New "-X exclusions-file" option for mconfig

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.

4 files changed, 37 insertions, 1 deletions

diff --git a/mcon/man/mconfig.SH b/mcon/man/mconfig.SH
index f205fb7..ba415e2 100755
--- a/mcon/man/mconfig.SH
+++ b/mcon/man/mconfig.SH
@@ -528,6 +528,17 @@ option permanently.
 .TP
 .B \-V
 Print version number and exit.
+.TP
+\fB\-X\fI file\fR
+When examining the source files, ignore any symbols listed in the \fIfile\fR.
+This is useful in situations where a particular unit is known not to be needed
+for your package's portability targets, but your source files nevertheless
+contain occurrences of words that look to \fImetaconfig\fR like symbols defined
+in that unit. (For example, you might need the word "index" in a source file,
+but not need the unit that determines whether \fIstrcpy\fR or \fIindex\fR
+should be used.)
+The \fIfile\fR can contain blank lines, comment lines introduced with '#', and
+lines containing a single symbol.
 '''
 ''' T u t o r i a l
 '''
diff --git a/mcon/mconfig.SH b/mcon/mconfig.SH
index c9c295f..7f89325 100755
--- a/mcon/mconfig.SH
+++ b/mcon/mconfig.SH
@@ -68,8 +68,10 @@ chop($date = `date`);
 &profile;						# Read ~/.dist_profile
 
 use Getopt::Std;
-&usage unless getopts("dhkmostvwGMVL:");
+&usage unless getopts("dhkmostvwGMVL: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
@@ -164,6 +166,7 @@ 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;
 }
diff --git a/mcon/pl/depend.pl b/mcon/pl/depend.pl
index fc88f1a..e31eded 100644
--- a/mcon/pl/depend.pl
+++ b/mcon/pl/depend.pl
@@ -52,6 +52,9 @@ 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
diff --git a/mcon/pl/wanted.pl b/mcon/pl/wanted.pl
index 20d218c..6a44039 100644
--- a/mcon/pl/wanted.pl
+++ b/mcon/pl/wanted.pl
@@ -39,6 +39,25 @@
 ;#
 ;# The manifake() routine has to be provided externally.
 ;#
+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