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avoid overflows in computation of step size

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Roberto Ierusalimschy
2017-06-01 16:16:34 -03:00
parent 8821746841
commit 4bc33d64de
2 changed files with 12 additions and 3 deletions
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6
lgc.c
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@@ -1,5 +1,5 @@
/*
** $Id: lgc.c,v 2.228 2017/05/04 13:32:01 roberto Exp roberto $
** $Id: lgc.c,v 2.229 2017/05/26 19:14:29 roberto Exp roberto $
** Garbage Collector
** See Copyright Notice in lua.h
*/
@@ -1486,7 +1486,9 @@ void luaC_runtilstate (lua_State *L, int statesmask) {
static void incstep (lua_State *L, global_State *g) {
int stepmul = (g->gcstepmul | 1); /* avoid division by 0 */
l_mem debt = (g->GCdebt / WORK2MEM) * stepmul;
l_mem stepsize = cast(l_mem, 1) << g->gcstepsize;
l_mem stepsize = (g->gcstepsize <= log2maxs(l_mem))
? cast(l_mem, 1) << g->gcstepsize
: MAX_LMEM;
stepsize = -((stepsize / WORK2MEM) * stepmul);
do { /* repeat until pause or enough "credit" (negative debt) */
lu_mem work = singlestep(L); /* perform one single step */