Can you run this by Sascha <[EMAIL PROTECTED]> who wrote this code?
I sent him a message but he never responded.
-- Ard
Thanks,
Andi
At 04:50 PM 3/9/2004 +0100, Ard Biesheuvel wrote:
This code fails on 64-bit archs because it relies on the accuracy of a double to be sufficient to represent LONG_MAX. The patch adresses it by checking for overflow by reversing the calculation instead of casting to a double and back to long.
#include "build/php5-cvs/Zend/zend_multiply.h"
#define LONG_MIN (1L << (8*sizeof(long)-1)) #define LONG_MAX ~LONG_MIN
int main() { long res = 0; double d = 0; int overflow;
/* obviously (LONG_MAX-1) * 1 can be represented by a long */ ZEND_SIGNED_MULTIPLY_LONG(LONG_MAX-1,1,res,d,overflow);
printf("res: %ld/%.4f, %soverflow\n", result, d, overflow?"":"no "); return 0; }
-- Ard
--- Zend/zend_multiply.h Sun Mar 7 13:59:35 2004 +++ Zend/zend_multiply.h.new Wed Mar 3 09:14:04 2004 @@ -33,13 +33,13 @@ #else
#define ZEND_SIGNED_MULTIPLY_LONG(a, b, lval, dval, usedval) do { \
- double __tmpvar = (double) (a) * (double) (b); \
+ long __tmpvar = (a) * (b); \
\
- if (__tmpvar >= LONG_MAX || __tmpvar <= LONG_MIN) { \
- (dval) = __tmpvar; \
+ if ((a) != 0 && __tmpvar / (a) != (b)) { \
+ (dval) = (double)(a) * (double)(b); \
(usedval) = 1; \
} else { \
- (lval) = (a) * (b); \
+ (lval) = __tmpvar; \
(usedval) = 0; \
} \
} while (0)
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