Am 18.12.24 um 19:09 schrieb Jerry D:
On 12/18/24 4:11 AM, Harald Anlauf wrote:
Hi Steve,
thanks for the draft patch.
I haven't looked close enough, but you may have to add support
for 'asis' being an optional dummy variable. The following
example crashes here with a segfault:
program foo
use iso_c_binding, only : c_null_char, c_char, f_c_string, c_size_t
implicit none
logical asis
character(len=6, kind=c_char) :: s1
character(len=:, kind=c_char), allocatable :: s2
interface
!
! strlen() counts up to '\0', and excludes it from the count
!
function strlen(s) bind(c,name="strlen")
import c_char, c_size_t
integer(c_size_t) strlen
character(len=1,kind=c_char), intent(in) :: s(*)
end function strlen
end interface
s1 = 'abc '
asis = .true.
call check (asis) ! OK
asis = .false.
call check (asis) ! OK
call check () ! segfault
contains
subroutine check (asis)
logical, optional, intent(in) :: asis
s2 = f_c_string(s1, asis)
print *, len_trim(s1), int(strlen(s2))
end subroutine check
end program foo
--- snip ---
This is interesting. In my tests I tried:
print *, len(s1), len(f_c_string(s1))
Which works fine. Is the user required to check for the presence of the
optional argument before using it? From the 'view' of the subroutine
'asis' exists but is undefined.
Since the standard defines the argument as optional, we have to
handle it. This is similar to e.g. the SIZE intrinsic:
program p
implicit none
integer :: a(3) = [1,2,3]
integer :: dim = 1
call check_size (dim)
call check_size ()
contains
subroutine check_size (dim)
integer, optional, intent(in) :: dim
print *, size (a, dim=dim)
end subroutine check_size
end
Also other intrinsics (e.g. minloc/maxloc/lbound/ubound/...)
need to do it right (and I think/hope they do).
Cheers,
Harald
Regards,
Jerry
