lavu/opt: deprecate av_opt_ptr()

It has no more internal callers, and we do not want to support direct
pointer access via AVOptions, as that constrains AVOption API
extensions.

libavutil/opt.c

@@ -2046,6 +2046,7 @@ const AVClass *av_opt_child_class_iterate(const AVClass *parent, void **iter)
     return NULL;
 }
 
+#if FF_API_OPT_PTR
 void *av_opt_ptr(const AVClass *class, void *obj, const char *name)
 {
     const AVOption *opt= av_opt_find2(&class, name, NULL, 0, AV_OPT_SEARCH_FAKE_OBJ, NULL);
@@ -2055,6 +2056,7 @@ void *av_opt_ptr(const AVClass *class, void *obj, const char *name)
         return NULL;
     return (uint8_t*)obj + opt->offset;
 }
+#endif
 
 static int opt_copy_elem(void *logctx, enum AVOptionType type,
                          void *dst, const void *src)

libavutil/opt.h

@@ -1071,6 +1071,7 @@ int av_opt_eval_q     (void *obj, const AVOption *o, const char *val, AVRational
  * @}
  */
 
+#if FF_API_OPT_PTR
 /**
  * Gets a pointer to the requested field in a struct.
  * This function allows accessing a struct even when its fields are moved or
@@ -1078,8 +1079,12 @@ int av_opt_eval_q     (void *obj, const AVOption *o, const char *val, AVRational
  *
  * @returns a pointer to the field, it can be cast to the correct type and read
  *          or written to.
+ *
+ * @deprecated direct access to AVOption-exported fields is not supported
  */
+attribute_deprecated
 void *av_opt_ptr(const AVClass *avclass, void *obj, const char *name);
+#endif
 
 /**
  * Check if given option is set to its default value.

libavutil/version.h

@@ -116,6 +116,7 @@
 #define FF_API_RISCV_FD_ZBA             (LIBAVUTIL_VERSION_MAJOR < 60)
 #define FF_API_VULKAN_FIXED_QUEUES      (LIBAVUTIL_VERSION_MAJOR < 60)
 #define FF_API_OPT_INT_LIST             (LIBAVUTIL_VERSION_MAJOR < 60)
+#define FF_API_OPT_PTR                  (LIBAVUTIL_VERSION_MAJOR < 60)
 
 /**
  * @}