commit 96f9643f330a4bf0f8cd1973fecdd7161ffbbf68
parent 84058b15068a382e66f4eeb4e29a2dbf1704fa8b
Author: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Wed, 11 Jul 2018 16:11:23 -0300
Bug: wrong 'nCcalls' when resuming a coroutine
The counter 'nCcalls' now includes the number of CallInfo structures
pre-allocated (so that these "potential" C calls can be made without
checking 'nCcalls'). So, when copying this value from a thread to
another, in 'lua_resume', it must be corrected to the number of
CallInfo structures in the thread being resumed.
Diffstat:
2 files changed, 24 insertions(+), 5 deletions(-)
diff --git a/ldo.c b/ldo.c
@@ -1,5 +1,5 @@
/*
-** $Id: ldo.c,v 2.201 2018/05/22 12:02:36 roberto Exp roberto $
+** $Id: ldo.c $
** Stack and Call structure of Lua
** See Copyright Notice in lua.h
*/
@@ -137,6 +137,7 @@ l_noret luaD_throw (lua_State *L, int errcode) {
int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
unsigned short oldnCcalls = L->nCcalls - L->nci;
struct lua_longjmp lj;
+ lua_assert(L->nCcalls >= L->nci);
lj.status = LUA_OK;
lj.previous = L->errorJmp; /* chain new error handler */
L->errorJmp = &lj;
@@ -653,7 +654,10 @@ LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs,
}
else if (L->status != LUA_YIELD)
return resume_error(L, "cannot resume dead coroutine", nargs);
- L->nCcalls = (from) ? from->nCcalls + 1 : 1;
+ if (from == NULL)
+ L->nCcalls = 1;
+ else /* correct 'nCcalls' for this thread */
+ L->nCcalls = from->nCcalls - from->nci + L->nci + 1;
if (L->nCcalls >= LUAI_MAXCCALLS)
return resume_error(L, "C stack overflow", nargs);
luai_userstateresume(L, nargs);
@@ -677,7 +681,6 @@ LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs,
*nresults = (status == LUA_YIELD) ? L->ci->u2.nyield
: cast_int(L->top - (L->ci->func + 1));
L->nny = oldnny; /* restore 'nny' */
- L->nCcalls--;
lua_unlock(L);
return status;
}
diff --git a/lstate.h b/lstate.h
@@ -1,5 +1,5 @@
/*
-** $Id: lstate.h,v 2.159 2018/06/15 19:31:22 roberto Exp roberto $
+** $Id: lstate.h $
** Global State
** See Copyright Notice in lua.h
*/
@@ -49,6 +49,22 @@
*/
+/*
+
+** About 'nCcalls': each thread in Lua (a lua_State) keeps a count of
+** how many "C calls" it has in the C stack, to avoid C-stack overflow.
+** This count is very rough approximation; it considers only recursive
+** functions inside the interpreter, as non-recursive calls can be
+** considered using a fixed (although unknown) amount of stack space.
+**
+** The proper count also includes the number of CallInfo structures
+** allocated by Lua, as a kind of "potential" calls. So, when Lua
+** calls a function (and "consumes" one CallInfo), it needs neither to
+** increment nor to check 'nCcalls', as its use of C stack is already
+** accounted for.
+
+*/
+
struct lua_longjmp; /* defined in ldo.c */
@@ -212,7 +228,7 @@ struct lua_State {
int basehookcount;
int hookcount;
unsigned short nny; /* number of non-yieldable calls in stack */
- unsigned short nCcalls; /* number of nested C calls */
+ unsigned short nCcalls; /* number of nested C calls + 'nny' */
l_signalT hookmask;
lu_byte allowhook;
};