https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64958
--- Comment #8 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
As long as we use a single file, it would be possible to
warn about this.
What we could do is to analyze dusty and check that its argument
n may be redefined. If it appears in a variable definition
context, we could set it to a new intent like INTENT_UNKNOWN_REDEFINED,
which would for all intents and purposes be treated like INTENT_UNKNOWN
except that we would warn if such an argument were passed a
constant, or if it is passed an INTENT(OUT) variable.
This would not even break our module format.
We already warn for
subroutine rusty(n)
integer, intent(out) :: n
end
module foo
implicit none
contains
subroutine bar(n)
integer, intent(in) :: n
print *,"bar before rusty", n
call rusty(n)
print *,"bar after rusty", n
end subroutine bar
end module foo
program main
use foo
implicit none
integer :: n
n = 5
call bar(n)
end program main
so most of the machinery is in place already.
