Merge pull request #636 from visitorckw/preserve-none

Adopt preserve_none attribute for MUST_TAIL optimization

Author: jserv

src/common.h

@@ -191,7 +191,11 @@ static inline uint8_t ilog2(uint32_t x)
  * even without optimizations enabled.
  */
 #if defined(__has_attribute) && __has_attribute(musttail)
+#if __has_attribute(preserve_none)
+#define MUST_TAIL __attribute__((musttail)) __attribute__((preserve_none))
+#else
 #define MUST_TAIL __attribute__((musttail))
+#endif
 #else
 #define MUST_TAIL
 #endif