From b117bdb3448778d9e7f9a0302791e8ac3bb97ddd Mon Sep 17 00:00:00 2001 From: Roberto Ierusalimschy Date: Sat, 16 Nov 2024 12:00:28 -0300 Subject: Counter for length of chains of __call metamethods This counter will allow (in a later commit) error messages to correct argument numbers in functions called through __call metamethods. --- ldo.c | 41 +++++++++++++++++++++++++++-------------- 1 file changed, 27 insertions(+), 14 deletions(-) (limited to 'ldo.c') diff --git a/ldo.c b/ldo.c index 72a1e306..cb7e5aef 100644 --- a/ldo.c +++ b/ldo.c @@ -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 */ } } -- cgit v1.2.3-55-g6feb