define LUA_ERRGCMM code for return values

2 files changed, 14 insertions, 0 deletions

diff --git a/README.md b/README.md
index d80405c..eaaf6ee 100644
--- a/README.md
+++ b/README.md
@@ -142,6 +142,7 @@ For Lua 5.1 additionally:
 
 For Lua 5.1 additionally:
 * `LUA_OK`
+* `LUA_ERRGCMM`
 * `LUA_OP*` macros for `lua_arith` and `lua_compare`
 * `lua_Unsigned`
 * `lua_absindex`
diff --git a/c-api/compat-5.3.h b/c-api/compat-5.3.h
index 3d20d21..6c76930 100644
--- a/c-api/compat-5.3.h
+++ b/c-api/compat-5.3.h
@@ -88,6 +88,19 @@ extern "C" {
 #  define LUA_OPLE 2
 #endif
 
+/* LuaJIT/Lua 5.1 does not have the updated 
+ * error codes for thread status/function returns (but some patched versions do)
+ * define it only if it's not found
+ */
+#if !defined(LUA_ERRGCMM)
+/* Use + 2 because in some versions of Lua (Lua 5.1) 
+ * LUA_ERRFILE is defined as (LUA_ERRERR+1)
+ * so we need to avoid it (LuaJIT might have something at this
+ * integer value too)
+ */
+#  define LUA_ERRGCMM (LUA_ERRERR + 2)
+#endif /* LUA_ERRGCMM define */
+
 typedef size_t lua_Unsigned;
 
 typedef struct luaL_Buffer_53 {