Add ffi.NULL as a copy of ffi.C.NULL

The ffi.NULL constant is preferable to ffi.C.NULL because it can be used in
both LuaJIT and LuaFFI code. (In LuaJIT it's just nil)

2 files changed, 6 insertions, 1 deletions

diff --git a/README.md b/README.md
index b79fcdb..10f2ab3 100644
--- a/README.md
+++ b/README.md
@@ -27,7 +27,7 @@ Build
 Known Issues

 ------------

 - Comparing a ctype pointer to nil doesn't work the same as luajit. This is

-  unfixable with the current metamethod semantics. Instead use ffi.C.NULL

+  unfixable with the current metamethod semantics. Instead use ffi.NULL

 - Constant expressions can't handle non integer intermediate values (eg

   offsetof won't work because it manipulates pointers)

 - Not all metamethods work with lua 5.1 (eg char* + number). This is due to

diff --git a/ffi.c b/ffi.c
index 91f592a..4d1e140 100644
--- a/ffi.c
+++ b/ffi.c
@@ -3287,9 +3287,14 @@ static int setup_upvals(lua_State* L)
         ct.pointers = 1;
         ct.is_null = 1;
 
+        /* add ffi.C.NULL */
         push_cdata(L, 0, &ct);
         lua_setfield(L, -2, "NULL");
 
+        /* add ffi.NULL */
+        push_cdata(L, 0, &ct);
+        lua_setfield(L, 1, "NULL");
+
         memset(&ct, 0, sizeof(ct));
         ct.type = COMPLEX_DOUBLE_TYPE;
         ct.is_defined = 1;