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Mon, 29 Jun 2020 16:28:05 +0000 (UTC) From: Eric Blake To: qemu-devel@nongnu.org Subject: [PATCH v2] coverity: provide Coverity-friendly MIN_CONST and MAX_CONST Date: Mon, 29 Jun 2020 11:28:04 -0500 Message-Id: <20200629162804.1096180-1-eblake@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=205.139.110.120; envelope-from=eblake@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/29 01:10:03 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.maydell@linaro.org, pbonzini@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Coverity has problems seeing through __builtin_choose_expr, which result in it abandoning analysis of later functions that utilize a definition that used MIN_CONST or MAX_CONST, such as in qemu-file.c: 50 DECLARE_BITMAP(may_free, MAX_IOV_SIZE); CID 1429992 (#1 of 1): Unrecoverable parse warning (PARSE_ERROR)1. expr_not_constant: expression must have a constant value As has been done in the past (see 07d66672), it's okay to dumb things down when compiling for static analyzers. (Of course, now the syntax-checker has a false positive on our reference to __COVERITY__...) Reported-by: Peter Maydell Fixes: CID 1429992, CID 1429995, CID 1429997, CID 1429999 Signed-off-by: Eric Blake --- Improvements over Paolo's v1: - proper use of () - add comment explaining the COVERITY section - add indentation for easier read of #if/#else flow include/qemu/osdep.h | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h index 0d26a1b9bd07..0fc206ae6154 100644 --- a/include/qemu/osdep.h +++ b/include/qemu/osdep.h @@ -250,7 +250,8 @@ extern int daemon(int, int); * Note that neither form is usable as an #if condition; if you truly * need to write conditional code that depends on a minimum or maximum * determined by the pre-processor instead of the compiler, you'll - * have to open-code it. + * have to open-code it. Sadly, Coverity is severely confused by the + * constant variants, so we have to dumb things down there. */ #undef MIN #define MIN(a, b) \ @@ -258,22 +259,28 @@ extern int daemon(int, int); typeof(1 ? (a) : (b)) _a = (a), _b = (b); \ _a < _b ? _a : _b; \ }) -#define MIN_CONST(a, b) \ - __builtin_choose_expr( \ - __builtin_constant_p(a) && __builtin_constant_p(b), \ - (a) < (b) ? (a) : (b), \ - ((void)0)) #undef MAX #define MAX(a, b) \ ({ \ typeof(1 ? (a) : (b)) _a = (a), _b = (b); \ _a > _b ? _a : _b; \ }) -#define MAX_CONST(a, b) \ + +#ifdef __COVERITY__ +# define MIN_CONST(a, b) ((a) < (b) ? (a) : (b)) +# define MAX_CONST(a, b) ((a) > (b) ? (a) : (b)) +#else +# define MIN_CONST(a, b) \ + __builtin_choose_expr( \ + __builtin_constant_p(a) && __builtin_constant_p(b), \ + (a) < (b) ? (a) : (b), \ + ((void)0)) +# define MAX_CONST(a, b) \ __builtin_choose_expr( \ __builtin_constant_p(a) && __builtin_constant_p(b), \ (a) > (b) ? (a) : (b), \ ((void)0)) +#endif /* * Minimum function that returns zero only if both values are zero. -- 2.27.0