Sources Bugzilla – Full Text Bug Listing
|Summary:||erfc() does not set errno for underflow|
|Product:||glibc||Reporter:||Michael Kerrisk <mtk.manpages>|
|Component:||math||Assignee:||Not yet assigned to anyone <unassigned>|
Description Michael Kerrisk 2008-07-30 14:52:55 UTC
When erfc() is given an argument that causes underflow (e.g., erfc(106.9) on x8632) it raises an underflow exception. However, errno is not set. It should be set to ERANGE for this case. 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 08:52:25 UTC
Created attachment 2851 [details] test program (I got the underflow value wrong in my initial report. I think 106.9 gives underflow with the long double variant. 27 doies the trick for the double version.) Sample run showing problem: $ /tmp/mt_erfc 27 errno == 0 fetestexcept() says: FE_UNDERFLOW FE_INEXACT erfc(2.70000000000000000e+01)=5.23704643935262924e-319 0 FE_UNDERFLOW subnormal
Comment 2 Joseph Myers 2012-02-29 21:06:48 UTC
Confirmed with current sources on both x86 and x86_64.