Change in the handling of 'L->top' when calling metamethods

Instead of updating 'L->top' in every place that may call a
metamethod, the metamethod functions themselves (luaT_trybinTM and
luaT_callorderTM) correct the top. (When calling metamethods from
the C API, however, the callers must preserve 'L->top'.)

1 files changed, 9 insertions, 3 deletions

diff --git a/ltm.c b/ltm.c
index 24739444..19233a87 100644
--- a/ltm.c
+++ b/ltm.c
@@ -147,11 +147,9 @@ static int callbinTM (lua_State *L, const TValue *p1, const TValue *p2,
 
 void luaT_trybinTM (lua_State *L, const TValue *p1, const TValue *p2,
                     StkId res, TMS event) {
+  L->top = L->ci->top;
   if (!callbinTM(L, p1, p2, res, event)) {
     switch (event) {
-      case TM_CONCAT:
-        luaG_concaterror(L, p1, p2);
-      /* call never returns, but to avoid warnings: *//* FALLTHROUGH */
       case TM_BAND: case TM_BOR: case TM_BXOR:
       case TM_SHL: case TM_SHR: case TM_BNOT: {
         if (ttisnumber(p1) && ttisnumber(p2))
@@ -167,6 +165,13 @@ void luaT_trybinTM (lua_State *L, const TValue *p1, const TValue *p2,
 }
 
 
+void luaT_tryconcatTM (lua_State *L) {
+  StkId top = L->top;
+  if (!callbinTM(L, s2v(top - 2), s2v(top - 1), top - 2, TM_CONCAT))
+    luaG_concaterror(L, s2v(top - 2), s2v(top - 1));
+}
+
+
 void luaT_trybinassocTM (lua_State *L, const TValue *p1, const TValue *p2,
                                        StkId res, int flip, TMS event) {
   if (flip)
@@ -186,6 +191,7 @@ void luaT_trybiniTM (lua_State *L, const TValue *p1, lua_Integer i2,
 
 int luaT_callorderTM (lua_State *L, const TValue *p1, const TValue *p2,
                       TMS event) {
+  L->top = L->ci->top;
   if (callbinTM(L, p1, p2, L->top, event))  /* try original event */
     return !l_isfalse(s2v(L->top));
 #if defined(LUA_COMPAT_LT_LE)