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[Bug math/3866] New: pow(double, double) does not fulfil several of C99's requirements
- From: "kreckel at ginac dot de" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: 12 Jan 2007 23:30:59 -0000
- Subject: [Bug math/3866] New: pow(double, double) does not fulfil several of C99's requirements
- Reply-to: sourceware-bugzilla at sourceware dot org
Here is a list of bugs in GlibCs pow implementation.
1) pow(-1, 1e100):
Returns NaN and raises the "invalid" floating-point exception.
It should return 1 and raise no exception. (This is because all large
floating-point numbers are even integers if the radix is even. This
motivates pow(-1, inf) = +1, which is treated correctly by GlibC).
2) pow(-1, -1e100):
Same as above.
3) pow(-3.141592, 1e100):
Returns NaN and raises the "invalid" floating-point exception.
It should return +inf and raise the "overflow" floating-point exception flag.
4) pow(-3.141592, -1e100):
Returns NaN and raises the "invalid" floating-point exception.
It should return +0 and raise the "underflow" floating-point exception flag.
4) pow(-0, -1e100):
Raises the "invalid" floating point exception.
It shouldn't do that: this is just a case of exact division by
zero. Division by zero is correctly flagged and +inf is returned, but
the "invalid" flag is wrong.
5) pow(-inf, -1e100):
Raises the "invalid" floating point exception.
It shouldn't do that. After all, it correctly returns 0.
6) pow(-inf, 1e100):
Raises the "invalid" floating point exception.
It shouldn't do that. After all, it correctly returns +inf.
7) pow(-0, -9.0071991544401990e+15)
This returns +inf.
It should return -inf, since the double precision exponent is an odd number
(fabs(fmod(-9.0071991544401990e+15,2.0))==1.0 exactly).
--
Summary: pow(double, double) does not fulfil several of C99's
requirements
Product: glibc
Version: 2.4
Status: NEW
Severity: normal
Priority: P2
Component: math
AssignedTo: aj at suse dot de
ReportedBy: kreckel at ginac dot de
CC: glibc-bugs at sources dot redhat dot com
GCC host triplet: i386-linux-gnu
http://sourceware.org/bugzilla/show_bug.cgi?id=3866
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