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add function for checked mrb_int subtraction

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cremno
2014-05-05 15:28:26 +02:00
parent 0f39304265
commit cf8df563c0
3 changed files with 14 additions and 12 deletions
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include/mruby/numeric.h
+10
View File
@@ -45,6 +45,16 @@ mrb_int_add_overflow(mrb_int augend, mrb_int addend, mrb_int *sum)
return !!(((x ^ z) & (y ^ z)) & MRB_INT_OVERFLOW_MASK);
}
static inline mrb_bool
mrb_int_sub_overflow(mrb_int minuend, mrb_int subtrahend, mrb_int *difference)
{
mrb_uint x = (mrb_uint)minuend;
mrb_uint y = (mrb_uint)subtrahend;
mrb_uint z = (mrb_uint)(x - y);
*difference = (mrb_int)z;
return !!(((x ^ z) & (~y ^ z)) & MRB_INT_OVERFLOW_MASK);
}
#undef MRB_INT_OVERFLOW_MASK
#undef mrb_uint
#undef MRB_UINT_MAKE
src/numeric.c
+1 -3
View File
@@ -1145,9 +1145,7 @@ mrb_fixnum_minus(mrb_state *mrb, mrb_value x, mrb_value y)
mrb_int b, c;
b = mrb_fixnum(y);
c = a - b;
if (((a < 0) ^ (b < 0)) != 0 && (a < 0) != (c < 0)) {
/* integer overflow */
if (mrb_int_sub_overflow(a, b, &c)) {
return mrb_float_value(mrb, (mrb_float)a - (mrb_float)b);
}
return mrb_fixnum_value(c);
src/vm.c
+3 -9
View File
@@ -1669,12 +1669,7 @@ RETRY_TRY_BLOCK:
x = mrb_fixnum(regs[a]);
y = mrb_fixnum(regs[a+1]);
z = x - y;
#ifdef MRB_WORD_BOXING
z = (z << MRB_FIXNUM_SHIFT) / (1 << MRB_FIXNUM_SHIFT);
#endif
if (((x < 0) ^ (y < 0)) != 0 && (x < 0) != (z < 0)) {
/* integer overflow */
if (mrb_int_sub_overflow(x, y, &z)) {
SET_FLT_VALUE(mrb, regs[a], (mrb_float)x - (mrb_float)y);
break;
}
@@ -1876,10 +1871,9 @@ RETRY_TRY_BLOCK:
{
mrb_int x = regs_a[0].attr_i;
mrb_int y = GETARG_C(i);
mrb_int z = x - y;
mrb_int z;
if ((x < 0) != (z < 0) && ((x < 0) ^ (y < 0)) != 0) {
/* integer overflow */
if (mrb_int_sub_overflow(x, y, &z)) {
SET_FLT_VALUE(mrb, regs_a[0], (mrb_float)x - (mrb_float)y);
}
else {