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Max size of the flop operator range.
[perl5.git] / pp_ctl.c
index af9c6dc..a5c29a0 100644 (file)
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -1185,25 +1185,33 @@ PP(pp_flop)
        SvGETMAGIC(right);
 
        if (RANGE_IS_NUMERIC(left,right)) {
-           IV i, j;
-           IV max;
+           IV i, j, n;
            if ((SvOK(left) && !SvIOK(left) && SvNV_nomg(left) < IV_MIN) ||
                (SvOK(right) && (SvIOK(right)
                                 ? SvIsUV(right) && SvUV(right) > IV_MAX
                                 : SvNV_nomg(right) > IV_MAX)))
                DIE(aTHX_ "Range iterator outside integer range");
            i = SvIV_nomg(left);
-           max = SvIV_nomg(right);
-           if (max >= i) {
-               j = max - i + 1;
-               if (j > SSize_t_MAX)
-                   Perl_croak(aTHX_ "Out of memory during list extend");
-               EXTEND_MORTAL(j);
-               EXTEND(SP, j);
+           j = SvIV_nomg(right);
+           if (j >= i) {
+                /* Dance carefully around signed max. */
+                bool overflow = (i <= 0 && j > SSize_t_MAX + i - 1);
+                if (!overflow) {
+                    n = j - i + 1;
+                    /* The wraparound of signed integers is undefined
+                     * behavior, but here we aim for count >=1, and
+                     * negative count is just wrong. */
+                    if (n < 1)
+                        overflow = TRUE;
+                }
+                if (overflow)
+                    Perl_croak(aTHX_ "Out of memory during list extend");
+               EXTEND_MORTAL(n);
+               EXTEND(SP, n);
            }
            else
-               j = 0;
-           while (j--) {
+               n = 0;
+           while (n--) {
                SV * const sv = sv_2mortal(newSViv(i++));
                PUSHs(sv);
            }