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* [Bug math/13956] New: logbl() produces wrong results for subnormal 'long double' numbers @ 2012-04-06 14:23 bruno at clisp dot org 2012-04-06 14:57 ` [Bug math/13956] " bruno at clisp dot org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: bruno at clisp dot org @ 2012-04-06 14:23 UTC (permalink / raw) To: glibc-bugs http://sourceware.org/bugzilla/show_bug.cgi?id=13956 Bug #: 13956 Summary: logbl() produces wrong results for subnormal 'long double' numbers Product: glibc Version: 2.11 Status: NEW Severity: normal Priority: P2 Component: math AssignedTo: unassigned@sourceware.org ReportedBy: bruno@clisp.org Classification: Unclassified Created attachment 6326 --> http://sourceware.org/bugzilla/attachment.cgi?id=6326 test case Seen on glibc 2.11 Linux/PowerPC, on glibc 2.7 Linux/SPARC, on glibc 2.7 Linux/HP-PA. The function logbl() produces a wrong result for subnormal (denormalized) arguments. POSIX:2008 specifies the behaviour of this function for subnormal numbers: <http://pubs.opengroup.org/onlinepubs/9699919799/>. In particular, if x = 2^i is > 0, logb(x) must be = i. But in glibc on the specified platforms, for some values of i < LDBL_MIN_EXP-1, logb(x) is too large. How to reproduce: ================================== foo.c ================================== #include <float.h> #include <math.h> volatile long double x; int main () { int i; for (i = 0, x = 1.0L; i >= LDBL_MIN_EXP - 55; i--, x *= 0.5L) /* Either x = 2^i or x = 0.0. */ if ((i == LDBL_MIN_EXP - 2 || i == LDBL_MIN_EXP - 55) && (x > 0.0L && !(logbl (x) == (long double)i))) return 1; return 0; } =========================================================================== $ gcc foo.c -Wall -lm $ ./a.out; echo $? Expected result: 0 Actual result: 1 -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug math/13956] logbl() produces wrong results for subnormal 'long double' numbers 2012-04-06 14:23 [Bug math/13956] New: logbl() produces wrong results for subnormal 'long double' numbers bruno at clisp dot org @ 2012-04-06 14:57 ` bruno at clisp dot org 2012-05-10 23:47 ` azanella at linux dot vnet.ibm.com ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: bruno at clisp dot org @ 2012-04-06 14:57 UTC (permalink / raw) To: glibc-bugs http://sourceware.org/bugzilla/show_bug.cgi?id=13956 Bruno Haible <bruno at clisp dot org> changed: What |Removed |Added ---------------------------------------------------------------------------- See Also| |http://sourceware.org/bugzi | |lla/show_bug.cgi?id=13954, | |http://sourceware.org/bugzi | |lla/show_bug.cgi?id=13955 -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug math/13956] logbl() produces wrong results for subnormal 'long double' numbers 2012-04-06 14:23 [Bug math/13956] New: logbl() produces wrong results for subnormal 'long double' numbers bruno at clisp dot org 2012-04-06 14:57 ` [Bug math/13956] " bruno at clisp dot org @ 2012-05-10 23:47 ` azanella at linux dot vnet.ibm.com 2012-05-11 9:26 ` jsm28 at gcc dot gnu.org 2014-06-25 11:20 ` fweimer at redhat dot com 3 siblings, 0 replies; 5+ messages in thread From: azanella at linux dot vnet.ibm.com @ 2012-05-10 23:47 UTC (permalink / raw) To: glibc-bugs http://sourceware.org/bugzilla/show_bug.cgi?id=13956 Adhemerval Zanella Netto <azanella at linux dot vnet.ibm.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |azanella at linux dot | |vnet.ibm.com --- Comment #1 from Adhemerval Zanella Netto <azanella at linux dot vnet.ibm.com> 2012-05-10 23:47:04 UTC --- Fix commited to master (89c9aa491a7cee97bf78a29cddbf0a25c902a671). -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug math/13956] logbl() produces wrong results for subnormal 'long double' numbers 2012-04-06 14:23 [Bug math/13956] New: logbl() produces wrong results for subnormal 'long double' numbers bruno at clisp dot org 2012-04-06 14:57 ` [Bug math/13956] " bruno at clisp dot org 2012-05-10 23:47 ` azanella at linux dot vnet.ibm.com @ 2012-05-11 9:26 ` jsm28 at gcc dot gnu.org 2014-06-25 11:20 ` fweimer at redhat dot com 3 siblings, 0 replies; 5+ messages in thread From: jsm28 at gcc dot gnu.org @ 2012-05-11 9:26 UTC (permalink / raw) To: glibc-bugs http://sourceware.org/bugzilla/show_bug.cgi?id=13956 Joseph Myers <jsm28 at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution| |FIXED --- Comment #2 from Joseph Myers <jsm28 at gcc dot gnu.org> 2012-05-11 09:25:46 UTC --- I presume you intended to close this as fixed.... -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug math/13956] logbl() produces wrong results for subnormal 'long double' numbers 2012-04-06 14:23 [Bug math/13956] New: logbl() produces wrong results for subnormal 'long double' numbers bruno at clisp dot org ` (2 preceding siblings ...) 2012-05-11 9:26 ` jsm28 at gcc dot gnu.org @ 2014-06-25 11:20 ` fweimer at redhat dot com 3 siblings, 0 replies; 5+ messages in thread From: fweimer at redhat dot com @ 2014-06-25 11:20 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=13956 Florian Weimer <fweimer at redhat dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- Flags| |security- -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2014-06-25 11:20 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2012-04-06 14:23 [Bug math/13956] New: logbl() produces wrong results for subnormal 'long double' numbers bruno at clisp dot org 2012-04-06 14:57 ` [Bug math/13956] " bruno at clisp dot org 2012-05-10 23:47 ` azanella at linux dot vnet.ibm.com 2012-05-11 9:26 ` jsm28 at gcc dot gnu.org 2014-06-25 11:20 ` fweimer at redhat dot com
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