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Revamp around 'L->nCcalls' count

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The field 'L->nCcalls' now counts downwards, so that the C-stack
limits do not depend on the stack size.
This commit is contained in:
Roberto Ierusalimschy
2019-06-12 10:31:38 -03:00
parent d2a9b4ffb8
commit 3cd9b56ae6
4 changed files with 80 additions and 51 deletions
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53
lstate.c
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@@ -97,35 +97,34 @@ void luaE_setdebt (global_State *g, l_mem debt) {
/*
** Increment count of "C calls" and check for overflows. In case of
** Decrement count of "C calls" and check for overflows. In case of
** a stack overflow, check appropriate error ("regular" overflow or
** overflow while handling stack overflow).
** If 'nCcalls' is larger than LUAI_MAXCSTACK but smaller than
** LUAI_MAXCSTACK + CSTACKCF (plus 2 to avoid by-one errors), it means
** it has just entered the "overflow zone", so the function raises an
** overflow error.
** If 'nCcalls' is larger than LUAI_MAXCSTACK + CSTACKCF + 2
** (which means it is already handling an overflow) but smaller than
** 9/8 of LUAI_MAXCSTACK, does not report an error (to allow message
** handling to work).
** Otherwise, report a stack overflow while handling a stack overflow
** (probably caused by a repeating error in the message handling
** function).
** overflow while handling stack overflow). If 'nCcalls' is smaller
** than CSTACKERR but larger than CSTACKMARK, it means it has just
** entered the "overflow zone", so the function raises an overflow
** error. If 'nCcalls' is smaller than CSTACKMARK (which means it is
** already handling an overflow) but larger than CSTACKERRMARK, does
** not report an error (to allow message handling to work). Otherwise,
** report a stack overflow while handling a stack overflow (probably
** caused by a repeating error in the message handling function).
*/
void luaE_enterCcall (lua_State *L) {
int ncalls = getCcalls(L);
L->nCcalls++;
if (ncalls >= LUAI_MAXCSTACK) { /* possible overflow? */
L->nCcalls--;
if (ncalls <= CSTACKERR) { /* possible overflow? */
luaE_freeCI(L); /* release unused CIs */
ncalls = getCcalls(L); /* update call count */
if (ncalls >= LUAI_MAXCSTACK) { /* still overflow? */
if (ncalls <= LUAI_MAXCSTACK + CSTACKCF + 2) {
/* no error before increments; raise the error now */
L->nCcalls += (CSTACKCF + 4); /* avoid raising it again */
luaG_runerror(L, "C stack overflow");
}
else if (ncalls >= (LUAI_MAXCSTACK + (LUAI_MAXCSTACK >> 3)))
if (ncalls <= CSTACKERR) { /* still overflow? */
if (ncalls <= CSTACKERRMARK) /* below error-handling zone? */
luaD_throw(L, LUA_ERRERR); /* error while handling stack error */
else if (ncalls >= CSTACKMARK) {
/* not in error-handling zone; raise the error now */
L->nCcalls = (CSTACKMARK - 1); /* enter error-handling zone */
luaG_runerror(L, "C stack overflow1");
}
/* else stack is in the error-handling zone;
allow message handler to work */
}
}
}
@@ -153,13 +152,13 @@ void luaE_freeCI (lua_State *L) {
CallInfo *ci = L->ci;
CallInfo *next = ci->next;
ci->next = NULL;
L->nCcalls -= L->nci; /* subtract removed elements from 'nCcalls' */
L->nCcalls += L->nci; /* add removed elements back to 'nCcalls' */
while ((ci = next) != NULL) {
next = ci->next;
luaM_free(L, ci);
L->nci--;
}
L->nCcalls += L->nci; /* adjust result */
L->nCcalls -= L->nci; /* adjust result */
}
@@ -169,7 +168,7 @@ void luaE_freeCI (lua_State *L) {
void luaE_shrinkCI (lua_State *L) {
CallInfo *ci = L->ci;
CallInfo *next2; /* next's next */
L->nCcalls -= L->nci; /* subtract removed elements from 'nCcalls' */
L->nCcalls += L->nci; /* add removed elements back to 'nCcalls' */
/* while there are two nexts */
while (ci->next != NULL && (next2 = ci->next->next) != NULL) {
luaM_free(L, ci->next); /* free next */
@@ -178,7 +177,7 @@ void luaE_shrinkCI (lua_State *L) {
next2->previous = ci;
ci = next2; /* keep next's next */
}
L->nCcalls += L->nci; /* adjust result */
L->nCcalls -= L->nci; /* adjust result */
}
@@ -264,7 +263,7 @@ static void preinit_thread (lua_State *L, global_State *g) {
L->stacksize = 0;
L->twups = L; /* thread has no upvalues */
L->errorJmp = NULL;
L->nCcalls = 0;
L->nCcalls = LUAI_MAXCSTACK + CSTACKERR;
L->hook = NULL;
L->hookmask = 0;
L->basehookcount = 0;