Better document fix-gnulib.

[cdecl99.git] / fix-gnulib.pl

diff --git a/fix-gnulib.pl b/fix-gnulib.pl
index ee7a0c94a70a88c6ca6e5f59ae5181da037e1ab9..85ae6321980e743632f2e3c911e3b2314f460139 100755 (executable)
--- a/fix-gnulib.pl
+++ b/fix-gnulib.pl
@@ -1,8 +1,40 @@
 #!/usr/bin/env perl
 #
-# Copyright © 2011 Nick Bowler
+# Copyright © 2011-2012 Nick Bowler
 #
 # Prepare the Gnulib tree for inclusion into a non-recursive automake build.
+# While the output of gnulib-tool is "include"-able if the --makefile-name
+# option is used, it is still not suitable for non-recursive use for a couple
+# reasons; chief among them is that filenames are not relative to the top
+# source directory.
+#
+# This script postprocesses the gnulib-tool output to produce something that
+# is intended to be suitable for inclusion into such non-recursive build
+# environments.  Since the integration involves both configure.ac and
+# Makefile.am, the output must be included into _both_.  Supposing the output
+# is written to lib/gnulib.mk, you would add:
+#
+#   m4_include([lib/gnulib.mk]) # to configure.ac, after any call to gl_INIT
+#   include $(top_srcdir)/lib/gnulib.mk # to Makefile.am
+#
+# You must also arrange for the Gnulib-generated header files to be built
+# before the object files which depend on them; the most robust way to do this
+# is by explicit prerequisites, for example:
+#
+#   bin_PROGRAMS = foo
+#   $(foo_OBJECTS): $(gnulib_headers)
+#
+# The $(gnulib_headers) variable will expand to GNU-make order-only
+# prerequisites when available, avoiding spurious incremental rebuilds when
+# unused headers are changed.  If this feature is not available, it will
+# expand to ordinary prerequisites.  It is therefore only appropriate for use
+# in target prerequisites; the $(gnulib_raw_headers) variable may be used in
+# other contexts when only the list of header files is required.
+#
+# This script also provides machinery for Gnulib symbol renaming via the
+# glconfig.mk Makefile.am snippet; use of this feature is optional.
+#
+# Most of the specific transformations are documented below.
 #
 # License WTFPL2: Do What The Fuck You Want To Public License, version 2.
 # This is free software: you are free to do what the fuck you want to.
@@ -14,8 +46,6 @@ use Getopt::Long;
 
 my $output   = undef;
 my $input    = undef;
-my $m4output = undef;
-my $m4macro  = "DX_FIX_GNULIB";
 
 my $line     = 0;
 
@@ -23,8 +53,6 @@ Getopt::Long::Configure("gnu_getopt", "no_auto_abbrev");
 GetOptions(
        "o|output=s"   => \$output,
        "i|input=s"    => \$input,
-       "m|m4output=s" => \$m4output,
-       "M|m4macro=s"  => \$m4macro,
 );
 
 open STDOUT, ">", $output or die "$output: $!\n" if (defined $output);
@@ -100,12 +128,16 @@ while (<STDIN>) {
        if (!$printed_header) {
                print "# Postprocessed by ", basename($0), "\n\n";
                print <<'EOF';
+# BEGIN AUTOMAKE/M4 POLYGLOT \
+m4_unquote(m4_argn([2], [
+.PHONY: # Automake code follows
+
 # This trick should define gnulib_orderonly to | iff we're using GNU make.
 gnulib_have_orderonly = $(findstring order-only,$(.FEATURES))
 gnulib_orderonly = $(gnulib_have_orderonly:order-only=|)
-gnulib_core_headers = $(gnulib_orderonly)
-gnulib_src_headers = $(gnulib_core_headers)
-gnulib_headers = $(gnulib_src_headers)
+gnulib_core_headers =
+gnulib_raw_headers = $(gnulib_core_headers)
+gnulib_headers = $(gnulib_orderonly) $(gnulib_raw_headers)
 EOF
 
                $printed_header = 1;
@@ -178,7 +210,7 @@ EOF
 
 print <<'EOF';
 gnulib_lt_objects = $(libgnu_la_OBJECTS) $(gl_LTLIBOBJS)
-$(gnulib_lt_objects): $(gnulib_src_headers)
+$(gnulib_lt_objects): $(gnulib_headers)
 EOF
 print @cleanfiles;
 
@@ -186,26 +218,17 @@ print @cleanfiles;
 # prepend lib/ if and only if they're not empty.  Unfortunately, make is not
 # powerful to do this, so we need to put this transformation into configure
 # itself by defining a new autoconf macro.
-if (defined $m4output) {
-       my $lc = List::Compare->new('-u', '-a', \%sourcevars, \%allvars);
-       my @vars = $lc->get_unique;
-
-       open(M4OUT, '>', $m4output) or die "$m4output: $!\n";
-
-       print M4OUT <<EOF;
-dnl This file was generated by fix-gnulib.pl
-dnl
-dnl Usage: DX_FIX_GNULIB([symbol-prefix])
-dnl   where symbol-prefix is the application-specific symbol prefix to apply
-dnl   to Gnulib's symbols.  Defaults to \${PACKAGE}__.
-dnl   top-level source directory; e.g. lib.
-AC_DEFUN([$m4macro], [dnl
-EOF
-       print M4OUT <<'EOF';
-GLSRC=lib
-GLSYM_PREFIX='ifelse([$1], [], [${PACKAGE}__], [$1])'
-AC_SUBST([GLSRC])
-AC_SUBST([GLSYM_PREFIX])
+
+my $lc = List::Compare->new('-u', '-a', \%sourcevars, \%allvars);
+my @vars = $lc->get_unique;
+
+print <<'EOF';
+if FALSE
+], [dnl M4 code follows
+
+AC_SUBST([GLSRC], [lib])
+AC_DEFUN_ONCE([DX_GLSYM_PREFIX], [AC_SUBST([GLSYM_PREFIX], [$1])])
+AC_CONFIG_COMMANDS_PRE([DX_GLSYM_PREFIX([${PACKAGE}__])])
 
 m4_foreach([gl_objvar], [[gl_LIBOBJS], [gl_LTLIBOBJS]], [dnl
 set x $gl_objvar; shift
@@ -215,10 +238,14 @@ while test ${#} -gt 0; do
 done
 ])
 EOF
-       foreach (@vars) {
-               print M4OUT "$_=\${$_:+lib/\$$_}\n";
-       }
-       print M4OUT "])\n";
 
-       close M4OUT;
+foreach (@vars) {
+       print "$_=\${$_:+lib/\$$_}\n";
 }
+
+print <<'EOF';
+], [
+endif
+# ]))dnl
+# END AUTOMAKE/M4 POLYGLOT
+EOF