[FFmpeg-devel] [PR] tests/swscale: don't pass fake object to av_opt_eval_* (PR #22266)

[Niklas Haas via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #22266 opened by Niklas Haas (haasn)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/22266
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/22266.patch

This is UB, as the fake object may be used for logging.

Reported-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Fixes: ea791a4ef17478693c231f04d8ba60985866f5bc


>From 374bf3e26fec841e56c6f776b1186ac542ed6268 Mon Sep 17 00:00:00 2001
From: Niklas Haas <git@haasn.dev>
Date: Mon, 23 Feb 2026 19:37:00 +0100
Subject: [PATCH] tests/swscale: don't pass fake object to av_opt_eval_*

This is UB, as the fake object may be used for logging.

Reported-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Fixes: ea791a4ef17478693c231f04d8ba60985866f5bc
---
 libswscale/tests/swscale.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/libswscale/tests/swscale.c b/libswscale/tests/swscale.c
index 3e05c97bbf..3f203e1a41 100644
--- a/libswscale/tests/swscale.c
+++ b/libswscale/tests/swscale.c
@@ -509,9 +509,8 @@ int main(int argc, char **argv)
     AVLFG rand;
     int ret = -1;
 
-    const AVClass *sws_class = sws_get_class();
-    const AVOption *flags_opt = av_opt_find(&sws_class, "sws_flags", NULL, 0,
-                                            AV_OPT_SEARCH_FAKE_OBJ);
+    SwsContext *dummy = sws_alloc_context(); /* for parsing flags */
+    const AVOption *flags_opt = av_opt_find(dummy, "sws_flags", NULL, 0, 0);
     av_assert0(flags_opt);
 
     for (int i = 1; i < argc; i += 2) {
@@ -581,7 +580,7 @@ int main(int argc, char **argv)
             opts.w = 1920;
             opts.h = 1080;
         } else if (!strcmp(argv[i], "-flags")) {
-            ret = av_opt_eval_flags(&sws_class, flags_opt, argv[i + 1], &opts.flags);
+            ret = av_opt_eval_flags(dummy, flags_opt, argv[i + 1], &opts.flags);
             if (ret < 0) {
                 fprintf(stderr, "invalid flags %s\n", argv[i + 1]);
                 goto error;
@@ -603,6 +602,7 @@ bad_option:
         }
     }
 
+    sws_free_context(&dummy);
     ff_sfc64_init(&prng_state, 0, 0, 0, 12);
     av_lfg_init(&rand, 1);
     signal(SIGINT, exit_handler);
@@ -651,5 +651,6 @@ error:
     av_frame_free(&ref);
     if (fp)
         fclose(fp);
+    sws_free_context(&dummy);
     exit_handler(ret);
 }
-- 
2.52.0

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