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IABSD.fr/xenocara/lib/libpng/scripts/options.awk

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  • Author : ajacoutot
    Date : 2025-09-17 14:44:36
    Hash : e8681e75
    Message : Import source for libpng 1.6.50 (verbatim).

  • lib/libpng/scripts/options.awk
  • #!/bin/awk -f
    
    # scripts/options.awk - library build configuration control
    #
    # 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), preceded 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 ancillary 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; iterations
       # settings x depth, outputting 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
       }
    }