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Avoid signed shift overflow in pow (bug 21309). 

As noted in bug 21309, dbl-64/e_pow.c contains signed int shifts that,
although the shift count is in the range [0, 31], shift bits into and
beyond the sign bit and so are undefined in ISO C.  Although this is
defined in GNU C, this patch from the bug cleans up the code to avoid
those shifts.

Tested for x86_64.

	[BZ #21309]
	* sysdeps/ieee754/dbl-64/e_pow.c (checkint): Make m and n
	unsigned.
This commit is contained in:
Bernd Edlinger 2017-12-19 18:41:01 +00:00 committed by Joseph Myers
parent f1e005022e
commit 648615e13f
2 changed files with 8 additions and 1 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
2017-12-19 Bernd Edlinger <bernd.edlinger@hotmail.de>
[BZ #21309]
* sysdeps/ieee754/dbl-64/e_pow.c (checkint): Make m and n
unsigned.
2017-12-19 Joseph Myers <joseph@codesourcery.com>
Revert:

3
sysdeps/ieee754/dbl-64/e_pow.c
View File

@ -452,7 +452,8 @@ checkint (double x)
int4 i[2];
double x;
} u;
int k, m, n;
int k;
unsigned int m, n;
u.x = x;
m = u.i[HIGH_HALF] & 0x7fffffff; /* no sign */
if (m >= 0x7ff00000)