[Bug c/39036] Decimal floating-point exception flags done wrong
--- Comment #6 from joseph at codesourcery dot com 2009-01-30 23:14 --- Subject: Re: Decimal floating-point exception flags done wrong On Fri, 30 Jan 2009, tydeman at tybor dot com wrote: > I consider emulation of decimal FP to be part of the compiler's job. Part of > that emulation is setting the FP execption flags as per IEEE-754-2008. The implementation of decimal FP for the GNU system is partly in GCC and partly in (E)GLIBC (available as patches or an EGLIBC branch). The implementation approach chosen is that the versions of the arithmetic/conversion functions that handle exceptions and rounding modes are included only in the libdfp included with (E)GLIBC, not in libgcc. (Depending on the target, copies of libm functions to handle exceptions and rounding modes may need including in libdfp to avoid a dependency on libm, and this can only be done as part of the libc/libm/libdfp implementation.) So, if you want exceptions and rounding modes support for decimal FP, use an appropriate libc version and link against the associated libdfp. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39036
[Bug c/39036] Decimal floating-point exception flags done wrong
--- Comment #5 from tydeman at tybor dot com 2009-01-30 22:42 --- I consider emulation of decimal FP to be part of the compiler's job. Part of that emulation is setting the FP execption flags as per IEEE-754-2008. There is one set of FP exception flags (used for both binary FP and decimal FP). Given that the functions work correctly for binary FP exceptions (and they mostly do on Intel x86/x87), then they should work correctly for decimal FP exceptions. The full set of command line options I give gcc is: -std=gnu99 -pedantic -H -fno-builtin -frounding-math My understanding is -frounding-math is supposed to act like a global #pragma STDC FENV_ACCESS ON -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39036
[Bug c/39036] Decimal floating-point exception flags done wrong
--- Comment #4 from kreckel at ginac dot de 2009-01-30 22:37 --- (In reply to comment #3) > From the point of view of GCC it is invalid because and the functions > it declares are not provided by GCC, but by the C library. On the other hand, one can argue that if GCC cannot guarantee that these C library functions get executed in the proper order, it should provide replacements of these functions for which it can make this guarantee. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39036
[Bug c/39036] Decimal floating-point exception flags done wrong
--- Comment #3 from janis at gcc dot gnu dot org 2009-01-30 21:31 --- The bug is a duplicate of 20785 because the pragma is not implemented. >From the point of view of GCC it is invalid because and the functions it declares are not provided by GCC, but by the C library. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39036
[Bug c/39036] Decimal floating-point exception flags done wrong
--- Comment #2 from rguenth at gcc dot gnu dot org 2009-01-30 07:19 --- STDC FENV_ACCESS is not implemented. *** This bug has been marked as a duplicate of 20785 *** -- rguenth at gcc dot gnu dot org changed: What|Removed |Added Status|UNCONFIRMED |RESOLVED Resolution||DUPLICATE http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39036
[Bug c/39036] Decimal floating-point exception flags done wrong
--- Comment #1 from pinskia at gmail dot com 2009-01-30 02:41 ---
Subject: Re: New: Decimal floating-point exception flags done wrong
Sent from my iPhone
On Jan 29, 2009, at 6:00 PM, "tydeman at tybor dot com"
wrote:
> Using gcc 4.3.2-7 on Intel Pentium 4 running Linux Fedora Core 10 and
> -std=gnu99
There were some dfp fixes on the trunk relating to fp exceptions so
you should try the trunk before reporting any more bugs.
>
>
> /* DFP TR 24732 == WG14 / N1176, N1312 */
> #define __STDC_WANT_DEC_FP__ /* Tell implementation that we want
> Decimal FP */
> #pragma STDC FENV_ACCESS ON /* will be testing FP exception
> flags */
>
> #include /* printf() */
> #include/* fetestexcept(), FE_* */
> #include /* DEC*_MIN, DEC*_MAX */
>
>
> int main(void){
> _Decimal64 d10;
> int before;
> int after;
>
> before = feclearexcept( FE_ALL_EXCEPT );
> d10 = 1.0DD;
> d10 /= 3.0DD;
> after = fetestexcept( FE_ALL_EXCEPT );
> if( FE_INEXACT & after ){
>printf("Inexact raised as expected\n");
> }else{
>printf("Inexact wrong; after=%i\n", after);
> }
>
> before = feclearexcept( FE_ALL_EXCEPT );
> d10 = DEC64_MIN;
> d10 *= d10;
> after = fetestexcept( FE_ALL_EXCEPT );
> if( FE_UNDERFLOW & after ){
>printf("Underflow raised as expected\n");
> }else{
>printf("Underflow wrong; after=%i\n", after);
> }
>
> before = feclearexcept( FE_ALL_EXCEPT );
> d10 = DEC64_MAX;
> d10 *= d10;
> after = fetestexcept( FE_ALL_EXCEPT );
> if( FE_OVERFLOW & after ){
>printf("Overflow raised as expected\n");
> }else{
>printf("Overflow wrong; after=%i\n", after);
> }
>
> before = feclearexcept( FE_ALL_EXCEPT );
> d10 = DEC64_MIN;
> d10 /= (d10-d10);
> after = fetestexcept( FE_ALL_EXCEPT );
> if( FE_DIVBYZERO & after ){
>printf("Divbyzero raised as expected\n");
> }else{
>printf("Divbyzero wrong; after=%i\n", after);
> }
>
> before = feclearexcept( FE_ALL_EXCEPT );
> d10 = 0.0e-15DD;
> d10 /= d10;
> after = fetestexcept( FE_ALL_EXCEPT );
> if( FE_INVALID & after ){
>printf("Invalid raised as expected\n");
> }else{
>printf("Invalid wrong; after=%i\n", after);
> }
>
> printf("%2i = FE_INEXACT\n", FE_INEXACT);
> printf("%2i = FE_UNDERFLOW\n", FE_UNDERFLOW);
> printf("%2i = FE_OVERFLOW\n", FE_OVERFLOW);
> printf("%2i = FE_DIVBYZERO\n", FE_DIVBYZERO);
> printf("%2i = FE_INVALID\n", FE_INVALID);
>
> return 0;
> }
>
> gets:
>
> Inexact wrong; after=0
> Underflow wrong; after=0
> Overflow wrong; after=32
> Divbyzero wrong; after=0
> Invalid wrong; after=0
> 32 = FE_INEXACT
> 16 = FE_UNDERFLOW
> 8 = FE_OVERFLOW
> 4 = FE_DIVBYZERO
> 1 = FE_INVALID
>
>
> --
> Summary: Decimal floating-point exception flags done wrong
> Product: gcc
> Version: 4.3.2
>Status: UNCONFIRMED
> Severity: normal
> Priority: P3
> Component: c
>AssignedTo: unassigned at gcc dot gnu dot org
>ReportedBy: tydeman at tybor dot com
> GCC host triplet: 4.3.2
> GCC target triplet: 4.3.2
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39036
>
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39036
