Compilation failed when using gfortran flag default-real-8 and stdlib

[cyrilgandon]

Description

I am trying to compile my program in 64 bits. I use gfortran and the option default-real-8 to compile :

-fdefault-real-8 Set the default real type to an 8 byte wide type.

but got an error:

build\dependencies\stdlib\src\stdlib_specialfunctions_gamma.f90:1175:18:

 1175 |             res = l_gamma(n + 1, 1.0D0)
      |                  1
Error: There is no specific function for the generic 'l_gamma' at (1)

If I believe the error, the function containing this call is

impure elemental function l_factorial_iint64(n) result(res)
    integer(int64), intent(in) :: n

    [...]
    
    res = l_gamma(n + 1, 1.0D0)
end function

So n being int(8) and 1.0D0 being real(8), I think it should find this overload:

impure elemental function l_gamma_iint64dp(z, x) result(res)
    integer(int64), intent(in) :: z
    real(dp), intent(in) :: x

    [...]

end function

But apparently not. Pretty new to Fortran and the kind stuff, I guess I am missing something!

Edit: I extract the code, and the error is more clear:

Type mismatch in argument 'x' at (1); passed REAL(16) to REAL(8)

So I guess default-real-8 is promoting 1.0D0 from REAL(8) to REAL(16)

Expected Behaviour

The stdlib should compile with a default real of size 8.

Version of stdlib

ccdba91

Platform and Architecture

Windows

Additional Information

Also post a question on SO: https://stackoverflow.com/questions/79013476/compilation-failed-when-using-gfortran-flag-default-real-8-and-stdlib