https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109861
--- Comment #4 from anlauf at gcc dot gnu.org --- (In reply to Scot Breitenfeld from comment #3) > I guess the issue is whether marking TYPE(C_PTR) as CLOBBER is correct. I > looked through the 2018 standard and could not locate anything that > addresses this use case. Are you interpreting the possibility that a > TYPE(C_PTR) should not be declared INTENT(OUT)? Maybe I am missing your intention, but I interpret your code that you want to pass a (C) pointer to variable attr_rdata0 to return your result. But that needs to be intent(in). Your subroutine is not really supposed to return a pointer but a result in the location the pointer dereferences. Feel free to correct me. > I can instead change the subroutine to declare buf as > > INTEGER(C_INT), INTENT(OUT), TARGET :: buf > > and f_ptr = C_LOC(buf) and there is no issue. I cannot confirm this with my gcc installations, and there is no reason that this should make a difference. > So it seems to depend on the > TYPE of the argument being passed. There are cases where no clobber is currently generated. For example, if the dummy variable is a Fortran pointer, which has a completely different semantics from TYPE(C_PTR). Still I don't understand why you don't use INTENT(IN) for the pointer. In that case you could do things in the main like: CALL H5Aread_async_f(C_LOC(attr_rdata0)) which appears to represent what I am guessing, and which gets rejected for INTENT /= IN with a possibly more helpful error message.
