Compiler Bug: cmplx does not handle Y argument correctly

[emilybo]

The following is a reproducer for the problem:

module intel_bug

implicit none

contains

subroutine to_complex(arr, Out_1, Out_2)
integer(8), intent(in) :: arr(0:)
complex(4), intent(out) :: Out_1
complex(4), intent(out) :: Out_2

complex(4), allocatable :: a(:)

allocate(a(0:size(arr, kind=8) - 1_8))
a = cmplx(arr, 0, kind=4) ! <----------- Problematic line v1
!a = cmplx(arr, 0.0, kind=4) ! <----------- Problematic line v2
!a = cmplx(arr, kind=4) ! <----------- Problematic line fix

Out_1 = a(0_8)
Out_2 = a(1_8)

end subroutine to_complex

end module intel_bug
program my_prog

use intel_bug

integer(8), allocatable :: arr(:)
complex(4) :: test1
complex(4) :: test2

allocate(arr(0:9))

do i=0,9
arr(i) = i
end do

call to_complex(arr, test1, test2)

print *, test1, test2

end program my_prog

The output of the code is:

# v1
(0.0000000E+00,0.0000000E+00) (0.0000000E+00,0.0000000E+00)

# v2
(0.0000000E+00,0.0000000E+00) (0.0000000E+00,0.0000000E+00)

# v3
(0.0000000E+00,0.0000000E+00) (1.000000,0.0000000E+00)

The standard says:

CMPLX (X [, Y, KIND])

Y (optional)    shall be of type integer or real, or a boz-literal-constant. If X is of type
complex, Y shall not be present, nor shall Y be associated with an optional
dummy argument.
If Y is absent and X is not complex, it is as if Y were present with the value
zero

This post may be related: https://community.intel.com/t5/Intel-Fortran-Compiler/ifort-and-ifx-internal-compiler-error/m-p/1620305

Compiler version information:

ifx (IFX) 2024.2.1 20240711
Copyright (C) 1985-2024 Intel Corporation. All rights reserved.

[Ron_Green · Accepted solution]

We did see the earlier issue.  and we fixed it an it's in the upcoming v2025.0 ifx compiler.  Output matches NAG and Gfortran for cmplx and follows the standard. 

$ ifx -what -V cmplx_v1.f90 && ./a.out
Intel(R) Fortran Compiler for applications running on Intel(R) 64, Version 2025.0.0 Build 20240930
Copyright (C) 1985-2024 Intel Corporation. All rights reserved.
 Intel(R) Fortran 25.0-1205
GNU ld version 2.41-34.fc40
 (0.0000000E+00,0.0000000E+00) (1.000000,0.0000000E+00)

$ ifx -what -V cmplx_v2.f90 && ./a.out
Intel(R) Fortran Compiler for applications running on Intel(R) 64, Version 2025.0.0 Build 20240930
Copyright (C) 1985-2024 Intel Corporation. All rights reserved.
 Intel(R) Fortran 25.0-1205
GNU ld version 2.41-34.fc40
 (0.0000000E+00,0.0000000E+00) (1.000000,0.0000000E+00)

$ ifx -what -V cmplx_v3.f90 && ./a.out
Intel(R) Fortran Compiler for applications running on Intel(R) 64, Version 2025.0.0 Build 20240930
Copyright (C) 1985-2024 Intel Corporation. All rights reserved.
 Intel(R) Fortran 25.0-1205
GNU ld version 2.41-34.fc40
 (0.0000000E+00,0.0000000E+00) (1.000000,0.0000000E+00)