bin/mconfig: new "-X FILE" option

Packages can use this option to list symbols that shouldn't bring in the
corresponding units. For example, Perl need not provide support for BSD
index(3) as an alternative to C89 strchr(3), but "index" is the name of a
Perl builtin, so that string in the source files is misunderstood by
metaconfig as an attempt to use the BSD function.

With this change, Perl can deal with this situation by adding "index" (and
"rindex") to an exclusion list.

diff --git a/bin/mconfig b/bin/mconfig
index 51dbf5f..698d118 100755 (executable)
--- a/bin/mconfig
+++ b/bin/mconfig
@@ -57,8 +57,10 @@ $patchlevel = '0';
 $grep = '/usr/bin/grep';
 chop($date = `date`);
 &profile;                                              # Read ~/.dist_profile
-&usage unless getopts("dhkmoOstvwGMVL:");
+&usage unless getopts("dhkmoOstvwGMVL:X:");
 
+my %excluded_symbol;
+read_exclusions($opt_X) if defined $opt_X;
 $MC = $opt_L if $opt_L;                        # May override public library path
 $MC = &tilda_expand($MC);              # ~name expansion
 chop($WD = `pwd`);                             # Working directory
@@ -154,6 +156,7 @@ Usage: metaconfig [-dhkmostvwGMV] [-L dir]
   -L : specify main units repository.
   -M : activate production of confmagic.h.
   -V : print version number and exits.
+  -X FILE : read symbol exclusions from FILE
 EOH
        exit 1;
 }
@@ -524,6 +527,9 @@ sub p_wanted {
                $cmaster{$_} = undef;                                   # Asks for look-up in C files
                $cwanted{$_} = "$active" if $active;    # Shell symbols to activate
        }
+
+       delete @cmaster{keys %excluded_symbol};
+       delete @cwanted{keys %excluded_symbol};
 }
 
 # Process the ?INIT: lines
@@ -807,6 +813,25 @@ sub q {
        $_;
 }
 
+sub read_exclusions {
+       my ($filename) = @_;
+       print "Reading exclusions from $filename...\n" unless $opt_s;
+       open(EXCLUSIONS, "< $filename\0") || die "Can't read $filename: $!\n";
+       local $_;
+       while (<EXCLUSIONS>) {
+               if (/^\s*#|^\s*$/) {
+                       # comment or blank line, ignore
+               }
+               elsif (/^\s*(\w+)\s*$/) {
+                       $excluded_symbol{$1} = 1;
+               }
+               else {
+                       die "$filename:$.: unrecognised line\n";
+               }
+       }
+       close(EXCLUSIONS) || die "Can't close $filename: $!\n";
+}
+
 # Build a wanted file from the files held in @SHlist and @clist arrays
 sub build_wanted {
        # If wanted file is already there, parse it to map obsolete if -o option