common: helper to suppress 'may be used uninitialized' warnings.

When gcc still warns at -O3 and you are sure it's not necessary,
this marks it appropriately.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

common/utils.h

@@ -54,4 +54,9 @@ STRUCTEQ_DEF(sha256, 0, u);
 /* Define ripemd160_eq. */
 STRUCTEQ_DEF(ripemd160, 0, u);
 
+/* If gcc complains about 'may be uninitialized' even at -O3, and the code is
+ * clear, use this to suppress it.  Argument should be gcc version it
+ * complained on, so we can re-test as gcc evolves. */
+#define COMPILER_WANTS_INIT(compiler_versions) = 0
+
 #endif /* LIGHTNING_COMMON_UTILS_H */