[Bug c/56651] New: sin() and tan() has different values during compile time and run time.

[Bug c/56651] New: sin() and tan() has different values during compile time and run time.

[sergey.s at samsung dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56651

             Bug #: 56651
           Summary: sin() and tan() has different values during compile
                    time and run time.
    Classification: Unclassified
           Product: gcc
           Version: 4.6.3
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: sergey.s@samsung.com


Created attachment 29689
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29689
Source code with sine test

Sources with test cases are attached.
Current output:
Compile-time value of sine is -2.44929359829470641e-16
Runtime value of sine is -2.44921270764475452e-16

Compile-time value of tangent is -1.63312393531953700e+16
Runtime value of tangent is -1.63317787283838440e+16

[Bug c/56651] sin() and tan() has different values during compile time and run time.

[sergey.s at samsung dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56651

--- Comment #1 from sergey.s at samsung dot com 2013-03-18 09:50:25 UTC ---
Created attachment 29690
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29690
Source code with tangent test

[Bug c/56651] sin() and tan() have different values during compile time and run time.

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56651

Steven Bosscher <steven at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2013-03-18
     Ever Confirmed|0                           |1

--- Comment #2 from Steven Bosscher <steven at gcc dot gnu.org> 2013-03-18 10:57:38 UTC ---
For what target is this?

[Bug c/56651] sin() and tan() have different values during compile time and run time.

[sergey.s at samsung dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56651

--- Comment #3 from sergey.s at samsung dot com 2013-03-18 11:06:55 UTC ---
(In reply to comment #2)
> For what target is this?
x86, host also is x86.

[Bug c/56651] sin() and tan() have different values during compile time and run time.

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56651

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
         Resolution|                            |WONTFIX

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> 2013-03-18 11:29:12 UTC ---
This is not a bug in GCC.  GCC evaluates to 0.5ulp precision at compile-time
using MPFR (for a cross-compiler it would have no way to invoke the actual
targets math library routine for example).  Thus the "bug" is in your
math library which does not evaluate to the same precision.

OTOH this is not a bug at all, but a "feature".  We cannot fix it.