n^-m gives float result (instead of error)

lcode.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lcode.c,v 2.86 2014/04/01 14:39:55 roberto Exp roberto $
+** $Id: lcode.c,v 2.87 2014/04/02 16:44:42 roberto Exp roberto $
 ** Code generator for Lua
 ** See Copyright Notice in lua.h
 */
@@ -768,8 +768,6 @@ static int validop (int op, TValue *v1, TValue *v2) {
       return (tointeger(v1, &i) && tointeger(v2, &i));
     case LUA_OPMOD:  /* integer module by 0 */
       return !(ttisinteger(v1) && ttisinteger(v2) && ivalue(v2) == 0);
-    case LUA_OPPOW:  /* negative integer exponentiation */
-      return !(ttisinteger(v1) && ttisinteger(v2) && ivalue(v2) < 0);
     default: return 1;  /* everything else is valid */
   }
 }

lobject.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lobject.c,v 2.79 2014/04/15 14:28:20 roberto Exp roberto $
+** $Id: lobject.c,v 2.80 2014/04/15 16:32:49 roberto Exp roberto $
 ** Some generic functions over Lua objects
 ** See Copyright Notice in lua.h
 */
@@ -77,7 +77,7 @@ static lua_Integer intarith (lua_State *L, int op, lua_Integer v1,
     case LUA_OPSUB:return intop(-, v1, v2);
     case LUA_OPMUL:return intop(*, v1, v2);
     case LUA_OPMOD: return luaV_mod(L, v1, v2);
-    case LUA_OPPOW: return luaV_pow(L, v1, v2);
+    case LUA_OPPOW: return luaV_pow(v1, v2);
     case LUA_OPIDIV: return luaV_div(L, v1, v2);
     case LUA_OPBAND: return intop(&, v1, v2);
     case LUA_OPBOR: return intop(|, v1, v2);
@@ -133,7 +133,8 @@ void luaO_arith (lua_State *L, int op, const TValue *p1, const TValue *p2,
     }
     default: {  /* other operations */
       lua_Number n1; lua_Number n2;
-      if (ttisinteger(p1) && ttisinteger(p2)) {
+      if (ttisinteger(p1) && ttisinteger(p2) &&
+          (op != LUA_OPPOW || ivalue(p2) >= 0)) {
         setivalue(res, intarith(L, op, ivalue(p1), ivalue(p2)));
         return;
       }

lvm.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lvm.c,v 2.197 2014/04/15 14:28:20 roberto Exp roberto $
+** $Id: lvm.c,v 2.198 2014/04/15 16:32:49 roberto Exp roberto $
 ** Lua virtual machine
 ** See Copyright Notice in lua.h
 */
@@ -374,12 +374,10 @@ lua_Integer luaV_mod (lua_State *L, lua_Integer x, lua_Integer y) {
 }
 
 
-lua_Integer luaV_pow (lua_State *L, lua_Integer x, lua_Integer y) {
-  if (y <= 0) {  /* special cases: 0 or negative exponent */
-    if (y < 0)
-      luaG_runerror(L, "integer exponentiation with negative exponent");
+lua_Integer luaV_pow (lua_Integer x, lua_Integer y) {
+  lua_assert(y >= 0);
+  if (y == 0)
     return 1;  /* x^0 == 1 */
-  }
   else {
     lua_Integer r = 1;
     for (; y > 1; y >>= 1) {
@@ -765,9 +763,10 @@ void luaV_execute (lua_State *L) {
         TValue *rb = RKB(i);
         TValue *rc = RKC(i);
         lua_Number nb; lua_Number nc;
-        if (ttisinteger(rb) && ttisinteger(rc)) {
-          lua_Integer ib = ivalue(rb); lua_Integer ic = ivalue(rc);
-          setivalue(ra, luaV_pow(L, ib, ic));
+        lua_Integer ic;
+        if (ttisinteger(rb) && ttisinteger(rc) && (ic = ivalue(rc)) >= 0) {
+          lua_Integer ib = ivalue(rb);
+          setivalue(ra, luaV_pow(ib, ic));
         }
         else if (tonumber(rb, &nb) && tonumber(rc, &nc)) {
           setnvalue(ra, luai_numpow(L, nb, nc));

lvm.h

@@ -1,5 +1,5 @@
 /*
-** $Id: lvm.h,v 2.27 2014/04/15 14:28:20 roberto Exp roberto $
+** $Id: lvm.h,v 2.28 2014/04/15 16:32:49 roberto Exp roberto $
 ** Lua virtual machine
 ** See Copyright Notice in lua.h
 */
@@ -40,7 +40,7 @@ LUAI_FUNC void luaV_execute (lua_State *L);
 LUAI_FUNC void luaV_concat (lua_State *L, int total);
 LUAI_FUNC lua_Integer luaV_div (lua_State *L, lua_Integer x, lua_Integer y);
 LUAI_FUNC lua_Integer luaV_mod (lua_State *L, lua_Integer x, lua_Integer y);
-LUAI_FUNC lua_Integer luaV_pow (lua_State *L, lua_Integer x, lua_Integer y);
+LUAI_FUNC lua_Integer luaV_pow (lua_Integer x, lua_Integer y);
 LUAI_FUNC lua_Integer luaV_shiftl (lua_Integer x, lua_Integer y);
 LUAI_FUNC void luaV_objlen (lua_State *L, StkId ra, const TValue *rb);