[PATCH v2 2/4] banned.h: mark strcat() as banned

[Jeff King <peff@peff.net>]

The strcat() function has all of the same overflow problems
as strcpy(). And as a bonus, it's easy to end up
accidentally quadratic, as each subsequent call has to walk
through the existing string.

The last strcat() call went away in f063d38b80 (daemon: use
cld->env_array when re-spawning, 2015-09-24). In general,
strcat() can be replaced either with a dynamic string
(strbuf or xstrfmt), or with xsnprintf if you know the
length is bounded.

Signed-off-by: Jeff King <peff@peff.net>
---
 banned.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/banned.h b/banned.h
index c50091ad7d..32e0bae01d 100644
--- a/banned.h
+++ b/banned.h
@@ -12,5 +12,7 @@
 
 #undef strcpy
 #define strcpy(x,y) BANNED(strcpy)
+#undef strcat
+#define strcat(x,y) BANNED(strcat)
 
 #endif /* BANNED_H */
-- 
2.18.0.542.g2bf2fc4f7e