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Fix spurious "inexact" exceptions from dbl-64 sqrt (bug 15631).

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Joseph Myers 2013-06-15 19:59:41 +00:00
parent 8fc75e6fb7
commit 3711a167f6
3 changed files with 21 additions and 3 deletions
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5
ChangeLog
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@ -1,5 +1,10 @@
2013-06-15 Joseph Myers <joseph@codesourcery.com>
[BZ #15631]
* sysdeps/ieee754/dbl-64/e_sqrt.c (__ieee754_sqrt): Save and
restore exception state around main square root computation, then
check for inexactness explicitly.
* math/libm-test.inc (fma_test_data): Add another test.
2013-06-15 Siddhesh Poyarekar <siddhesh@redhat.com>

2
NEWS
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@ -20,7 +20,7 @@ Version 2.18
15366, 15380, 15381, 15394, 15395, 15405, 15406, 15409, 15416, 15418,
15419, 15423, 15424, 15426, 15429, 15431, 15432, 15441, 15442, 15448,
15465, 15480, 15485, 15488, 15490, 15492, 15493, 15497, 15506, 15529,
15536, 15553, 15577, 15583, 15618, 15627.
15536, 15553, 15577, 15583, 15618, 15627, 15631.
* CVE-2013-0242 Buffer overrun in regexp matcher has been fixed (Bugzilla
#15078).

17
sysdeps/ieee754/dbl-64/e_sqrt.c
View file

@ -63,6 +63,9 @@ double __ieee754_sqrt(double x) {
s=a.x;
/*----------------- 2^-1022 <= | x |< 2^1024 -----------------*/
if (k>0x000fffff && k<0x7ff00000) {
fenv_t env;
libc_feholdexcept (&env);
double ret;
y=1.0-t*(t*s);
t=t*(rt0+y*(rt1+y*(rt2+y*rt3)));
c.i[HIGH_HALF]=0x20000000+((k&0x7fe00000)>>1);
@ -70,12 +73,22 @@ double __ieee754_sqrt(double x) {
hy=(y+big)-big;
del=0.5*t*((s-hy*hy)-(y-hy)*(y+hy));
res=y+del;
if (res == (res+1.002*((y-res)+del))) return res*c.x;
if (res == (res+1.002*((y-res)+del))) ret = res*c.x;
else {
res1=res+1.5*((y-res)+del);
EMULV(res,res1,z,zz,p,hx,tx,hy,ty); /* (z+zz)=res*res1 */
return ((((z-s)+zz)<0)?max(res,res1):min(res,res1))*c.x;
ret = ((((z-s)+zz)<0)?max(res,res1):min(res,res1))*c.x;
}
math_force_eval (ret);
libc_fesetenv (&env);
if (x / ret != ret)
{
double force_inexact = 1.0 / 3.0;
math_force_eval (force_inexact);
}
/* Otherwise (x / ret == ret), either the square root was exact or
the division was inexact. */
return ret;
}
else {
if ((k & 0x7ff00000) == 0x7ff00000)