Edit report at https://bugs.php.net/bug.php?id=62240&edit=1
ID: 62240
User updated by: zuallauz at gmail dot com
Reported by: zuallauz at gmail dot com
Summary: 5.4.3 regression, converting from float to int gives
incorrect output
Status: Not a bug
Type: Bug
Package: *General Issues
Operating System: Ubuntu 12.04 32-bit
PHP Version: 5.4.3
Block user comment: N
Private report: N
New Comment:
Yeah Memtest came back with no errors. The test C program returns the same
result on both machines. Difference between the machines:
Working machine:
Intel Pentium 4 single core @2Ghz desktop
Ubuntu 10.04 32 bit
glibc 2.11.1
gcc 4.4
Not working machine:
Intel dual core T2300 @1.66Ghz laptop
Ubuntu 12.04 32 bit
glibc 2.15
gcc 4.6
Previous Comments:
------------------------------------------------------------------------
[2012-06-07 14:08:56] [email protected]
I doubt it is bad memory. What's the difference between the two machines? Same
architecture? Intel vs. AMD perhaps? Different glibc versions? Different
compiler
versions? It would be interesting to know what would cause this on some
machines
but not others. What about the little test C program? Does that return the same
result on both machines?
------------------------------------------------------------------------
[2012-06-07 10:38:18] zuallauz at gmail dot com
Yeah originally I had compiled my own PHP using the flags in the first post. I
re-downloaded php-5.4.3.tar.bz2 from PHP.net and just did a basic ./configure
&& make then ran log(8,2) using sapi/cli/php test.php and the output was still
the same incorrect result:
float(3)
int(2)
However I have just tried the same thing on my other machine running 32bit
Ubuntu 10.04 with 5.4.3 and it outputs correctly:
float(3)
int(3)
So maybe there's a screw loose/bad memory in the first machine or something. I
don't have an explanation for it. Probably not a bug after all, sorry!
------------------------------------------------------------------------
[2012-06-07 09:14:24] [email protected]
That's interesting because that is exactly what is happening when you call
PHP's
log() function. log(8,2) in PHP ends up being log(8)/log(2) in C. Did you
compile
your PHP yourself? If not, could you try grabbing the 5.4.3 tarball and doing a
simple: ./configure && make
Building just the cli version is enough. Then run your log(8,2) test with
sapi/cli/php test.php
------------------------------------------------------------------------
[2012-06-07 08:48:37] zuallauz at gmail dot com
Hmm, I get the same output with 64 zeros:
3.0000000000000000000000000000000000000000000000000000000000000000
------------------------------------------------------------------------
[2012-06-07 08:08:25] [email protected]
Well, float to int conversion issues isn't a PHP-specific thing. Try this
little
C program on your machine, for example:
#include <stdio.h>
#include <math.h>
int main(char *argv[], int argc) {
printf("%.64f\n",log(8)/log(2));
}
If you name the file, "a.c" you can just type: make a
then run it with: ./a
My output on 64-bit Ubuntu:
10:07am x220:~> ./a
3.0000000000000000000000000000000000000000000000000000000000000000
It would be interesting to see your output.
------------------------------------------------------------------------
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