Bug 6801 - fma() does not set errno for various errors
Summary: fma() does not set errno for various errors
Status: NEW
Alias: None
Product: glibc
Classification: Unclassified
Component: math (show other bugs)
Version: unspecified
: P2 normal
Target Milestone: ---
Assignee: Not yet assigned to anyone
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2008-07-31 10:49 UTC by Michael Kerrisk
Modified: 2014-07-04 05:44 UTC (History)
1 user (show)

See Also:
Host:
Target:
Build:
Last reconfirmed:
fweimer: security-


Attachments
test program (2.75 KB, text/plain)
2008-07-31 10:52 UTC, Michael Kerrisk
Details

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Description Michael Kerrisk 2008-07-31 10:49:50 UTC
For domain, overflow, and underflow errors, fma() correctlry raises exceptions.
 However errno is not set in any case.  errno should be set (respectively EDOM,
ERANGE, ERANGE).


Background: 
On error, many glibc math functions both set errno and raise an exception
(fetestexcept(3)).  For example, the following  function all do this: acos(),
asin(), cosh(), sinh(), acosh(), asinh(), exp(), exp2(), ldexp(), log(),
log10(), log2().  However, there is much inconsistency.  Some functions raise an
exception, but don't set errno.  Some functions set errno for some errors, but
not others.  A few set errno, but don't raise an exception.  This series of bug
reports documents deviations from what I consider the ideal: all functions
should BOTH set errno AND raise an exception for all errors.

All of these reports relate to tests on glibc 2.8 (as provided by SUSE 11.0).
Comment 1 Michael Kerrisk 2008-07-31 10:52:15 UTC
Created attachment 2865 [details]
test program

Sample runs demonstrating the problem:

$ /tmp/mt_fma inf 0 0
errno == 0
fetestexcept() says:  FE_INVALID
fma(inf,0.00000000000000000e+00,0.00000000000000000e+00)=nan
0 FE_INVALID nan

$ /tmp/mt_fma dbl_max dbl_max 0
errno == 0
fetestexcept() says:  FE_OVERFLOW FE_INEXACT
fma(1.79769313486231571e+308,1.79769313486231571e+308,0.00000000000000000e+00)=inf

0 FE_OVERFLOW +inf

$ /tmp/mt_fma dbl_min dbl_min 0
errno == 0
fetestexcept() says:  FE_UNDERFLOW FE_INEXACT
fma(2.22507385850720138e-308,2.22507385850720138e-308,0.00000000000000000e+00)=0.00000000000000000e+00

0 FE_UNDERFLOW +0
Comment 2 Joseph Myers 2012-03-01 17:23:47 UTC
Confirmed with current sources on x86 and x86_64.