More strict compile time checks.

Author: moteus

src/lceasy.c

@@ -1593,9 +1593,11 @@ void lcurl_easy_initlib(lua_State *L, int nup){
   /* Hack. We ensure that lcurl_easy_t and lcurl_hpost_stream_t
      compatiable for readfunction
   */
-  LCURL_STATIC_ASSERT(offsetof(lcurl_easy_t, magic)     == offsetof(lcurl_hpost_stream_t, magic));
-  LCURL_STATIC_ASSERT(offsetof(lcurl_easy_t, L)         == offsetof(lcurl_hpost_stream_t, L));
-  LCURL_STATIC_ASSERT(offsetof(lcurl_easy_t, rd)        == offsetof(lcurl_hpost_stream_t, rd));
+  LCURL_ASSERT_SAME_OFFSET(lcurl_easy_t, magic,   lcurl_hpost_stream_t, magic);
+  LCURL_ASSERT_SAME_OFFSET(lcurl_easy_t, L,       lcurl_hpost_stream_t, L);
+  LCURL_ASSERT_SAME_OFFSET(lcurl_easy_t, rd,      lcurl_hpost_stream_t, rd);
+  LCURL_ASSERT_SAME_OFFSET(lcurl_easy_t, rbuffer, lcurl_hpost_stream_t, rbuffer);
+  LCURL_ASSERT_SAME_FIELD_SIZE(lcurl_easy_t, rbuffer, lcurl_hpost_stream_t, rbuffer);
 
   if(!lutil_createmetap(L, LCURL_EASY, lcurl_easy_methods, nup))
     lua_pop(L, nup);

src/lcutils.h

@@ -28,8 +28,14 @@
 #define LCURL_MAKE_VERSION(MIN, MAJ, PAT) ((MIN<<16) + (MAJ<<8) + PAT)
 #define LCURL_CURL_VER_GE(MIN, MAJ, PAT) (LIBCURL_VERSION_NUM >= LCURL_MAKE_VERSION(MIN, MAJ, PAT))
 
-//! @fixme on mingw32 (gcc 4.8.1) this does not work
-#define LCURL_STATIC_ASSERT(A) {(void)(int(*)[(A)?1:0])0;}
+//! @todo test on mingw32 (gcc 4.8.1)
+#define LCURL_CONCAT_STATIC_ASSERT_IMPL_(x, y) LCURL_CONCAT1_STATIC_ASSERT_IMPL_ (x, y)
+#define LCURL_CONCAT1_STATIC_ASSERT_IMPL_(x, y) x##y
+#define LCURL_STATIC_ASSERT(expr) typedef char LCURL_CONCAT_STATIC_ASSERT_IMPL_(static_assert_failed_at_line_, __LINE__) [(expr) ? 1 : -1]
+
+#define LCURL_ASSERT_SAME_SIZE(a, b) LCURL_STATIC_ASSERT( sizeof(a) == sizeof(b) )
+#define LCURL_ASSERT_SAME_OFFSET(a, am, b, bm) LCURL_STATIC_ASSERT( (offsetof(a,am)) == (offsetof(b,bm)) )
+#define LCURL_ASSERT_SAME_FIELD_SIZE(a, am, b, bm) LCURL_ASSERT_SAME_SIZE(((a*)0)->am, ((b*)0)->bm)
 
 typedef struct lcurl_const_tag{
   const char *name;