Fix debug information about finalizers

The flag CIST_FIN does not mark a finalizer, but the function that was
running when the finalizer was called. (So, the function did not call
the finalizer, but it looks that way in the stack.)

ldebug.c

@@ -34,7 +34,7 @@
 #define noLuaClosure(f)		((f) == NULL || (f)->c.tt == LUA_VCCL)
 
 
-static const char *funcnamefromcode (lua_State *L, CallInfo *ci,
+static const char *funcnamefromcall (lua_State *L, CallInfo *ci,
                                                    const char **name);
 
 
@@ -317,15 +317,9 @@ static void collectvalidlines (lua_State *L, Closure *f) {
 
 
 static const char *getfuncname (lua_State *L, CallInfo *ci, const char **name) {
-  if (ci == NULL)  /* no 'ci'? */
-    return NULL;  /* no info */
-  else if (ci->callstatus & CIST_FIN) {  /* is this a finalizer? */
-    *name = "__gc";
-    return "metamethod";  /* report it as such */
-  }
-  /* calling function is a known Lua function? */
-  else if (!(ci->callstatus & CIST_TAIL) && isLua(ci->previous))
-    return funcnamefromcode(L, ci->previous, name);
+  /* calling function is a known function? */
+  if (ci != NULL && !(ci->callstatus & CIST_TAIL))
+    return funcnamefromcall(L, ci->previous, name);
   else return NULL;  /* no way to find a name */
 }
 
@@ -597,16 +591,10 @@ static const char *getobjname (const Proto *p, int lastpc, int reg,
 ** Returns what the name is (e.g., "for iterator", "method",
 ** "metamethod") and sets '*name' to point to the name.
 */
-static const char *funcnamefromcode (lua_State *L, CallInfo *ci,
-                                     const char **name) {
+static const char *funcnamefromcode (lua_State *L, const Proto *p,
+                                     int pc, const char **name) {
   TMS tm = (TMS)0;  /* (initial value avoids warnings) */
-  const Proto *p = ci_func(ci)->p;  /* calling function */
-  int pc = currentpc(ci);  /* calling instruction index */
   Instruction i = p->code[pc];  /* calling instruction */
-  if (ci->callstatus & CIST_HOOKED) {  /* was it called inside a hook? */
-    *name = "?";
-    return "hook";
-  }
   switch (GET_OPCODE(i)) {
     case OP_CALL:
     case OP_TAILCALL:
@@ -643,6 +631,26 @@ static const char *funcnamefromcode (lua_State *L, CallInfo *ci,
   return "metamethod";
 }
 
+
+/*
+** Try to find a name for a function based on how it was called.
+*/
+static const char *funcnamefromcall (lua_State *L, CallInfo *ci,
+                                                   const char **name) {
+  if (ci->callstatus & CIST_HOOKED) {  /* was it called inside a hook? */
+    *name = "?";
+    return "hook";
+  }
+  else if (ci->callstatus & CIST_FIN) {  /* was it called as a finalizer? */
+    *name = "__gc";
+    return "metamethod";  /* report it as such */
+  }
+  else if (isLua(ci))
+    return funcnamefromcode(L, ci_func(ci)->p, currentpc(ci), name);
+  else
+    return NULL;
+}
+
 /* }====================================================== */
 
 
@@ -728,14 +736,14 @@ l_noret luaG_typeerror (lua_State *L, const TValue *o, const char *op) {
 
 
 /*
-** Raise an error for calling a non-callable object. Try to find
-** a name for the object based on the code that made the call
-** ('funcnamefromcode'); if it cannot get a name there, try 'varinfo'.
+** Raise an error for calling a non-callable object. Try to find a name
+** for the object based on how it was called ('funcnamefromcall'); if it
+** cannot get a name there, try 'varinfo'.
 */
 l_noret luaG_callerror (lua_State *L, const TValue *o) {
   CallInfo *ci = L->ci;
   const char *name = NULL;  /* to avoid warnings */
-  const char *kind = (isLua(ci)) ? funcnamefromcode(L, ci, &name) : NULL;
+  const char *kind = funcnamefromcall(L, ci, &name);
   const char *extra = kind ? formatvarinfo(L, kind, name) : varinfo(L, o);
   typeerror(L, o, "call", extra);
 }

lgc.c

@@ -917,7 +917,7 @@ static void GCTM (lua_State *L) {
     L->allowhook = oldah;  /* restore hooks */
     g->gcstp = oldgcstp;  /* restore state */
     if (l_unlikely(status != LUA_OK)) {  /* error while running __gc? */
-      luaE_warnerror(L, "__gc metamethod");
+      luaE_warnerror(L, "__gc");
       L->top--;  /* pops error object */
     }
   }

lstate.h

@@ -209,7 +209,7 @@ typedef struct CallInfo {
 #define CIST_YPCALL	(1<<4)	/* doing a yieldable protected call */
 #define CIST_TAIL	(1<<5)	/* call was tail called */
 #define CIST_HOOKYIELD	(1<<6)	/* last hook called yielded */
-#define CIST_FIN	(1<<7)	/* call is running a finalizer */
+#define CIST_FIN	(1<<7)	/* function "called" a finalizer */
 #define CIST_TRAN	(1<<8)	/* 'ci' has transfer information */
 #define CIST_CLSRET	(1<<9)  /* function is closing tbc variables */
 /* Bits 10-12 are used for CIST_RECST (see below) */

testes/db.lua

@@ -887,7 +887,7 @@ do   -- testing debug info for finalizers
 
   -- create a piece of garbage with a finalizer
   setmetatable({}, {__gc = function ()
-    local t = debug.getinfo(2)   -- get callee information
+    local t = debug.getinfo(1)   -- get function information
     assert(t.namewhat == "metamethod")
     name = t.name
   end})

testes/gc.lua

@@ -371,7 +371,7 @@ if T then
 
   warn("@on"); warn("@store")
   collectgarbage()
-  assert(string.find(_WARN, "error in __gc metamethod"))
+  assert(string.find(_WARN, "error in __gc"))
   assert(string.match(_WARN, "@(.-)@") == "expected"); _WARN = false
   for i = 8, 10 do assert(s[i]) end