[Tarantool-patches] [PATCH luajit 4/4] Restore cur_L for specific Lua/C API use case.
Maxim Kokryashkin
max.kokryashkin at gmail.com
Thu Sep 28 20:08:49 MSK 2023
From: Mike Pall <mike>
Thanks to Peter Cawley.
(cherry-picked from commit e86990f7f24a94b0897061f25a84547fe1108bed)
Consider the following Lua C API function:
```
static int error_after_coroutine_return(lua_State *L)
{
lua_State *innerL = lua_newthread(L);
luaL_loadstring(innerL, "print('inner coro')");
lua_pcall(innerL, 0, 0, 0);
luaL_error(L, "my fancy error");
return 0;
}
```
And the following Lua script:
```
local libcur_L = require('libcur_L')
local function onesnap_f(var)
if var then
return 1
else
return 0
end
end
-- Compile function to trace with snapshot.
if jit then jit.opt.start('hotloop=1') end
onesnap_f(true)
onesnap_f(true)
local r, s = pcall(libcur_L.error_after_coroutine_return)
onesnap_f(false)
```
This is the only case when `cur_L` is not restored, according to
the analysis done in https://github.com/LuaJIT/LuaJIT/issues/1066.
This patch changes the error-catching routine, so now the patch
sets the actual cur_L there.
Now it is possible to throw errors on non-executing coroutines,
which is a violation of the Lua C API. So, even though it is now
possible, that behavior should be avoided anyway.
Maxim Kokryashkin:
* added the description for the problem
Resolves tarantool/tarantool#6323
---
src/lj_err.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/src/lj_err.c b/src/lj_err.c
index 46fb81ee..1a9a2f2b 100644
--- a/src/lj_err.c
+++ b/src/lj_err.c
@@ -174,12 +174,15 @@ static void *err_unwind(lua_State *L, void *stopcf, int errcode)
case FRAME_PCALL: /* FF pcall() frame. */
case FRAME_PCALLH: /* FF pcall() frame inside hook. */
if (errcode) {
+ global_State *g;
if (errcode == LUA_YIELD) {
frame = frame_prevd(frame);
break;
}
+ g = G(L);
+ setgcref(g->cur_L, obj2gco(L));
if (frame_typep(frame) == FRAME_PCALL)
- hook_leave(G(L));
+ hook_leave(g);
L->base = frame_prevd(frame) + 1;
L->cframe = cf;
unwindstack(L, L->base);
--
2.42.0
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