[Bug libfortran/87247] New: intrinsic acosh violates 2008 Standard rule 13.7.5 line 5

[zeccav at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87247

            Bug ID: 87247
           Summary: intrinsic acosh violates 2008 Standard rule 13.7.5
                    line 5
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libfortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zeccav at gmail dot com
  Target Milestone: ---

! Intrinsic acosh violates 2008 Standard rule 13.7.5 line 5
! "If the result is complex the imaginary part is expressed in radians and lies
! in the range 0<= AIMAG(ACOSH(X)) <= pi" pi is approx 3.14
! Imaginary part must be >=0 and <= pi so it may not be negative

      complex :: cc=(-1.0,-1.0)
      print *,acosh(cc) ! Imaginary part negative
      print *,log(cc+sqrt(cc**2-1)) ! this is correct acosh(cc)
      end


            (1.06127512,-2.23703575)
            (-1.06127524,2.23703575)

Fortran acosh provides negative of correct answer.