Check libpng directly into third_party/

third_party/libpng/contrib/libtests/pngunknown.c

+
+/* pngunknown.c - test the read side unknown chunk handling
+ *
+ * Last changed in libpng 1.6.22 [(PENDING RELEASE)]
+ * Copyright (c) 2015,2016 Glenn Randers-Pehrson
+ * Written by John Cunningham Bowler
+ *
+ * This code is released under the libpng license.
+ * For conditions of distribution and use, see the disclaimer
+ * and license in png.h
+ *
+ * NOTES:
+ *   This is a C program that is intended to be linked against libpng.  It
+ *   allows the libpng unknown handling code to be tested by interpreting
+ *   arguments to save or discard combinations of chunks.  The program is
+ *   currently just a minimal validation for the built-in libpng facilities.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <setjmp.h>
+
+/* Define the following to use this test against your installed libpng, rather
+ * than the one being built here:
+ */
+#ifdef PNG_FREESTANDING_TESTS
+#  include <png.h>
+#else
+#  include "../../png.h"
+#endif
+
+/* 1.6.1 added support for the configure test harness, which uses 77 to indicate
+ * a skipped test, in earlier versions we need to succeed on a skipped test, so:
+ */
+#if PNG_LIBPNG_VER >= 10601 && defined(HAVE_CONFIG_H)
+#  define SKIP 77
+#else
+#  define SKIP 0
+#endif
+
+
+/* Since this program tests the ability to change the unknown chunk handling
+ * these must be defined:
+ */
+#if defined(PNG_SET_UNKNOWN_CHUNKS_SUPPORTED) &&\
+   defined(PNG_STDIO_SUPPORTED) &&\
+   defined(PNG_READ_SUPPORTED)
+
+/* One of these must be defined to allow us to find out what happened.  It is
+ * still useful to set unknown chunk handling without either of these in order
+ * to cause *known* chunks to be discarded.  This can be a significant
+ * efficiency gain, but it can't really be tested here.
+ */
+#if defined(PNG_READ_USER_CHUNKS_SUPPORTED) ||\
+   defined(PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED)
+
+#if PNG_LIBPNG_VER < 10500
+/* This deliberately lacks the PNG_CONST. */
+typedef png_byte *png_const_bytep;
+
+/* This is copied from 1.5.1 png.h: */
+#define PNG_INTERLACE_ADAM7_PASSES 7
+#define PNG_PASS_START_ROW(pass) (((1U&~(pass))<<(3-((pass)>>1)))&7)
+#define PNG_PASS_START_COL(pass) (((1U& (pass))<<(3-(((pass)+1)>>1)))&7)
+#define PNG_PASS_ROW_SHIFT(pass) ((pass)>2?(8-(pass))>>1:3)
+#define PNG_PASS_COL_SHIFT(pass) ((pass)>1?(7-(pass))>>1:3)
+#define PNG_PASS_ROWS(height, pass) (((height)+(((1<<PNG_PASS_ROW_SHIFT(pass))\
+   -1)-PNG_PASS_START_ROW(pass)))>>PNG_PASS_ROW_SHIFT(pass))
+#define PNG_PASS_COLS(width, pass) (((width)+(((1<<PNG_PASS_COL_SHIFT(pass))\
+   -1)-PNG_PASS_START_COL(pass)))>>PNG_PASS_COL_SHIFT(pass))
+#define PNG_ROW_FROM_PASS_ROW(yIn, pass) \
+   (((yIn)<<PNG_PASS_ROW_SHIFT(pass))+PNG_PASS_START_ROW(pass))
+#define PNG_COL_FROM_PASS_COL(xIn, pass) \
+   (((xIn)<<PNG_PASS_COL_SHIFT(pass))+PNG_PASS_START_COL(pass))
+#define PNG_PASS_MASK(pass,off) ( \
+   ((0x110145AFU>>(((7-(off))-(pass))<<2)) & 0xFU) | \
+   ((0x01145AF0U>>(((7-(off))-(pass))<<2)) & 0xF0U))
+#define PNG_ROW_IN_INTERLACE_PASS(y, pass) \
+   ((PNG_PASS_MASK(pass,0) >> ((y)&7)) & 1)
+#define PNG_COL_IN_INTERLACE_PASS(x, pass) \
+   ((PNG_PASS_MASK(pass,1) >> ((x)&7)) & 1)
+
+/* These are needed too for the default build: */
+#define PNG_WRITE_16BIT_SUPPORTED
+#define PNG_READ_16BIT_SUPPORTED
+
+/* This comes from pnglibconf.h afer 1.5: */
+#define PNG_FP_1 100000
+#define PNG_GAMMA_THRESHOLD_FIXED\
+   ((png_fixed_point)(PNG_GAMMA_THRESHOLD * PNG_FP_1))
+#endif
+
+#if PNG_LIBPNG_VER < 10600
+   /* 1.6.0 constifies many APIs. The following exists to allow pngvalid to be
+    * compiled against earlier versions.
+    */
+#  define png_const_structp png_structp
+#endif
+
+#if PNG_LIBPNG_VER < 10700
+   /* Copied from libpng 1.7.0 png.h */
+#define PNG_u2(b1, b2) (((unsigned int)(b1) << 8) + (b2))
+
+#define PNG_U16(b1, b2) ((png_uint_16)PNG_u2(b1, b2))
+#define PNG_U32(b1, b2, b3, b4)\
+   (((png_uint_32)PNG_u2(b1, b2) << 16) + PNG_u2(b3, b4))
+
+/* Constants for known chunk types.
+ */
+#define png_IDAT PNG_U32( 73,  68,  65,  84)
+#define png_IEND PNG_U32( 73,  69,  78,  68)
+#define png_IHDR PNG_U32( 73,  72,  68,  82)
+#define png_PLTE PNG_U32( 80,  76,  84,  69)
+#define png_bKGD PNG_U32( 98,  75,  71,  68)
+#define png_cHRM PNG_U32( 99,  72,  82,  77)
+#define png_fRAc PNG_U32(102,  82,  65,  99) /* registered, not defined */
+#define png_gAMA PNG_U32(103,  65,  77,  65)
+#define png_gIFg PNG_U32(103,  73,  70, 103)
+#define png_gIFt PNG_U32(103,  73,  70, 116) /* deprecated */
+#define png_gIFx PNG_U32(103,  73,  70, 120)
+#define png_hIST PNG_U32(104,  73,  83,  84)
+#define png_iCCP PNG_U32(105,  67,  67,  80)
+#define png_iTXt PNG_U32(105,  84,  88, 116)
+#define png_oFFs PNG_U32(111,  70,  70, 115)
+#define png_pCAL PNG_U32(112,  67,  65,  76)
+#define png_pHYs PNG_U32(112,  72,  89, 115)
+#define png_sBIT PNG_U32(115,  66,  73,  84)
+#define png_sCAL PNG_U32(115,  67,  65,  76)
+#define png_sPLT PNG_U32(115,  80,  76,  84)
+#define png_sRGB PNG_U32(115,  82,  71,  66)
+#define png_sTER PNG_U32(115,  84,  69,  82)
+#define png_tEXt PNG_U32(116,  69,  88, 116)
+#define png_tIME PNG_U32(116,  73,  77,  69)
+#define png_tRNS PNG_U32(116,  82,  78,  83)
+#define png_zTXt PNG_U32(122,  84,  88, 116)
+
+/* Test on flag values as defined in the spec (section 5.4): */
+#define PNG_CHUNK_ANCILLARY(c)    (1 & ((c) >> 29))
+#define PNG_CHUNK_CRITICAL(c)     (!PNG_CHUNK_ANCILLARY(c))
+#define PNG_CHUNK_PRIVATE(c)      (1 & ((c) >> 21))
+#define PNG_CHUNK_RESERVED(c)     (1 & ((c) >> 13))
+#define PNG_CHUNK_SAFE_TO_COPY(c) (1 & ((c) >>  5))
+
+#endif /* PNG_LIBPNG_VER < 10700 */
+
+#ifdef __cplusplus
+#  define this not_the_cpp_this
+#  define new not_the_cpp_new
+#  define voidcast(type, value) static_cast<type>(value)
+#else
+#  define voidcast(type, value) (value)
+#endif /* __cplusplus */
+
+/* Unused formal parameter errors are removed using the following macro which is
+ * expected to have no bad effects on performance.
+ */
+#ifndef UNUSED
+#  if defined(__GNUC__) || defined(_MSC_VER)
+#     define UNUSED(param) (void)param;
+#  else
+#     define UNUSED(param)
+#  endif
+#endif
+
+/* Types of chunks not known to libpng */
+#define png_vpAg PNG_U32(118, 112, 65, 103)
+
+/* Chunk information */
+#define PNG_INFO_tEXt 0x10000000U
+#define PNG_INFO_iTXt 0x20000000U
+#define PNG_INFO_zTXt 0x40000000U
+
+#define PNG_INFO_sTER 0x01000000U
+#define PNG_INFO_vpAg 0x02000000U
+
+#define ABSENT  0
+#define START   1
+#define END     2
+
+static struct
+{
+   char        name[5];
+   png_uint_32 flag;
+   png_uint_32 tag;
+   int         unknown;    /* Chunk not known to libpng */
+   int         all;        /* Chunk set by the '-1' option */
+   int         position;   /* position in pngtest.png */
+   int         keep;       /* unknown handling setting */
+} chunk_info[] = {
+   /* Critical chunks */
+   { "IDAT", PNG_INFO_IDAT, png_IDAT, 0, 0,  START, 0 }, /* must be [0] */
+   { "PLTE", PNG_INFO_PLTE, png_PLTE, 0, 0, ABSENT, 0 },
+
+   /* Non-critical chunks that libpng handles */
+   /* This is a mess but it seems to be the only way to do it - there is no way
+    * to check for a definition outside a #if.
+    */
+   { "bKGD", PNG_INFO_bKGD, png_bKGD,
+#     ifdef PNG_READ_bKGD_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1,  START, 0 },
+   { "cHRM", PNG_INFO_cHRM, png_cHRM,
+#     ifdef PNG_READ_cHRM_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1,  START, 0 },
+   { "gAMA", PNG_INFO_gAMA, png_gAMA,
+#     ifdef PNG_READ_gAMA_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1,  START, 0 },
+   { "hIST", PNG_INFO_hIST, png_hIST,
+#     ifdef PNG_READ_hIST_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1, ABSENT, 0 },
+   { "iCCP", PNG_INFO_iCCP, png_iCCP,
+#     ifdef PNG_READ_iCCP_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1, ABSENT, 0 },
+   { "iTXt", PNG_INFO_iTXt, png_iTXt,
+#     ifdef PNG_READ_iTXt_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1, ABSENT, 0 },
+   { "oFFs", PNG_INFO_oFFs, png_oFFs,
+#     ifdef PNG_READ_oFFs_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1,  START, 0 },
+   { "pCAL", PNG_INFO_pCAL, png_pCAL,
+#     ifdef PNG_READ_pCAL_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1,  START, 0 },
+   { "pHYs", PNG_INFO_pHYs, png_pHYs,
+#     ifdef PNG_READ_pHYs_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1,  START, 0 },
+   { "sBIT", PNG_INFO_sBIT, png_sBIT,
+#     ifdef PNG_READ_sBIT_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1,  START, 0 },
+   { "sCAL", PNG_INFO_sCAL, png_sCAL,
+#     ifdef PNG_READ_sCAL_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1,  START, 0 },
+   { "sPLT", PNG_INFO_sPLT, png_sPLT,
+#     ifdef PNG_READ_sPLT_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1, ABSENT, 0 },
+   { "sRGB", PNG_INFO_sRGB, png_sRGB,
+#     ifdef PNG_READ_sRGB_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1,  START, 0 },
+   { "tEXt", PNG_INFO_tEXt, png_tEXt,
+#     ifdef PNG_READ_tEXt_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1,  START, 0 },
+   { "tIME", PNG_INFO_tIME, png_tIME,
+#     ifdef PNG_READ_tIME_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1,  START, 0 },
+   { "tRNS", PNG_INFO_tRNS, png_tRNS,
+#     ifdef PNG_READ_tRNS_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      0, ABSENT, 0 },
+   { "zTXt", PNG_INFO_zTXt, png_zTXt,
+#     ifdef PNG_READ_zTXt_SUPPORTED
+         0,
+#     else
+         1,
+#     endif
+      1,    END, 0 },
+
+   /* No libpng handling */
+   { "sTER", PNG_INFO_sTER, png_sTER, 1, 1,  START, 0 },
+   { "vpAg", PNG_INFO_vpAg, png_vpAg, 1, 0,  START, 0 },
+};
+
+#define NINFO ((int)((sizeof chunk_info)/(sizeof chunk_info[0])))
+
+static void
+clear_keep(void)
+{
+   int i = NINFO;
+   while (--i >= 0)
+      chunk_info[i].keep = 0;
+}
+
+static int
+find(const char *name)
+{
+   int i = NINFO;
+   while (--i >= 0)
+   {
+      if (memcmp(chunk_info[i].name, name, 4) == 0)
+         break;
+   }
+
+   return i;
+}
+
+static int
+findb(const png_byte *name)
+{
+   int i = NINFO;
+   while (--i >= 0)
+   {
+      if (memcmp(chunk_info[i].name, name, 4) == 0)
+         break;
+   }
+
+   return i;
+}
+
+static int
+find_by_flag(png_uint_32 flag)
+{
+   int i = NINFO;
+
+   while (--i >= 0) if (chunk_info[i].flag == flag) return i;
+
+   fprintf(stderr, "pngunknown: internal error\n");
+   exit(4);
+}
+
+static int
+ancillary(const char *name)
+{
+   return PNG_CHUNK_ANCILLARY(PNG_U32(name[0], name[1], name[2], name[3]));
+}
+
+#ifdef PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
+static int
+ancillaryb(const png_byte *name)
+{
+   return PNG_CHUNK_ANCILLARY(PNG_U32(name[0], name[1], name[2], name[3]));
+}
+#endif
+
+/* Type of an error_ptr */
+typedef struct
+{
+   jmp_buf     error_return;
+   png_structp png_ptr;
+   png_infop   info_ptr, end_ptr;
+   png_uint_32 before_IDAT;
+   png_uint_32 after_IDAT;
+   int         error_count;
+   int         warning_count;
+   int         keep; /* the default value */
+   const char *program;
+   const char *file;
+   const char *test;
+} display;
+
+static const char init[] = "initialization";
+static const char cmd[] = "command line";
+
+static void
+init_display(display *d, const char *program)
+{
+   memset(d, 0, sizeof *d);
+   d->png_ptr = NULL;
+   d->info_ptr = d->end_ptr = NULL;
+   d->error_count = d->warning_count = 0;
+   d->program = program;
+   d->file = program;
+   d->test = init;
+}
+
+static void
+clean_display(display *d)
+{
+   png_destroy_read_struct(&d->png_ptr, &d->info_ptr, &d->end_ptr);
+
+   /* This must not happen - it might cause an app crash */
+   if (d->png_ptr != NULL || d->info_ptr != NULL || d->end_ptr != NULL)
+   {
+      fprintf(stderr, "%s(%s): png_destroy_read_struct error\n", d->file,
+         d->test);
+      exit(1);
+   }
+}
+
+PNG_FUNCTION(void, display_exit, (display *d), static PNG_NORETURN)
+{
+   ++(d->error_count);
+
+   if (d->png_ptr != NULL)
+      clean_display(d);
+
+   /* During initialization and if this is a single command line argument set
+    * exit now - there is only one test, otherwise longjmp to do the next test.
+    */
+   if (d->test == init || d->test == cmd)
+      exit(1);
+
+   longjmp(d->error_return, 1);
+}
+
+static int
+display_rc(const display *d, int strict)
+{
+   return d->error_count + (strict ? d->warning_count : 0);
+}
+
+/* libpng error and warning callbacks */
+PNG_FUNCTION(void, (PNGCBAPI error), (png_structp png_ptr, const char *message),
+   static PNG_NORETURN)
+{
+   display *d = (display*)png_get_error_ptr(png_ptr);
+
+   fprintf(stderr, "%s(%s): libpng error: %s\n", d->file, d->test, message);
+   display_exit(d);
+}
+
+static void PNGCBAPI
+warning(png_structp png_ptr, const char *message)
+{
+   display *d = (display*)png_get_error_ptr(png_ptr);
+
+   fprintf(stderr, "%s(%s): libpng warning: %s\n", d->file, d->test, message);
+   ++(d->warning_count);
+}
+
+static png_uint_32
+get_valid(display *d, png_infop info_ptr)
+{
+   png_uint_32 flags = png_get_valid(d->png_ptr, info_ptr, (png_uint_32)~0);
+
+   /* Map the text chunks back into the flags */
+   {
+      png_textp text;
+      png_uint_32 ntext = png_get_text(d->png_ptr, info_ptr, &text, NULL);
+
+      while (ntext-- > 0) switch (text[ntext].compression)
+      {
+         case -1:
+            flags |= PNG_INFO_tEXt;
+            break;
+         case 0:
+            flags |= PNG_INFO_zTXt;
+            break;
+         case 1:
+         case 2:
+            flags |= PNG_INFO_iTXt;
+            break;
+         default:
+            fprintf(stderr, "%s(%s): unknown text compression %d\n", d->file,
+               d->test, text[ntext].compression);
+            display_exit(d);
+      }
+   }
+
+   return flags;
+}
+
+#ifdef PNG_READ_USER_CHUNKS_SUPPORTED
+static int PNGCBAPI
+read_callback(png_structp pp, png_unknown_chunkp pc)
+{
+   /* This function mimics the behavior of png_set_keep_unknown_chunks by
+    * returning '0' to keep the chunk and '1' to discard it.
+    */
+   display *d = voidcast(display*, png_get_user_chunk_ptr(pp));
+   int chunk = findb(pc->name);
+   int keep, discard;
+
+   if (chunk < 0) /* not one in our list, so not a known chunk */
+      keep = d->keep;
+
+   else
+   {
+      keep = chunk_info[chunk].keep;
+      if (keep == PNG_HANDLE_CHUNK_AS_DEFAULT)
+      {
+         /* See the comments in png.h - use the default for unknown chunks,
+          * do not keep known chunks.
+          */
+         if (chunk_info[chunk].unknown)
+            keep = d->keep;
+
+         else
+            keep = PNG_HANDLE_CHUNK_NEVER;
+      }
+   }
+
+   switch (keep)
+   {
+      default:
+         fprintf(stderr, "%s(%s): %d: unrecognized chunk option\n", d->file,
+            d->test, chunk_info[chunk].keep);
+         display_exit(d);
+
+      case PNG_HANDLE_CHUNK_AS_DEFAULT:
+      case PNG_HANDLE_CHUNK_NEVER:
+         discard = 1/*handled; discard*/;
+         break;
+
+      case PNG_HANDLE_CHUNK_IF_SAFE:
+      case PNG_HANDLE_CHUNK_ALWAYS:
+         discard = 0/*not handled; keep*/;
+         break;
+   }
+
+   /* Also store information about this chunk in the display, the relevant flag
+    * is set if the chunk is to be kept ('not handled'.)
+    */
+   if (chunk >= 0) if (!discard) /* stupidity to stop a GCC warning */
+   {
+      png_uint_32 flag = chunk_info[chunk].flag;
+
+      if (pc->location & PNG_AFTER_IDAT)
+         d->after_IDAT |= flag;
+
+      else
+         d->before_IDAT |= flag;
+   }
+
+   /* However if there is no support to store unknown chunks don't ask libpng to
+    * do it; there will be an png_error.
+    */
+#  ifdef PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
+      return discard;
+#  else
+      return 1; /*handled; discard*/
+#  endif
+}
+#endif /* READ_USER_CHUNKS_SUPPORTED */
+
+#ifdef PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
+static png_uint_32
+get_unknown(display *d, png_infop info_ptr, int after_IDAT)
+{
+   /* Create corresponding 'unknown' flags */
+   png_uint_32 flags = 0;
+
+   UNUSED(after_IDAT)
+
+   {
+      png_unknown_chunkp unknown;
+      int num_unknown = png_get_unknown_chunks(d->png_ptr, info_ptr, &unknown);
+
+      while (--num_unknown >= 0)
+      {
+         int chunk = findb(unknown[num_unknown].name);
+
+         /* Chunks not known to pngunknown must be validated here; since they
+          * must also be unknown to libpng the 'display->keep' behavior should
+          * have been used.
+          */
+         if (chunk < 0) switch (d->keep)
+         {
+            default: /* impossible */
+            case PNG_HANDLE_CHUNK_AS_DEFAULT:
+            case PNG_HANDLE_CHUNK_NEVER:
+               fprintf(stderr, "%s(%s): %s: %s: unknown chunk saved\n",
+                  d->file, d->test, d->keep ? "discard" : "default",
+                  unknown[num_unknown].name);
+               ++(d->error_count);
+               break;
+
+            case PNG_HANDLE_CHUNK_IF_SAFE:
+               if (!ancillaryb(unknown[num_unknown].name))
+               {
+                  fprintf(stderr,
+                     "%s(%s): if-safe: %s: unknown critical chunk saved\n",
+                     d->file, d->test, unknown[num_unknown].name);
+                  ++(d->error_count);
+                  break;
+               }
+               /* FALL THROUGH (safe) */
+            case PNG_HANDLE_CHUNK_ALWAYS:
+               break;
+         }
+
+         else
+            flags |= chunk_info[chunk].flag;
+      }
+   }
+
+   return flags;
+}
+#else /* SAVE_UNKNOWN_CHUNKS */
+static png_uint_32
+get_unknown(display *d, png_infop info_ptr, int after_IDAT)
+   /* Otherwise this will return the cached values set by any user callback */
+{
+   UNUSED(info_ptr);
+
+   if (after_IDAT)
+      return d->after_IDAT;
+
+   else
+      return d->before_IDAT;
+}
+
+#  ifndef PNG_READ_USER_CHUNKS_SUPPORTED
+      /* The #defines above should mean this is never reached, it's just here as
+       * a check to ensure the logic is correct.
+       */
+#     error No store support and no user chunk support, this will not work
+#  endif /* READ_USER_CHUNKS */
+#endif /* SAVE_UNKNOWN_CHUNKS */
+
+static int
+check(FILE *fp, int argc, const char **argv, png_uint_32p flags/*out*/,
+   display *d, int set_callback)
+{
+   int i, npasses, ipass;
+   png_uint_32 height;
+
+   d->keep = PNG_HANDLE_CHUNK_AS_DEFAULT;
+   d->before_IDAT = 0;
+   d->after_IDAT = 0;
+
+   /* Some of these errors are permanently fatal and cause an exit here, others
+    * are per-test and cause an error return.
+    */
+   d->png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, d, error,
+      warning);
+   if (d->png_ptr == NULL)
+   {
+      fprintf(stderr, "%s(%s): could not allocate png struct\n", d->file,
+         d->test);
+      /* Terminate here, this error is not test specific. */
+      exit(1);
+   }
+
+   d->info_ptr = png_create_info_struct(d->png_ptr);
+   d->end_ptr = png_create_info_struct(d->png_ptr);
+   if (d->info_ptr == NULL || d->end_ptr == NULL)
+   {
+      fprintf(stderr, "%s(%s): could not allocate png info\n", d->file,
+         d->test);
+      clean_display(d);
+      exit(1);
+   }
+
+   png_init_io(d->png_ptr, fp);
+
+#  ifdef PNG_READ_USER_CHUNKS_SUPPORTED
+      /* This is only done if requested by the caller; it interferes with the
+       * standard store/save mechanism.
+       */
+      if (set_callback)
+         png_set_read_user_chunk_fn(d->png_ptr, d, read_callback);
+#  else
+      UNUSED(set_callback)
+#  endif
+
+   /* Handle each argument in turn; multiple settings are possible for the same
+    * chunk and multiple calls will occur (the last one should override all
+    * preceding ones).
+    */
+   for (i=0; i<argc; ++i)
+   {
+      const char *equals = strchr(argv[i], '=');
+
+      if (equals != NULL)
+      {
+         int chunk, option;
+
+         if (strcmp(equals+1, "default") == 0)
+            option = PNG_HANDLE_CHUNK_AS_DEFAULT;
+         else if (strcmp(equals+1, "discard") == 0)
+            option = PNG_HANDLE_CHUNK_NEVER;
+         else if (strcmp(equals+1, "if-safe") == 0)
+            option = PNG_HANDLE_CHUNK_IF_SAFE;
+         else if (strcmp(equals+1, "save") == 0)
+            option = PNG_HANDLE_CHUNK_ALWAYS;
+         else
+         {
+            fprintf(stderr, "%s(%s): %s: unrecognized chunk option\n", d->file,
+               d->test, argv[i]);
+            display_exit(d);
+         }
+
+         switch (equals - argv[i])
+         {
+            case 4: /* chunk name */
+               chunk = find(argv[i]);
+
+               if (chunk >= 0)
+               {
+                  /* These #if tests have the effect of skipping the arguments
+                   * if SAVE support is unavailable - we can't do a useful test
+                   * in this case, so we just check the arguments!  This could
+                   * be improved in the future by using the read callback.
+                   */
+#                 if PNG_LIBPNG_VER >= 10700 &&\
+                     !defined(PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED)
+                     if (option < PNG_HANDLE_CHUNK_IF_SAFE)
+#                 endif /* 1.7+ SAVE_UNKNOWN_CHUNKS */
+                  {
+                     png_byte name[5];
+
+                     memcpy(name, chunk_info[chunk].name, 5);
+                     png_set_keep_unknown_chunks(d->png_ptr, option, name, 1);
+                     chunk_info[chunk].keep = option;
+                  }
+                  continue;
+               }
+
+               break;
+
+            case 7: /* default */
+               if (memcmp(argv[i], "default", 7) == 0)
+               {
+#                 if PNG_LIBPNG_VER >= 10700 &&\
+                     !defined(PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED)
+                     if (option < PNG_HANDLE_CHUNK_IF_SAFE)
+#                 endif /* 1.7+ SAVE_UNKNOWN_CHUNKS */
+                     png_set_keep_unknown_chunks(d->png_ptr, option, NULL, 0);
+
+                  d->keep = option;
+                  continue;
+               }
+
+               break;
+
+            case 3: /* all */
+               if (memcmp(argv[i], "all", 3) == 0)
+               {
+#                 if PNG_LIBPNG_VER >= 10700 &&\
+                     !defined(PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED)
+                     if (option < PNG_HANDLE_CHUNK_IF_SAFE)
+#                 endif /* 1.7+ SAVE_UNKNOWN_CHUNKS */
+                     png_set_keep_unknown_chunks(d->png_ptr, option, NULL, -1);
+
+                  d->keep = option;
+
+                  for (chunk = 0; chunk < NINFO; ++chunk)
+                     if (chunk_info[chunk].all)
+                        chunk_info[chunk].keep = option;
+                  continue;
+               }
+
+               break;
+
+            default: /* some misplaced = */
+
+               break;
+         }
+      }
+
+      fprintf(stderr, "%s(%s): %s: unrecognized chunk argument\n", d->file,
+         d->test, argv[i]);
+      display_exit(d);
+   }
+
+   png_read_info(d->png_ptr, d->info_ptr);
+
+   switch (png_get_interlace_type(d->png_ptr, d->info_ptr))
+   {
+      case PNG_INTERLACE_NONE:
+         npasses = 1;
+         break;
+
+      case PNG_INTERLACE_ADAM7:
+         npasses = PNG_INTERLACE_ADAM7_PASSES;
+         break;
+
+      default:
+         /* Hard error because it is not test specific */
+         fprintf(stderr, "%s(%s): invalid interlace type\n", d->file, d->test);
+         clean_display(d);
+         exit(1);
+   }
+
+   /* Skip the image data, if IDAT is not being handled then don't do this
+    * because it will cause a CRC error.
+    */
+   if (chunk_info[0/*IDAT*/].keep == PNG_HANDLE_CHUNK_AS_DEFAULT)
+   {
+      png_start_read_image(d->png_ptr);
+      height = png_get_image_height(d->png_ptr, d->info_ptr);
+
+      if (npasses > 1)
+      {
+         png_uint_32 width = png_get_image_width(d->png_ptr, d->info_ptr);
+
+         for (ipass=0; ipass<npasses; ++ipass)
+         {
+            png_uint_32 wPass = PNG_PASS_COLS(width, ipass);
+
+            if (wPass > 0)
+            {
+               png_uint_32 y;
+
+               for (y=0; y<height; ++y) if (PNG_ROW_IN_INTERLACE_PASS(y, ipass))
+                  png_read_row(d->png_ptr, NULL, NULL);
+            }
+         }
+      } /* interlaced */
+
+      else /* not interlaced */
+      {
+         png_uint_32 y;
+
+         for (y=0; y<height; ++y)
+            png_read_row(d->png_ptr, NULL, NULL);
+      }
+   }
+
+   png_read_end(d->png_ptr, d->end_ptr);
+
+   flags[0] = get_valid(d, d->info_ptr);
+   flags[1] = get_unknown(d, d->info_ptr, 0/*before IDAT*/);
+
+   /* Only png_read_png sets PNG_INFO_IDAT! */
+   flags[chunk_info[0/*IDAT*/].keep != PNG_HANDLE_CHUNK_AS_DEFAULT] |=
+      PNG_INFO_IDAT;
+
+   flags[2] = get_valid(d, d->end_ptr);
+   flags[3] = get_unknown(d, d->end_ptr, 1/*after IDAT*/);
+
+   clean_display(d);
+
+   return d->keep;
+}
+
+static void
+check_error(display *d, png_uint_32 flags, const char *message)
+{
+   while (flags)
+   {
+      png_uint_32 flag = flags & -(png_int_32)flags;
+      int i = find_by_flag(flag);
+
+      fprintf(stderr, "%s(%s): chunk %s: %s\n", d->file, d->test,
+         chunk_info[i].name, message);
+      ++(d->error_count);
+
+      flags &= ~flag;
+   }
+}
+
+static void
+check_handling(display *d, int def, png_uint_32 chunks, png_uint_32 known,
+   png_uint_32 unknown, const char *position, int set_callback)
+{
+   while (chunks)
+   {
+      png_uint_32 flag = chunks & -(png_int_32)chunks;
+      int i = find_by_flag(flag);
+      int keep = chunk_info[i].keep;
+      const char *type;
+      const char *errorx = NULL;
+
+      if (chunk_info[i].unknown)
+      {
+         if (keep == PNG_HANDLE_CHUNK_AS_DEFAULT)
+         {
+            type = "UNKNOWN (default)";
+            keep = def;
+         }
+
+         else
+            type = "UNKNOWN (specified)";
+
+         if (flag & known)
+            errorx = "chunk processed";
+
+         else switch (keep)
+         {
+            case PNG_HANDLE_CHUNK_AS_DEFAULT:
+               if (flag & unknown)
+                  errorx = "DEFAULT: unknown chunk saved";
+               break;
+
+            case PNG_HANDLE_CHUNK_NEVER:
+               if (flag & unknown)
+                  errorx = "DISCARD: unknown chunk saved";
+               break;
+
+            case PNG_HANDLE_CHUNK_IF_SAFE:
+               if (ancillary(chunk_info[i].name))
+               {
+                  if (!(flag & unknown))
+                     errorx = "IF-SAFE: unknown ancillary chunk lost";
+               }
+
+               else if (flag & unknown)
+                  errorx = "IF-SAFE: unknown critical chunk saved";
+               break;
+
+            case PNG_HANDLE_CHUNK_ALWAYS:
+               if (!(flag & unknown))
+                  errorx = "SAVE: unknown chunk lost";
+               break;
+
+            default:
+               errorx = "internal error: bad keep";
+               break;
+         }
+      } /* unknown chunk */
+
+      else /* known chunk */
+      {
+         type = "KNOWN";
+
+         if (flag & known)
+         {
+            /* chunk was processed, it won't have been saved because that is
+             * caught below when checking for inconsistent processing.
+             */
+            if (keep != PNG_HANDLE_CHUNK_AS_DEFAULT)
+               errorx = "!DEFAULT: known chunk processed";
+         }
+
+         else /* not processed */ switch (keep)
+         {
+            case PNG_HANDLE_CHUNK_AS_DEFAULT:
+               errorx = "DEFAULT: known chunk not processed";
+               break;
+
+            case PNG_HANDLE_CHUNK_NEVER:
+               if (flag & unknown)
+                  errorx = "DISCARD: known chunk saved";
+               break;
+
+            case PNG_HANDLE_CHUNK_IF_SAFE:
+               if (ancillary(chunk_info[i].name))
+               {
+                  if (!(flag & unknown))
+                     errorx = "IF-SAFE: known ancillary chunk lost";
+               }
+
+               else if (flag & unknown)
+                  errorx = "IF-SAFE: known critical chunk saved";
+               break;
+
+            case PNG_HANDLE_CHUNK_ALWAYS:
+               if (!(flag & unknown))
+                  errorx = "SAVE: known chunk lost";
+               break;
+
+            default:
+               errorx = "internal error: bad keep (2)";
+               break;
+         }
+      }
+
+      if (errorx != NULL)
+      {
+         ++(d->error_count);
+         fprintf(stderr, "%s(%s%s): %s %s %s: %s\n", d->file, d->test,
+            set_callback ? ",callback" : "",
+            type, chunk_info[i].name, position, errorx);
+      }
+
+      chunks &= ~flag;
+   }
+}
+
+static void
+perform_one_test(FILE *fp, int argc, const char **argv,
+   png_uint_32 *default_flags, display *d, int set_callback)
+{
+   int def;
+   png_uint_32 flags[2][4];
+
+   rewind(fp);
+   clear_keep();
+   memcpy(flags[0], default_flags, sizeof flags[0]);
+
+   def = check(fp, argc, argv, flags[1], d, set_callback);
+
+   /* If IDAT is being handled as unknown the image read is skipped and all the
+    * IDATs after the first end up in the end info struct, so in this case add
+    * IDAT to the list of unknowns.  (Do this after 'check' above sets the
+    * chunk_info 'keep' fields.)
+    *
+    * Note that the flag setting has to be in the 'known' field to avoid
+    * triggering the consistency check below and the flag must only be set if
+    * there are multiple IDATs, so if the check above did find an unknown IDAT
+    * after IDAT.
+    */
+   if (chunk_info[0/*IDAT*/].keep != PNG_HANDLE_CHUNK_AS_DEFAULT &&
+       (flags[1][3] & PNG_INFO_IDAT) != 0)
+      flags[0][2] |= PNG_INFO_IDAT;
+
+   /* Chunks should either be known or unknown, never both and this should apply
+    * whether the chunk is before or after the IDAT (actually, the app can
+    * probably change this by swapping the handling after the image, but this
+    * test does not do that.)
+    */
+   check_error(d, (flags[0][0]|flags[0][2]) & (flags[0][1]|flags[0][3]),
+      "chunk handled inconsistently in count tests");
+   check_error(d, (flags[1][0]|flags[1][2]) & (flags[1][1]|flags[1][3]),
+      "chunk handled inconsistently in option tests");
+
+   /* Now find out what happened to each chunk before and after the IDAT and
+    * determine if the behavior was correct.  First some basic sanity checks,
+    * any known chunk should be known in the original count, any unknown chunk
+    * should be either known or unknown in the original.
+    */
+   {
+      png_uint_32 test;
+
+      test = flags[1][0] & ~flags[0][0];
+      check_error(d, test, "new known chunk before IDAT");
+      test = flags[1][1] & ~(flags[0][0] | flags[0][1]);
+      check_error(d, test, "new unknown chunk before IDAT");
+      test = flags[1][2] & ~flags[0][2];
+      check_error(d, test, "new known chunk after IDAT");
+      test = flags[1][3] & ~(flags[0][2] | flags[0][3]);
+      check_error(d, test, "new unknown chunk after IDAT");
+   }
+
+   /* Now each chunk in the original list should have been handled according to
+    * the options set for that chunk, regardless of whether libpng knows about
+    * it or not.
+    */
+   check_handling(d, def, flags[0][0] | flags[0][1], flags[1][0], flags[1][1],
+      "before IDAT", set_callback);
+   check_handling(d, def, flags[0][2] | flags[0][3], flags[1][2], flags[1][3],
+      "after IDAT", set_callback);
+}
+
+static void
+perform_one_test_safe(FILE *fp, int argc, const char **argv,
+   png_uint_32 *default_flags, display *d, const char *test)
+{
+   if (setjmp(d->error_return) == 0)
+   {
+      d->test = test; /* allow use of d->error_return */
+#     ifdef PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
+         perform_one_test(fp, argc, argv, default_flags, d, 0);
+#     endif
+#     ifdef PNG_READ_USER_CHUNKS_SUPPORTED
+         perform_one_test(fp, argc, argv, default_flags, d, 1);
+#     endif
+      d->test = init; /* prevent use of d->error_return */
+   }
+}
+
+static const char *standard_tests[] =
+{
+ "discard", "default=discard", 0,
+ "save", "default=save", 0,
+ "if-safe", "default=if-safe", 0,
+ "vpAg", "vpAg=if-safe", 0,
+ "sTER", "sTER=if-safe", 0,
+ "IDAT", "default=discard", "IDAT=save", 0,
+ "sAPI", "bKGD=save", "cHRM=save", "gAMA=save", "all=discard", "iCCP=save",
+   "sBIT=save", "sRGB=save", 0,
+ 0/*end*/
+};
+
+static PNG_NORETURN void
+usage(const char *program, const char *reason)
+{
+   fprintf(stderr, "pngunknown: %s: usage:\n %s [--strict] "
+      "--default|{(CHNK|default|all)=(default|discard|if-safe|save)} "
+      "testfile.png\n", reason, program);
+   exit(99);
+}
+
+int
+main(int argc, const char **argv)
+{
+   FILE *fp;
+   png_uint_32 default_flags[4/*valid,unknown{before,after}*/];
+   int strict = 0, default_tests = 0;
+   const char *count_argv = "default=save";
+   const char *touch_file = NULL;
+   display d;
+
+   init_display(&d, argv[0]);
+
+   while (++argv, --argc > 0)
+   {
+      if (strcmp(*argv, "--strict") == 0)
+         strict = 1;
+
+      else if (strcmp(*argv, "--default") == 0)
+         default_tests = 1;
+
+      else if (strcmp(*argv, "--touch") == 0)
+      {
+         if (argc > 1)
+            touch_file = *++argv, --argc;
+
+         else
+            usage(d.program, "--touch: missing file name");
+      }
+
+      else
+         break;
+   }
+
+   /* A file name is required, but there should be no other arguments if
+    * --default was specified.
+    */
+   if (argc <= 0)
+      usage(d.program, "missing test file");
+
+   /* GCC BUG: if (default_tests && argc != 1) triggers some weird GCC argc
+    * optimization which causes warnings with -Wstrict-overflow!
+    */
+   else if (default_tests) if (argc != 1)
+      usage(d.program, "extra arguments");
+
+   /* The name of the test file is the last argument; remove it. */
+   d.file = argv[--argc];
+
+   fp = fopen(d.file, "rb");
+   if (fp == NULL)
+   {
+      perror(d.file);
+      exit(99);
+   }
+
+   /* First find all the chunks, known and unknown, in the test file, a failure
+    * here aborts the whole test.
+    *
+    * If 'save' is supported then the normal saving method should happen,
+    * otherwise if 'read' is supported then the read callback will do the
+    * same thing.  If both are supported the 'read' callback won't be
+    * instantiated by default.  If 'save' is *not* supported then a user
+    * callback is required even though we can call png_get_unknown_chunks.
+    */
+   if (check(fp, 1, &count_argv, default_flags, &d,
+#     ifdef PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
+         0
+#     else
+         1
+#     endif
+      ) != PNG_HANDLE_CHUNK_ALWAYS)
+   {
+      fprintf(stderr, "%s: %s: internal error\n", d.program, d.file);
+      exit(99);
+   }
+
+   /* Now find what the various supplied options cause to change: */
+   if (!default_tests)
+   {
+      d.test = cmd; /* acts as a flag to say exit, do not longjmp */
+#     ifdef PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
+         perform_one_test(fp, argc, argv, default_flags, &d, 0);
+#     endif
+#     ifdef PNG_READ_USER_CHUNKS_SUPPORTED
+         perform_one_test(fp, argc, argv, default_flags, &d, 1);
+#     endif
+      d.test = init;
+   }
+
+   else
+   {
+      const char **test = standard_tests;
+
+      /* Set the exit_test pointer here so we can continue after a libpng error.
+       * NOTE: this leaks memory because the png_struct data from the failing
+       * test is never freed.
+       */
+      while (*test)
+      {
+         const char *this_test = *test++;
+         const char **next = test;
+         int count = display_rc(&d, strict), new_count;
+         const char *result;
+         int arg_count = 0;
+
+         while (*next) ++next, ++arg_count;
+
+         perform_one_test_safe(fp, arg_count, test, default_flags, &d,
+            this_test);
+
+         new_count = display_rc(&d, strict);
+
+         if (new_count == count)
+            result = "PASS";
+
+         else
+            result = "FAIL";
+
+         printf("%s: %s %s\n", result, d.program, this_test);
+
+         test = next+1;
+      }
+   }
+
+   fclose(fp);
+
+   if (display_rc(&d, strict) == 0)
+   {
+      /* Success, touch the success file if appropriate */
+      if (touch_file != NULL)
+      {
+         FILE *fsuccess = fopen(touch_file, "wt");
+
+         if (fsuccess != NULL)
+         {
+            int err = 0;
+            fprintf(fsuccess, "PNG unknown tests succeeded\n");
+            fflush(fsuccess);
+            err = ferror(fsuccess);
+
+            if (fclose(fsuccess) || err)
+            {
+               fprintf(stderr, "%s: write failed\n", touch_file);
+               exit(99);
+            }
+         }
+
+         else
+         {
+            fprintf(stderr, "%s: open failed\n", touch_file);
+            exit(99);
+         }
+      }
+
+      return 0;
+   }
+
+   return 1;
+}
+
+#else /* !(READ_USER_CHUNKS || SAVE_UNKNOWN_CHUNKS) */
+int
+main(void)
+{
+   fprintf(stderr,
+      " test ignored: no support to find out about unknown chunks\n");
+   /* So the test is skipped: */
+   return SKIP;
+}
+#endif /* READ_USER_CHUNKS || SAVE_UNKNOWN_CHUNKS */
+
+#else /* !(SET_UNKNOWN_CHUNKS && READ) */
+int
+main(void)
+{
+   fprintf(stderr,
+      " test ignored: no support to modify unknown chunk handling\n");
+   /* So the test is skipped: */
+   return SKIP;
+}
+#endif /* SET_UNKNOWN_CHUNKS && READ*/