+/**
+ * Define a function with only the non-default version specified.
+ *
+ * On systems with ELF shared libraries, all symbols exported from
+ * Libav libraries are tagged with the name and major version of the
+ * library to which they belong. If a function is moved from one
+ * library to another, a wrapper must be retained in the original
+ * location to preserve binary compatibility.
+ *
+ * Functions defined with this macro will never be used to resolve
+ * symbols by the build-time linker.
+ *
+ * @param type return type of function
+ * @param name name of function
+ * @param args argument list of function
+ * @param ver version tag to assign function
+ */
+#if HAVE_SYMVER_ASM_LABEL
+# define FF_SYMVER(type, name, args, ver) \
+ type ff_##name args __asm__ (EXTERN_PREFIX #name "@" ver); \
+ type ff_##name args
+#elif HAVE_SYMVER_GNU_ASM
+# define FF_SYMVER(type, name, args, ver) \
+ __asm__ (".symver ff_" #name "," EXTERN_PREFIX #name "@" ver); \
+ type ff_##name args; \
+ type ff_##name args
+#endif