git-compat-util: introduce ASSERT() macro

Create a ASSERT() macro which is similar to assert(), but will not be
compiled out when NDEBUG is defined, and is thus safe to use even if its
argument has side-effects.

We will use this new macro in a subsequent commit to convert a few
existing assert() invocations to ASSERT().  In particular, we'll
convert the handful of invocations which cannot be proven to be free of
side effects with a simple compiler/linker hack.

Signed-off-by: Elijah Newren <[email protected]>
Acked-by: Taylor Blau <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: newren

git-compat-util.h

@@ -1460,6 +1460,8 @@ extern int bug_called_must_BUG;
 __attribute__((format (printf, 3, 4))) NORETURN
 void BUG_fl(const char *file, int line, const char *fmt, ...);
 #define BUG(...) BUG_fl(__FILE__, __LINE__, __VA_ARGS__)
+/* ASSERT: like assert(), but won't be compiled out with NDEBUG */
+#define ASSERT(a) if (!(a)) BUG("Assertion `" #a "' failed.")
 __attribute__((format (printf, 3, 4)))
 void bug_fl(const char *file, int line, const char *fmt, ...);
 #define bug(...) bug_fl(__FILE__, __LINE__, __VA_ARGS__)