Make ReadMakefile() operate using the realpath(3) name for the file handed to

it, which means that relative paths will be expanded to absolute paths, and
filenames without a path will end up with their absolute path included as
well.  This aids tremendously in debugging a build using our make(1) with
multiple Makefile's, such as when there is a syntax error in a file in a
sub-directory as per <bsd.subdir.mk>.  Normally we'd end up with just
"Makefile" known about the Makefile in question, which means that an error
would be useless for someone trying to debug their build system, now we
end up with a complete real pathname for the Makefile.

So mostly this is useful in a debugging context, but possibly others too
(I haven't thought of them yet, but they probably are more useful if you
make Dir_FindFile use realpath(3), but that's another story).

Reviewed by:	-current
MFC after:	2 weeks

1 files changed, 7 insertions, 3 deletions

diff --git a/usr.bin/make/main.c b/usr.bin/make/main.c
index 58b4e50..0c8a2f5 100644
--- a/usr.bin/make/main.c
+++ b/usr.bin/make/main.c
@@ -919,12 +919,16 @@ ReadMakefile(p, q)
 		/* if we've chdir'd, rebuild the path name */
 		if (curdir != objdir && *fname != '/') {
 			(void)snprintf(path, MAXPATHLEN, "%s/%s", curdir, fname);
-			if ((stream = fopen(path, "r")) != NULL) {
+			if (realpath(path, path) != NULL &&
+			    (stream = fopen(path, "r")) != NULL) {
 				fname = path;
 				goto found;
 			}
-		} else if ((stream = fopen(fname, "r")) != NULL)
-			goto found;
+		} else if (realpath(fname, path) != NULL) {
+			fname = path;
+			if ((stream = fopen(fname, "r")) != NULL)
+				goto found;
+		}
 		/* look in -I and system include directories. */
 		name = Dir_FindFile(fname, parseIncPath);
 		if (!name)