[FFmpeg-devel] [PATCH] avutil/avassert: always implement av_assume with av_unreachable (PR #20167)

[Kacper Michajłow]

PR #20167 opened by Kacper Michajłow (kasper93)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20167
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20167.patch

One of the design goals of this macro is the ability to support static
inline predicate functions. Which is emitting warning in clang that a
function may have side-effects and the condition will be ignored. MSVC
doesn't emit warning, but also ignore predicate in such cases.

Instead of using assume builtins, implement it using unreachable. Which
solves this case for MSVC and Clang.

This reverts ea56fe60acc139a4dc7c531f2cb9f5319cef7a09, but also extends
it to MSVC, which is affected in the similar way.


From 8da2001023ec098b972053f7a61568583db2849e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kacper=20Michaj=C5=82ow?= <kasper93 at gmail.com>
Date: Fri, 8 Aug 2025 00:57:18 +0200
Subject: [PATCH] avutil/avassert: always implement av_assume with
 av_unreachable
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

One of the design goals of this macro is the ability to support static
inline predicate functions. Which is emitting warning in clang that a
function may have side-effects and the condition will be ignored. MSVC
doesn't emit warning, but also ignore predicate in such cases.

Instead of using assume builtins, implement it using unreachable. Which
solves this case for MSVC and Clang.

This reverts ea56fe60acc139a4dc7c531f2cb9f5319cef7a09, but also extends
it to MSVC, which is affected in the similar way.

Signed-off-by: Kacper Michajłow <kasper93 at gmail.com>
---
 libavutil/avassert.h | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/libavutil/avassert.h b/libavutil/avassert.h
index f4f039dfb0..209c0d9d17 100644
--- a/libavutil/avassert.h
+++ b/libavutil/avassert.h
@@ -108,16 +108,10 @@ do {                                                                    \
 #define av_unreachable(msg) ((void)0)
 #endif
 
-#if AV_HAS_BUILTIN(__builtin_assume)
-#define av_assume(cond) __builtin_assume(cond)
-#elif defined(_MSC_VER)
-#define av_assume(cond) __assume(cond)
-#else
 #define av_assume(cond) do { \
     if (!(cond))             \
         av_unreachable();    \
 } while (0)
 #endif
-#endif
 
 #endif /* AVUTIL_AVASSERT_H */
-- 
2.49.1