ldblib.c

@@ -190,6 +190,31 @@ static int db_getinfo (lua_State *L) {
 }
 
 
+static int db_getconstant (lua_State *L) {
+  int arg;
+  lua_State *L1 = getthread(L, &arg);
+  lua_Debug ar;
+  int nvar = (int)luaL_checkinteger(L, arg + 2);  /* local-variable index */
+  if (lua_isfunction(L, arg + 1)) {  /* function argument? */
+    lua_pushvalue(L, arg + 1);  /* push function */
+    return lua_getconstant(L, NULL, nvar);
+  }
+  else {  /* stack-level argument */
+    int level = (int)luaL_checkinteger(L, arg + 1);
+    if (!lua_getstack(L1, level, &ar))  /* out of range? */
+      return luaL_argerror(L, arg+1, "level out of range");
+    checkstack(L, L1, 1);
+    if (lua_getconstant(L1, &ar, nvar)) {
+      lua_xmove(L1, L, 1);  /* move value */
+      return 1;
+    }
+    else {
+      return 0;
+    }
+  }
+}
+
+
 static int db_getlocal (lua_State *L) {
   int arg;
   lua_State *L1 = getthread(L, &arg);
@@ -433,6 +458,7 @@ static const luaL_Reg dblib[] = {
   {"getuservalue", db_getuservalue},
   {"gethook", db_gethook},
   {"getinfo", db_getinfo},
+  {"getconstant", db_getconstant},
   {"getlocal", db_getlocal},
   {"getregistry", db_getregistry},
   {"getmetatable", db_getmetatable},

ldebug.c

@@ -130,6 +130,31 @@ static const char *upvalname (Proto *p, int uv) {
 }
 
 
+LUA_API int lua_getconstant (lua_State *L, const lua_Debug *ar, int n) {
+  int ret = 0;
+  Proto *p = NULL;
+  lua_lock(L);
+  if (ar == NULL) {
+    if (isLfunction(L->top - 1))
+      p = clLvalue(L->top - 1)->p;
+  }
+  else {
+    StkId func = ar->i_ci->func;
+    if (ttisclosure(func))
+      p = clvalue(func)->l.p;
+  }
+  if (p && n > 0 && n <= p->sizek) {
+    TValue *v;
+    v = &p->k[n-1];
+    setobj2s(L, L->top, v);
+    api_incr_top(L);
+    ret = 1;
+  }
+  lua_unlock(L);
+  return ret;
+}
+
+
 static const char *findvararg (CallInfo *ci, int n, StkId *pos) {
   int nparams = clLvalue(ci->func)->p->numparams;
   if (n >= cast_int(ci->u.l.base - ci->func) - nparams)

lua.h

@@ -423,6 +423,7 @@ typedef void (*lua_Hook) (lua_State *L, lua_Debug *ar);
 
 LUA_API int (lua_getstack) (lua_State *L, int level, lua_Debug *ar);
 LUA_API int (lua_getinfo) (lua_State *L, const char *what, lua_Debug *ar);
+LUA_API int (lua_getconstant) (lua_State *L, const lua_Debug *ar, int n);
 LUA_API const char *(lua_getlocal) (lua_State *L, const lua_Debug *ar, int n);
 LUA_API const char *(lua_setlocal) (lua_State *L, const lua_Debug *ar, int n);
 LUA_API const char *(lua_getupvalue) (lua_State *L, int funcindex, int n);