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Fixed bug #54598 (bcpowmod() may return 1 if modulus is 1)

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`x mod 1` is always zero; we have to take the scale into account,
though.
This commit is contained in:
Christoph M. Becker 2017-09-07 00:30:05 +02:00
parent dea41f3c3a
commit b2919853f8
3 changed files with 32 additions and 8 deletions
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1
NEWS
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@ -7,6 +7,7 @@ PHP NEWS
- BCMath:
. Fixed bug #44995 (bcpowmod() fails if scale != 0). (cmb)
. Fixed bug #54598 (bcpowmod() may return 1 if modulus is 1). (okano1220, cmb)
- CLI server:
. Fixed bug #70470 (Built-in server truncates headers spanning over TCP

23
ext/bcmath/libbcmath/src/raisemod.c
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@ -75,17 +75,24 @@ bc_raisemod (bc_num base, bc_num expo, bc_num mod, bc_num *result, int scale)
/* Do the calculation. */
rscale = MAX(scale, base->n_scale);
while ( !bc_is_zero(exponent) )
if ( !bc_compare(mod, BCG(_one_)) )
{
(void) bc_divmod (exponent, BCG(_two_), &exponent, &parity, 0);
if ( !bc_is_zero(parity) )
temp = bc_new_num (1, scale);
}
else
{
while ( !bc_is_zero(exponent) )
{
bc_multiply (temp, power, &temp, rscale);
(void) bc_modulo (temp, mod, &temp, scale);
}
(void) bc_divmod (exponent, BCG(_two_), &exponent, &parity, 0);
if ( !bc_is_zero(parity) )
{
bc_multiply (temp, power, &temp, rscale);
(void) bc_modulo (temp, mod, &temp, scale);
}
bc_multiply (power, power, &power, rscale);
(void) bc_modulo (power, mod, &power, scale);
bc_multiply (power, power, &power, rscale);
(void) bc_modulo (power, mod, &power, scale);
}
}
/* Assign the value. */

16
ext/bcmath/tests/bug54598.phpt Normal file
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@ -0,0 +1,16 @@
--TEST--
Bug #54598 (bcpowmod() may return 1 if modulus is 1)
--SKIPIF--
<?php
if (!extension_loaded('bcmath')) die('skip bcmath extension is not available');
?>
--FILE--
<?php
var_dump(bcpowmod(5, 0, 1));
var_dump(bcpowmod(5, 0, 1, 3));
?>
===DONE===
--EXPECT--
string(1) "0"
string(5) "0.000"
===DONE===