Re: lua_getlocal crashes after yield from a debug hook

I try to fix it, but maybe there is a better solution :)

diff --git a/src/ldebug.c b/src/ldebug.c

index 6986bf0..acddc3b 100644

--- a/src/ldebug.c

+++ b/src/ldebug.c

@@ -85,8 +85,16 @@ LUA_API int lua_getstack (lua_State *L, int level, lua_Debug *ar) {

CallInfo *ci;

if (level < 0) return 0; /* invalid (negative) level */

lua_lock(L);

- for (ci = L->ci; level > 0 && ci != &L->base_ci; ci = ci->previous)

- level--;

+ if (level == 0 && L->status == LUA_YIELD && isLua(L->ci)) {

+ ci = &(L->temp_ci);

+ *ci = *(L->ci);

+ ci->func = restorestack(L, ci->extra);

+ status = 1;

+ ar->i_ci = ci;

+ } else {

+ for (ci = L->ci; level > 0 && ci != &L->base_ci; ci = ci->previous)

+ level--;

+ }

if (level == 0 && ci != &L->base_ci) { /* level found? */

status = 1;

ar->i_ci = ci;

@@ -130,7 +138,7 @@ static const char *findlocal (lua_State *L, CallInfo *ci, int n,

else

base = ci->func + 1;

if (name == NULL) { /* no 'standard' name? */

- StkId limit = (ci == L->ci) ? L->top : ci->next->func;

+ StkId limit = (ci == L->ci || ci == &(L->temp_ci)) ? L->top : ci->next->func;

if (limit - base >= n && n > 0) /* is 'n' inside 'ci' stack? */

name = "(*temporary)"; /* generic name for any valid slot */

else

diff --git a/src/lstate.h b/src/lstate.h

index 81e12c4..c89b910 100644

--- a/src/lstate.h

+++ b/src/lstate.h

@@ -160,6 +160,7 @@ struct lua_State {

struct lua_State *twups; /* list of threads with open upvalues */

struct lua_longjmp *errorJmp; /* current error recover point */

CallInfo base_ci; /* CallInfo for first level (C calling Lua) */

+ CallInfo temp_ci; /* CallInfo for yield from hook (debug api use) */

lua_Hook hook;

ptrdiff_t errfunc; /* current error handling function (stack index) */

int stacksize;

2015-02-11 1:01 GMT+08:00 云风 <cloudwu@gmail.com>:

If I call lua_yield(L,0) from a lua_Hook function , and then call lua_getlocal on this yielded thread, it crashes. (Both on lua 5.2 and lua 5.3)

-----
local hook = require "hook"

local co = coroutine.create(function(a)
return a
end)
hook(co)
coroutine.resume(co, 1)
debug.getlocal(co, 0, 1) -- crashes
------
#include <lua.h>
#include <lauxlib.h>

static void
lhook(lua_State *L, lua_Debug *ar) {
lua_yield(L,0);
}

static int
hook(lua_State *L) {
lua_State *L1 = lua_tothread(L, 1);
lua_sethook(L1, lhook, LUA_MASKLINE, 0);
return 0;
}

int
luaopen_hook(lua_State *L) {
lua_pushcfunction(L, hook);
return 1;
}
---------

I guess the reason is : when yield from a hook, the top function in the yielded thread is a lua function, but the L->ci->func is not a valid lua function object. so lua_getlocal (and other debug api) can't work.

--
http://blog.codingnow.com

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