From 0adfa773b96d815cab3f17afd7bcafd3eeee7c49 Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Mon, 5 Jan 2015 11:51:39 -0200
Subject: new macro 'cast_func' adds '__extension__' (in gnu compilers) when
 converting void* to function, to avoid warnings

---
 loadlib.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

(limited to 'loadlib.c')

diff --git a/loadlib.c b/loadlib.c
index 4e1cdf80..e7201c6c 100644
--- a/loadlib.c
+++ b/loadlib.c
@@ -1,5 +1,5 @@
 /*
-** $Id: loadlib.c,v 1.122 2014/11/10 14:28:31 roberto Exp roberto $
+** $Id: loadlib.c,v 1.123 2014/11/12 13:31:51 roberto Exp roberto $
 ** Dynamic library loader for Lua
 ** See Copyright Notice in lua.h
 **
@@ -135,6 +135,18 @@ static lua_CFunction lsys_sym (lua_State *L, void *lib, const char *sym);
 
 #include <dlfcn.h>
 
+/*
+** Macro to covert pointer to void* to pointer to function. This cast
+** is undefined according to ISO C, but POSIX assumes that it must work.
+** (The '__extension__' in gnu compilers is only to avoid warnings.)
+*/
+#if defined(__GNUC__)
+#define cast_func(p) (__extension__ (lua_CFunction)(p))
+#else
+#define cast_func(p) ((lua_CFunction)(p))
+#endif
+
+
 static void lsys_unloadlib (void *lib) {
   dlclose(lib);
 }
@@ -148,7 +160,7 @@ static void *lsys_load (lua_State *L, const char *path, int seeglb) {
 
 
 static lua_CFunction lsys_sym (lua_State *L, void *lib, const char *sym) {
-  lua_CFunction f = (lua_CFunction)dlsym(lib, sym);
+  lua_CFunction f = cast_func(dlsym(lib, sym));
   if (f == NULL) lua_pushstring(L, dlerror());
   return f;
 }
-- 
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