#40115 [Bgs->Csd]: String Comparison shows odd results for integer values around -2^31
ID: 40115 User updated by: jannisbreitwieser at web dot de Reported By: jannisbreitwieser at web dot de -Status: Bogus +Status: Closed Bug Type: Strings related Operating System: Linux 2.6 PHP Version: 5.2.0 New Comment: just wanted to mention that this problem ist NOT fixed in the dev versions of php 4.x and 6.x Previous Comments: [2007-01-15 10:35:27] jannisbreitwieser at web dot de @php_lists at realplain dot com: Thank you for the first elaborate attempt to answer my problem. I did not try 5.2.1 yet afaik 5.2.0 is the current offical version. @tony: I don´t know which version you are using. This report is for version 5.2.0 on linux where the problem definitely still occurs: [EMAIL PROTECTED]:~$ php -v PHP 5.2.0 (cli) (built: Jan 01 2007 15:28:45) Copyright (c) 1997-2006 The PHP Group Zend Engine v2.2.0, Copyright (c) 1998-2006 Zend Technologies [EMAIL PROTECTED]:~$ cat test.php (string) 1); //bool(true) var_dump((int) -2147483648 > (int) 1); //bool(false) ?> [EMAIL PROTECTED]:~$ php test.php bool(true) bool(false) [2007-01-15 09:41:22] [EMAIL PROTECTED] var_dump((string) -2147483648 > (string) 1); //bool(false) var_dump((int) -2147483648 > (int) 1); //bool(false) what are you talking about? [2007-01-15 04:39:34] php_lists at realplain dot com Tony and Ilia, yes this IS from integer overflow but it's a bug in zendi_smart_strcmp(). Ilia, remember I sent the patch to fix this just a couple weeks ago? ;-) See v1.208.2.4.2.18 of zend_operators.c: http://cvs.php.net/viewvc.cgi/ZendEngine2/zend_operators.c?r1=1.208.2.4.2.17&r2=1.208.2.4.2.18&view=patch The same bug was fixed with non-string integers over 6 years ago, in v1.90. To the bug reporter, have you tried PHP 5.2.1RC2? I think you'll find these things work as expected there. :-) BTW, on your "WTF?" var_dump(), that's a float because the number is parsed on its own in scripts (without the "-"), and then negated in another operation. As a string however, it's all converted at once so it's still an integer. If that helps explain things there... -------------------- [2007-01-13 17:56:17] jannisbreitwieser at web dot de Hi again. I´m not sure if you dont understand me or if I don´t understand you. To quote the manual: http://www.php.net/manual/en/language.operators.comparison.php "If you compare an integer with a string, the string is converted to a number. If you compare two numerical strings, they are compared as integers." The comparison table on the same page says for string comparison: "Translate strings and resources to numbers, usual math" This implies to me that the comparison: " -2147483648>1:" has got the same result for integers and string. (string) -2147483648 > (string) 1 --> true (int) -2147483648 > (int) 1 --> false Please try to explain to me why this is not the case. Either there is a bug in the documentation or there is a bug in the implementation. But obviously implementation and documentation do not match. [2007-01-13 15:32:11] [EMAIL PROTECTED] Thank you for taking the time to write to us, but this is not a bug. Please double-check the documentation available at http://www.php.net/manual/ and the instructions on how to report a bug at http://bugs.php.net/how-to-report.php This is due to integer overflow. The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at http://bugs.php.net/40115 -- Edit this bug report at http://bugs.php.net/?id=40115&edit=1
#40115 [Bgs]: String Comparison shows odd results for integer values around -2^31
ID: 40115
User updated by: jannisbreitwieser at web dot de
Reported By: jannisbreitwieser at web dot de
Status: Bogus
Bug Type: Strings related
Operating System: Linux 2.6
PHP Version: 5.2.0
New Comment:
@php_lists at realplain dot com:
Thank you for the first elaborate attempt to answer my problem.
I did not try 5.2.1 yet
afaik 5.2.0 is the current offical version.
@tony: I don´t know which version you are using.
This report is for version 5.2.0 on linux where the problem definitely
still occurs:
[EMAIL PROTECTED]:~$ php -v
PHP 5.2.0 (cli) (built: Jan 01 2007 15:28:45)
Copyright (c) 1997-2006 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2006 Zend Technologies
[EMAIL PROTECTED]:~$ cat test.php
(string) 1); //bool(true)
var_dump((int) -2147483648 > (int) 1); //bool(false)
?>
[EMAIL PROTECTED]:~$ php test.php
bool(true)
bool(false)
Previous Comments:
[2007-01-15 09:41:22] [EMAIL PROTECTED]
var_dump((string) -2147483648 > (string) 1); //bool(false)
var_dump((int) -2147483648 > (int) 1); //bool(false)
what are you talking about?
[2007-01-15 04:39:34] php_lists at realplain dot com
Tony and Ilia, yes this IS from integer overflow but it's a bug in
zendi_smart_strcmp(). Ilia, remember I sent the patch to fix this just
a couple weeks ago? ;-) See v1.208.2.4.2.18 of zend_operators.c:
http://cvs.php.net/viewvc.cgi/ZendEngine2/zend_operators.c?r1=1.208.2.4.2.17&r2=1.208.2.4.2.18&view=patch
The same bug was fixed with non-string integers over 6 years ago, in
v1.90.
To the bug reporter, have you tried PHP 5.2.1RC2? I think you'll find
these things work as expected there. :-) BTW, on your "WTF?"
var_dump(), that's a float because the number is parsed on its own in
scripts (without the "-"), and then negated in another operation. As a
string however, it's all converted at once so it's still an integer. If
that helps explain things there...
--------------------
[2007-01-13 17:56:17] jannisbreitwieser at web dot de
Hi again.
I´m not sure if you dont understand me or if I don´t understand you.
To quote the manual:
http://www.php.net/manual/en/language.operators.comparison.php
"If you compare an integer with a string, the string is converted to a
number. If you compare two numerical strings, they are compared as
integers."
The comparison table on the same page says for string comparison:
"Translate strings and resources to numbers, usual math"
This implies to me that
the comparison:
" -2147483648>1:" has got the same result for integers and string.
(string) -2147483648 > (string) 1 --> true
(int) -2147483648 > (int) 1 --> false
Please try to explain to me why this is not the case.
Either there is a bug in the documentation or there is a bug in the
implementation. But obviously implementation and documentation do not
match.
[2007-01-13 15:32:11] [EMAIL PROTECTED]
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php
This is due to integer overflow.
--------------------
[2007-01-13 11:41:44] jannisbreitwieser at web dot de
I´m afraid the answert doesn´t explain php´s odd behavior.
Just run the code on the bottom and try to figure out its behavior.
It´s definitely not as it should be!
String-String Comparisons are handley incorrectly internally somehow.
Int-Int Comparisons also work without being affected by overflows.
Run This:
/
%7s", gettype($a), gettype($b) ) .
" | " . ( $a>$b ? "true " : "false" ) .
" | " . "a-b = "; var_dump($c);
}
echo '$a as an int - unexpected results ';
for ($b = -2; $b <= 2; $b+=1) {
$a = '-2147483647'; // the strings number value of $a is an int for
php - see above
$b = (string)$b;
echo "$a>$b:\n";
echo "\n";
$a = (string)$a;
$b = (string)$b;
print_results( $a, $b );
$a = (int)$a;
$b = (string)$b;
print_results( $a, $b );
$a = (string)$a;
$b = (int)$b;
print_results( $a, $b );
$a = (int)$a;
$b = (int)$b;
print_results( $a, $b );
echo "\n";
}
echo '$a as a fake float - unexpected results';
for ($b = -2; $b <= 2; $b+=1) {
$a = '-2147483648'; // This time $a is a float for php - still wrong
result, probably its internally handled as an int since pow(2,-31) is
still in the int ra
#40115 [Bgs->Opn]: String Comparison shows odd results for integer values around -2^31
ID: 40115
User updated by: jannisbreitwieser at web dot de
Reported By: jannisbreitwieser at web dot de
-Status: Bogus
+Status: Open
Bug Type: Strings related
Operating System: Linux 2.6
PHP Version: 5.2.0
New Comment:
Hi again.
I´m not sure if you dont understand me or if I don´t understand you.
To quote the manual:
http://www.php.net/manual/en/language.operators.comparison.php
"If you compare an integer with a string, the string is converted to a
number. If you compare two numerical strings, they are compared as
integers."
The comparison table on the same page says for string comparison:
"Translate strings and resources to numbers, usual math"
This implies to me that
the comparison:
" -2147483648>1:" has got the same result for integers and string.
(string) -2147483648 > (string) 1 --> true
(int) -2147483648 > (int) 1 --> false
Please try to explain to me why this is not the case.
Either there is a bug in the documentation or there is a bug in the
implementation. But obviously implementation and documentation do not
match.
Previous Comments:
[2007-01-13 15:32:11] [EMAIL PROTECTED]
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php
This is due to integer overflow.
--------
[2007-01-13 11:41:44] jannisbreitwieser at web dot de
I´m afraid the answert doesn´t explain php´s odd behavior.
Just run the code on the bottom and try to figure out its behavior.
It´s definitely not as it should be!
String-String Comparisons are handley incorrectly internally somehow.
Int-Int Comparisons also work without being affected by overflows.
Run This:
/
%7s", gettype($a), gettype($b) ) .
" | " . ( $a>$b ? "true " : "false" ) .
" | " . "a-b = "; var_dump($c);
}
echo '$a as an int - unexpected results ';
for ($b = -2; $b <= 2; $b+=1) {
$a = '-2147483647'; // the strings number value of $a is an int for
php - see above
$b = (string)$b;
echo "$a>$b:\n";
echo "\n";
$a = (string)$a;
$b = (string)$b;
print_results( $a, $b );
$a = (int)$a;
$b = (string)$b;
print_results( $a, $b );
$a = (string)$a;
$b = (int)$b;
print_results( $a, $b );
$a = (int)$a;
$b = (int)$b;
print_results( $a, $b );
echo "\n";
}
echo '$a as a fake float - unexpected results';
for ($b = -2; $b <= 2; $b+=1) {
$a = '-2147483648'; // This time $a is a float for php - still wrong
result, probably its internally handled as an int since pow(2,-31) is
still in the int range of normal programming languages like c
$b = (string)$b;
echo "$a>$b:\n";
echo "\n";
$a = (string)$a;
$b = (string)$b;
print_results( $a, $b );
$a = (int)$a;
$b = (string)$b;
print_results( $a, $b );
$a = (string)$a;
$b = (int)$b;
print_results( $a, $b );
$a = (int)$a;
$b = (int)$b;
print_results( $a, $b );
echo "\n";
}
echo '$a as a real float - results as expected';
for ($b = -2; $b <= 2; $b+=1) {
$a = '-2147483649'; // This time the number value of $a is a "real"
float since it is out of a normal integers range. - results are as
expected.
$b = (string)$b;
echo "$a>$b:\n";
echo "\n";
$a = (string)$a;
$b = (string)$b;
print_results( $a, $b );
$a = (int)$a;
$b = (string)$b;
print_results( $a, $b );
$a = (string)$a;
$b = (int)$b;
print_results( $a, $b );
$a = (int)$a;
$b = (int)$b;
print_results( $a, $b );
echo "\n";
}
?>
--------
[2007-01-12 22:23:11] [EMAIL PROTECTED]
Integers tend to overflow and this is expected.
[2007-01-12 22:19:44] jannisbreitwieser at web dot de
Description:
-2147483670; $a-=1000) {
$a = (string) $a;
$b = '5';
echo $a > $b ? "$a - true\n" : "$a - false\n";
}
?>
-> The comparison should always return false but it doesnt - for some
reason some of the comparisons return true.
Reproduce code:
---
according to
http://www.php.net/manual/en/language.operators.comparison.php
Quote:"If you compare two numerical strings, they are compared as
integers."
This is not the case since
$a = '-2147483648';
for ($a = -2147373648 ; $a > -2147483670; $a-=1000) {
// No longer cast to string
$b = '5';
echo $a > $b ? "$a - true\n" : "$a - false\n";
}
returns different values (which is 'false' as expected).
--
Edit this bug report at http://bugs.php.net/?id=40115&edit=1
#40115 [Bgs->Opn]: String Comparison shows odd results for integer values around -2^31
ID: 40115
User updated by: jannisbreitwieser at web dot de
Reported By: jannisbreitwieser at web dot de
-Status: Bogus
+Status: Open
Bug Type: Strings related
Operating System: Linux 2.6
PHP Version: 5.2.0
New Comment:
I´m afraid the answert doesn´t explain php´s odd behavior.
Just run the code on the bottom and try to figure out its behavior.
It´s definitely not as it should be!
String-String Comparisons are handley incorrectly internally somehow.
Int-Int Comparisons also work without being affected by overflows.
Run This:
/
%7s", gettype($a), gettype($b) ) .
" | " . ( $a>$b ? "true " : "false" ) .
" | " . "a-b = "; var_dump($c);
}
echo '$a as an int - unexpected results ';
for ($b = -2; $b <= 2; $b+=1) {
$a = '-2147483647'; // the strings number value of $a is an int for
php - see above
$b = (string)$b;
echo "$a>$b:\n";
echo "\n";
$a = (string)$a;
$b = (string)$b;
print_results( $a, $b );
$a = (int)$a;
$b = (string)$b;
print_results( $a, $b );
$a = (string)$a;
$b = (int)$b;
print_results( $a, $b );
$a = (int)$a;
$b = (int)$b;
print_results( $a, $b );
echo "\n";
}
echo '$a as a fake float - unexpected results';
for ($b = -2; $b <= 2; $b+=1) {
$a = '-2147483648'; // This time $a is a float for php - still wrong
result, probably its internally handled as an int since pow(2,-31) is
still in the int range of normal programming languages like c
$b = (string)$b;
echo "$a>$b:\n";
echo "\n";
$a = (string)$a;
$b = (string)$b;
print_results( $a, $b );
$a = (int)$a;
$b = (string)$b;
print_results( $a, $b );
$a = (string)$a;
$b = (int)$b;
print_results( $a, $b );
$a = (int)$a;
$b = (int)$b;
print_results( $a, $b );
echo "\n";
}
echo '$a as a real float - results as expected';
for ($b = -2; $b <= 2; $b+=1) {
$a = '-2147483649'; // This time the number value of $a is a "real"
float since it is out of a normal integers range. - results are as
expected.
$b = (string)$b;
echo "$a>$b:\n";
echo "\n";
$a = (string)$a;
$b = (string)$b;
print_results( $a, $b );
$a = (int)$a;
$b = (string)$b;
print_results( $a, $b );
$a = (string)$a;
$b = (int)$b;
print_results( $a, $b );
$a = (int)$a;
$b = (int)$b;
print_results( $a, $b );
echo "\n";
}
?>
Previous Comments:
----------------
[2007-01-12 22:23:11] [EMAIL PROTECTED]
Integers tend to overflow and this is expected.
[2007-01-12 22:19:44] jannisbreitwieser at web dot de
Description:
-2147483670; $a-=1000) {
$a = (string) $a;
$b = '5';
echo $a > $b ? "$a - true\n" : "$a - false\n";
}
?>
-> The comparison should always return false but it doesnt - for some
reason some of the comparisons return true.
Reproduce code:
---
according to
http://www.php.net/manual/en/language.operators.comparison.php
Quote:"If you compare two numerical strings, they are compared as
integers."
This is not the case since
$a = '-2147483648';
for ($a = -2147373648 ; $a > -2147483670; $a-=1000) {
// No longer cast to string
$b = '5';
echo $a > $b ? "$a - true\n" : "$a - false\n";
}
returns different values (which is 'false' as expected).
--
Edit this bug report at http://bugs.php.net/?id=40115&edit=1
#40115 [NEW]: String Comparison shows odd results for integer values around -2^31
From: jannisbreitwieser at web dot de
Operating system: Linux 2.6
PHP version: 5.2.0
PHP Bug Type: Strings related
Bug description: String Comparison shows odd results for integer values around
-2^31
Description:
-2147483670; $a-=1000) {
$a = (string) $a;
$b = '5';
echo $a > $b ? "$a - true\n" : "$a - false\n";
}
?>
-> The comparison should always return false but it doesnt - for some
reason some of the comparisons return true.
Reproduce code:
---
according to
http://www.php.net/manual/en/language.operators.comparison.php
Quote:"If you compare two numerical strings, they are compared as
integers."
This is not the case since
$a = '-2147483648';
for ($a = -2147373648 ; $a > -2147483670; $a-=1000) {
// No longer cast to string
$b = '5';
echo $a > $b ? "$a - true\n" : "$a - false\n";
}
returns different values (which is 'false' as expected).
--
Edit bug report at http://bugs.php.net/?id=40115&edit=1
--
Try a CVS snapshot (PHP 4.4):
http://bugs.php.net/fix.php?id=40115&r=trysnapshot44
Try a CVS snapshot (PHP 5.2):
http://bugs.php.net/fix.php?id=40115&r=trysnapshot52
Try a CVS snapshot (PHP 6.0):
http://bugs.php.net/fix.php?id=40115&r=trysnapshot60
Fixed in CVS: http://bugs.php.net/fix.php?id=40115&r=fixedcvs
Fixed in release:
http://bugs.php.net/fix.php?id=40115&r=alreadyfixed
Need backtrace: http://bugs.php.net/fix.php?id=40115&r=needtrace
Need Reproduce Script:http://bugs.php.net/fix.php?id=40115&r=needscript
Try newer version:http://bugs.php.net/fix.php?id=40115&r=oldversion
Not developer issue: http://bugs.php.net/fix.php?id=40115&r=support
Expected behavior:http://bugs.php.net/fix.php?id=40115&r=notwrong
Not enough info:
http://bugs.php.net/fix.php?id=40115&r=notenoughinfo
Submitted twice:
http://bugs.php.net/fix.php?id=40115&r=submittedtwice
register_globals: http://bugs.php.net/fix.php?id=40115&r=globals
PHP 3 support discontinued: http://bugs.php.net/fix.php?id=40115&r=php3
Daylight Savings: http://bugs.php.net/fix.php?id=40115&r=dst
IIS Stability:http://bugs.php.net/fix.php?id=40115&r=isapi
Install GNU Sed: http://bugs.php.net/fix.php?id=40115&r=gnused
Floating point limitations: http://bugs.php.net/fix.php?id=40115&r=float
No Zend Extensions: http://bugs.php.net/fix.php?id=40115&r=nozend
MySQL Configuration Error:http://bugs.php.net/fix.php?id=40115&r=mysqlcfg
