banned.h: mark non-reentrant gmtime, etc as banned

The traditional gmtime(), localtime(), ctime(), and asctime() functions
return pointers to shared storage. This means they're not thread-safe,
and they also run the risk of somebody holding onto the result across
multiple calls (where each call invalidates the previous result).

All callers should be using their reentrant counterparts.

Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/banned.h b/banned.h
index 60a18d4403..ed11300bb2 100644
--- a/banned.h
+++ b/banned.h
@@ -29,4 +29,13 @@
 #define vsprintf(buf,fmt,arg) BANNED(vsprintf)
 #endif
 
+#undef gmtime
+#define gmtime(t) BANNED(gmtime)
+#undef localtime
+#define localtime(t) BANNED(localtime)
+#undef ctime
+#define ctime(t) BANNED(ctime)
+#undef asctime
+#define asctime(t) BANNED(asctime)
+
 #endif /* BANNED_H */