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Merge pull request #2200 from cremno/add-functions-for-safe-addition-and-subtraction

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Add functions for safe addition and subtraction
This commit is contained in:
Yukihiro "Matz" Matsumoto
2014-05-05 22:54:55 +09:00
parent 2ceb71f970 cf8df563c0
commit 260d38d5ee
3 changed files with 44 additions and 24 deletions
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include/mruby/numeric.h
+35
View File
@@ -25,6 +25,41 @@ mrb_value mrb_fixnum_mul(mrb_state *mrb, mrb_value x, mrb_value y);
mrb_value mrb_num_div(mrb_state *mrb, mrb_value x, mrb_value y);
mrb_float mrb_to_flo(mrb_state *mrb, mrb_value x);
#define MRB_UINT_MAKE2(n) uint ## n ## _t
#define MRB_UINT_MAKE(n) MRB_UINT_MAKE2(n)
#define mrb_uint MRB_UINT_MAKE(MRB_INT_BIT)
#ifdef MRB_WORD_BOXING
# define MRB_INT_OVERFLOW_MASK ((mrb_uint)1 << (MRB_INT_BIT - 1 - MRB_FIXNUM_SHIFT))
#else
# define MRB_INT_OVERFLOW_MASK ((mrb_uint)1 << (MRB_INT_BIT - 1))
#endif
static inline mrb_bool
mrb_int_add_overflow(mrb_int augend, mrb_int addend, mrb_int *sum)
{
mrb_uint x = (mrb_uint)augend;
mrb_uint y = (mrb_uint)addend;
mrb_uint z = (mrb_uint)(x + y);
*sum = (mrb_int)z;
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
#undef MRB_UINT_MAKE2
#if defined(__cplusplus)
} /* extern "C" { */
#endif
src/numeric.c
+2 -6
View File
@@ -1109,9 +1109,7 @@ mrb_fixnum_plus(mrb_state *mrb, mrb_value x, mrb_value y)
if (a == 0) return y;
b = mrb_fixnum(y);
c = a + b;
if (((a < 0) ^ (b < 0)) == 0 && (a < 0) != (c < 0)) {
/* integer overflow */
if (mrb_int_add_overflow(a, b, &c)) {
return mrb_float_value(mrb, (mrb_float)a + (mrb_float)b);
}
return mrb_fixnum_value(c);
@@ -1147,9 +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
+7 -18
View File
@@ -12,6 +12,7 @@
#include "mruby/class.h"
#include "mruby/hash.h"
#include "mruby/irep.h"
#include "mruby/numeric.h"
#include "mruby/proc.h"
#include "mruby/range.h"
#include "mruby/string.h"
@@ -1610,12 +1611,7 @@ RETRY_TRY_BLOCK:
x = mrb_fixnum(regs_a[0]);
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) != (z < 0) && ((x < 0) ^ (y < 0)) == 0) {
/* integer overflow */
if (mrb_int_add_overflow(x, y, &z)) {
SET_FLT_VALUE(mrb, regs_a[0], (mrb_float)x + (mrb_float)y);
break;
}
@@ -1673,12 +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;
}
@@ -1842,10 +1833,9 @@ RETRY_TRY_BLOCK:
{
mrb_int x = regs[a].attr_i;
mrb_int y = GETARG_C(i);
mrb_int z = x + y;
mrb_int z;
if (((x < 0) ^ (y < 0)) == 0 && (x < 0) != (z < 0)) {
/* integer overflow */
if (mrb_int_add_overflow(x, y, &z)) {
SET_FLT_VALUE(mrb, regs[a], (mrb_float)x + (mrb_float)y);
break;
}
@@ -1881,10 +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 {