[FFmpeg-devel] [PATCH] avcodec/hevcdec: fix out of bounds index -1 for inter prediction

[Nuo Mi <nuomi2021@gmail.com>]

It's a false positive. We use -1 to index an array, but it's not actually used.
This patch will make the "GCC UndefinedBehaviorSanitizer" happy.

Found by: checkasm-hevc_pel in https://fate.ffmpeg.org/report.cgi?time=20240211011905&slot=x86_64-archlinux-gcc-ubsan
Reported-by: James Almer <jamrial@gmail.com>
---
 libavcodec/hevcdsp_template.c | 6 +++---
 libavcodec/x86/hevcdsp_init.c | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/libavcodec/hevcdsp_template.c b/libavcodec/hevcdsp_template.c
index 9b48bdf08e..a4b8901e5d 100644
--- a/libavcodec/hevcdsp_template.c
+++ b/libavcodec/hevcdsp_template.c
@@ -301,9 +301,9 @@ IDCT_DC(32)
 //
 ////////////////////////////////////////////////////////////////////////////////
 #define ff_hevc_pel_filters ff_hevc_qpel_filters
-#define DECL_HV_FILTER(f)                                  \
-    const uint8_t *hf = ff_hevc_ ## f ## _filters[mx - 1]; \
-    const uint8_t *vf = ff_hevc_ ## f ## _filters[my - 1];
+#define DECL_HV_FILTER(f)                                               \
+    const uint8_t *hf = mx ? ff_hevc_ ## f ## _filters[mx - 1] : NULL;  \
+    const uint8_t *vf = my ? ff_hevc_ ## f ## _filters[my - 1] : NULL;
 
 #define FW_PUT(p, f, t)                                                                                   \
 static void FUNC(put_hevc_## f)(int16_t *dst, const uint8_t *src, ptrdiff_t srcstride, int height,        \
diff --git a/libavcodec/x86/hevcdsp_init.c b/libavcodec/x86/hevcdsp_init.c
index 31e81eb11f..e0f65177c4 100644
--- a/libavcodec/x86/hevcdsp_init.c
+++ b/libavcodec/x86/hevcdsp_init.c
@@ -87,9 +87,9 @@ IDCT_FUNCS(avx)
 
 
 #define ff_hevc_pel_filters ff_hevc_qpel_filters
-#define DECL_HV_FILTER(f)                                  \
-    const uint8_t *hf = ff_hevc_ ## f ## _filters[mx - 1]; \
-    const uint8_t *vf = ff_hevc_ ## f ## _filters[my - 1];
+#define DECL_HV_FILTER(f)                                               \
+    const uint8_t *hf = mx ? ff_hevc_ ## f ## _filters[mx - 1] : NULL;  \
+    const uint8_t *vf = my ? ff_hevc_ ## f ## _filters[my - 1] : NULL;  \
 
 #define FW_PUT(p, a, b, depth, opt) \
 void ff_hevc_put_hevc_ ## a ## _ ## depth ## _##opt(int16_t *dst, const uint8_t *src, ptrdiff_t srcstride,   \
-- 
2.25.1

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