[Bug c/93743] New: swapped arguments in atan2l

[development at drmh dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93743

            Bug ID: 93743
           Summary: swapped arguments in atan2l
           Product: gcc
           Version: 9.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: development at drmh dot de
  Target Milestone: ---

Created attachment 47843
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47843&action=edit
all files to reproduce

Hi.

Compared to atan2() the atan2l() function gets their arguments swapped, it is
reproducable by the attached script and sourcecode. I checked aginast clang
which doesn't have the issue.

Thanks.

#include <stdio.h>
#include <math.h>

void test ( const long double y, const long double x ) {

  const long double  ldbl_n = atan2l (y, x);
  const long double  ldbl_s = atan2l (x, y);  // arguments swapped

  printf ("normal : y=%Lf, x=%Lf, atan2=%Lf\n", y, x, ldbl_n);
  printf ("swapped: y=%Lf, x=%Lf, atan2=%Lf\n", y, x, ldbl_s);

  if ( ldbl_n < 1.L  ||  1.L < ldbl_s ) {
    printf ("BUG!\n");
  }

  const double  dbl_n = atan2  (y, x);
  const double  dbl_s = atan2  (x, y);  // arguments swapped

  printf ("normal : y=%Lf, x=%Lf, atan2=%lf\n", y, x, dbl_n);
  printf ("swapped: y=%Lf, x=%Lf, atan2=%lf\n", y, x, dbl_s);

  if ( dbl_n < 1.L  ||  1.L < dbl_s ) {
    printf ("BUG!\n");
  }

  printf ("\n");
}


int main ( void ) {

  const long double  y = 0.922766L;
  const long double  x = 0.080466L;

  test (y, x);

  return 0;
}

gcc-output:

normal : y=0.922766, x=0.080466, atan2=0.086981
swapped: y=0.922766, x=0.080466, atan2=1.483815
BUG!
normal : y=0.922766, x=0.080466, atan2=1.483815
swapped: y=0.922766, x=0.080466, atan2=0.086981

normal : y=0.922766, x=0.080466, atan2=1.483815
swapped: y=0.922766, x=0.080466, atan2=0.086981
normal : y=0.922766, x=0.080466, atan2=1.483815
swapped: y=0.922766, x=0.080466, atan2=0.086981

clang-output:

normal : y=0.922766, x=0.080466, atan2=1.483815
swapped: y=0.922766, x=0.080466, atan2=0.086981
normal : y=0.922766, x=0.080466, atan2=1.483815
swapped: y=0.922766, x=0.080466, atan2=0.086981

normal : y=0.922766, x=0.080466, atan2=1.483815
swapped: y=0.922766, x=0.080466, atan2=0.086981
normal : y=0.922766, x=0.080466, atan2=1.483815
swapped: y=0.922766, x=0.080466, atan2=0.086981


Full details attached in the tar-archive.