*: `frr-format` with unmodified GCC

Since there's very few locations where the `frr-format` actually prints
false positive warnings, consensus seems to be to just work around the
false positives even if the code is correct.

In fact, there is only one pattern of false positives currently, in
`bfdd/dplane.c` which does `vty_out("%"PRIu64, (uint64_t)be64toh(...))`.
The workaround/fix for this is a replacement `be64toh` whose type is
always `uint64_t` regardless of what OS we're on, making the cast
unnecessary.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

1 files changed, 36 insertions, 0 deletions

diff --git a/lib/network.h b/lib/network.h
index 4a9666984f..10ed917572 100644
--- a/lib/network.h
+++ b/lib/network.h
@@ -22,6 +22,13 @@
 #ifndef _ZEBRA_NETWORK_H
 #define _ZEBRA_NETWORK_H
 
+#ifdef HAVE_SYS_ENDIAN_H
+#include <sys/endian.h>
+#endif
+#ifdef HAVE_ENDIAN_H
+#include <endian.h>
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -45,6 +52,35 @@ extern int set_cloexec(int fd);
 extern float htonf(float);
 extern float ntohf(float);
 
+/* force type for be64toh/htobe64 to be uint64_t, *without* a direct cast
+ *
+ * this is a workaround for false-positive printfrr warnings from FRR's
+ * frr-format GCC plugin that would be triggered from
+ * { printfrr("%"PRIu64, (uint64_t)be64toh(...)); }
+ *
+ * the key element here is that "(uint64_t)expr" causes the warning, while
+ * "({ uint64_t x = expr; x; })" does not.  (The cast is the trigger, a
+ * variable of the same type works correctly.)
+ */
+
+/* zap system definitions... */
+#ifdef be64toh
+#undef be64toh
+#endif
+#ifdef htobe64
+#undef htobe64
+#endif
+
+#if BYTE_ORDER == LITTLE_ENDIAN
+#define be64toh(x)	({ uint64_t r = __builtin_bswap64(x); r; })
+#define htobe64(x)	({ uint64_t r = __builtin_bswap64(x); r; })
+#elif BYTE_ORDER == BIG_ENDIAN
+#define be64toh(x)	({ uint64_t r = (x); r; })
+#define htobe64(x)	({ uint64_t r = (x); r; })
+#else
+#error nobody expects the endianish inquisition. check OS endian.h headers.
+#endif
+
 /**
  * Helper function that returns a random long value. The main purpose of
  * this function is to hide a `random()` call that gets flagged by coverity