udp: Ignore bogus -Wstringop-overread for write() from gcc 12.1

With current OpenSUSE Tumbleweed on aarch64 (gcc-12-1.3.aarch64) and
on x86_64 (gcc-12-1.4.x86_64), but curiously not on armv7hl
(gcc-12-1.3.armv7hl), gcc warns about using the _pointer_ to the
802.3 header to write the whole frame to the tap descriptor:
  reading between 62 and 4294967357 bytes from a region of size 14

which is bogus:
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103483

Probably declaring udp_sock_fill_data_v{4,6}() as noinline would
"fix" this, but that's on the data path, so I'd rather not. Use
a gcc pragma instead.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/util.h b/util.h
index f85a87a..6f2c702 100644
--- a/util.h
+++ b/util.h
@@ -102,6 +102,29 @@ enum {
 		      (void *)(arg));					\
 	} while (0)
 
+
+#ifdef __has_warning
+# if __has_warning("-Wstringop-overread")
+#  define PRAGMA_STRINGOP_OVERREAD_IGNORE				\
+     _Pragma("GCC diagnostic ignored \"-Wstringop-overread\"")
+#  define PRAGMA_STRINGOP_OVERREAD_IGNORE_POP				\
+     _Pragma("GCC diagnostic pop")
+# else
+#  define PRAGMA_STRINGOP_OVERREAD_IGNORE
+#  define PRAGMA_STRINGOP_OVERREAD_IGNORE_POP
+# endif
+#else
+# if defined(__GNUC__) && __GNUC__ >= 11
+#  define PRAGMA_STRINGOP_OVERREAD_IGNORE				\
+     _Pragma("GCC diagnostic ignored \"-Wstringop-overread\"")
+#  define PRAGMA_STRINGOP_OVERREAD_IGNORE_POP				\
+     _Pragma("GCC diagnostic pop")
+# else
+#  define PRAGMA_STRINGOP_OVERREAD_IGNORE
+#  define PRAGMA_STRINGOP_OVERREAD_IGNORE_POP
+# endif
+#endif
+
 #if __BYTE_ORDER == __BIG_ENDIAN
 #define L2_BUF_ETH_IP4_INIT						\
 	{								\