From 8534ffc15c44bfd2f7a72ee745afd284255d17c7 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sat, 28 Dec 2019 12:59:11 +0000
Subject: [PATCH] Warnings: Infrastructure for tracking and warning about
 variables

We are going to track when we see FOO or &FOO.  If we see both, we
issue a warning, as that might mean the programmer forgot a &.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---
 generate | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/generate b/generate
index 9be1cfb..03aabb0 100755
--- a/generate
+++ b/generate
@@ -152,6 +152,8 @@ Makefile run-main.mk:
 END
 }
 
+our %varref;
+
 our ($dir_prefix, $dir_suffix, $dir_name,
      $var_prefix, $var_prefix_name);
 
@@ -235,6 +237,13 @@ sub process_input_mk ($$$$) {
 	$ddbl = (shift @nest)[1];
     };
 
+    # Our detection of variable settings does not have to be completely
+    # accurate, since it is only going to be used for advice to the user.
+    my $note_varref = sub {
+	my ($vn,$amp) = @_;
+	$varref{$vn}{$amp}{"$f:$."} = 1;
+    };
+
     while (<$input>) {
 	if (s#^\s*$esc\:changequote\s+(\S+)\s+$##) {
 	    $$esclitr = $1;
@@ -440,6 +449,20 @@ sub process_tree() {
     oraw "include \$(SUBDIRMK_MAKEFILES)\n";
 }
 
+sub print_varref_warnings () {
+    foreach my $vn (sort keys %varref) {
+	my $vv = $varref{$vn};
+	next unless $vv->{''} && $vv->{1};
+	print STDERR "subdirmk: warning: saw both $vn and &$vn\n";
+	foreach my $amp ('', 1) {
+	    printf STDERR " saw %s%s at %s\n",
+		($amp ? '&' : ''), $vn, $_
+		foreach sort keys %{ $vv->{$amp} };
+	}
+    }
+}
+
 build_tree();
 process_tree();
+print_varref_warnings();
 install_output_files();
-- 
2.30.2