[Bug fortran/96486] get_environment_variable fails for zero-length values

[kargl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96486

--- Comment #7 from kargl at gcc dot gnu.org ---
(In reply to kargl from comment #6)
> I do note there are other problems with get_environment_variable.
> 
> 1) Neither length nor status can be integer(1).  gfortran should issue
>    an error.
> 
> 2) Fortran 2018 has added an optional errmsg argument.  This is not
>    supported.
> 
> 3) gfortran is issuing errors that don't make sence (to me).
> 
> program foo
>    integer( 1) i01
>    integer( 2) i02
>    integer( 4) i04
>    integer( 8) i08
> #ifdef __GFC_INT_16__
>    integer(16) i16
> #endif
>    character(len=20) name
> 
>    print '(A,I0)', 'range(i01) = ', range(i01)
>    print '(A,I0)', 'range(i02) = ', range(i02)
>    print '(A,I0)', 'range(i04) = ', range(i04)
>    print '(A,I0)', 'range(i08) = ', range(i08)
> #ifdef __GFC_INT_16__
>    print '(A,I0)', 'range(i16) = ', range(i16)
> #endif
> 
>    name = ''
>    ! Although valid Fortran, this should probably raise a warning.
>    call get_environment_variable(name);
> 
>    name = 'FOO'
>    call get_environment_variable(name,length=i01);  ! Should be an error
>    call get_environment_variable(name,length=i02);  ! Should be ok
>    call get_environment_variable(name,length=i04);  ! Should be ok
>    call get_environment_variable(name,length=i08);  ! Should be ok
> #ifdef __GFC_INT_16__
>    call get_environment_variable(name,length=i16);  ! Should be ok
> #endif
> 
> end program foo
> 
> mobile:kargl[256] gfcx -o z a.F90 && ./z
> a.F90:29:45:
> 
>    29 |    call get_environment_variable(name,length=i01);  ! Should be an
> error
>       |                                             1
> Error: In call to 'get_environment_variable' at (1), type mismatch in
> argument length'; pass 'INTEGER(1)' to 'INTEGER(4)'
> a.F90:30:45:
> 
>    30 |    call get_environment_variable(name,length=i02);
>       |                                             1
> Error: In call to 'get_environment_variable' at (1), type mismatch in
> argument length'; pass 'INTEGER(2)' to 'INTEGER(4)'
> a.F90:32:45:
> 
>    32 |    call get_environment_variable(name,length=i08);
>       |                                             1
> Error: In call to 'get_environment_variable' at (1), type mismatch in
> argument length'; pass 'INTEGER(8)' to 'INTEGER(4)'

Need to add a gfc_check_get_environment_variable routine to get pass these
errors.