Re: [PATCH] Fortran: fix passing array component to polymorphic argument [PR105658]

[Peter Hill <peter.hill@york.ac.uk>]

Hi Harald,

Thanks for your help, please see the updated and signed-off patch below.

> (I am not entirely sure whether we need to exclude pointer and
> allocatable attributes here explicitly, given the constraints
> in F2023:15.5.2.6, but other may have an opinion, too.
> The above should be safe anyway.)

I've included them in the patch here, but it does seem to work fine
without checking those attributes here -- and invalid code is still
caught with that change.

It also occurred to me that array temporaries aren't _required_ here
(for arrays of derived type components), but in the general case with
a type with differently sized components, the stride wouldn't be a
multiple of the component's type's size. Is it possible in principle
to have an arbitrary stride?

Cheers,
Peter

From 907a104facfc7f35f48ebcfa9ef5f8f5430d4d3c Mon Sep 17 00:00:00 2001
From: Peter Hill <peter.hill@york.ac.uk>
Date: Thu, 15 Feb 2024 16:58:33 +0000
Subject: [PATCH] Fortran: fix passing array component ref to polymorphic
 procedures

         PR fortran/105658

gcc/fortran/ChangeLog

        * trans-expr.cc (gfc_conv_intrinsic_to_class): When passing an
        array component reference of intrinsic type to a procedure
        with an unlimited polymorphic dummy argument, a temporary
        should be created.

gcc/testsuite/ChangeLog

        * gfortran.dg/PR105658.f90: New test.

Signed-off-by: Peter Hill <peter.hill@york.ac.uk>
---
 gcc/fortran/trans-expr.cc              |  9 +++++
 gcc/testsuite/gfortran.dg/PR105658.f90 | 50 ++++++++++++++++++++++++++
 2 files changed, 59 insertions(+)
 create mode 100644 gcc/testsuite/gfortran.dg/PR105658.f90

diff --git a/gcc/fortran/trans-expr.cc b/gcc/fortran/trans-expr.cc
index a0593b76f18..004081aa6c3 100644
--- a/gcc/fortran/trans-expr.cc
+++ b/gcc/fortran/trans-expr.cc
@@ -1019,6 +1019,14 @@ gfc_conv_intrinsic_to_class (gfc_se *parmse, gfc_expr *e,
   tmp = gfc_typenode_for_spec (&class_ts);
   var = gfc_create_var (tmp, "class");

+  /* Force a temporary for component or substring references */
+  if (unlimited_poly
+      && class_ts.u.derived->components->attr.dimension
+      && !class_ts.u.derived->components->attr.allocatable
+      && !class_ts.u.derived->components->attr.class_pointer
+      && is_subref_array (e))
+    parmse->force_tmp = 1;
+
   /* Set the vptr.  */
   ctree = gfc_class_vptr_get (var);

@@ -6439,6 +6447,7 @@ gfc_conv_procedure_call (gfc_se * se, gfc_symbol * sym,
       CLASS object for the unlimited polymorphic formal.  */
    gfc_find_vtab (&e->ts);
    gfc_init_se (&parmse, se);
+
    gfc_conv_intrinsic_to_class (&parmse, e, fsym->ts);

  }
diff --git a/gcc/testsuite/gfortran.dg/PR105658.f90
b/gcc/testsuite/gfortran.dg/PR105658.f90
new file mode 100644
index 00000000000..8aacecf806e
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/PR105658.f90
@@ -0,0 +1,50 @@
+! { dg-do compile }
+! { dg-options "-Warray-temporaries" }
+! Test fix for incorrectly passing array component to unlimited
polymorphic procedure
+
+module test_PR105658_mod
+   implicit none
+   type :: foo
+     integer :: member1
+     integer :: member2
+   end type foo
+contains
+   subroutine print_poly(array)
+     class(*), dimension(:), intent(in) :: array
+     select type(array)
+     type is (integer)
+       print*, array
+     type is (character(*))
+       print *, array
+     end select
+   end subroutine print_poly
+
+   subroutine do_print(thing)
+     type(foo), dimension(3), intent(in) :: thing
+     type(foo), parameter :: y(3) = [foo(1,2),foo(3,4),foo(5,6)]
+     integer :: i, j, uu(5,6)
+
+     call print_poly(thing%member1)   ! { dg-warning "array temporary" }
+     call print_poly(y%member2)       ! { dg-warning "array temporary" }
+     call print_poly(y(1::2)%member2) ! { dg-warning "array temporary" }
+
+     ! The following array sections work without temporaries
+     uu = reshape([(((10*i+j),i=1,5),j=1,6)],[5,6])
+     print *, uu(2,2::2)
+     call print_poly (uu(2,2::2))     ! no temp needed!
+     print *, uu(1::2,6)
+     call print_poly (uu(1::2,6))     ! no temp needed!
+   end subroutine do_print
+
+   subroutine do_print2(thing2)
+     class(foo), dimension(:), intent(in) :: thing2
+     call print_poly (thing2% member2) ! { dg-warning "array temporary" }
+   end subroutine do_print2
+
+   subroutine do_print3 ()
+     character(3) :: c(3) = ["abc","def","ghi"]
+     call print_poly (c(1::2))      ! no temp needed!
+     call print_poly (c(1::2)(2:3)) ! { dg-warning "array temporary" }
+   end subroutine do_print3
+
+end module test_PR105658_mod
-- 
2.43.0