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Counter for length of chains of __call metamethods

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This counter will allow (in a later commit) error messages to correct
argument numbers in functions called through __call metamethods.
This commit is contained in:
Roberto Ierusalimschy
2024-11-16 12:00:28 -03:00
parent f12ce4029d
commit b117bdb344
4 changed files with 68 additions and 28 deletions
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41
ldo.c
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@@ -464,21 +464,26 @@ static void rethook (lua_State *L, CallInfo *ci, int nres) {
/*
** Check whether 'func' has a '__call' metafield. If so, put it in the
** stack, below original 'func', so that 'luaD_precall' can call it. Raise
** an error if there is no '__call' metafield.
** stack, below original 'func', so that 'luaD_precall' can call it.
** Raise an error if there is no '__call' metafield.
** Bits CIST_CCMT in status count how many _call metamethods were
** invoked and how many corresponding extra arguments were pushed.
** (This count will be saved in the 'callstatus' of the call).
** Raise an error if this counter overflows.
*/
static StkId tryfuncTM (lua_State *L, StkId func) {
static unsigned tryfuncTM (lua_State *L, StkId func, unsigned status) {
const TValue *tm;
StkId p;
checkstackp(L, 1, func); /* space for metamethod */
tm = luaT_gettmbyobj(L, s2v(func), TM_CALL); /* (after previous GC) */
if (l_unlikely(ttisnil(tm)))
luaG_callerror(L, s2v(func)); /* nothing to call */
tm = luaT_gettmbyobj(L, s2v(func), TM_CALL);
if (l_unlikely(ttisnil(tm))) /* no metamethod? */
luaG_callerror(L, s2v(func));
for (p = L->top.p; p > func; p--) /* open space for metamethod */
setobjs2s(L, p, p-1);
L->top.p++; /* stack space pre-allocated by the caller */
setobj2s(L, func, tm); /* metamethod is the new function to be called */
return func;
if ((status & MAX_CCMT) == MAX_CCMT) /* is counter full? */
luaG_runerror(L, "'__call' chain too long");
return status + (1u << CIST_CCMT); /* increment counter */
}
@@ -564,11 +569,17 @@ void luaD_poscall (lua_State *L, CallInfo *ci, int nres) {
#define next_ci(L) (L->ci->next ? L->ci->next : luaE_extendCI(L))
/*
** Allocate and initialize CallInfo structure. At this point, the
** only valid fields in the call status are number of results,
** CIST_C (if it's a C function), and number of extra arguments.
** (All these bit-fields fit in 16-bit values.)
*/
l_sinline CallInfo *prepCallInfo (lua_State *L, StkId func, unsigned status,
StkId top) {
CallInfo *ci = L->ci = next_ci(L); /* new frame */
ci->func.p = func;
lua_assert((status & ~(CIST_NRESULTS | CIST_C)) == 0);
lua_assert((status & ~(CIST_NRESULTS | CIST_C | MAX_CCMT)) == 0);
ci->callstatus = status;
ci->top.p = top;
return ci;
@@ -607,12 +618,13 @@ l_sinline int precallC (lua_State *L, StkId func, unsigned status,
*/
int luaD_pretailcall (lua_State *L, CallInfo *ci, StkId func,
int narg1, int delta) {
unsigned status = LUA_MULTRET + 1;
retry:
switch (ttypetag(s2v(func))) {
case LUA_VCCL: /* C closure */
return precallC(L, func, LUA_MULTRET + 1, clCvalue(s2v(func))->f);
return precallC(L, func, status, clCvalue(s2v(func))->f);
case LUA_VLCF: /* light C function */
return precallC(L, func, LUA_MULTRET + 1, fvalue(s2v(func)));
return precallC(L, func, status, fvalue(s2v(func)));
case LUA_VLCL: { /* Lua function */
Proto *p = clLvalue(s2v(func))->p;
int fsize = p->maxstacksize; /* frame size */
@@ -633,8 +645,8 @@ int luaD_pretailcall (lua_State *L, CallInfo *ci, StkId func,
return -1;
}
default: { /* not a function */
func = tryfuncTM(L, func); /* try to get '__call' metamethod */
/* return luaD_pretailcall(L, ci, func, narg1 + 1, delta); */
checkstackp(L, 1, func); /* space for metamethod */
status = tryfuncTM(L, func, status); /* try '__call' metamethod */
narg1++;
goto retry; /* try again */
}
@@ -676,7 +688,8 @@ CallInfo *luaD_precall (lua_State *L, StkId func, int nresults) {
return ci;
}
default: { /* not a function */
func = tryfuncTM(L, func); /* try to get '__call' metamethod */
checkstackp(L, 1, func); /* space for metamethod */
status = tryfuncTM(L, func, status); /* try '__call' metamethod */
goto retry; /* try again with metamethod */
}
}