Bug: finalizer calling exit can corrupt finalization order
'os.exit' can call lua_close again, separating new finalizers
created after all previous finalizers were already separated.
diff --git a/lgc.c b/lgc.c
index d3f5b5b..42a73d8 100644
--- a/lgc.c
+++ b/lgc.c
@@ -907,7 +907,7 @@
int status;
lu_byte oldah = L->allowhook;
int oldgcstp = g->gcstp;
- g->gcstp = GCSTPGC; /* avoid GC steps */
+ g->gcstp |= GCSTPGC; /* avoid GC steps */
L->allowhook = 0; /* stop debug hooks during GC metamethod */
setobj2s(L, L->top++, tm); /* push finalizer... */
setobj2s(L, L->top++, &v); /* ... and its argument */
@@ -1011,7 +1011,8 @@
void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
global_State *g = G(L);
if (tofinalize(o) || /* obj. is already marked... */
- gfasttm(g, mt, TM_GC) == NULL) /* or has no finalizer? */
+ gfasttm(g, mt, TM_GC) == NULL || /* or has no finalizer... */
+ (g->gcstp & GCSTPCLS)) /* or closing state? */
return; /* nothing to be done */
else { /* move 'o' to 'finobj' list */
GCObject **p;
@@ -1502,14 +1503,13 @@
*/
void luaC_freeallobjects (lua_State *L) {
global_State *g = G(L);
- g->gcstp = GCSTPGC;
+ g->gcstp = GCSTPCLS; /* no extra finalizers after here */
luaC_changemode(L, KGC_INC);
separatetobefnz(g, 1); /* separate all objects with finalizers */
lua_assert(g->finobj == NULL);
- g->gcstp = 0;
callallpendingfinalizers(L);
deletelist(L, g->allgc, obj2gco(g->mainthread));
- deletelist(L, g->finobj, NULL);
+ lua_assert(g->finobj == NULL); /* no new finalizers */
deletelist(L, g->fixedgc, NULL); /* collect fixed objects */
lua_assert(g->strt.nuse == 0);
}
diff --git a/lgc.h b/lgc.h
index 024a432..4a12563 100644
--- a/lgc.h
+++ b/lgc.h
@@ -154,6 +154,7 @@
*/
#define GCSTPUSR 1 /* bit true when GC stopped by user */
#define GCSTPGC 2 /* bit true when GC stopped by itself */
+#define GCSTPCLS 4 /* bit true when closing Lua state */
#define gcrunning(g) ((g)->gcstp == 0)
diff --git a/testes/main.lua b/testes/main.lua
index 52c7795..9def638 100644
--- a/testes/main.lua
+++ b/testes/main.lua
@@ -261,6 +261,34 @@
RUN('lua -W %s 2> %s', prog, out)
checkprogout("ZYX)\nXYZ)\n")
+-- bug since 5.2: finalizer called when closing a state could
+-- subvert finalization order
+prepfile[[
+-- should be called last
+print("creating 1")
+setmetatable({}, {__gc = function () print(1) end})
+
+print("creating 2")
+setmetatable({}, {__gc = function ()
+ print("2")
+ print("creating 3")
+ -- this finalizer should not be called, as object will be
+ -- created after 'lua_close' has been called
+ setmetatable({}, {__gc = function () print(3) end})
+ print(collectgarbage()) -- cannot call collector here
+ os.exit(0, true)
+end})
+]]
+RUN('lua -W %s > %s', prog, out)
+checkout[[
+creating 1
+creating 2
+2
+creating 3
+nil
+1
+]]
+
-- test many arguments
prepfile[[print(({...})[30])]]
