scripts/bake-config.awk

   1 #!/bin/awk -f
   2 #
   3 # Copyright © 2023 Nick Bowler
   4 #
   5 # Usage: bake-config.awk config.h some_header.h
   6 #
   7 # Looks for #define and #undef lines in config.h to identify configuration
   8 # macros, then looks for uses of those macros in some_header.h and substitutes
   9 # them accordingly.  The result is a header file that does not directly depend
  10 # on config.h, which can be installed normally.
  11 #
  12 # Presently, two kinds of substitions are made.
  13 #
  14 # - For a #define in config.h, any occurrence of that macro is substituted with
  15 #   its replacement text.
  16 #
  17 # - For an #undef in config.h, any occurrence of that macro in an #if or #elif
  18 #   directive is replaced with a literal 0.
  19 #
  20 # Almost no attempt is made to understand C syntax so the replacement is very
  21 # simplistic, and won't work well in many cases.  Inspect the output!
  22 #
  23 # License WTFPL2: Do What The Fuck You Want To Public License, version 2.
  24 # This is free software: you are free to do what the fuck you want to.
  25 # There is NO WARRANTY, to the extent permitted by law.
  26
  27 BEGIN {
  28   filenum = 0;
  29   idclass = "[abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0-9_]";
  30 }
  31
  32 FNR == 1 { filenum++; }
  33 filenum == 1 && $1 == "#define" && $2 !~ /[(]/ {
  34   key = $2;
  35   $1 = $2 = "";
  36   sub(/^ */, "", $0);
  37   config[key] = $0 " /* " key " */";
  38 }
  39
  40 # Autoconf comments out #undef lines in config.h, so we're looking for
  41 #    /* #undef FOO */
  42 filenum == 1 && $2 == "#undef" {
  43   undef[$3] = 0 " /* " $3 " */";
  44 }
  45
  46 filenum == 2 {
  47   CHANGED = 0;
  48   tok = $0;
  49
  50   # Mark identifier boundaries to avoid replacing substrings.  Use ` as
  51   # it is not valid in C code (outside of string/character literals).
  52   gsub(idclass"+", "`&`", tok);
  53
  54   # Replace all occurrences of configuration macros normally.
  55   tok = do_replace(tok, config);
  56
  57   # Replace explicitly undefined configuration macros in #if/#elif
  58   if ($0 ~ /^[ \t]*#[ \t]*(el)?if[ \t]/)
  59     tok = do_replace(tok, undef);
  60
  61   if (CHANGED) {
  62     gsub(/`/, "", tok);
  63     print tok;
  64   } else {
  65     print $0;
  66   }
  67 }
  68
  69 function do_replace(s, config, result, t)
  70 {
  71   while (match(s, "`" idclass "+`")) {
  72     t = substr(s, RSTART+1, RLENGTH-2);
  73     if (t in config) {
  74       result = result substr(s, 1, RSTART - 1) config[t];
  75       CHANGED = 1;
  76     } else {
  77       result = result substr(s, 1, RSTART + RLENGTH - 1);
  78     }
  79
  80     s = substr(s, RSTART + RLENGTH);
  81   }
  82
  83   return result s;
  84 }