENGTH ||
          length == 0)
       {
          png_crc_finish(png_ptr, length);
          png_chunk_benign_error(png_ptr, "invalid");
          return;
       }
 
       png_crc_read(png_ptr, readbuf, length);
       png_ptr->num_trans = (png_uint_16)length;
    }
 
    else
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "invalid with alpha channel");
       return;
    }
 
-   if (png_crc_finish(png_ptr, 0))
+   if (png_crc_finish(png_ptr, 0) != 0)
    {
       png_ptr->num_trans = 0;
       return;
    }
 
    /* TODO: this is a horrible side effect in the palette case because the
     * png_struct ends up with a pointer to the tRNS buffer owned by the
     * png_info.  Fix this.
     */
    png_set_tRNS(png_ptr, info_ptr, readbuf, png_ptr->num_trans,
        &(png_ptr->trans_color));
 }
 #endif
 
 #ifdef PNG_READ_bKGD_SUPPORTED
 void /* PRIVATE */
 png_handle_bKGD(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
    unsigned int truelen;
    png_byte buf[6];
    png_color_16 background;
 
    png_debug(1, "in png_handle_bKGD");
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   else if ((png_ptr->mode & PNG_HAVE_IDAT) ||
-      (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
-       !(png_ptr->mode & PNG_HAVE_PLTE)))
+   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0 ||
+       (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
+       (png_ptr->mode & PNG_HAVE_PLTE) == 0))
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of place");
       return;
    }
 
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_bKGD))
+   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_bKGD) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "duplicate");
       return;
    }
 
    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
       truelen = 1;
 
-   else if (png_ptr->color_type & PNG_COLOR_MASK_COLOR)
+   else if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
       truelen = 6;
 
    else
       truelen = 2;
 
    if (length != truelen)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "invalid");
       return;
    }
 
    png_crc_read(png_ptr, buf, truelen);
 
-   if (png_crc_finish(png_ptr, 0))
+   if (png_crc_finish(png_ptr, 0) != 0)
       return;
 
    /* We convert the index value into RGB components so that we can allow
     * arbitrary RGB values for background when we have transparency, and
     * so it is easy to determine the RGB values of the background color
     * from the info_ptr struct.
     */
    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
    {
       background.index = buf[0];
 
-      if (info_ptr && info_ptr->num_palette)
+      if (info_ptr != NULL && info_ptr->num_palette != 0)
       {
          if (buf[0] >= info_ptr->num_palette)
          {
             png_chunk_benign_error(png_ptr, "invalid index");
             return;
          }
 
          background.red = (png_uint_16)png_ptr->palette[buf[0]].red;
          background.green = (png_uint_16)png_ptr->palette[buf[0]].green;
          background.blue = (png_uint_16)png_ptr->palette[buf[0]].blue;
       }
 
       else
          background.red = background.green = background.blue = 0;
 
       background.gray = 0;
    }
 
-   else if (!(png_ptr->color_type & PNG_COLOR_MASK_COLOR)) /* GRAY */
+   else if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) == 0) /* GRAY */
    {
       background.index = 0;
       background.red =
       background.green =
       background.blue =
       background.gray = png_get_uint_16(buf);
    }
 
    else
    {
@@ skipping 10 matching lines @@
 
 #ifdef PNG_READ_hIST_SUPPORTED
 void /* PRIVATE */
 png_handle_hIST(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
    unsigned int num, i;
    png_uint_16 readbuf[PNG_MAX_PALETTE_LENGTH];
 
    png_debug(1, "in png_handle_hIST");
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   else if ((png_ptr->mode & PNG_HAVE_IDAT) || !(png_ptr->mode & PNG_HAVE_PLTE))
+   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0 ||
+       (png_ptr->mode & PNG_HAVE_PLTE) == 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of place");
       return;
    }
 
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_hIST))
+   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_hIST) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "duplicate");
       return;
    }
 
    num = length / 2 ;
 
-   if (num != png_ptr->num_palette || num > PNG_MAX_PALETTE_LENGTH)
+   if (num != (unsigned int) png_ptr->num_palette ||
+       num > (unsigned int) PNG_MAX_PALETTE_LENGTH)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "invalid");
       return;
    }
 
    for (i = 0; i < num; i++)
    {
       png_byte buf[2];
 
       png_crc_read(png_ptr, buf, 2);
       readbuf[i] = png_get_uint_16(buf);
    }
 
-   if (png_crc_finish(png_ptr, 0))
+   if (png_crc_finish(png_ptr, 0) != 0)
       return;
 
    png_set_hIST(png_ptr, info_ptr, readbuf);
 }
 #endif
 
 #ifdef PNG_READ_pHYs_SUPPORTED
 void /* PRIVATE */
 png_handle_pHYs(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
    png_byte buf[9];
    png_uint_32 res_x, res_y;
    int unit_type;
 
    png_debug(1, "in png_handle_pHYs");
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   else if (png_ptr->mode & PNG_HAVE_IDAT)
+   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of place");
       return;
    }
 
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_pHYs))
+   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_pHYs) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "duplicate");
       return;
    }
 
    if (length != 9)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "invalid");
       return;
    }
 
    png_crc_read(png_ptr, buf, 9);
 
-   if (png_crc_finish(png_ptr, 0))
+   if (png_crc_finish(png_ptr, 0) != 0)
       return;
 
    res_x = png_get_uint_32(buf);
    res_y = png_get_uint_32(buf + 4);
    unit_type = buf[8];
    png_set_pHYs(png_ptr, info_ptr, res_x, res_y, unit_type);
 }
 #endif
 
 #ifdef PNG_READ_oFFs_SUPPORTED
 void /* PRIVATE */
 png_handle_oFFs(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
    png_byte buf[9];
    png_int_32 offset_x, offset_y;
    int unit_type;
 
    png_debug(1, "in png_handle_oFFs");
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   else if (png_ptr->mode & PNG_HAVE_IDAT)
+   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of place");
       return;
    }
 
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_oFFs))
+   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_oFFs) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "duplicate");
       return;
    }
 
    if (length != 9)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "invalid");
       return;
    }
 
    png_crc_read(png_ptr, buf, 9);
 
-   if (png_crc_finish(png_ptr, 0))
+   if (png_crc_finish(png_ptr, 0) != 0)
       return;
 
    offset_x = png_get_int_32(buf);
    offset_y = png_get_int_32(buf + 4);
    unit_type = buf[8];
    png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y, unit_type);
 }
 #endif
 
 #ifdef PNG_READ_pCAL_SUPPORTED
 /* Read the pCAL chunk (described in the PNG Extensions document) */
 void /* PRIVATE */
 png_handle_pCAL(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
    png_int_32 X0, X1;
    png_byte type, nparams;
    png_bytep buffer, buf, units, endptr;
    png_charpp params;
    int i;
 
    png_debug(1, "in png_handle_pCAL");
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   else if (png_ptr->mode & PNG_HAVE_IDAT)
+   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of place");
       return;
    }
 
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_pCAL))
+   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_pCAL) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "duplicate");
       return;
    }
 
    png_debug1(2, "Allocating and reading pCAL chunk data (%u bytes)",
        length + 1);
 
    buffer = png_read_buffer(png_ptr, length+1, 2/*silent*/);
 
    if (buffer == NULL)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of memory");
       return;
    }
 
    png_crc_read(png_ptr, buffer, length);
 
-   if (png_crc_finish(png_ptr, 0))
+   if (png_crc_finish(png_ptr, 0) != 0)
       return;
 
    buffer[length] = 0; /* Null terminate the last string */
 
    png_debug(3, "Finding end of pCAL purpose string");
    for (buf = buffer; *buf; buf++)
       /* Empty loop */ ;
 
    endptr = buffer + length;
 
    /* We need to have at least 12 bytes after the purpose string
     * in order to get the parameter information.
     */
-   if (endptr <= buf + 12)
+   if (endptr - buf <= 12)
    {
       png_chunk_benign_error(png_ptr, "invalid");
       return;
    }
 
    png_debug(3, "Reading pCAL X0, X1, type, nparams, and units");
    X0 = png_get_int_32((png_bytep)buf+1);
    X1 = png_get_int_32((png_bytep)buf+5);
    type = buf[9];
    nparams = buf[10];
@@ skipping 61 matching lines @@
 /* Read the sCAL chunk */
 void /* PRIVATE */
 png_handle_sCAL(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
    png_bytep buffer;
    png_size_t i;
    int state;
 
    png_debug(1, "in png_handle_sCAL");
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   else if (png_ptr->mode & PNG_HAVE_IDAT)
+   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of place");
       return;
    }
 
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_sCAL))
+   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_sCAL) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "duplicate");
       return;
    }
 
    /* Need unit type, width, \0, height: minimum 4 bytes */
    else if (length < 4)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "invalid");
       return;
    }
 
    png_debug1(2, "Allocating and reading sCAL chunk data (%u bytes)",
       length + 1);
 
    buffer = png_read_buffer(png_ptr, length+1, 2/*silent*/);
 
    if (buffer == NULL)
    {
       png_chunk_benign_error(png_ptr, "out of memory");
       png_crc_finish(png_ptr, length);
       return;
    }
 
    png_crc_read(png_ptr, buffer, length);
    buffer[length] = 0; /* Null terminate the last string */
 
-   if (png_crc_finish(png_ptr, 0))
+   if (png_crc_finish(png_ptr, 0) != 0)
       return;
 
    /* Validate the unit. */
    if (buffer[0] != 1 && buffer[0] != 2)
    {
       png_chunk_benign_error(png_ptr, "invalid unit");
       return;
    }
 
    /* Validate the ASCII numbers, need two ASCII numbers separated by
     * a '\0' and they need to fit exactly in the chunk data.
     */
    i = 1;
    state = 0;
 
-   if (!png_check_fp_number((png_const_charp)buffer, length, &state, &i) ||
+   if (png_check_fp_number((png_const_charp)buffer, length, &state, &i) == 0 ||
        i >= length || buffer[i++] != 0)
       png_chunk_benign_error(png_ptr, "bad width format");
 
-   else if (!PNG_FP_IS_POSITIVE(state))
+   else if (PNG_FP_IS_POSITIVE(state) == 0)
       png_chunk_benign_error(png_ptr, "non-positive width");
 
    else
    {
       png_size_t heighti = i;
 
       state = 0;
-      if (!png_check_fp_number((png_const_charp)buffer, length, &state, &i) ||
-         i != length)
+      if (png_check_fp_number((png_const_charp)buffer, length,
+          &state, &i) == 0 || i != length)
          png_chunk_benign_error(png_ptr, "bad height format");
 
-      else if (!PNG_FP_IS_POSITIVE(state))
+      else if (PNG_FP_IS_POSITIVE(state) == 0)
          png_chunk_benign_error(png_ptr, "non-positive height");
 
       else
          /* This is the (only) success case. */
          png_set_sCAL_s(png_ptr, info_ptr, buffer[0],
             (png_charp)buffer+1, (png_charp)buffer+heighti);
    }
 }
 #endif
 
 #ifdef PNG_READ_tIME_SUPPORTED
 void /* PRIVATE */
 png_handle_tIME(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
    png_byte buf[7];
    png_time mod_time;
 
    png_debug(1, "in png_handle_tIME");
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tIME))
+   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tIME) != 0)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "duplicate");
       return;
    }
 
-   if (png_ptr->mode & PNG_HAVE_IDAT)
+   if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
       png_ptr->mode |= PNG_AFTER_IDAT;
 
    if (length != 7)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "invalid");
       return;
    }
 
    png_crc_read(png_ptr, buf, 7);
 
-   if (png_crc_finish(png_ptr, 0))
+   if (png_crc_finish(png_ptr, 0) != 0)
       return;
 
    mod_time.second = buf[6];
    mod_time.minute = buf[5];
    mod_time.hour = buf[4];
    mod_time.day = buf[3];
    mod_time.month = buf[2];
    mod_time.year = png_get_uint_16(buf);
 
    png_set_tIME(png_ptr, info_ptr, &mod_time);
@@ skipping 24 matching lines @@
 
       if (--png_ptr->user_chunk_cache_max == 1)
       {
          png_crc_finish(png_ptr, length);
          png_chunk_benign_error(png_ptr, "no space in chunk cache");
          return;
       }
    }
 #endif
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   if (png_ptr->mode & PNG_HAVE_IDAT)
+   if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
       png_ptr->mode |= PNG_AFTER_IDAT;
 
 #ifdef PNG_MAX_MALLOC_64K
    if (length > 65535U)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "too large to fit in memory");
       return;
    }
 #endif
 
    buffer = png_read_buffer(png_ptr, length+1, 1/*warn*/);
 
    if (buffer == NULL)
    {
      png_chunk_benign_error(png_ptr, "out of memory");
      return;
    }
 
    png_crc_read(png_ptr, buffer, length);
 
-   if (png_crc_finish(png_ptr, skip))
+   if (png_crc_finish(png_ptr, skip) != 0)
       return;
 
    key = (png_charp)buffer;
    key[length] = 0;
 
    for (text = key; *text; text++)
       /* Empty loop to find end of key */ ;
 
    if (text != key + length)
       text++;
 
    text_info.compression = PNG_TEXT_COMPRESSION_NONE;
    text_info.key = key;
    text_info.lang = NULL;
    text_info.lang_key = NULL;
    text_info.itxt_length = 0;
    text_info.text = text;
    text_info.text_length = strlen(text);
 
-   if (png_set_text_2(png_ptr, info_ptr, &text_info, 1))
+   if (png_set_text_2(png_ptr, info_ptr, &text_info, 1) != 0)
       png_warning(png_ptr, "Insufficient memory to process text chunk");
 }
 #endif
 
 #ifdef PNG_READ_zTXt_SUPPORTED
 /* Note: this does not correctly handle chunks that are > 64K under DOS */
 void /* PRIVATE */
 png_handle_zTXt(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
    png_const_charp errmsg = NULL;
@@ skipping 13 matching lines @@
 
       if (--png_ptr->user_chunk_cache_max == 1)
       {
          png_crc_finish(png_ptr, length);
          png_chunk_benign_error(png_ptr, "no space in chunk cache");
          return;
       }
    }
 #endif
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   if (png_ptr->mode & PNG_HAVE_IDAT)
+   if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
       png_ptr->mode |= PNG_AFTER_IDAT;
 
    buffer = png_read_buffer(png_ptr, length, 2/*silent*/);
 
    if (buffer == NULL)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of memory");
       return;
    }
 
    png_crc_read(png_ptr, buffer, length);
 
-   if (png_crc_finish(png_ptr, 0))
+   if (png_crc_finish(png_ptr, 0) != 0)
       return;
 
    /* TODO: also check that the keyword contents match the spec! */
    for (keyword_length = 0;
       keyword_length < length && buffer[keyword_length] != 0;
       ++keyword_length)
       /* Empty loop to find end of name */ ;
 
    if (keyword_length > 79 || keyword_length < 1)
       errmsg = "bad keyword";
@@ skipping 29 matching lines @@
          buffer[uncompressed_length+(keyword_length+2)] = 0;
 
          text.compression = PNG_TEXT_COMPRESSION_zTXt;
          text.key = (png_charp)buffer;
          text.text = (png_charp)(buffer + keyword_length+2);
          text.text_length = uncompressed_length;
          text.itxt_length = 0;
          text.lang = NULL;
          text.lang_key = NULL;
 
-         if (png_set_text_2(png_ptr, info_ptr, &text, 1))
+         if (png_set_text_2(png_ptr, info_ptr, &text, 1) != 0)
             errmsg = "insufficient memory";
       }
 
       else
          errmsg = png_ptr->zstream.msg;
    }
 
    if (errmsg != NULL)
       png_chunk_benign_error(png_ptr, errmsg);
 }
@@ skipping 21 matching lines @@
 
       if (--png_ptr->user_chunk_cache_max == 1)
       {
          png_crc_finish(png_ptr, length);
          png_chunk_benign_error(png_ptr, "no space in chunk cache");
          return;
       }
    }
 #endif
 
-   if (!(png_ptr->mode & PNG_HAVE_IHDR))
+   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
       png_chunk_error(png_ptr, "missing IHDR");
 
-   if (png_ptr->mode & PNG_HAVE_IDAT)
+   if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
       png_ptr->mode |= PNG_AFTER_IDAT;
 
    buffer = png_read_buffer(png_ptr, length+1, 1/*warn*/);
 
    if (buffer == NULL)
    {
       png_crc_finish(png_ptr, length);
       png_chunk_benign_error(png_ptr, "out of memory");
       return;
    }
 
    png_crc_read(png_ptr, buffer, length);
 
-   if (png_crc_finish(png_ptr, 0))
+   if (png_crc_finish(png_ptr, 0) != 0)
       return;
 
    /* First the keyword. */
    for (prefix_length=0;
       prefix_length < length && buffer[prefix_length] != 0;
       ++prefix_length)
       /* Empty loop */ ;
 
    /* Perform a basic check on the keyword length here. */
    if (prefix_length > 79 || prefix_length < 1)
@@ skipping 25 matching lines @@
       /* WARNING: the length may be invalid here, this is checked below. */
       translated_keyword_offset = ++prefix_length;
 
       for (; prefix_length < length && buffer[prefix_length] != 0;
          ++prefix_length)
          /* Empty loop */ ;
 
       /* prefix_length should now be at the trailing '\0' of the translated
        * keyword, but it may already be over the end.  None of this arithmetic
        * can overflow because chunks are at most 2^31 bytes long, but on 16-bit
-       * systems the available allocaton may overflow.
+       * systems the available allocation may overflow.
        */
       ++prefix_length;
 
-      if (!compressed && prefix_length <= length)
+      if (compressed == 0 && prefix_length <= length)
          uncompressed_length = length - prefix_length;
 
-      else if (compressed && prefix_length < length)
+      else if (compressed != 0 && prefix_length < length)
       {
          uncompressed_length = PNG_SIZE_MAX;
 
          /* TODO: at present png_decompress_chunk imposes a single application
           * level memory limit, this should be split to different values for
           * iCCP and text chunks.
           */
          if (png_decompress_chunk(png_ptr, length, prefix_length,
             &uncompressed_length, 1/*terminate*/) == Z_STREAM_END)
             buffer = png_ptr->read_buffer;
 
          else
             errmsg = png_ptr->zstream.msg;
       }
 
       else
          errmsg = "truncated";
 
       if (errmsg == NULL)
       {
          png_text text;
 
          buffer[uncompressed_length+prefix_length] = 0;
 
-         if (compressed)
+         if (compressed == 0)
             text.compression = PNG_ITXT_COMPRESSION_NONE;
 
          else
             text.compression = PNG_ITXT_COMPRESSION_zTXt;
 
          text.key = (png_charp)buffer;
          text.lang = (png_charp)buffer + language_offset;
          text.lang_key = (png_charp)buffer + translated_keyword_offset;
          text.text = (png_charp)buffer + prefix_length;
          text.text_length = 0;
          text.itxt_length = uncompressed_length;
 
-         if (png_set_text_2(png_ptr, info_ptr, &text, 1))
+         if (png_set_text_2(png_ptr, info_ptr, &text, 1) != 0)
             errmsg = "insufficient memory";
       }
    }
 
    else
       errmsg = "bad compression info";
 
    if (errmsg != NULL)
       png_chunk_benign_error(png_ptr, errmsg);
 }
 #endif
 
 #ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
 /* Utility function for png_handle_unknown; set up png_ptr::unknown_chunk */
 static int
 png_cache_unknown_chunk(png_structrp png_ptr, png_uint_32 length)
 {
    png_alloc_size_t limit = PNG_SIZE_MAX;
 
    if (png_ptr->unknown_chunk.data != NULL)
    {
       png_free(png_ptr, png_ptr->unknown_chunk.data);
       png_ptr->unknown_chunk.data = NULL;
    }
 
-#  ifdef PNG_SET_CHUNK_MALLOC_LIMIT_SUPPORTED
-      if (png_ptr->user_chunk_malloc_max > 0 &&
-         png_ptr->user_chunk_malloc_max < limit)
-         limit = png_ptr->user_chunk_malloc_max;
+#  ifdef PNG_SET_USER_LIMITS_SUPPORTED
+   if (png_ptr->user_chunk_malloc_max > 0 &&
+       png_ptr->user_chunk_malloc_max < limit)
+      limit = png_ptr->user_chunk_malloc_max;
 
 #  elif PNG_USER_CHUNK_MALLOC_MAX > 0
-      if (PNG_USER_CHUNK_MALLOC_MAX < limit)
-         limit = PNG_USER_CHUNK_MALLOC_MAX;
+   if (PNG_USER_CHUNK_MALLOC_MAX < limit)
+      limit = PNG_USER_CHUNK_MALLOC_MAX;
 #  endif
 
    if (length <= limit)
    {
       PNG_CSTRING_FROM_CHUNK(png_ptr->unknown_chunk.name, png_ptr->chunk_name);
       /* The following is safe because of the PNG_SIZE_MAX init above */
       png_ptr->unknown_chunk.size = (png_size_t)length/*SAFE*/;
       /* 'mode' is a flag array, only the bottom four bits matter here */
       png_ptr->unknown_chunk.location = (png_byte)png_ptr->mode/*SAFE*/;
 
@@ skipping 17 matching lines @@
    }
 
    else
    {
       if (length > 0)
          png_crc_read(png_ptr, png_ptr->unknown_chunk.data, length);
       png_crc_finish(png_ptr, 0);
       return 1;
    }
 }
-#endif /* PNG_READ_UNKNOWN_CHUNKS_SUPPORTED */
+#endif /* READ_UNKNOWN_CHUNKS */
 
 /* Handle an unknown, or known but disabled, chunk */
 void /* PRIVATE */
 png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length, int keep)
 {
    int handled = 0; /* the chunk was handled */
 
    png_debug(1, "in png_handle_unknown");
 
 #ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
    /* NOTE: this code is based on the code in libpng-1.4.12 except for fixing
     * the bug which meant that setting a non-default behavior for a specific
     * chunk would be ignored (the default was always used unless a user
     * callback was installed).
     *
     * 'keep' is the value from the png_chunk_unknown_handling, the setting for
     * this specific chunk_name, if PNG_HANDLE_AS_UNKNOWN_SUPPORTED, if not it
     * will always be PNG_HANDLE_CHUNK_AS_DEFAULT and it needs to be set here.
     * This is just an optimization to avoid multiple calls to the lookup
     * function.
     */
 #  ifndef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
 #     ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
-         keep = png_chunk_unknown_handling(png_ptr, png_ptr->chunk_name);
+   keep = png_chunk_unknown_handling(png_ptr, png_ptr->chunk_name);
 #     endif
 #  endif
 
    /* One of the following methods will read the chunk or skip it (at least one
     * of these is always defined because this is the only way to switch on
     * PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
     */
 #  ifdef PNG_READ_USER_CHUNKS_SUPPORTED
-      /* The user callback takes precedence over the chunk keep value, but the
-       * keep value is still required to validate a save of a critical chunk.
-       */
-      if (png_ptr->read_user_chunk_fn != NULL)
-      {
-         if (png_cache_unknown_chunk(png_ptr, length))
+   /* The user callback takes precedence over the chunk keep value, but the
+    * keep value is still required to validate a save of a critical chunk.
+    */
+   if (png_ptr->read_user_chunk_fn != NULL)
+   {
+      if (png_cache_unknown_chunk(png_ptr, length) != 0)
+      {
+         /* Callback to user unknown chunk handler */
+         int ret = (*(png_ptr->read_user_chunk_fn))(png_ptr,
+            &png_ptr->unknown_chunk);
+
+         /* ret is:
+          * negative: An error occurred; png_chunk_error will be called.
+          *     zero: The chunk was not handled, the chunk will be discarded
+          *           unless png_set_keep_unknown_chunks has been used to set
+          *           a 'keep' behavior for this particular chunk, in which
+          *           case that will be used.  A critical chunk will cause an
+          *           error at this point unless it is to be saved.
+          * positive: The chunk was handled, libpng will ignore/discard it.
+          */
+         if (ret < 0)
+            png_chunk_error(png_ptr, "error in user chunk");
+
+         else if (ret == 0)
          {
-            /* Callback to user unknown chunk handler */
-            int ret = (*(png_ptr->read_user_chunk_fn))(png_ptr,
-               &png_ptr->unknown_chunk);
-
-            /* ret is:
-             * negative: An error occured, png_chunk_error will be called.
-             *     zero: The chunk was not handled, the chunk will be discarded
-             *           unless png_set_keep_unknown_chunks has been used to set
-             *           a 'keep' behavior for this particular chunk, in which
-             *           case that will be used.  A critical chunk will cause an
-             *           error at this point unless it is to be saved.
-             * positive: The chunk was handled, libpng will ignore/discard it.
+            /* If the keep value is 'default' or 'never' override it, but
+             * still error out on critical chunks unless the keep value is
+             * 'always'  While this is weird it is the behavior in 1.4.12.
+             * A possible improvement would be to obey the value set for the
+             * chunk, but this would be an API change that would probably
+             * damage some applications.
+             *
+             * The png_app_warning below catches the case that matters, where
+             * the application has not set specific save or ignore for this
+             * chunk or global save or ignore.
              */
-            if (ret < 0)
-               png_chunk_error(png_ptr, "error in user chunk");
-
-            else if (ret == 0)
+            if (keep < PNG_HANDLE_CHUNK_IF_SAFE)
             {
-               /* If the keep value is 'default' or 'never' override it, but
-                * still error out on critical chunks unless the keep value is
-                * 'always'  While this is weird it is the behavior in 1.4.12.
-                * A possible improvement would be to obey the value set for the
-                * chunk, but this would be an API change that would probably
-                * damage some applications.
-                *
-                * The png_app_warning below catches the case that matters, where
-                * the application has not set specific save or ignore for this
-                * chunk or global save or ignore.
-                */
-               if (keep < PNG_HANDLE_CHUNK_IF_SAFE)
+#              ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
+               if (png_ptr->unknown_default < PNG_HANDLE_CHUNK_IF_SAFE)
                {
-#                 ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
-                     if (png_ptr->unknown_default < PNG_HANDLE_CHUNK_IF_SAFE)
-                     {
-                        png_chunk_warning(png_ptr, "Saving unknown chunk:");
-                        png_app_warning(png_ptr,
-                           "forcing save of an unhandled chunk;"
-                           " please call png_set_keep_unknown_chunks");
-                           /* with keep = PNG_HANDLE_CHUNK_IF_SAFE */
-                     }
-#                 endif
-                  keep = PNG_HANDLE_CHUNK_IF_SAFE;
+                  png_chunk_warning(png_ptr, "Saving unknown chunk:");
+                  png_app_warning(png_ptr,
+                     "forcing save of an unhandled chunk;"
+                     " please call png_set_keep_unknown_chunks");
+                     /* with keep = PNG_HANDLE_CHUNK_IF_SAFE */
                }
-            }
-
-            else /* chunk was handled */
-            {
-               handled = 1;
-               /* Critical chunks can be safely discarded at this point. */
-               keep = PNG_HANDLE_CHUNK_NEVER;
+#              endif
+               keep = PNG_HANDLE_CHUNK_IF_SAFE;
             }
          }
 
-         else
-            keep = PNG_HANDLE_CHUNK_NEVER; /* insufficient memory */
+         else /* chunk was handled */
+         {
+            handled = 1;
+            /* Critical chunks can be safely discarded at this point. */
+            keep = PNG_HANDLE_CHUNK_NEVER;
+         }
       }
 
       else
-         /* Use the SAVE_UNKNOWN_CHUNKS code or skip the chunk */
-#  endif /* PNG_READ_USER_CHUNKS_SUPPORTED */
+         keep = PNG_HANDLE_CHUNK_NEVER; /* insufficient memory */
+   }
+
+   else
+   /* Use the SAVE_UNKNOWN_CHUNKS code or skip the chunk */
+#  endif /* READ_USER_CHUNKS */
 
 #  ifdef PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
-      {
-         /* keep is currently just the per-chunk setting, if there was no
-          * setting change it to the global default now (not that this may
-          * still be AS_DEFAULT) then obtain the cache of the chunk if required,
-          * if not simply skip the chunk.
-          */
-         if (keep == PNG_HANDLE_CHUNK_AS_DEFAULT)
-            keep = png_ptr->unknown_default;
-
-         if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
-            (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
-             PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
-         {
-            if (!png_cache_unknown_chunk(png_ptr, length))
-               keep = PNG_HANDLE_CHUNK_NEVER;
-         }
-
-         else
-            png_crc_finish(png_ptr, length);
-      }
+   {
+      /* keep is currently just the per-chunk setting, if there was no
+       * setting change it to the global default now (not that this may
+       * still be AS_DEFAULT) then obtain the cache of the chunk if required,
+       * if not simply skip the chunk.
+       */
+      if (keep == PNG_HANDLE_CHUNK_AS_DEFAULT)
+         keep = png_ptr->unknown_default;
+
+      if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
+         (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
+          PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
+      {
+         if (png_cache_unknown_chunk(png_ptr, length) == 0)
+            keep = PNG_HANDLE_CHUNK_NEVER;
+      }
+
+      else
+         png_crc_finish(png_ptr, length);
+   }
 #  else
 #     ifndef PNG_READ_USER_CHUNKS_SUPPORTED
 #        error no method to support READ_UNKNOWN_CHUNKS
 #     endif
 
-      {
-         /* If here there is no read callback pointer set and no support is
-          * compiled in to just save the unknown chunks, so simply skip this
-          * chunk.  If 'keep' is something other than AS_DEFAULT or NEVER then
-          * the app has erroneously asked for unknown chunk saving when there
-          * is no support.
-          */
-         if (keep > PNG_HANDLE_CHUNK_NEVER)
-            png_app_error(png_ptr, "no unknown chunk support available");
-
-         png_crc_finish(png_ptr, length);
-      }
+   {
+      /* If here there is no read callback pointer set and no support is
+       * compiled in to just save the unknown chunks, so simply skip this
+       * chunk.  If 'keep' is something other than AS_DEFAULT or NEVER then
+       * the app has erroneously asked for unknown chunk saving when there
+       * is no support.
+       */
+      if (keep > PNG_HANDLE_CHUNK_NEVER)
+         png_app_error(png_ptr, "no unknown chunk support available");
+
+      png_crc_finish(png_ptr, length);
+   }
 #  endif
 
 #  ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
-      /* Now store the chunk in the chunk list if appropriate, and if the limits
-       * permit it.
-       */
-      if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
-         (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
-          PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
-      {
+   /* Now store the chunk in the chunk list if appropriate, and if the limits
+    * permit it.
+    */
+   if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
+      (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
+       PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
+   {
 #     ifdef PNG_USER_LIMITS_SUPPORTED
-         switch (png_ptr->user_chunk_cache_max)
-         {
-            case 2:
-               png_ptr->user_chunk_cache_max = 1;
-               png_chunk_benign_error(png_ptr, "no space in chunk cache");
-               /* FALL THROUGH */
-            case 1:
-               /* NOTE: prior to 1.6.0 this case resulted in an unknown critical
-                * chunk being skipped, now there will be a hard error below.
-                */
-               break;
-
-            default: /* not at limit */
-               --(png_ptr->user_chunk_cache_max);
-               /* FALL THROUGH */
-            case 0: /* no limit */
-#     endif /* PNG_USER_LIMITS_SUPPORTED */
-               /* Here when the limit isn't reached or when limits are compiled
-                * out; store the chunk.
-                */
-               png_set_unknown_chunks(png_ptr, info_ptr,
-                  &png_ptr->unknown_chunk, 1);
-               handled = 1;
-#     ifdef PNG_USER_LIMITS_SUPPORTED
-               break;
-         }
-#     endif
-      }
-#  else /* no store support! */
-      PNG_UNUSED(info_ptr)
-#     error untested code (reading unknown chunks with no store support)
+      switch (png_ptr->user_chunk_cache_max)
+      {
+         case 2:
+            png_ptr->user_chunk_cache_max = 1;
+            png_chunk_benign_error(png_ptr, "no space in chunk cache");
+            /* FALL THROUGH */
+         case 1:
+            /* NOTE: prior to 1.6.0 this case resulted in an unknown critical
+             * chunk being skipped, now there will be a hard error below.
+             */
+            break;
+
+         default: /* not at limit */
+            --(png_ptr->user_chunk_cache_max);
+            /* FALL THROUGH */
+         case 0: /* no limit */
+#  endif /* USER_LIMITS */
+            /* Here when the limit isn't reached or when limits are compiled
+             * out; store the chunk.
+             */
+            png_set_unknown_chunks(png_ptr, info_ptr,
+               &png_ptr->unknown_chunk, 1);
+            handled = 1;
+#  ifdef PNG_USER_LIMITS_SUPPORTED
+            break;
+      }
+#  endif
+   }
+#  else /* no store support: the chunk must be handled by the user callback */
+   PNG_UNUSED(info_ptr)
 #  endif
 
    /* Regardless of the error handling below the cached data (if any) can be
     * freed now.  Notice that the data is not freed if there is a png_error, but
     * it will be freed by destroy_read_struct.
     */
    if (png_ptr->unknown_chunk.data != NULL)
       png_free(png_ptr, png_ptr->unknown_chunk.data);
    png_ptr->unknown_chunk.data = NULL;
 
 #else /* !PNG_READ_UNKNOWN_CHUNKS_SUPPORTED */
    /* There is no support to read an unknown chunk, so just skip it. */
    png_crc_finish(png_ptr, length);
    PNG_UNUSED(info_ptr)
    PNG_UNUSED(keep)
-#endif /* !PNG_READ_UNKNOWN_CHUNKS_SUPPORTED */
+#endif /* !READ_UNKNOWN_CHUNKS */
 
    /* Check for unhandled critical chunks */
-   if (!handled && PNG_CHUNK_CRITICAL(png_ptr->chunk_name))
+   if (handled == 0 && PNG_CHUNK_CRITICAL(png_ptr->chunk_name))
       png_chunk_error(png_ptr, "unhandled critical chunk");
 }
 
 /* This function is called to verify that a chunk name is valid.
  * This function can't have the "critical chunk check" incorporated
  * into it, since in the future we will need to be able to call user
  * functions to handle unknown critical chunks after we check that
  * the chunk name itself is valid.
  */
 
@@ skipping 25 matching lines @@
  * handles the two methods of progressive display of interlaced images,
  * depending on the 'display' value; if 'display' is true then the whole row
  * (dp) is filled from the start by replicating the available pixels.  If
  * 'display' is false only those pixels present in the pass are filled in.
  */
 void /* PRIVATE */
 png_combine_row(png_const_structrp png_ptr, png_bytep dp, int display)
 {
    unsigned int pixel_depth = png_ptr->transformed_pixel_depth;
    png_const_bytep sp = png_ptr->row_buf + 1;
-   png_uint_32 row_width = png_ptr->width;
+   png_alloc_size_t row_width = png_ptr->width;
    unsigned int pass = png_ptr->pass;
    png_bytep end_ptr = 0;
    png_byte end_byte = 0;
    unsigned int end_mask;
 
    png_debug(1, "in png_combine_row");
 
    /* Added in 1.5.6: it should not be possible to enter this routine until at
     * least one row has been read from the PNG data and transformed.
     */
@@ skipping 16 matching lines @@
     * the multiply below may overflow, we don't care because ANSI-C guarantees
     * we get the low bits.
     */
    end_mask = (pixel_depth * row_width) & 7;
    if (end_mask != 0)
    {
       /* end_ptr == NULL is a flag to say do nothing */
       end_ptr = dp + PNG_ROWBYTES(pixel_depth, row_width) - 1;
       end_byte = *end_ptr;
 #     ifdef PNG_READ_PACKSWAP_SUPPORTED
-         if (png_ptr->transformations & PNG_PACKSWAP) /* little-endian byte */
-            end_mask = 0xff << end_mask;
-
-         else /* big-endian byte */
+      if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
+         /* little-endian byte */
+         end_mask = 0xff << end_mask;
+
+      else /* big-endian byte */
 #     endif
-         end_mask = 0xff >> end_mask;
+      end_mask = 0xff >> end_mask;
       /* end_mask is now the bits to *keep* from the destination row */
    }
 
    /* For non-interlaced images this reduces to a memcpy(). A memcpy()
     * will also happen if interlacing isn't supported or if the application
     * does not call png_set_interlace_handling().  In the latter cases the
     * caller just gets a sequence of the unexpanded rows from each interlace
     * pass.
     */
 #ifdef PNG_READ_INTERLACING_SUPPORTED
-   if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE) &&
-      pass < 6 && (display == 0 ||
-      /* The following copies everything for 'display' on passes 0, 2 and 4. */
-      (display == 1 && (pass & 1) != 0)))
+   if (png_ptr->interlaced != 0 &&
+       (png_ptr->transformations & PNG_INTERLACE) != 0 &&
+       pass < 6 && (display == 0 ||
+       /* The following copies everything for 'display' on passes 0, 2 and 4. */
+       (display == 1 && (pass & 1) != 0)))
    {
       /* Narrow images may have no bits in a pass; the caller should handle
        * this, but this test is cheap:
        */
       if (row_width <= PNG_PASS_START_COL(pass))
          return;
 
       if (pixel_depth < 8)
       {
          /* For pixel depths up to 4 bpp the 8-pixel mask can be expanded to fit
@@ skipping 75 matching lines @@
 
 #if PNG_USE_COMPILE_TIME_MASKS
          /* Utility macros to construct all the masks for a depth/swap
           * combination.  The 's' parameter says whether the format is PNG
           * (big endian bytes) or not.  Only the three odd-numbered passes are
           * required for the display/block algorithm.
           */
 #        define S_MASKS(d,s) { S_MASK(0,d,s), S_MASK(1,d,s), S_MASK(2,d,s),\
             S_MASK(3,d,s), S_MASK(4,d,s), S_MASK(5,d,s) }
 
-#        define B_MASKS(d,s) { B_MASK(1,d,s), S_MASK(3,d,s), S_MASK(5,d,s) }
+#        define B_MASKS(d,s) { B_MASK(1,d,s), B_MASK(3,d,s), B_MASK(5,d,s) }
 
 #        define DEPTH_INDEX(d) ((d)==1?0:((d)==2?1:2))
 
          /* Hence the pre-compiled masks indexed by PACKSWAP (or not), depth and
           * then pass:
           */
          static PNG_CONST png_uint_32 row_mask[2/*PACKSWAP*/][3/*depth*/][6] =
          {
             /* Little-endian byte masks for PACKSWAP */
             { S_MASKS(1,0), S_MASKS(2,0), S_MASKS(4,0) },
@@ skipping 15 matching lines @@
 #        define MASK(pass,depth,display,png)\
             ((display)?display_mask[png][DEPTH_INDEX(depth)][pass>>1]:\
                row_mask[png][DEPTH_INDEX(depth)][pass])
 
 #else /* !PNG_USE_COMPILE_TIME_MASKS */
          /* This is the runtime alternative: it seems unlikely that this will
           * ever be either smaller or faster than the compile time approach.
           */
 #        define MASK(pass,depth,display,png)\
             ((display)?B_MASK(pass,depth,png):S_MASK(pass,depth,png))
-#endif /* !PNG_USE_COMPILE_TIME_MASKS */
+#endif /* !USE_COMPILE_TIME_MASKS */
 
          /* Use the appropriate mask to copy the required bits.  In some cases
-          * the byte mask will be 0 or 0xff, optimize these cases.  row_width is
+          * the byte mask will be 0 or 0xff; optimize these cases.  row_width is
           * the number of pixels, but the code copies bytes, so it is necessary
           * to special case the end.
           */
          png_uint_32 pixels_per_byte = 8 / pixel_depth;
          png_uint_32 mask;
 
 #        ifdef PNG_READ_PACKSWAP_SUPPORTED
-            if (png_ptr->transformations & PNG_PACKSWAP)
-               mask = MASK(pass, pixel_depth, display, 0);
-
-            else
+         if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
+            mask = MASK(pass, pixel_depth, display, 0);
+
+         else
 #        endif
-            mask = MASK(pass, pixel_depth, display, 1);
+         mask = MASK(pass, pixel_depth, display, 1);
 
          for (;;)
          {
             png_uint_32 m;
 
             /* It doesn't matter in the following if png_uint_32 has more than
              * 32 bits because the high bits always match those in m<<24; it is,
              * however, essential to use OR here, not +, because of this.
              */
             m = mask;
@@ skipping 38 matching lines @@
           */
          {
             unsigned int offset = PNG_PASS_START_COL(pass) * pixel_depth;
 
             row_width -= offset;
             dp += offset;
             sp += offset;
          }
 
          /* Work out the bytes to copy. */
-         if (display)
+         if (display != 0)
          {
             /* When doing the 'block' algorithm the pixel in the pass gets
              * replicated to adjacent pixels.  This is why the even (0,2,4,6)
              * passes are skipped above - the entire expanded row is copied.
              */
             bytes_to_copy = (1<<((6-pass)>>1)) * pixel_depth;
 
             /* But don't allow this number to exceed the actual row width. */
             if (bytes_to_copy > row_width)
-               bytes_to_copy = row_width;
+               bytes_to_copy = (unsigned int)/*SAFE*/row_width;
          }
 
          else /* normal row; Adam7 only ever gives us one pixel to copy. */
             bytes_to_copy = pixel_depth;
 
          /* In Adam7 there is a constant offset between where the pixels go. */
          bytes_to_jump = PNG_PASS_COL_OFFSET(pass) * pixel_depth;
 
          /* And simply copy these bytes.  Some optimization is possible here,
           * depending on the value of 'bytes_to_copy'.  Special case the low
@@ skipping 36 matching lines @@
                while (row_width > 1);
 
                /* And there can only be one byte left at this point: */
                *dp = *sp;
                return;
 
             case 3:
                /* This can only be the RGB case, so each copy is exactly one
                 * pixel and it is not necessary to check for a partial copy.
                 */
-               for(;;)
+               for (;;)
                {
                   dp[0] = sp[0], dp[1] = sp[1], dp[2] = sp[2];
 
                   if (row_width <= bytes_to_jump)
                      return;
 
                   sp += bytes_to_jump;
                   dp += bytes_to_jump;
                   row_width -= bytes_to_jump;
                }
 
             default:
 #if PNG_ALIGN_TYPE != PNG_ALIGN_NONE
                /* Check for double byte alignment and, if possible, use a
                 * 16-bit copy.  Don't attempt this for narrow images - ones that
                 * are less than an interlace panel wide.  Don't attempt it for
                 * wide bytes_to_copy either - use the memcpy there.
                 */
                if (bytes_to_copy < 16 /*else use memcpy*/ &&
-                  png_isaligned(dp, png_uint_16) &&
-                  png_isaligned(sp, png_uint_16) &&
-                  bytes_to_copy % (sizeof (png_uint_16)) == 0 &&
-                  bytes_to_jump % (sizeof (png_uint_16)) == 0)
+                   png_isaligned(dp, png_uint_16) &&
+                   png_isaligned(sp, png_uint_16) &&
+                   bytes_to_copy % (sizeof (png_uint_16)) == 0 &&
+                   bytes_to_jump % (sizeof (png_uint_16)) == 0)
                {
                   /* Everything is aligned for png_uint_16 copies, but try for
                    * png_uint_32 first.
                    */
-                  if (png_isaligned(dp, png_uint_32) &&
-                     png_isaligned(sp, png_uint_32) &&
-                     bytes_to_copy % (sizeof (png_uint_32)) == 0 &&
-                     bytes_to_jump % (sizeof (png_uint_32)) == 0)
+                  if (png_isaligned(dp, png_uint_32) != 0 &&
+                      png_isaligned(sp, png_uint_32) != 0 &&
+                      bytes_to_copy % (sizeof (png_uint_32)) == 0 &&
+                      bytes_to_jump % (sizeof (png_uint_32)) == 0)
                   {
                      png_uint_32p dp32 = png_aligncast(png_uint_32p,dp);
                      png_const_uint_32p sp32 = png_aligncastconst(
-                        png_const_uint_32p, sp);
+                         png_const_uint_32p, sp);
                      size_t skip = (bytes_to_jump-bytes_to_copy) /
-                        (sizeof (png_uint_32));
+                         (sizeof (png_uint_32));
 
                      do
                      {
                         size_t c = bytes_to_copy;
                         do
                         {
                            *dp32++ = *sp32++;
                            c -= (sizeof (png_uint_32));
                         }
                         while (c > 0);
@@ skipping 51 matching lines @@
 
                      /* End of row - 1 byte left, bytes_to_copy > row_width: */
                      dp = (png_bytep)dp16;
                      sp = (png_const_bytep)sp16;
                      do
                         *dp++ = *sp++;
                      while (--row_width > 0);
                      return;
                   }
                }
-#endif /* PNG_ALIGN_ code */
+#endif /* ALIGN_TYPE code */
 
                /* The true default - use a memcpy: */
                for (;;)
                {
                   memcpy(dp, sp, bytes_to_copy);
 
                   if (row_width <= bytes_to_jump)
                      return;
 
                   sp += bytes_to_jump;
                   dp += bytes_to_jump;
                   row_width -= bytes_to_jump;
                   if (bytes_to_copy > row_width)
-                     bytes_to_copy = row_width;
+                     bytes_to_copy = (unsigned int)/*SAFE*/row_width;
                }
          }
 
          /* NOT REACHED*/
       } /* pixel_depth >= 8 */
 
       /* Here if pixel_depth < 8 to check 'end_ptr' below. */
    }
    else
-#endif
+#endif /* READ_INTERLACING */
 
    /* If here then the switch above wasn't used so just memcpy the whole row
     * from the temporary row buffer (notice that this overwrites the end of the
     * destination row if it is a partial byte.)
     */
    memcpy(dp, sp, PNG_ROWBYTES(pixel_depth, row_width));
 
    /* Restore the overwritten bits from the last byte if necessary. */
    if (end_ptr != NULL)
       *end_ptr = (png_byte)((end_byte & end_mask) | (*end_ptr & ~end_mask));
@@ skipping 22 matching lines @@
             png_bytep sp = row + (png_size_t)((row_info->width - 1) >> 3);
             png_bytep dp = row + (png_size_t)((final_width - 1) >> 3);
             int sshift, dshift;
             int s_start, s_end, s_inc;
             int jstop = png_pass_inc[pass];
             png_byte v;
             png_uint_32 i;
             int j;
 
 #ifdef PNG_READ_PACKSWAP_SUPPORTED
-            if (transformations & PNG_PACKSWAP)
+            if ((transformations & PNG_PACKSWAP) != 0)
             {
                 sshift = (int)((row_info->width + 7) & 0x07);
                 dshift = (int)((final_width + 7) & 0x07);
                 s_start = 7;
                 s_end = 0;
                 s_inc = -1;
             }
 
             else
 #endif
@@ skipping 39 matching lines @@
          case 2:
          {
             png_bytep sp = row + (png_uint_32)((row_info->width - 1) >> 2);
             png_bytep dp = row + (png_uint_32)((final_width - 1) >> 2);
             int sshift, dshift;
             int s_start, s_end, s_inc;
             int jstop = png_pass_inc[pass];
             png_uint_32 i;
 
 #ifdef PNG_READ_PACKSWAP_SUPPORTED
-            if (transformations & PNG_PACKSWAP)
+            if ((transformations & PNG_PACKSWAP) != 0)
             {
                sshift = (int)(((row_info->width + 3) & 0x03) << 1);
                dshift = (int)(((final_width + 3) & 0x03) << 1);
                s_start = 6;
                s_end = 0;
                s_inc = -2;
             }
 
             else
 #endif
@@ skipping 42 matching lines @@
          case 4:
          {
             png_bytep sp = row + (png_size_t)((row_info->width - 1) >> 1);
             png_bytep dp = row + (png_size_t)((final_width - 1) >> 1);
             int sshift, dshift;
             int s_start, s_end, s_inc;
             png_uint_32 i;
             int jstop = png_pass_inc[pass];
 
 #ifdef PNG_READ_PACKSWAP_SUPPORTED
-            if (transformations & PNG_PACKSWAP)
+            if ((transformations & PNG_PACKSWAP) != 0)
             {
                sshift = (int)(((row_info->width + 1) & 0x01) << 2);
                dshift = (int)(((final_width + 1) & 0x01) << 2);
                s_start = 4;
                s_end = 0;
                s_inc = -4;
             }
 
             else
 #endif
@@ skipping 69 matching lines @@
          }
       }
 
       row_info->width = final_width;
       row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, final_width);
    }
 #ifndef PNG_READ_PACKSWAP_SUPPORTED
    PNG_UNUSED(transformations)  /* Silence compiler warning */
 #endif
 }
-#endif /* PNG_READ_INTERLACING_SUPPORTED */
+#endif /* READ_INTERLACING */
 
 static void
 png_read_filter_row_sub(png_row_infop row_info, png_bytep row,
    png_const_bytep prev_row)
 {
    png_size_t i;
    png_size_t istop = row_info->rowbytes;
    unsigned int bpp = (row_info->pixel_depth + 7) >> 3;
    png_bytep rp = row + bpp;
 
@@ skipping 65 matching lines @@
    while (row < rp_end)
    {
       int b, pa, pb, pc, p;
 
       a &= 0xff; /* From previous iteration or start */
       b = *prev_row++;
 
       p = b - c;
       pc = a - c;
 
-#     ifdef PNG_USE_ABS
-         pa = abs(p);
-         pb = abs(pc);
-         pc = abs(p + pc);
-#     else
-         pa = p < 0 ? -p : p;
-         pb = pc < 0 ? -pc : pc;
-         pc = (p + pc) < 0 ? -(p + pc) : p + pc;
-#     endif
+#ifdef PNG_USE_ABS
+      pa = abs(p);
+      pb = abs(pc);
+      pc = abs(p + pc);
+#else
+      pa = p < 0 ? -p : p;
+      pb = pc < 0 ? -pc : pc;
+      pc = (p + pc) < 0 ? -(p + pc) : p + pc;
+#endif
 
       /* Find the best predictor, the least of pa, pb, pc favoring the earlier
        * ones in the case of a tie.
        */
       if (pb < pa) pa = pb, a = b;
       if (pc < pa) a = c;
 
       /* Calculate the current pixel in a, and move the previous row pixel to c
        * for the next time round the loop
        */
@@ skipping 26 matching lines @@
    {
       int a, b, c, pa, pb, pc, p;
 
       c = *(prev_row - bpp);
       a = *(row - bpp);
       b = *prev_row++;
 
       p = b - c;
       pc = a - c;
 
-#     ifdef PNG_USE_ABS
-         pa = abs(p);
-         pb = abs(pc);
-         pc = abs(p + pc);
-#     else
-         pa = p < 0 ? -p : p;
-         pb = pc < 0 ? -pc : pc;
-         pc = (p + pc) < 0 ? -(p + pc) : p + pc;
-#     endif
+#ifdef PNG_USE_ABS
+      pa = abs(p);
+      pb = abs(pc);
+      pc = abs(p + pc);
+#else
+      pa = p < 0 ? -p : p;
+      pb = pc < 0 ? -pc : pc;
+      pc = (p + pc) < 0 ? -(p + pc) : p + pc;
+#endif
 
       if (pb < pa) pa = pb, a = b;
       if (pc < pa) a = c;
 
-      c = b;
       a += *row;
       *row++ = (png_byte)a;
    }
 }
 
 static void
 png_init_filter_functions(png_structrp pp)
-   /* This function is called once for every PNG image to set the
+   /* This function is called once for every PNG image (except for PNG images
+    * that only use PNG_FILTER_VALUE_NONE for all rows) to set the
     * implementations required to reverse the filtering of PNG rows.  Reversing
     * the filter is the first transformation performed on the row data.  It is
     * performed in place, therefore an implementation can be selected based on
     * the image pixel format.  If the implementation depends on image width then
     * take care to ensure that it works correctly if the image is interlaced -
     * interlacing causes the actual row width to vary.
     */
 {
    unsigned int bpp = (pp->pixel_depth + 7) >> 3;
 
@@ skipping 21 matching lines @@
 }
 
 void /* PRIVATE */
 png_read_filter_row(png_structrp pp, png_row_infop row_info, png_bytep row,
    png_const_bytep prev_row, int filter)
 {
    /* OPTIMIZATION: DO NOT MODIFY THIS FUNCTION, instead #define
     * PNG_FILTER_OPTIMIZATIONS to a function that overrides the generic
     * implementations.  See png_init_filter_functions above.
     */
-   if (pp->read_filter[0] == NULL)
-      png_init_filter_functions(pp);
    if (filter > PNG_FILTER_VALUE_NONE && filter < PNG_FILTER_VALUE_LAST)
+   {
+      if (pp->read_filter[0] == NULL)
+         png_init_filter_functions(pp);
+
       pp->read_filter[filter-1](row_info, row, prev_row);
+   }
 }
 
 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
 void /* PRIVATE */
 png_read_IDAT_data(png_structrp png_ptr, png_bytep output,
    png_alloc_size_t avail_out)
 {
    /* Loop reading IDATs and decompressing the result into output[avail_out] */
    png_ptr->zstream.next_out = output;
    png_ptr->zstream.avail_out = 0; /* safety: set below */
@@ skipping 60 matching lines @@
          png_ptr->zstream.avail_out = (sizeof tmpbuf);
       }
 
       /* Use NO_FLUSH; this gives zlib the maximum opportunity to optimize the
        * process.  If the LZ stream is truncated the sequential reader will
        * terminally damage the stream, above, by reading the chunk header of the
        * following chunk (it then exits with png_error).
        *
        * TODO: deal more elegantly with truncated IDAT lists.
        */
-      ret = inflate(&png_ptr->zstream, Z_NO_FLUSH);
+      ret = PNG_INFLATE(png_ptr, Z_NO_FLUSH);
 
       /* Take the unconsumed output back. */
       if (output != NULL)
          avail_out += png_ptr->zstream.avail_out;
 
       else /* avail_out counts the extra bytes */
          avail_out += (sizeof tmpbuf) - png_ptr->zstream.avail_out;
 
       png_ptr->zstream.avail_out = 0;
 
@@ skipping 39 matching lines @@
 }
 
 void /* PRIVATE */
 png_read_finish_IDAT(png_structrp png_ptr)
 {
    /* We don't need any more data and the stream should have ended, however the
     * LZ end code may actually not have been processed.  In this case we must
     * read it otherwise stray unread IDAT data or, more likely, an IDAT chunk
     * may still remain to be consumed.
     */
-   if (!(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
+   if ((png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED) == 0)
    {
       /* The NULL causes png_read_IDAT_data to swallow any remaining bytes in
        * the compressed stream, but the stream may be damaged too, so even after
        * this call we may need to terminate the zstream ownership.
        */
       png_read_IDAT_data(png_ptr, NULL, 0);
       png_ptr->zstream.next_out = NULL; /* safety */
 
       /* Now clear everything out for safety; the following may not have been
        * done.
        */
-      if (!(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
+      if ((png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED) == 0)
       {
          png_ptr->mode |= PNG_AFTER_IDAT;
          png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
       }
    }
 
    /* If the zstream has not been released do it now *and* terminate the reading
     * of the final IDAT chunk.
     */
    if (png_ptr->zowner == png_IDAT)
@@ skipping 10 matching lines @@
        * crc_finish here.  If idat_size is non-zero we also need to read the
        * spurious bytes at the end of the chunk now.
        */
       (void)png_crc_finish(png_ptr, png_ptr->idat_size);
    }
 }
 
 void /* PRIVATE */
 png_read_finish_row(png_structrp png_ptr)
 {
-#ifdef PNG_READ_INTERLACING_SUPPORTED
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
    /* Start of interlace block */
    static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
 
    /* Offset to next interlace block */
    static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
 
    /* Start of interlace block in the y direction */
    static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
 
    /* Offset to next interlace block in the y direction */
    static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
-#endif /* PNG_READ_INTERLACING_SUPPORTED */
 
    png_debug(1, "in png_read_finish_row");
    png_ptr->row_number++;
    if (png_ptr->row_number < png_ptr->num_rows)
       return;
 
-#ifdef PNG_READ_INTERLACING_SUPPORTED
-   if (png_ptr->interlaced)
+   if (png_ptr->interlaced != 0)
    {
       png_ptr->row_number = 0;
 
       /* TO DO: don't do this if prev_row isn't needed (requires
        * read-ahead of the next row's filter byte.
        */
       memset(png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
 
       do
       {
          png_ptr->pass++;
 
          if (png_ptr->pass >= 7)
             break;
 
          png_ptr->iwidth = (png_ptr->width +
             png_pass_inc[png_ptr->pass] - 1 -
             png_pass_start[png_ptr->pass]) /
             png_pass_inc[png_ptr->pass];
 
-         if (!(png_ptr->transformations & PNG_INTERLACE))
+         if ((png_ptr->transformations & PNG_INTERLACE) == 0)
          {
             png_ptr->num_rows = (png_ptr->height +
                 png_pass_yinc[png_ptr->pass] - 1 -
                 png_pass_ystart[png_ptr->pass]) /
                 png_pass_yinc[png_ptr->pass];
          }
 
          else  /* if (png_ptr->transformations & PNG_INTERLACE) */
             break; /* libpng deinterlacing sees every row */
 
       } while (png_ptr->num_rows == 0 || png_ptr->iwidth == 0);
 
       if (png_ptr->pass < 7)
          return;
    }
-#endif /* PNG_READ_INTERLACING_SUPPORTED */
 
    /* Here after at the end of the last row of the last pass. */
    png_read_finish_IDAT(png_ptr);
 }
-#endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
+#endif /* SEQUENTIAL_READ */
 
 void /* PRIVATE */
 png_read_start_row(png_structrp png_ptr)
 {
-#ifdef PNG_READ_INTERLACING_SUPPORTED
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
    /* Start of interlace block */
    static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
 
    /* Offset to next interlace block */
    static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
 
    /* Start of interlace block in the y direction */
    static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
 
    /* Offset to next interlace block in the y direction */
    static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
-#endif
 
    int max_pixel_depth;
    png_size_t row_bytes;
 
    png_debug(1, "in png_read_start_row");
 
 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
    png_init_read_transformations(png_ptr);
 #endif
-#ifdef PNG_READ_INTERLACING_SUPPORTED
-   if (png_ptr->interlaced)
-   {
-      if (!(png_ptr->transformations & PNG_INTERLACE))
+   if (png_ptr->interlaced != 0)
+   {
+      if ((png_ptr->transformations & PNG_INTERLACE) == 0)
          png_ptr->num_rows = (png_ptr->height + png_pass_yinc[0] - 1 -
              png_pass_ystart[0]) / png_pass_yinc[0];
 
       else
          png_ptr->num_rows = png_ptr->height;
 
       png_ptr->iwidth = (png_ptr->width +
           png_pass_inc[png_ptr->pass] - 1 -
           png_pass_start[png_ptr->pass]) /
           png_pass_inc[png_ptr->pass];
    }
 
    else
-#endif /* PNG_READ_INTERLACING_SUPPORTED */
    {
       png_ptr->num_rows = png_ptr->height;
       png_ptr->iwidth = png_ptr->width;
    }
 
    max_pixel_depth = png_ptr->pixel_depth;
 
-   /* WARNING: * png_read_transform_info (pngrtran.c) performs a simpliar set of
+   /* WARNING: * png_read_transform_info (pngrtran.c) performs a simpler set of
     * calculations to calculate the final pixel depth, then
     * png_do_read_transforms actually does the transforms.  This means that the
     * code which effectively calculates this value is actually repeated in three
     * separate places.  They must all match.  Innocent changes to the order of
     * transformations can and will break libpng in a way that causes memory
     * overwrites.
     *
     * TODO: fix this.
     */
 #ifdef PNG_READ_PACK_SUPPORTED
-   if ((png_ptr->transformations & PNG_PACK) && png_ptr->bit_depth < 8)
+   if ((png_ptr->transformations & PNG_PACK) != 0 && png_ptr->bit_depth < 8)
       max_pixel_depth = 8;
 #endif
 
 #ifdef PNG_READ_EXPAND_SUPPORTED
-   if (png_ptr->transformations & PNG_EXPAND)
+   if ((png_ptr->transformations & PNG_EXPAND) != 0)
    {
       if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
       {
-         if (png_ptr->num_trans)
+         if (png_ptr->num_trans != 0)
             max_pixel_depth = 32;
 
          else
             max_pixel_depth = 24;
       }
 
       else if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
       {
          if (max_pixel_depth < 8)
             max_pixel_depth = 8;
 
-         if (png_ptr->num_trans)
+         if (png_ptr->num_trans != 0)
             max_pixel_depth *= 2;
       }
 
       else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
       {
-         if (png_ptr->num_trans)
+         if (png_ptr->num_trans != 0)
          {
             max_pixel_depth *= 4;
             max_pixel_depth /= 3;
          }
       }
    }
 #endif
 
 #ifdef PNG_READ_EXPAND_16_SUPPORTED
-   if (png_ptr->transformations & PNG_EXPAND_16)
-   {
-#     ifdef PNG_READ_EXPAND_SUPPORTED
-         /* In fact it is an error if it isn't supported, but checking is
-          * the safe way.
-          */
-         if (png_ptr->transformations & PNG_EXPAND)
-         {
-            if (png_ptr->bit_depth < 16)
-               max_pixel_depth *= 2;
-         }
-         else
-#     endif
-         png_ptr->transformations &= ~PNG_EXPAND_16;
+   if ((png_ptr->transformations & PNG_EXPAND_16) != 0)
+   {
+#  ifdef PNG_READ_EXPAND_SUPPORTED
+      /* In fact it is an error if it isn't supported, but checking is
+       * the safe way.
+       */
+      if ((png_ptr->transformations & PNG_EXPAND) != 0)
+      {
+         if (png_ptr->bit_depth < 16)
+            max_pixel_depth *= 2;
+      }
+      else
+#  endif
+      png_ptr->transformations &= ~PNG_EXPAND_16;
    }
 #endif
 
 #ifdef PNG_READ_FILLER_SUPPORTED
-   if (png_ptr->transformations & (PNG_FILLER))
+   if ((png_ptr->transformations & (PNG_FILLER)) != 0)
    {
       if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
       {
          if (max_pixel_depth <= 8)
             max_pixel_depth = 16;
 
          else
             max_pixel_depth = 32;
       }
 
       else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB ||
          png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
       {
          if (max_pixel_depth <= 32)
             max_pixel_depth = 32;
 
          else
             max_pixel_depth = 64;
       }
    }
 #endif
 
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
-   if (png_ptr->transformations & PNG_GRAY_TO_RGB)
+   if ((png_ptr->transformations & PNG_GRAY_TO_RGB) != 0)
    {
       if (
 #ifdef PNG_READ_EXPAND_SUPPORTED
-          (png_ptr->num_trans && (png_ptr->transformations & PNG_EXPAND)) ||
+          (png_ptr->num_trans != 0 &&
+          (png_ptr->transformations & PNG_EXPAND) != 0) ||
 #endif
 #ifdef PNG_READ_FILLER_SUPPORTED
-          (png_ptr->transformations & (PNG_FILLER)) ||
+          (png_ptr->transformations & (PNG_FILLER)) != 0 ||
 #endif
           png_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
       {
          if (max_pixel_depth <= 16)
             max_pixel_depth = 32;
 
          else
             max_pixel_depth = 64;
       }
 
@@ skipping 12 matching lines @@
             max_pixel_depth = 64;
 
          else
             max_pixel_depth = 48;
       }
    }
 #endif
 
 #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) && \
 defined(PNG_USER_TRANSFORM_PTR_SUPPORTED)
-   if (png_ptr->transformations & PNG_USER_TRANSFORM)
+   if ((png_ptr->transformations & PNG_USER_TRANSFORM) != 0)
    {
       int user_pixel_depth = png_ptr->user_transform_depth *
          png_ptr->user_transform_channels;
 
       if (user_pixel_depth > max_pixel_depth)
          max_pixel_depth = user_pixel_depth;
    }
 #endif
 
    /* This value is stored in png_struct and double checked in the row read
@@ skipping 15 matching lines @@
 #ifdef PNG_MAX_MALLOC_64K
    if (row_bytes > (png_uint_32)65536L)
       png_error(png_ptr, "This image requires a row greater than 64KB");
 #endif
 
    if (row_bytes + 48 > png_ptr->old_big_row_buf_size)
    {
      png_free(png_ptr, png_ptr->big_row_buf);
      png_free(png_ptr, png_ptr->big_prev_row);
 
-     if (png_ptr->interlaced)
+     if (png_ptr->interlaced != 0)
         png_ptr->big_row_buf = (png_bytep)png_calloc(png_ptr,
             row_bytes + 48);
 
      else
         png_ptr->big_row_buf = (png_bytep)png_malloc(png_ptr, row_bytes + 48);
 
      png_ptr->big_prev_row = (png_bytep)png_malloc(png_ptr, row_bytes + 48);
 
 #ifdef PNG_ALIGNED_MEMORY_SUPPORTED
      /* Use 16-byte aligned memory for row_buf with at least 16 bytes
@@ skipping 36 matching lines @@
    png_debug1(3, "iwidth = %u,", png_ptr->iwidth);
    png_debug1(3, "num_rows = %u,", png_ptr->num_rows);
    png_debug1(3, "rowbytes = %lu,", (unsigned long)png_ptr->rowbytes);
    png_debug1(3, "irowbytes = %lu",
        (unsigned long)PNG_ROWBYTES(png_ptr->pixel_depth, png_ptr->iwidth) + 1);
 
    /* The sequential reader needs a buffer for IDAT, but the progressive reader
     * does not, so free the read buffer now regardless; the sequential reader
     * reallocates it on demand.
     */
-   if (png_ptr->read_buffer)
+   if (png_ptr->read_buffer != 0)
    {
       png_bytep buffer = png_ptr->read_buffer;
 
       png_ptr->read_buffer_size = 0;
       png_ptr->read_buffer = NULL;
       png_free(png_ptr, buffer);
    }
 
    /* Finally claim the zstream for the inflate of the IDAT data, use the bits
     * value from the stream (note that this will result in a fatal error if the
     * IDAT stream has a bogus deflate header window_bits value, but this should
     * not be happening any longer!)
     */
    if (png_inflate_claim(png_ptr, png_IDAT) != Z_OK)
       png_error(png_ptr, png_ptr->zstream.msg);
 
    png_ptr->flags |= PNG_FLAG_ROW_INIT;
 }
-#endif /* PNG_READ_SUPPORTED */
+#endif /* READ */