Unit tests: ABSINT() returns bad result for large or long numbers

[pbearne]

Hi All

See the attached unit tests.

The ABSINT() function will return unexpected numbers with some edge cases.

This ticket is here as much as anything to document them as mySQL will have imploded before this hit most of these tests are working

Here are some quick examples (see unit test patch for more)

we round up not down if we have lots of .9+16

$this->assertEquals( absint( 4.999999999999999 ), 4, '4.999999999999999' );
$this->assertEquals( absint( 4.9999999999999999 ), 5, '4.9999999999999999' ); 

//64 bit
$this->assertEquals( absint( 49999999999999999999 ), 5340232221128654848, '49999999999999999999' );
// 32 bit
$this->assertEquals( absint( 4999999999.9999999999 ), 705032704, '4999999999.9999999999' );

$this->assertEquals( absint( PHP_INT_MAX +1 ), 2147483648, 'PHP_INT_MAX+1-32bit' );
$this->assertEquals( absint( PHP_INT_MAX +11 ), 2147483638, 'PHP_INT_MAX+11-32bit' );
$this->assertEquals( absint( PHP_INT_MAX +99 ), 2147483550, 'PHP_INT_MAX+99-32bit' );
$this->assertEquals( absint( PHP_INT_MAX +999 ), 2147482650, 'PHP_INT_MAX+999-32bit' );

[pbearne]

ABSINT() unit tests test/functions/absint.php

[pbearne]

ABSINT() unit tests test/functions/absint.php

[SergeyBiryukov]

Related: #23383

[pbearne]

Patch for the Unit Test

[pbearne]

patch with 64bit update

[nacin]

I have absolutely zero desire to work around these issues.

absint() is simply a wrapper for (int) and abs(). What about all of the times we're already using (int) instead? What about all of the times we should be using (int) instead? I struggle to see us wanting to do anything along these lines. Do any other PHP projects decide to not trust int casts? Should we just abandon PHP at this point? Or abandon 32-bit systems? Or, hell, 64-bit systems?

Cool bug, and an interesting mess, but wontfix.

[pbearne]

I agree with the wontfix :-) there is no clean way to fix it.

But I would ask the the patch is added to the test so we have coverage and to form part of the documentation / examples of the problem.

Paul

[pbearne]

Some throughts

In PHP 5.6 "GMP objects now support operator overloading and casting to scalar types."
​http://php.net/manual/en/migration56.new-features.php

Which means that we can do this -

function absint( $maybeint ) {
	if( 5.6 <= PHP_VERSION ){
		return gmp_abs( gmp_invert( $maybeint ) );
	}
	return abs( intval( $maybeint ) );
}

Not added as patch as I haven't got a PHP 5.6 install to test.

Will this fly?

Or we can get creative like this

function absint( $maybeint ) {
	$absint      = abs( intval( $maybeint ) );

	if( function_exists( 'gmp_abs' ) ) {
		$gmp_absint = gmp_abs( gmp_invert( $maybeint ) );

		if ( $absint != $gmp_absint ) {
			return $gmp_absint;
		}
	}

	return $absint;

This will return a gmp object if the number is over maxint and work's in pre 5.6

Testing etc. needed :-)

[aaroncampbell]

Using gmp_intval doesn't actually fix this (I don't think we'd want to try to use it even if it did, but it doesn't):

var_dump( (int) 4.999999999999999 ); // 4
var_dump( (int) 4.9999999999999999 ); // 5
var_dump( gmp_intval( 4.999999999999999 ) ); // 4
var_dump( gmp_intval( 4.9999999999999999 ) ); // 5

Having said that, it also seems to me like unit tests for abs() or casting to an int belong in PHP's unit tests not ours.