lib: use static assertion to check enum valuestmp-static-assert

We previously had checks of enum values with '#if', such as below:

 #define GNUTLS_EXTENSION_MAX_VALUE 31

 typedef enum extensions_t {
         ...
         GNUTLS_EXTENSION_MAX /* not real extension - used for iterators */
 } extensions_t;

 /* we must provide at least 16 extensions for users to register */
 #if GNUTLS_EXTENSION_MAX_VALUE - GNUTLS_EXTENSION_MAX < 16
 # error not enough extension types
 #endif

This doesn't work as expected; because GNUTLS_EXTENSION_MAX is not
defined as a preprocessor macro, it always expands to 0.  To properly
do this check, we need to use static assert as provided as the
'verify' macro in gnulib.

Signed-off-by: Daiki Ueno <dueno@redhat.com>

1 files changed, 12 insertions, 10 deletions

diff --git a/lib/gnutls_int.h b/lib/gnutls_int.h
index 058fce090c..4ea8159979 100644
--- a/lib/gnutls_int.h
+++ b/lib/gnutls_int.h
@@ -361,19 +361,21 @@ typedef enum extensions_t {
 #define GNUTLS_EXTENSION_MAX_VALUE 63
 #define ext_track_t uint64_t
 
-#if GNUTLS_EXTENSION_MAX >= GNUTLS_EXTENSION_MAX_VALUE
-# error over limit
-#endif
+#include <verify.h>
 
-#if GNUTLS_EXTENSION_MAX >= MAX_EXT_TYPES
-# error over limit
-#endif
+verify(GNUTLS_EXTENSION_MAX < GNUTLS_EXTENSION_MAX_VALUE);
+verify(GNUTLS_EXTENSION_MAX < MAX_EXT_TYPES);
 
-/* we must provide at least 16 extensions for users to register */
-#if GNUTLS_EXTENSION_MAX_VALUE - GNUTLS_EXTENSION_MAX < 16
-# error not enough extension types; increase GNUTLS_EXTENSION_MAX_VALUE, MAX_EXT_TYPES and used_exts type
-#endif
+/* we must provide at least 16 extensions for users to register;
+ * increase GNUTLS_EXTENSION_MAX_VALUE, MAX_EXT_TYPES and used_exts
+ * type if this fails
+ */
+verify(GNUTLS_EXTENSION_MAX_VALUE - GNUTLS_EXTENSION_MAX >= 16);
 
+/* The 'verify' symbol from <verify.h> is used extensively in the
+ * code; undef it to avoid clash
+ */
+#undef verify
 
 typedef enum { CIPHER_STREAM, CIPHER_BLOCK, CIPHER_AEAD } cipher_type_t;