Hi, gcc10 complains with two warnings when compiling libmicrohttpd using
#define NDEBUG 1 #define DAUTH_SUPPORT 1 so, "release build" with enabled "digest authentication": ../digestauth.c: In function 'MHD_digest_auth_check_digest2': ../digestauth.c:1287:9: warning: 'da.digest_size' may be used uninitialized in this function [-Wmaybe-uninitialized] 1287 | if (da.digest_size != digest_size) | ~~^~~~~~~~~~~~ ../digestauth.c: In function 'MHD_queue_auth_fail_response2': ../digestauth.c:1361:55: warning: 'da.digest_size' may be used uninitialized in this function [-Wmaybe-uninitialized] 1361 | char nonce[NONCE_STD_LEN (VLA_ARRAY_LEN_DIGEST (da.digest_size)) + 1]; | This is a minor issue, without any practical effect, unless when calling the MHD API with an invalid value for the MHD_DigestAuthAlgorithm enum. However, gcc is still right that there is a potential code path with undefined behaviour: the default-case in the switch statement in SETUP_DA does not set "da.digest_size". Two functions later still always read this value. And the "mhd_assert" has no effect, since it's disabled when NDEBUG is set. Trivial patch attached to silence the compiler warnings by also initializing "da.digest_size" in the default case of the switch statement: diff --git a/src/microhttpd/digestauth.c b/src/microhttpd/digestauth.c index 04c9f22a..aaed170e 100644 --- a/src/microhttpd/digestauth.c +++ b/src/microhttpd/digestauth.c @@ -1215,6 +1215,7 @@ MHD_digest_auth_check (struct MHD_Connection *connection, da.digest = &MHD_SHA256_finish; \ break; \ default: \ + da.digest_size = 0; \ mhd_assert (false); \ break; \ } \ Best Regards, Thorsten