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in 'for' loops, make the limit an integer whenever initial value and 

step are integers
This commit is contained in:
Roberto Ierusalimschy 2014-05-09 11:20:52 -03:00
parent a09bd59615
commit 06dc893f88
1 changed files with 40 additions and 3 deletions
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43
lvm.c
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@ -1,5 +1,5 @@
/*
** $Id: lvm.c,v 2.204 2014/04/30 19:29:51 roberto Exp roberto $
** $Id: lvm.c,v 2.205 2014/05/01 18:18:06 roberto Exp roberto $
** Lua virtual machine
** See Copyright Notice in lua.h
*/
@ -143,6 +143,41 @@ int luaV_tostring (lua_State *L, StkId obj) {
}
/*
** Try to convert a 'for' limit to an integer, preserving the
** semantics of the loop.
** (The following explanation assumes a non-negative step; it is valid
** for negative steps, mutatis mutandis.)
** If the limit can be converted to an integer, rounding down, that is
** it.
** Otherwise, check whether the limit can be converted to a number. If
** the number is too large, it is OK to set the limit as LUA_MAXINTEGER,
** which means no limit. If the number is too negative, the loop
** should not run, because any initial integer value is larger than the
** limit. So, it sets the limit to LUA_MININTEGER. 'stopnow' corrects
** the extreme case when the initial value is LUA_MININTEGER, in which
** case the LUA_MININTEGER limit would run the loop once.
*/
static int forlimit (const TValue *obj, lua_Integer *p, lua_Integer step,
int *stopnow) {
*stopnow = 0; /* usually, let loops run */
if (!tointeger_aux(obj, p, (step < 0))) { /* does not fit in integer? */
lua_Number n; /* try to convert to float */
if (!tonumber(obj, &n)) /* cannot convert to float? */
return 0; /* not a number */
if (n > 0) { /* if true, float is larger than max integer */
*p = LUA_MAXINTEGER;
if (step < 0) *stopnow = 1;
}
else { /* float is smaller than min integer */
*p = LUA_MININTEGER;
if (step >= 0) *stopnow = 1;
}
}
return 1;
}
void luaV_gettable (lua_State *L, const TValue *t, TValue *key, StkId val) {
int loop;
for (loop = 0; loop < MAXTAGLOOP; loop++) {
@ -980,11 +1015,13 @@ void luaV_execute (lua_State *L) {
TValue *plimit = ra + 1;
TValue *pstep = ra + 2;
lua_Integer ilimit;
int stopnow;
if (ttisinteger(init) && ttisinteger(pstep) &&
tointeger_aux(plimit, &ilimit, (ivalue(pstep) < 0))) {
forlimit(plimit, &ilimit, ivalue(pstep), &stopnow)) {
/* all values are integer */
setivalue(init, ivalue(init) - ivalue(pstep));
lua_Integer initv = (stopnow ? 0 : ivalue(init));
setivalue(plimit, ilimit);
setivalue(init, initv - ivalue(pstep));
}
else { /* try making all values floats */
lua_Number ninit; lua_Number nlimit; lua_Number nstep;