Avoid using addresses of static variables as unique keys

The addresses of static variables may be different for different
instances of Lua, making these instances incompatible if they use
these addresses as unique keys in the registry (or other tables).

1 files changed, 8 insertions, 10 deletions

diff --git a/ldblib.c b/ldblib.c
index 513a13cb..64158395 100644
--- a/ldblib.c
+++ b/ldblib.c
@@ -21,10 +21,10 @@
 
 
 /*
-** The hook table at registry[&HOOKKEY] maps threads to their current
-** hook function. (We only need the unique address of 'HOOKKEY'.)
+** The hook table at registry[HOOKKEY] maps threads to their current
+** hook function.
 */
-static const int HOOKKEY = 0;
+static const char* HOOKKEY = "_HOOKKEY";
 
 
 /*
@@ -314,7 +314,7 @@ static int db_upvaluejoin (lua_State *L) {
 static void hookf (lua_State *L, lua_Debug *ar) {
   static const char *const hooknames[] =
     {"call", "return", "line", "count", "tail call"};
-  lua_rawgetp(L, LUA_REGISTRYINDEX, &HOOKKEY);
+  lua_getfield(L, LUA_REGISTRYINDEX, HOOKKEY);
   lua_pushthread(L);
   if (lua_rawget(L, -2) == LUA_TFUNCTION) {  /* is there a hook function? */
     lua_pushstring(L, hooknames[(int)ar->event]);  /* push event name */
@@ -367,14 +367,12 @@ static int db_sethook (lua_State *L) {
     count = (int)luaL_optinteger(L, arg + 3, 0);
     func = hookf; mask = makemask(smask, count);
   }
-  if (lua_rawgetp(L, LUA_REGISTRYINDEX, &HOOKKEY) == LUA_TNIL) {
-    lua_createtable(L, 0, 2);  /* create a hook table */
-    lua_pushvalue(L, -1);
-    lua_rawsetp(L, LUA_REGISTRYINDEX, &HOOKKEY);  /* set it in position */
+  if (!luaL_getsubtable(L, LUA_REGISTRYINDEX, HOOKKEY)) {
+    /* table just created; initialize it */
     lua_pushstring(L, "k");
     lua_setfield(L, -2, "__mode");  /** hooktable.__mode = "k" */
     lua_pushvalue(L, -1);
-    lua_setmetatable(L, -2);  /* setmetatable(hooktable) = hooktable */
+    lua_setmetatable(L, -2);  /* metatable(hooktable) = hooktable */
   }
   checkstack(L, L1, 1);
   lua_pushthread(L1); lua_xmove(L1, L, 1);  /* key (thread) */
@@ -396,7 +394,7 @@ static int db_gethook (lua_State *L) {
   else if (hook != hookf)  /* external hook? */
     lua_pushliteral(L, "external hook");
   else {  /* hook table must exist */
-    lua_rawgetp(L, LUA_REGISTRYINDEX, &HOOKKEY);
+    lua_getfield(L, LUA_REGISTRYINDEX, HOOKKEY);
     checkstack(L, L1, 1);
     lua_pushthread(L1); lua_xmove(L1, L, 1);
     lua_rawget(L, -2);   /* 1st result = hooktable[L1] */