[FFmpeg-devel] [PATCH 09/19] swscale/internal: use static_assert for enforcing offsets

[Niklas Haas]

From: Niklas Haas <git at haasn.dev>

Instead of sprinkling av_assert0 into random init functions.

Sponsored-by: Sovereign Tech Fund
Signed-off-by: Niklas Haas <git at haasn.dev>
---
 libswscale/swscale_internal.h | 9 +++++++++
 libswscale/utils.c            | 3 ++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/libswscale/swscale_internal.h b/libswscale/swscale_internal.h
index 1817815b01..9b346c4fd9 100644
--- a/libswscale/swscale_internal.h
+++ b/libswscale/swscale_internal.h
@@ -22,6 +22,7 @@
 #define SWSCALE_SWSCALE_INTERNAL_H
 
 #include <stdatomic.h>
+#include <assert.h>
 
 #include "config.h"
 #include "swscale.h"
@@ -704,6 +705,14 @@ struct SwsInternal {
 };
 //FIXME check init (where 0)
 
+static_assert(offsetof(SwsInternal, redDither) + DITHER32_INT == offsetof(SwsInternal, dither32),
+              "dither32 must be at the same offset as redDither + DITHER32_INT");
+
+/* x86 yuv2gbrp uses the SwsInternal for yuv coefficients
+   if struct offsets change the asm needs to be updated too */
+static_assert(offsetof(SwsInternal, yuv2rgb_y_offset) == 40292,
+              "yuv2rgb_y_offset must be updated in x86 asm");
+
 SwsFunc ff_yuv2rgb_get_func_ptr(SwsInternal *c);
 int ff_yuv2rgb_c_init_tables(SwsInternal *c, const int inv_table[4],
                              int fullRange, int brightness,
diff --git a/libswscale/utils.c b/libswscale/utils.c
index 01fe474020..f5833548a7 100644
--- a/libswscale/utils.c
+++ b/libswscale/utils.c
@@ -1227,7 +1227,8 @@ SwsContext *sws_alloc_context(void)
 {
     SwsInternal *c = av_mallocz(sizeof(SwsInternal));
 
-    av_assert0(offsetof(SwsInternal, redDither) + DITHER32_INT == offsetof(SwsInternal, dither32));
+    static_assert(offsetof(SwsInternal, redDither) + DITHER32_INT == offsetof(SwsInternal, dither32),
+                  "dither32 must be at the same offset as redDither + DITHER32_INT");
 
     if (c) {
         c->av_class = &ff_sws_context_class;
-- 
2.46.1