[Bug c/122082] New: complex multiply: w * conj(w) should have zero imaginary part

[tydeman at tybor dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122082

            Bug ID: 122082
           Summary: complex multiply: w * conj(w) should have zero
                    imaginary part
           Product: gcc
           Version: 15.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tydeman at tybor dot com
  Target Milestone: ---

Intel x86_64, sse FPU, Fedora Linux

#include <assert.h>
#include <limits.h>
#include <errno.h>
#include <stdio.h>
#include <float.h>
#include <fenv.h>
#include <complex.h>
#include <math.h>       /* glibc 2.41-11 */

#pragma STDC FENV_ACCESS ON
#pragma STDC FP_CONTRACT OFF
#pragma STDC FENV_ROUND FE_TONEAREST
#pragma STDC FENV_DEC_ROUND FE_DEC_TONEAREST
#pragma STDC CX_LIMITED_RANGE OFF

int main(void){
  if(1){
    float complex fc26;
    int flags;
    errno = 0;
    feclearexcept(FE_ALL_EXCEPT);
    fc26 = CMPLXF(FLT_MAX,1.1F) * CMPLXF(FLT_MAX,-1.1F); /* w * conj(w) */
    flags = fetestexcept(FE_ALL_EXCEPT);
    assert( 0 == errno );
    assert( FE_OVERFLOW|FE_INEXACT == flags );
    assert( INFINITY == crealf(fc26) );
    assert( 0.f == cimagf(fc26) );      /* fails here with NAN */
  }
  return 0;
}