Check libpng directly into third_party/

third_party/libpng/scripts/options.awk

Index: third_party/libpng/scripts/options.awk
diff --git a/third_party/libpng/scripts/options.awk b/third_party/libpng/scripts/options.awk
new file mode 100755
index 0000000000000000000000000000000000000000..81b82ff09c5594c28b6112b59780d27800c822c1
--- /dev/null
+++ b/third_party/libpng/scripts/options.awk
@@ -0,0 +1,898 @@
+#!/bin/awk -f
+# scripts/options.awk - library build configuration control
+#
+# last changed in libpng version 1.6.11 - June 5, 2014
+#
+# Copyright (c) 1998-2014 Glenn Randers-Pehrson
+#
+# This code is released under the libpng license.
+# For conditions of distribution and use, see the disclaimer
+# and license in png.h
+
+# The output of this script is written to the file given by
+# the variable 'out'.  The script is run twice, once with
+# an intermediate output file, 'options.tmp' then again on
+# that file to produce the final output:
+#
+#  awk -f scripts/options.awk out=options.tmp scripts/options.dfa 1>&2
+#  awk -f scripts/options.awk out=options.dfn options.tmp 1>&2
+#
+# Some options may be specified on the command line:
+#
+#  deb=1            Causes debugging to be output
+#  logunsupported=1 Causes all options to be recorded in the output
+#  everything=off   Causes all options to be disabled by default
+#  everything=on    Causes all options to be enabled by default
+#
+# If awk fails on your platform, try nawk instead.
+#
+# These options may also be specified in the original input file (and
+# are copied to the preprocessed file).
+
+BEGIN{
+   out=""                       # intermediate, preprocessed, file
+   pre=-1                       # preprocess (first line)
+   version="libpng version unknown" # version information
+   version_file=""              # where to find the version
+   err=0                        # in-line exit sets this
+   # The following definitions prevent the C preprocessor noticing the lines
+   # that will be in the final output file.  Some C preprocessors tokenise
+   # the lines, for example by inserting spaces around operators, and all
+   # C preprocessors notice lines that start with '#', most remove comments.
+   # The technique adopted here is to make the final output lines into
+   # C strings (enclosed in double quotes), preceeded by PNG_DFN.  As a
+   # consequence the output cannot contain a 'raw' double quote - instead put
+   # @' in, this will be replaced by a single " afterward.  See the parser
+   # script dfn.awk for more capabilities (not required here).  Note that if
+   # you need a " in a 'setting' in pnglibconf.dfa it must also be @'!
+   dq="@'"                      # For a single double quote
+   start=" PNG_DFN \""          # Start stuff to output (can't contain a "!)
+   end="\" "                    # End stuff to output
+   subs="@\" "                  # Substitute start (substitute a C macro)
+   sube=" \"@"                  # Substitute end
+   comment=start "/*"           # Comment start
+   cend="*/" end                # Comment end
+   def=start "#define PNG_"     # Arbitrary define
+   sup="_SUPPORTED" end         # end supported option
+   und=comment "#undef PNG_"    # Unsupported option
+   une="_SUPPORTED" cend        # end unsupported option
+   error=start "ERROR:"         # error message, terminate with 'end'
+
+   # Variables
+   deb=0                        # debug - set on command line
+   everything=""                # do not override defaults
+   logunsupported=0             # write unsupported options too
+
+   # Precreate arrays
+   # for each option:
+   option[""] = ""    # list of all options: default enabled/disabled
+   done[""] = 1       # marks option as having been output
+   requires[""] = ""  # requires by option
+   iffs[""] = ""      # if by option
+   enabledby[""] = "" # options that enable it by option
+   sets[""] = ""      # settings set by each option
+   setval[""] = ""    # value to set (indexed: 'option sets[option]')
+   # for each setting:
+   setting[""] = ""   # requires by setting
+   defaults[""] = ""  # used for a defaulted value
+   doneset[""] = 1    # marks setting as having been output
+   r[""] = ""         # Temporary array
+
+   # For decorating the output file
+   protect = ""
+}
+
+# The output file must be specified before any input:
+out == "" {
+   print "out=output.file must be given on the command line"
+   err = 1
+   exit 1
+}
+
+# The very first line indicates whether we are reading pre-processed
+# input or not, this must come *first* because 'PREPROCESSED' needs
+# to be the very first line in the temporary file.
+pre == -1{
+   if ($0 == "PREPROCESSED") {
+      pre = 0
+      next
+   } else {
+      pre = 1
+      print "PREPROCESSED" >out
+      # And fall through to continue processing
+   }
+}
+
+# While pre-processing if version is set to "search" look for a version string
+# in the following file.
+pre && version == "search" && version_file == ""{
+   version_file = FILENAME
+}
+
+pre && version == "search" && version_file != FILENAME{
+   print "version string not found in", version_file
+   err = 1
+   exit 1
+}
+
+pre && version == "search" && $0 ~ /^ \* libpng version/{
+   version = substr($0, 4)
+   print "version =", version >out
+   next
+}
+
+pre && FILENAME == version_file{
+   next
+}
+
+# variable=value
+#   Sets the given variable to the given value (the syntax is fairly
+#   free form, except for deb (you are expected to understand how to
+#   set the debug variable...)
+#
+#   This happens before the check on 'pre' below skips most of the
+#   rest of the actions, so the variable settings happen during
+#   preprocessing but are recorded in the END action too.  This
+#   allows them to be set on the command line too.
+$0 ~ /^[ 	]*version[ 	]*=/{
+   sub(/^[  ]*version[  ]*=[  ]*/, "")
+   version = $0
+   next
+}
+$0 ~ /^[ 	]*everything[ 	=]*off[ 	]*$/{
+   everything = "off"
+   next
+}
+$0 ~ /^[ 	]*everything[ 	=]*on[ 	]*$/{
+   everything = "on"
+   next
+}
+$0 ~ /^[ 	]*logunsupported[ 	=]*0[ 	]*$/{
+   logunsupported = 0
+   next
+}
+$0 ~ /^[ 	]*logunsupported[ 	=]*1[ 	]*$/{
+   logunsupported = 1
+   next
+}
+$1 == "deb" && $2 == "=" && NF == 3{
+   deb = $3
+   next
+}
+
+# Preprocessing - this just copies the input file with lines
+# that need preprocessing (just chunk at present) expanded
+# The bare "pre" instead of "pre != 0" crashes under Sunos awk
+pre && $1 != "chunk"{
+   print >out
+   next
+}
+
+# The first characters of the line determine how it is processed,
+# leading spaces are ignored.  In general tokens that are not
+# keywords are the names of options.  An option 'name' is
+# controlled by the definition of the corresponding macros:
+#
+#   PNG_name_SUPPORTED    The option is turned on
+#   PNG_NO_name
+#   PNG_NO_name_SUPPORTED If the first macro is not defined
+#                         either of these will turn the option off
+#
+# If none of these macros are defined the option is turned on, unless
+# the keyword 'off' is given in a line relating to the option.  The
+# keyword 'on' can also be given, but it will be ignored (since it is
+# the default.)
+#
+# In the syntax below a 'name' is indicated by "NAME", other macro
+# values are indicated by "MACRO", as with "NAME" the leading "PNG_"
+# is omitted, but in this case the "NO_" prefix and the "_SUPPORTED"
+# suffix are never used.
+#
+# Each line is introduced by a keyword - the first non-space characters
+# on the line.  A line starting with a '#' is a comment - it is totally
+# ignored.  Keywords are as follows, a NAME, is simply a macro name
+# without the leading PNG_, PNG_NO_ or the trailing _SUPPORTED.
+
+$1 ~ /^#/ || $0 ~ /^[ 	]*$/{
+   next
+}
+
+# com <comment>
+#   The whole line is placed in the output file as a comment with
+#   the preceding 'com' removed
+$1 == "com"{
+   if (NF > 1) {
+      # sub(/^[ 	]*com[ 	]*/, "")
+      $1 = ""
+      print comment $0, cend >out
+   } else
+      print start end >out
+   next
+}
+
+# version
+#   Inserts a version comment
+$1 == "version" && NF == 1{
+   if (version == "") {
+      print "ERROR: no version string set"
+      err = 1 # prevent END{} running
+      exit 1
+   }
+
+   print comment, version, cend >out
+   next
+}
+
+# file output input protect
+#   Informational: the official name of the input file (without
+#   make generated local directories), the official name of the
+#   output file and, if required, a name to use in a protection
+#   macro for the contents.
+$1 == "file" && NF >= 2{
+   print comment, $2, cend >out
+   print comment, "Machine generated file: DO NOT EDIT", cend >out
+   if (NF >= 3)
+      print comment, "Derived from:", $3, cend >out
+   protect = $4
+   if (protect != "") {
+      print start "#ifndef", protect end >out
+      print start "#define", protect end >out
+   }
+   next
+}
+
+# option NAME ( (requires|enables|if) NAME* | on | off | disabled |
+#                sets SETTING VALUE+ )*
+#     
+#   Declares an option 'NAME' and describes its default setting (disabled)
+#   and its relationship to other options.  The option is disabled
+#   unless *all* the options listed after 'requires' are set and at
+#   least one of the options listed after 'if' is set.  If the
+#   option is set then it turns on all the options listed after 'enables'.
+#
+#   Note that "enables" takes priority over the required/if/disabled/off
+#   setting of the target option.
+#
+#   The definition file may list an option as 'disabled': off by default,
+#   otherwise the option is enabled: on by default.  A later (and it must
+#   be later) entry may turn an option on or off explicitly.
+
+$1 == "option" && NF >= 2{
+   opt = $2
+   sub(/,$/,"",opt)
+   onoff = option[opt]  # records current (and the default is "", enabled)
+   key = ""
+   istart = 3
+   do {
+      if (istart == 1) {     # continuation line
+         val = getline
+
+         if (val != 1) { # error reading it
+            if (val == 0)
+               print "option", opt ": ERROR: missing continuation line"
+            else
+               print "option", opt ": ERROR: error reading continuation line"
+
+            # This is a hard error
+            err = 1 # prevent END{} running
+            exit 1
+         }
+      }
+
+      for (i=istart; i<=NF; ++i) {
+         val=$(i)
+         sub(/,$/,"",val)
+         if (val == "on" || val == "off" || val == "disabled" || val =="enabled") {
+            key = ""
+            if (onoff != val) {
+               # on or off can zap disabled or enabled:
+               if (onoff == "" || (onoff == "disabled" || onoff == "enabled") &&
+                   (val == "on" || val == "off")) {
+                  # It's easy to mis-spell the option when turning it
+                  # on or off, so warn about it here:
+                  if (onoff == "" && (val == "on" || val == "off")) {
+                     print "option", opt ": ERROR: turning unrecognized option", val
+                     # For the moment error out - it is safer
+                     err = 1 # prevent END{} running
+                     exit 1
+                  }
+                  onoff = val
+               } else {
+                  # Print a message, otherwise the error
+                  # below is incomprehensible
+                  print "option", opt ": currently", onoff ": attempt to turn", val
+                  break
+               }
+            }
+         } else if (val == "requires" || val == "if" || val == "enables" || val =="sets") {
+            key = val
+         } else if (key == "requires") {
+            requires[opt] = requires[opt] " " val
+         } else if (key == "if") {
+            iffs[opt] = iffs[opt] " " val
+         } else if (key == "enables") {
+            enabledby[val] = enabledby[val] " " opt
+         } else if (key == "sets") {
+            sets[opt] = sets[opt] " " val
+            key = "setval"
+            set = val
+         } else if (key == "setval") {
+            setval[opt " " set] = setval[opt " " set] " " val
+         } else
+            break # bad line format
+      }
+
+      istart = 1
+   } while (i > NF && $0 ~ /,$/)
+
+   if (i > NF) {
+      # Set the option, defaulting to 'enabled'
+      if (onoff == "") onoff = "enabled"
+      option[opt] = onoff
+      next
+   }
+   # Else fall through to the error handler
+}
+
+# chunk NAME [requires OPT] [enables LIST] [on|off|disabled]
+#   Expands to the 'option' settings appropriate to the reading and
+#   writing of an ancilliary PNG chunk 'NAME':
+#
+#   option READ_NAME requires READ_ANCILLARY_CHUNKS [READ_OPT]
+#   option READ_NAME enables NAME LIST
+#   [option READ_NAME off]
+#   option WRITE_NAME requires WRITE_ANCILLARY_CHUNKS [WRITE_OPT]
+#   option WRITE_NAME enables NAME LIST
+#   [option WRITE_NAME off]
+
+pre != 0 && $1 == "chunk" && NF >= 2{
+   # 'chunk' is handled on the first pass by writing appropriate
+   # 'option' lines into the intermediate file.
+   opt = $2
+   sub(/,$/,"",opt)
+   onoff = ""
+   reqread = ""
+   reqwrite = ""
+   enables = ""
+   req = 0
+   istart = 3
+   do {
+      if (istart == 1) {     # continuation line
+         val = getline
+
+         if (val != 1) { # error reading it
+            if (val == 0)
+               print "chunk", opt ": ERROR: missing continuation line"
+            else
+               print "chunk", opt ": ERROR: error reading continuation line"
+
+            # This is a hard error
+            err = 1 # prevent END{} running
+            exit 1
+         }
+      }
+
+      # read the keywords/additional OPTS
+      for (i=istart; i<=NF; ++i) {
+         val = $(i)
+         sub(/,$/,"",val)
+         if (val == "on" || val == "off" || val == "disabled") {
+            if (onoff != val) {
+               if (onoff == "")
+                  onoff = val
+               else
+                  break # on/off conflict
+            }
+            req = 0
+         } else if (val == "requires")
+            req = 1
+         else if (val == "enables")
+            req = 2
+         else if (req == 1){
+            reqread = reqread " READ_" val
+            reqwrite = reqwrite " WRITE_" val
+         } else if (req == 2)
+            enables = enables " " val
+         else
+            break # bad line: handled below
+      }
+
+      istart = 1
+   } while (i > NF && $0 ~ /,$/)
+
+   if (i > NF) {
+      # Output new 'option' lines to the intermediate file (out)
+      print "option READ_" opt, "requires READ_ANCILLARY_CHUNKS" reqread, "enables", opt enables , onoff >out
+      print "option WRITE_" opt, "requires WRITE_ANCILLARY_CHUNKS" reqwrite, "enables", opt enables, onoff >out
+      next
+   }
+   # Else hit the error handler below - bad line format!
+}
+
+# setting MACRO ( requires MACRO* )* [ default VALUE ]
+#   Behaves in a similar way to 'option' without looking for NO_ or
+#   _SUPPORTED; the macro is enabled if it is defined so long as all
+#   the 'requires' macros are also defined.  The definitions may be
+#   empty, an error will be issued if the 'requires' macros are
+#   *not* defined.  If given the 'default' value is used if the
+#   macro is not defined.  The default value will be re-tokenised.
+#   (BTW: this is somewhat restrictive, it mainly exists for the
+#   support of non-standard configurations and numeric parameters,
+#   see the uses in scripts/options.dat
+
+$1 == "setting" && (NF == 2 || NF >= 3 && ($3 == "requires" || $3 == "default")){
+   reqs = ""
+   deflt = ""
+   isdef = 0
+   key = ""
+   for (i=3; i<=NF; ++i)
+      if ($(i) == "requires" || $(i) == "default") {
+         key = $(i)
+         if (key == "default") isdef = 1
+      } else if (key == "requires")
+         reqs = reqs " " $(i)
+      else if (key == "default")
+         deflt = deflt " " $(i)
+      else
+         break # Format error, handled below
+
+   setting[$2] = reqs
+   # NOTE: this overwrites a previous value silently
+   if (isdef && deflt == "")
+      deflt = " " # as a flag to force output
+   defaults[$2] = deflt
+   next
+}
+
+# The order of the dependency lines (option, chunk, setting) is irrelevant
+# - the 'enables', 'requires' and 'if' settings will be used to determine
+# the correct order in the output and the final values in pnglibconf.h are
+# not order dependent.  'requires' and 'if' entries take precedence over
+# 'enables' from other options; if an option requires another option it
+# won't be set regardless of any options that enable it unless the other
+# option is also enabled.
+#
+# Similarly 'enables' trumps a NO_ definition in CFLAGS or pngusr.h
+#
+# For simplicity cycles in the definitions are regarded as errors,
+# even if they are not ambiguous.
+# A given NAME can be specified in as many 'option' lines as required, the
+# definitions are additive.
+
+# For backwards compatibility equivalent macros may be listed thus:
+#
+# = [NO_]NAME MACRO
+#   Makes -DMACRO equivalent to -DPNG_NO_NAME or -DPNG_NAME_SUPPORTED
+#   as appropriate.
+#
+# The definition is injected into the C compiler input when encountered
+# in the second pass (so all these definitions appear *after* the @
+# lines!)
+#
+# 'NAME' is as above, but 'MACRO' is the full text of the equivalent
+# old, deprecated, macro.
+
+$1 == "=" && NF == 3{
+   print "#ifdef PNG_" $3 >out
+   if ($2 ~ /^NO_/)
+      print "#   define PNG_" $2 >out
+   else
+      print "#   define PNG_" $2 "_SUPPORTED" >out
+   print "#endif" >out
+   next
+}
+
+# Lines may be injected into the C compiler input by preceding them
+# with an "@" character.  The line is copied with just the leading
+# @ removed.
+
+$1 ~ /^@/{
+   # sub(/^[ 	]*@/, "")
+   $1 = substr($1, 2)
+   print >out
+   next
+}
+
+# Check for unrecognized lines, because of the preprocessing chunk
+# format errors will be detected on the first pass independent of
+# any other format errors.
+{
+   print "options.awk: bad line (" NR "):", $0
+   err = 1 # prevent END{} running
+   exit 1
+}
+
+# For checking purposes names that start with "ok_" or "fail_" are
+# not output to pnglibconf.h and must be either enabled or disabled
+# respectively for the build to succeed.  This allows interdependencies
+# between options of the form "at least one of" or "at most one of"
+# to be checked.  For example:
+#
+# option FLOATING_POINT enables ok_math
+# option FIXED_POINT enables ok_math
+#   This ensures that at least one of FLOATING_POINT and FIXED_POINT
+#   must be set for the build to succeed.
+#
+# option fail_math requires FLOATING_POINT FIXED_POINT
+#   This means the build will fail if *both* FLOATING_POINT and
+#   FIXED_POINT are set (this is an example; in fact both are allowed.)
+#
+# If all these options were given the build would require exactly one
+# of the names to be enabled.
+
+END{
+   # END{} gets run on an exit (a traditional awk feature)
+   if (err) exit 1
+
+   if (pre) {
+      # Record the final value of the variables
+      print "deb =", deb >out
+      if (everything != "") {
+         print "everything =", everything >out
+      }
+      print "logunsupported =", logunsupported >out
+      exit 0
+   }
+
+   # Do the options first (allowing options to set settings).  The dependency
+   # tree is thus:
+   #
+   #   name     >     name
+   #   name requires  name
+   #   name if        name
+   #   name enabledby name
+   #
+   # First build a list 'tree' by option of all the things on which
+   # it depends.
+   print "" >out
+   print "/* OPTIONS */" >out
+   print comment, "options", cend >out
+   for (opt in enabledby) tree[opt] = 1  # may not be explicit options
+   for (opt in option) if (opt != "") {
+      o = option[opt]
+      # option should always be one of the following values
+      if (o != "on" && o != "off" && o != "disabled" && o != "enabled") {
+         print "internal option error (" o ")"
+         exit 1
+      }
+      tree[opt] = ""   # so unlisted options marked
+   }
+   for (opt in tree) if (opt != "") {
+      if (tree[opt] == 1) {
+         tree[opt] = ""
+         if (option[opt] != "") {
+            print "internal error (1)"
+            exit 1
+         }
+         # Macros only listed in 'enables' remain off unless
+         # one of the enabling macros is on.
+         option[opt] = "disabled"
+      }
+
+      split("", list) # clear 'list'
+      # Now add every requires, iffs or enabledby entry to 'list'
+      # so that we can add a unique list of requirements to tree[i]
+      split(requires[opt] iffs[opt] enabledby[opt], r)
+      for (i in r) list[r[i]] = 1
+      for (i in list) tree[opt] = tree[opt] " " i
+   }
+
+   # print the tree for extreme debugging
+   if (deb > 2) for (i in tree) if (i != "") print i, "depends-on" tree[i]
+
+   # Ok, now check all options marked explicitly 'on' or 'off':
+   #
+   # If an option[opt] is 'on' then turn on all requires[opt]
+   # If an option[opt] is 'off' then turn off all enabledby[opt]
+   #
+   # Error out if we have to turn 'on' to an 'off' option or vice versa.
+   npending = 0
+   for (opt in option) if (opt != "") {
+      if (option[opt] == "on" || option[opt] == "off") {
+         pending[++npending] = opt
+      }
+   }
+
+   err = 0 # set on error
+   while (npending > 0) {
+      opt = pending[npending--]
+      if (option[opt] == "on") {
+         nreqs = split(requires[opt], r)
+         for (j=1; j<=nreqs; ++j) {
+            if (option[r[j]] == "off") {
+               print "option", opt, "turned on, but requirement", r[j], "is turned off"
+               err = 1
+            } else if (option[r[j]] != "on") {
+               option[r[j]] = "on"
+               pending[++npending] = r[j]
+            }
+         }
+      } else {
+         if (option[opt] != "off") {
+            print "internal error (2)"
+            exit 1
+         }
+         nreqs = split(enabledby[opt], r)
+         for (j=1; j<=nreqs; ++j) {
+            if (option[r[j]] == "on") {
+               print "option", opt, "turned off, but enabled by", r[j], "which is turned on"
+               err = 1
+            } else if (option[r[j]] != "off") {
+               option[r[j]] = "off"
+               pending[++npending] = r[j]
+            }
+         }
+      }
+   }
+   if (err) exit 1
+
+   # Sort options:
+   print "PNG_DFN_START_SORT 2" >out
+
+   # option[i] is now the complete list of all the tokens we may
+   # need to output, go through it as above, depth first.
+   finished = 0
+   while (!finished) {
+      finished = 1
+      movement = 0 # done nothing
+      for (i in option) if (!done[i]) {
+         nreqs = split(tree[i], r)
+         if (nreqs > 0) {
+            for (j=1; j<=nreqs; ++j) if (!done[r[j]]) {
+               break
+            }
+            if (j<=nreqs) {
+               finished = 0
+               continue  # next option
+            }
+         }
+
+         # All the requirements have been processed, output
+         # this option.  An option is _SUPPORTED if:
+         #
+         # all 'requires' are _SUPPORTED AND
+         # at least one of the 'if' options are _SUPPORTED AND
+         # EITHER:
+         #   The name is _SUPPORTED (on the command line)
+         # OR:
+         #   an 'enabledby' is _SUPPORTED
+         # OR:
+         #   NO_name is not defined AND
+         #   the option is not disabled; an option is disabled if:
+         #    option == off
+         #    option == disabled && everything != on
+         #    option == "" && everything == off
+         if (deb) print "option", i
+         print "" >out
+         print "/* option:", i, option[i] >out
+         print " *   requires:  " requires[i] >out
+         print " *   if:        " iffs[i] >out
+         print " *   enabled-by:" enabledby[i] >out
+         print " *   sets:      " sets[i], "*/" >out
+         print "#undef PNG_on" >out
+         print "#define PNG_on 1" >out
+
+         # requires
+         nreqs = split(requires[i], r)
+         for (j=1; j<=nreqs; ++j) {
+            print "#ifndef PNG_" r[j] "_SUPPORTED" >out
+            print "#   undef PNG_on /*!" r[j] "*/" >out
+            # This error appears in the final output if something
+            # was switched 'on' but the processing above to force
+            # the requires did not work
+            if (option[i] == "on") {
+               print error, i, "requires", r[j] end >out
+            }
+            print "#endif" >out
+         }
+
+         # if
+         have_ifs = 0
+         nreqs = split(iffs[i], r)
+         print "#undef PNG_no_if" >out
+         if (nreqs > 0) {
+            have_ifs = 1
+            print "/* if" iffs[i], "*/" >out
+            print "#define PNG_no_if 1" >out
+            for (j=1; j<=nreqs; ++j) {
+               print "#ifdef PNG_" r[j] "_SUPPORTED" >out
+               print "#   undef PNG_no_if /*" r[j] "*/" >out
+               print "#endif" >out
+            }
+            print "#ifdef PNG_no_if /*missing if*/" >out
+            print "#   undef PNG_on" >out
+            # There is no checking above for this, because we
+            # don't know which 'if' to choose, so whine about
+            # it here:
+            if (option[i] == "on") {
+               print error, i, "needs one of:", iffs[i] end >out
+            }
+            print "#endif" >out
+         }
+
+         print "#ifdef PNG_on /*requires, if*/" >out
+         # enables
+         print "#   undef PNG_not_enabled" >out
+         print "#   define PNG_not_enabled 1" >out
+         print "   /* enabled by" enabledby[i], "*/" >out
+         nreqs = split(enabledby[i], r)
+         for (j=1; j<=nreqs; ++j) {
+            print "#ifdef PNG_" r[j] "_SUPPORTED" >out
+            print "#   undef PNG_not_enabled /*" r[j] "*/" >out
+            # Oops, probably not intended (should be factored
+            # out by the checks above).
+            if (option[i] == "off") {
+               print error, i, "enabled by:", r[j] end >out
+            }
+            print "#endif" >out
+         }
+
+         print "#   ifndef PNG_" i "_SUPPORTED /*!command line*/" >out
+         print "#    ifdef PNG_not_enabled /*!enabled*/" >out
+         # 'have_ifs' here means that everything = "off" still allows an 'if' on
+         # an otherwise enabled option to turn it on; otherwise the 'if'
+         # handling is effectively disabled by 'everything = off'
+         if (option[i] == "off" || option[i] == "disabled" && everything != "on" || option[i] == "enabled" && everything == "off" && !have_ifs) {
+            print "#      undef PNG_on /*default off*/" >out
+         } else {
+            print "#      ifdef PNG_NO_" i >out
+            print "#       undef PNG_on /*turned off*/" >out
+            print "#      endif" >out
+            print "#      ifdef PNG_NO_" i "_SUPPORTED" >out
+            print "#       undef PNG_on /*turned off*/" >out
+            print "#      endif" >out
+         }
+         print "#    endif /*!enabled*/" >out
+         print "#    ifdef PNG_on" >out
+         # The _SUPPORTED macro must be defined so that dependent
+         # options output later work.
+         print "#      define PNG_" i "_SUPPORTED" >out
+         print "#    endif" >out
+         print "#   endif /*!command line*/" >out
+         # If PNG_on is still set the option should be defined in
+         # pnglibconf.h
+         print "#   ifdef PNG_on" >out
+         if (i ~ /^fail_/) {
+            print error, i, "is on: enabled by:" iffs[i] enabledby[i] ", requires" requires[i] end >out
+         } else if (i !~ /^ok_/) {
+            print def i sup >out
+            # Supported option, set required settings
+            nreqs = split(sets[i], r)
+            for (j=1; j<=nreqs; ++j) {
+               print "#    ifdef PNG_set_" r[j] >out
+               # Some other option has already set a value:
+               print error, i, "sets", r[j] ": duplicate setting" end >out
+               print error, "   previous value: " end "PNG_set_" r[j] >out
+               print "#    else" >out
+               # Else set the default: note that this won't accept arbitrary
+               # values, the setval string must be acceptable to all the C
+               # compilers we use.  That means it must be VERY simple; a number,
+               # a name or a string.
+               print "#     define PNG_set_" r[j], setval[i " " r[j]] >out
+               print "#    endif" >out
+            }
+         }
+         print "#   endif /* definition */" >out
+         print "#endif /*requires, if*/" >out
+         if (logunsupported || i ~ /^ok_/) {
+            print "#ifndef  PNG_on" >out
+            if (logunsupported) {
+               print und i une >out
+            }
+            if (i ~ /^ok_/) {
+               print error, i, "not enabled: requires:" requires[i] ", enabled by:" iffs[i] enabledby[i] end >out
+            }
+            print "#endif" >out
+         }
+
+         done[i] = 1
+         ++movement
+      }
+
+      if (!finished && !movement) {
+         print "option: loop or missing option in dependency tree, cannot process:"
+         for (i in option) if (!done[i]) {
+            print "  option", i, "depends on" tree[i], "needs:"
+            nreqs = split(tree[i], r)
+            if (nreqs > 0) for (j=1; j<=nreqs; ++j) if (!done[r[j]]) {
+               print "   " r[j]
+            }
+         }
+         exit 1
+      }
+   }
+   print "PNG_DFN_END_SORT" >out
+   print comment, "end of options", cend >out
+
+   # Do the 'setting' values second, the algorithm the standard
+   # tree walk (O(1)) done in an O(2) while/for loop; interations
+   # settings x depth, outputing the deepest required macros
+   # first.
+   print "" >out
+   print "/* SETTINGS */" >out
+   print comment, "settings", cend >out
+   # Sort (in dfn.awk) on field 2, the setting name
+   print "PNG_DFN_START_SORT 2" >out
+   finished = 0
+   while (!finished) {
+      finished = 1
+      movement = 0 # done nothing
+      for (i in setting) if (!doneset[i]) {
+         nreqs = split(setting[i], r)
+         if (nreqs > 0) {
+            # By default assume the requires values are options, but if there
+            # is no option with that name check for a setting
+            for (j=1; j<=nreqs; ++j) if (option[r[j]] == "" && !doneset[r[j]]) {
+               break
+            }
+            if (j<=nreqs) {
+               finished = 0
+               continue # try a different setting
+            }
+         }
+
+         # All the requirements have been processed, output
+         # this setting.
+         if (deb) print "setting", i
+         deflt = defaults[i]
+         # Remove any spurious trailing spaces
+         sub(/ *$/,"",deflt)
+         # A leading @ means leave it unquoted so the preprocessor
+         # can substitute the build time value
+         if (deflt ~ /^ @/)
+            deflt = " " subs substr(deflt, 3) sube
+         print "" >out
+         print "/* setting: ", i >out
+         print " *   requires:" setting[i] >out
+         print " *   default: ", defaults[i] deflt, "*/" >out
+         for (j=1; j<=nreqs; ++j) {
+            if (option[r[j]] != "")
+               print "#ifndef PNG_" r[j] "_SUPPORTED" >out
+            else
+               print "#ifndef PNG_" r[j] >out
+            print error, i, "requires", r[j] end >out
+            print "# endif" >out
+         }
+         # The precedence is:
+         #
+         #  1) External definition; trumps:
+         #  2) Option 'sets' value; trumps:
+         #  3) Setting 'default'
+         #
+         print "#ifdef PNG_" i >out
+         # PNG_<i> is defined, so substitute the value:
+         print def i, subs "PNG_" i sube end >out
+         print "#else /* use default */" >out
+         print "# ifdef PNG_set_" i >out
+         # Value from an option 'sets' argument
+         print def i, subs "PNG_set_" i sube end >out
+         # This is so that subsequent tests on the setting work:
+         print "#  define PNG_" i, "1" >out
+         if (defaults[i] != "") {
+            print "# else /*default*/" >out
+            print def i deflt end >out
+            print "#  define PNG_" i, "1" >out
+         }
+         print "# endif /* defaults */" >out
+         print "#endif /* setting", i, "*/" >out
+
+         doneset[i] = 1
+         ++movement
+      }
+
+      if (!finished && !movement) {
+         print "setting: loop or missing setting in 'requires', cannot process:"
+         for (i in setting) if (!doneset[i]) {
+            print "  setting", i, "requires" setting[i]
+         }
+         exit 1
+      }
+   }
+   print "PNG_DFN_END_SORT" >out
+   print comment, "end of settings", cend >out
+
+   # Regular end - everything looks ok
+   if (protect != "") {
+      print start "#endif", "/*", protect, "*/" end >out
+   }
+}