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.
author: Roberto Ierusalimschy <roberto@inf.puc-rio.br> 2024-11-16 12:00:28 -0300
committer: Roberto Ierusalimschy <roberto@inf.puc-rio.br> 2024-11-16 12:00:28 -0300
commit: b117bdb3448778d9e7f9a0302791e8ac3bb97ddd (patch)
tree: cf83da22ab3ea7fae6bb2602c790f1a0ca9533c9
parent: f12ce4029dfbce7b89ec136e6b7ba5f6bca039da (diff)
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lua-b117bdb3448778d9e7f9a0302791e8ac3bb97ddd.zip
4 files changed, 68 insertions, 28 deletions
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
+** stack, below original 'func', so that 'luaD_precall' can call it.
-** an error if there is no '__call' metafield.
+** 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);
-  tm = luaT_gettmbyobj(L, s2v(func), TM_CALL);  /* (after previous GC) */
+  if (l_unlikely(ttisnil(tm)))  /* no metamethod? */
-  if (l_unlikely(ttisnil(tm)))
+    luaG_callerror(L, s2v(func));
-    luaG_callerror(L, s2v(func));  /* nothing to call */
  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 */
+      checkstackp(L, 1, func);  /* space for metamethod */
-      /* return luaD_pretailcall(L, ci, func, narg1 + 1, delta); */
+      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 */
    }
  }
diff --git a/lstate.h b/lstate.h
index ab567213..1c81b6ed 100644
--- a/lstate.h
+++ b/lstate.h
@@ -221,16 +221,24 @@ struct CallInfo {
 */
 /* bits 0-7 are the expected number of results from this function + 1 */
 #define CIST_NRESULTS   0xffu
-/* Bits 8-10 are used for CIST_RECST (see below) */
-#define CIST_RECST      8  /* the offset, not the mask */
+/* bits 8-11 count call metamethods (and their extra arguments) */
-/* original value of 'allowhook' */
+#define CIST_CCMT       8  /* the offset, not the mask */
-#define CIST_OAH        (cast(l_uint32, 1) << 11)
+#define MAX_CCMT        (0xfu << CIST_CCMT)
-/* call is running a C function */
-#define CIST_C          (CIST_OAH << 1)
+/* Bits 12-14 are used for CIST_RECST (see below) */
+#define CIST_RECST      12  /* the offset, not the mask */
+/* call is running a C function (still in first 16 bits) */
+#define CIST_C          (1u << (CIST_RECST + 3))
 /* call is on a fresh "luaV_execute" frame */
-#define CIST_FRESH      (CIST_C << 1)
+#define CIST_FRESH      cast(l_uint32, CIST_C << 1)
+/* function is closing tbc variables */
+#define CIST_CLSRET     (CIST_FRESH << 1)
+/* original value of 'allowhook' */
+#define CIST_OAH        (CIST_CLSRET << 1)
 /* call is running a debug hook */
-#define CIST_HOOKED     (CIST_FRESH << 1)
+#define CIST_HOOKED     (CIST_OAH << 1)
 /* doing a yieldable protected call */
 #define CIST_YPCALL     (CIST_HOOKED << 1)
 /* call was tail called */
@@ -239,11 +247,9 @@ struct CallInfo {
 #define CIST_HOOKYIELD  (CIST_TAIL << 1)
 /* function "called" a finalizer */
 #define CIST_FIN        (CIST_HOOKYIELD << 1)
- /* function is closing tbc variables */
-#define CIST_CLSRET     (CIST_FIN << 1)
 #if defined(LUA_COMPAT_LT_LE)
 /* using __lt for __le */
-#define CIST_LEQ        (CIST_CLSRET << 1)
+#define CIST_LEQ        (CIST_FIN << 1)
 #endif
diff --git a/manual/manual.of b/manual/manual.of
index f0b17b4c..ce42ff51 100644
--- a/manual/manual.of
+++ b/manual/manual.of
@@ -9392,6 +9392,10 @@ If you need to change it,
 declare a local variable with the same name in the loop body.
 }
+@item{
+A chain of @id{__call} metamethods can have at most 15 objects.
+}
 }
 }
diff --git a/testes/calls.lua b/testes/calls.lua
index 409a275d..12312d60 100644
--- a/testes/calls.lua
+++ b/testes/calls.lua
@@ -178,7 +178,7 @@ do   -- tail calls x chain of __call
  end
  -- build a chain of __call metamethods ending in function 'foo'
-  for i = 1, 100 do
+  for i = 1, 15 do
    foo = setmetatable({}, {__call = foo})
  end
@@ -190,8 +190,8 @@ end
 print('+')
-do  -- testing chains of '__call'
+do   print"testing chains of '__call'"
-  local N = 20
+  local N = 15
  local u = table.pack
  for i = 1, N do
    u = setmetatable({i}, {__call = u})
@@ -207,6 +207,23 @@ do  -- testing chains of '__call'
 end
+do    -- testing chains too long
+  local a = {}
+  for i = 1, 16 do    -- one too many
+    a = setmetatable({}, {__call = a})
+  end
+  local status, msg = pcall(a)
+  assert(not status and string.find(msg, "too long"))
+  setmetatable(a, {__call = a})   -- infinite chain
+  local status, msg = pcall(a)
+  assert(not status and string.find(msg, "too long"))
+  -- again, with a tail call
+  local status, msg = pcall(function () return a() end)
+  assert(not status and string.find(msg, "too long"))
+end
 a = nil
 (function (x) a=x end)(23)
 assert(a == 23 and (function (x) return x*2 end)(20) == 40)
author	Roberto Ierusalimschy <roberto@inf.puc-rio.br>	2024-11-16 12:00:28 -0300
committer	Roberto Ierusalimschy <roberto@inf.puc-rio.br>	2024-11-16 12:00:28 -0300
commit	b117bdb3448778d9e7f9a0302791e8ac3bb97ddd (patch)
tree	cf83da22ab3ea7fae6bb2602c790f1a0ca9533c9
parent	f12ce4029dfbce7b89ec136e6b7ba5f6bca039da (diff)
download	lua-b117bdb3448778d9e7f9a0302791e8ac3bb97ddd.tar.gz lua-b117bdb3448778d9e7f9a0302791e8ac3bb97ddd.tar.bz2 lua-b117bdb3448778d9e7f9a0302791e8ac3bb97ddd.zip

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) {
464		464
465	/*	465	/*
466	** Check whether 'func' has a '__call' metafield. If so, put it in the	466	** Check whether 'func' has a '__call' metafield. If so, put it in the
467	** stack, below original 'func', so that 'luaD_precall' can call it. Raise	467	** stack, below original 'func', so that 'luaD_precall' can call it.
468	** an error if there is no '__call' metafield.	468	** Raise an error if there is no '__call' metafield.
		469	** Bits CIST_CCMT in status count how many _call metamethods were
		470	** invoked and how many corresponding extra arguments were pushed.
		471	** (This count will be saved in the 'callstatus' of the call).
		472	** Raise an error if this counter overflows.
469	*/	473	*/
470	static StkId tryfuncTM (lua_State *L, StkId func) {	474	static unsigned tryfuncTM (lua_State *L, StkId func, unsigned status) {
471	const TValue *tm;	475	const TValue *tm;
472	StkId p;	476	StkId p;
473	checkstackp(L, 1, func); /* space for metamethod */	477	tm = luaT_gettmbyobj(L, s2v(func), TM_CALL);
474	tm = luaT_gettmbyobj(L, s2v(func), TM_CALL); /* (after previous GC) */	478	if (l_unlikely(ttisnil(tm))) /* no metamethod? */
475	if (l_unlikely(ttisnil(tm)))	479	luaG_callerror(L, s2v(func));
476	luaG_callerror(L, s2v(func)); /* nothing to call */
477	for (p = L->top.p; p > func; p--) /* open space for metamethod */	480	for (p = L->top.p; p > func; p--) /* open space for metamethod */
478	setobjs2s(L, p, p-1);	481	setobjs2s(L, p, p-1);
479	L->top.p++; /* stack space pre-allocated by the caller */	482	L->top.p++; /* stack space pre-allocated by the caller */
480	setobj2s(L, func, tm); /* metamethod is the new function to be called */	483	setobj2s(L, func, tm); /* metamethod is the new function to be called */
481	return func;	484	if ((status & MAX_CCMT) == MAX_CCMT) /* is counter full? */
		485	luaG_runerror(L, "'__call' chain too long");
		486	return status + (1u << CIST_CCMT); /* increment counter */
482	}	487	}
483		488
484		489
@@ -564,11 +569,17 @@ void luaD_poscall (lua_State L, CallInfo ci, int nres) {
564	#define next_ci(L) (L->ci->next ? L->ci->next : luaE_extendCI(L))	569	#define next_ci(L) (L->ci->next ? L->ci->next : luaE_extendCI(L))
565		570
566		571
		572	/*
		573	** Allocate and initialize CallInfo structure. At this point, the
		574	** only valid fields in the call status are number of results,
		575	** CIST_C (if it's a C function), and number of extra arguments.
		576	** (All these bit-fields fit in 16-bit values.)
		577	*/
567	l_sinline CallInfo prepCallInfo (lua_State L, StkId func, unsigned status,	578	l_sinline CallInfo prepCallInfo (lua_State L, StkId func, unsigned status,
568	StkId top) {	579	StkId top) {
569	CallInfo ci = L->ci = next_ci(L); / new frame */	580	CallInfo ci = L->ci = next_ci(L); / new frame */
570	ci->func.p = func;	581	ci->func.p = func;
571	lua_assert((status & ~(CIST_NRESULTS \| CIST_C)) == 0);	582	lua_assert((status & ~(CIST_NRESULTS \| CIST_C \| MAX_CCMT)) == 0);
572	ci->callstatus = status;	583	ci->callstatus = status;
573	ci->top.p = top;	584	ci->top.p = top;
574	return ci;	585	return ci;
@@ -607,12 +618,13 @@ l_sinline int precallC (lua_State *L, StkId func, unsigned status,
607	*/	618	*/
608	int luaD_pretailcall (lua_State L, CallInfo ci, StkId func,	619	int luaD_pretailcall (lua_State L, CallInfo ci, StkId func,
609	int narg1, int delta) {	620	int narg1, int delta) {
		621	unsigned status = LUA_MULTRET + 1;
610	retry:	622	retry:
611	switch (ttypetag(s2v(func))) {	623	switch (ttypetag(s2v(func))) {
612	case LUA_VCCL: /* C closure */	624	case LUA_VCCL: /* C closure */
613	return precallC(L, func, LUA_MULTRET + 1, clCvalue(s2v(func))->f);	625	return precallC(L, func, status, clCvalue(s2v(func))->f);
614	case LUA_VLCF: /* light C function */	626	case LUA_VLCF: /* light C function */
615	return precallC(L, func, LUA_MULTRET + 1, fvalue(s2v(func)));	627	return precallC(L, func, status, fvalue(s2v(func)));
616	case LUA_VLCL: { /* Lua function */	628	case LUA_VLCL: { /* Lua function */
617	Proto *p = clLvalue(s2v(func))->p;	629	Proto *p = clLvalue(s2v(func))->p;
618	int fsize = p->maxstacksize; /* frame size */	630	int fsize = p->maxstacksize; /* frame size */
@@ -633,8 +645,8 @@ int luaD_pretailcall (lua_State L, CallInfo ci, StkId func,
633	return -1;	645	return -1;
634	}	646	}
635	default: { /* not a function */	647	default: { /* not a function */
636	func = tryfuncTM(L, func); /* try to get '__call' metamethod */	648	checkstackp(L, 1, func); /* space for metamethod */
637	/* return luaD_pretailcall(L, ci, func, narg1 + 1, delta); */	649	status = tryfuncTM(L, func, status); /* try '__call' metamethod */
638	narg1++;	650	narg1++;
639	goto retry; /* try again */	651	goto retry; /* try again */
640	}	652	}
@@ -676,7 +688,8 @@ CallInfo luaD_precall (lua_State L, StkId func, int nresults) {
676	return ci;	688	return ci;
677	}	689	}
678	default: { /* not a function */	690	default: { /* not a function */
679	func = tryfuncTM(L, func); /* try to get '__call' metamethod */	691	checkstackp(L, 1, func); /* space for metamethod */
		692	status = tryfuncTM(L, func, status); /* try '__call' metamethod */
680	goto retry; /* try again with metamethod */	693	goto retry; /* try again with metamethod */
681	}	694	}
682	}	695	}


diff --git a/lstate.h b/lstate.h index ab567213..1c81b6ed 100644 --- a/lstate.h +++ b/lstate.h
@@ -221,16 +221,24 @@ struct CallInfo {
221	*/	221	*/
222	/* bits 0-7 are the expected number of results from this function + 1 */	222	/* bits 0-7 are the expected number of results from this function + 1 */
223	#define CIST_NRESULTS 0xffu	223	#define CIST_NRESULTS 0xffu
224	/* Bits 8-10 are used for CIST_RECST (see below) */	224
225	#define CIST_RECST 8 /* the offset, not the mask */	225	/* bits 8-11 count call metamethods (and their extra arguments) */
226	/* original value of 'allowhook' */	226	#define CIST_CCMT 8 /* the offset, not the mask */
227	#define CIST_OAH (cast(l_uint32, 1) << 11)	227	#define MAX_CCMT (0xfu << CIST_CCMT)
228	/* call is running a C function */	228
229	#define CIST_C (CIST_OAH << 1)	229	/* Bits 12-14 are used for CIST_RECST (see below) */
		230	#define CIST_RECST 12 /* the offset, not the mask */
		231
		232	/* call is running a C function (still in first 16 bits) */
		233	#define CIST_C (1u << (CIST_RECST + 3))
230	/* call is on a fresh "luaV_execute" frame */	234	/* call is on a fresh "luaV_execute" frame */
231	#define CIST_FRESH (CIST_C << 1)	235	#define CIST_FRESH cast(l_uint32, CIST_C << 1)
		236	/* function is closing tbc variables */
		237	#define CIST_CLSRET (CIST_FRESH << 1)
		238	/* original value of 'allowhook' */
		239	#define CIST_OAH (CIST_CLSRET << 1)
232	/* call is running a debug hook */	240	/* call is running a debug hook */
233	#define CIST_HOOKED (CIST_FRESH << 1)	241	#define CIST_HOOKED (CIST_OAH << 1)
234	/* doing a yieldable protected call */	242	/* doing a yieldable protected call */
235	#define CIST_YPCALL (CIST_HOOKED << 1)	243	#define CIST_YPCALL (CIST_HOOKED << 1)
236	/* call was tail called */	244	/* call was tail called */
@@ -239,11 +247,9 @@ struct CallInfo {
239	#define CIST_HOOKYIELD (CIST_TAIL << 1)	247	#define CIST_HOOKYIELD (CIST_TAIL << 1)
240	/* function "called" a finalizer */	248	/* function "called" a finalizer */
241	#define CIST_FIN (CIST_HOOKYIELD << 1)	249	#define CIST_FIN (CIST_HOOKYIELD << 1)
242	/* function is closing tbc variables */
243	#define CIST_CLSRET (CIST_FIN << 1)
244	#if defined(LUA_COMPAT_LT_LE)	250	#if defined(LUA_COMPAT_LT_LE)
245	/* using __lt for __le */	251	/* using __lt for __le */
246	#define CIST_LEQ (CIST_CLSRET << 1)	252	#define CIST_LEQ (CIST_FIN << 1)
247	#endif	253	#endif
248		254
249		255


diff --git a/manual/manual.of b/manual/manual.of index f0b17b4c..ce42ff51 100644 --- a/manual/manual.of +++ b/manual/manual.of
@@ -9392,6 +9392,10 @@ If you need to change it,
9392	declare a local variable with the same name in the loop body.	9392	declare a local variable with the same name in the loop body.
9393	}	9393	}
9394		9394
		9395	@item{
		9396	A chain of @id{__call} metamethods can have at most 15 objects.
		9397	}
		9398
9395	}	9399	}
9396		9400
9397	}	9401	}


diff --git a/testes/calls.lua b/testes/calls.lua index 409a275d..12312d60 100644 --- a/testes/calls.lua +++ b/testes/calls.lua
@@ -178,7 +178,7 @@ do -- tail calls x chain of __call
178	end	178	end
179		179
180	-- build a chain of __call metamethods ending in function 'foo'	180	-- build a chain of __call metamethods ending in function 'foo'
181	for i = 1, 100 do	181	for i = 1, 15 do
182	foo = setmetatable({}, {__call = foo})	182	foo = setmetatable({}, {__call = foo})
183	end	183	end
184		184
@@ -190,8 +190,8 @@ end
190	print('+')	190	print('+')
191		191
192		192
193	do -- testing chains of '__call'	193	do print"testing chains of '__call'"
194	local N = 20	194	local N = 15
195	local u = table.pack	195	local u = table.pack
196	for i = 1, N do	196	for i = 1, N do
197	u = setmetatable({i}, {__call = u})	197	u = setmetatable({i}, {__call = u})
@@ -207,6 +207,23 @@ do -- testing chains of '__call'
207	end	207	end
208		208
209		209
		210	do -- testing chains too long
		211	local a = {}
		212	for i = 1, 16 do -- one too many
		213	a = setmetatable({}, {__call = a})
		214	end
		215	local status, msg = pcall(a)
		216	assert(not status and string.find(msg, "too long"))
		217
		218	setmetatable(a, {__call = a}) -- infinite chain
		219	local status, msg = pcall(a)
		220	assert(not status and string.find(msg, "too long"))
		221
		222	-- again, with a tail call
		223	local status, msg = pcall(function () return a() end)
		224	assert(not status and string.find(msg, "too long"))
		225	end
		226
210	a = nil	227	a = nil
211	(function (x) a=x end)(23)	228	(function (x) a=x end)(23)
212	assert(a == 23 and (function (x) return x*2 end)(20) == 40)	229	assert(a == 23 and (function (x) return x*2 end)(20) == 40)