[PATCH] Fix for 64-bit arch errors in zend_operators.c

22 years ago by Ard Biesheuvel — view source — reply

unread

Hello group,

Currently, the +, - en * operations in zend_operators in C do their
calculcations on long arguments with doubles, and check if the result
would fit in a long.

This failed for me on FreeBSD/alpha (in some of the math tests), because
doubles are not accurate enough to represent LONG_MIN or LONG_MAX. This
causes the comparison

'((double) LONG_MAX) + 1 > (double) LONG_MAX'

to result in 'false' because they have the same double representation.
Since a lot of tests use LONG_MAX in comparisons, this caused a lot of
them to fail on this architecture.

One solution could be to use long doubles, but in my opinion it is
better to check the sign bit directly.

A patch is attached.

--
Ard

22 years ago by Zeev Suraski — view source — reply

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The patch looks good - I committed it. Thanks!

Zeev

At 18:01 13/09/2003, Ard Biesheuvel wrote:

Hello group,

Currently, the +, - en * operations in zend_operators in C do their
calculcations on long arguments with doubles, and check if the result
would fit in a long.

This failed for me on FreeBSD/alpha (in some of the math tests), because
doubles are not accurate enough to represent LONG_MIN or LONG_MAX. This
causes the comparison

'((double) LONG_MAX) + 1 > (double) LONG_MAX'

to result in 'false' because they have the same double representation.
Since a lot of tests use LONG_MAX in comparisons, this caused a lot of
them to fail on this architecture.

One solution could be to use long doubles, but in my opinion it is better
to check the sign bit directly.

A patch is attached.

--
Ard

Index: zend_operators.c

RCS file: /repository/ZendEngine2/zend_operators.c,v
retrieving revision 1.160
diff -u -r1.160 zend_operators.c
--- zend_operators.c 17 Aug 2003 19:11:48 -0000 1.160
+++ zend_operators.c 13 Sep 2003 13:15:30 -0000
@@ -33,6 +33,8 @@
#include "ext/bcmath/number.h"
#endif

+#define LONG_SIGN_MASK (1L << (8*SIZEOF_LONG-1))

ZEND_API int zend_atoi(const char *str, int str_len)
{
int retval;
@@ -664,13 +666,16 @@
    if (op1->type == IS_LONG && op2->type == IS_LONG) {
          double dval = (double) op1->value.lval + (double) 
op2->value.lval;
          long lval = op1->value.lval + op2->value.lval;
          /* check for overflow by comparing sign bits */
          if ( (op1->value.lval & LONG_SIGN_MASK) == 
(op2->value.lval & LONG_SIGN_MASK)
                  && (op1->value.lval & LONG_SIGN_MASK) != (lval & 
LONG_SIGN_MASK)) {
          if ((dval > (double) LONG_MAX) || (dval < (double) 
LONG_MIN)) {
                  result->value.dval = dval;
                  result->value.dval = (double) op1->value.lval + 
(double) op2->value.lval;
result->type = IS_DOUBLE;
} else {
                  result->value.lval = op1->value.lval + 
op2->value.lval;
                  result->value.lval = lval;
                  result->type = IS_LONG;
          }
          return SUCCESS;
@@ -701,13 +706,16 @@
zendi_convert_scalar_to_number(op2, op2_copy, result);
    if (op1->type == IS_LONG && op2->type == IS_LONG) {
          double dval = (double) op1->value.lval - (double) 
op2->value.lval;
          long lval = op1->value.lval - op2->value.lval;
          /* check for overflow by comparing sign bits */
          if ( (op1->value.lval & LONG_SIGN_MASK) != 
(op2->value.lval & LONG_SIGN_MASK)
                  && (op1->value.lval & LONG_SIGN_MASK) != (lval & 
LONG_SIGN_MASK)) {
          if ((dval < (double) LONG_MIN) || (dval > (double) 
LONG_MAX)) {
                  result->value.dval = dval;
                  result->value.dval = (double) op1->value.lval - 
(double) op2->value.lval;
result->type = IS_DOUBLE;
} else {
                  result->value.lval = op1->value.lval - 
op2->value.lval;
                  result->value.lval = lval;
                  result->type = IS_LONG;
          }
          return SUCCESS;
@@ -738,13 +746,14 @@
zendi_convert_scalar_to_number(op2, op2_copy, result);
    if (op1->type == IS_LONG && op2->type == IS_LONG) {
          double dval = (double) op1->value.lval * (double) 
op2->value.lval;
          if ((dval > (double) LONG_MAX) || (dval < (double) 
LONG_MIN)) {
                  result->value.dval = dval;
          long lval = op1->value.lval * op2->value.lval;
          /* check for overflow by applying the reverse calculation */
          if (op1->value.lval != 0 && lval / op1->value.lval != 
op2->value.lval) {
                  result->value.dval = (double) op1->value.lval * 
(double) op2->value.lval;
result->type = IS_DOUBLE;
} else {
                  result->value.lval = op1->value.lval * 
op2->value.lval;
                  result->value.lval = lval;
                  result->type = IS_LONG;
          }
          return SUCCESS;