https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101308
Bug ID: 101308
Summary: Bind(C): gfortran does not create C descriptors for
scalar pointer/allocatable arguments
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: sandra at gcc dot gnu.org
Target Milestone: ---
gfortran is completely failing to create C descriptors for scalar arguments to
bind(c) functions that have the POINTER or ALLOCATABLE attribute. E.g. for
this trivial test case
subroutine f ()
use iso_c_binding
interface
subroutine ctest (pp) bind (c)
use iso_c_binding
integer(C_INT), pointer :: pp
end subroutine
end interface
integer(C_INT), pointer :: p
p => NULL ()
call ctest (p)
end subroutine
-fdump-tree-original produces this output:
__attribute__((fn spec (". ")))
void f ()
{
integer(kind=4) * p;
p = 0B;
ctest (&p);
}
showing that it is passing a raw pointer by reference instead.
The 2018 Fortran standard is clear that pointers/allocatables are passed as
pointers to C descriptors; it's item (5) in section 18.3.6.
This bug is causing many failures in my WIP TS29113 testsuite, posted at
https://gcc.gnu.org/pipermail/gcc-patches/2021-July/574115.html
interoperability/fc-descriptor-3.f90
interoperability/fc-out-descriptor-3.f90
interoperability/typecodes-scalar.f90
interoperability/typecodes-scalar-ext.f90
procedures/allocatable-dummy.f90
Is it an accident that the related tests passing descriptors from C to Fortran
functions for pointer/allocatable scalars appear to work? The called Fortran
function expects a pointer to a pointer to the effective argument, and the C
function is passing a pointer to a descriptor structure whose first element
happens to be a pointer to the effective argument.
