Bug #52906 [PATCH]: gmp_mod returns negative result when non-negative is expected

Edit report at http://bugs.php.net/bug.php?id=52906&edit=1 ID: 52906 Patch added by: cataphract@php.net Reported by: kkcagg at gmail dot com Summary: gmp_mod returns negative result when non-negative is expected Status: Analyzed Type: Bug Package: GNU MP related Operating System: Linux PHP Version: 5.3.3 Block user comment: N New Comment: The following patch has been added/updated: Patch Name: gmp_mod Revision: 1285170233 URL: http://bugs.php.net/patch-display.php?bug=52906&patch=gmp_mod&revision=1285170233 Previous Comments: ------------------------------------------------------------------------ [2010-09-22 17:21:09] cataphract@php.net This is a bug in the PHP extension. Worse, the result differs if you pass a GMP resource instead of an integer: $ php -r "echo gmp_intval(gmp_mod(-2, gmp_add(6,1)));" 5 The problem is that gmp_zval_binary_ui_op_ex changes the sign of the result if it uses the unsigned integer variant of the GMP API and the first operand is negative. This may be the correct for other binary functions (I haven't checked), but it isn't for mod. The documentation mirrors the upstream documentation, which says: « — Function: void mpz_mod (mpz_t r, mpz_t n, mpz_t d) — Function: unsigned long int mpz_mod_ui (mpz_t r, mpz_t n, unsigned long int d) Set r to n mod d. The sign of the divisor is ignored; the result is always non-negative. » http://gmplib.org/manual/Integer-Division.html#Integer-Division ------------------------------------------------------------------------ [2010-09-22 11:48:29] kkcagg at gmail dot com Description: ------------ GMP version 4.2.2 Running the function in test script returns the output of -5 when 5 is expected. Documentation (http://us.php.net/manual/en/function.gmp-mod.php) asserts that the result is always non-negative. This is not the case in actuality. Bug type could be either a bug or documentation problem. Test script: --------------- <?php echo gmp_intval(gmp_mod(-2,7)); ?> Expected result: ---------------- 5 Actual result: -------------- -5 ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/bug.php?id=52906&edit=1