prefer git_pathdup to git_path in some possibly-dangerous cases

Because git_path uses a static buffer that is shared with
calls to git_path, mkpath, etc, it can be dangerous to
assign the result to a variable or pass it to a non-trivial
function. The value may change unexpectedly due to other
calls.

None of the cases changed here has a known bug, but they're
worth converting away from git_path because:

  1. It's easy to use git_pathdup in these cases.

  2. They use constructs (like assignment) that make it
     hard to tell whether they're safe or not.

The extra malloc overhead should be trivial, as an
allocation should be an order of magnitude cheaper than a
system call (which we are clearly about to make, since we
are constructing a filename). The real cost is that we must
remember to free the result.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/fast-import.c b/fast-import.c
index 2ad4fee07..ad8848bef 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -407,7 +407,7 @@ static void dump_marks_helper(FILE *, uintmax_t, struct mark_set *);
 
 static void write_crash_report(const char *err)
 {
-	const char *loc = git_path("fast_import_crash_%"PRIuMAX, (uintmax_t) getpid());
+	char *loc = git_pathdup("fast_import_crash_%"PRIuMAX, (uintmax_t) getpid());
 	FILE *rpt = fopen(loc, "w");
 	struct branch *b;
 	unsigned long lu;
@@ -415,6 +415,7 @@ static void write_crash_report(const char *err)
 
 	if (!rpt) {
 		error("can't write crash report %s: %s", loc, strerror(errno));
+		free(loc);
 		return;
 	}
 
@@ -488,6 +489,7 @@ static void write_crash_report(const char *err)
 	fputs("-------------------\n", rpt);
 	fputs("END OF CRASH REPORT\n", rpt);
 	fclose(rpt);
+	free(loc);
 }
 
 static void end_packfile(void);