[Patch, Fortran] Fix PR 71047

[Fritz Reese <fritzoreese at gmail dot com>]

Here's the fix and a test case for the regression PR 71047 introduced
by the DEC STRUCTURE/UNION patch (commit 235999).

Turns out I was a bit greedy about adding component refs to structure
constructors in gfc_default_initializer. Fixed to only add them to
FL_STRUCTURE and FL_UNION symbols, which expect them during
translation. The component ref was being added to constructors for the
hidden _data and _vptr members of CLASS components, causing the code
for their real initialization to be skipped by the middle-end.

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71047

---
Fritz Reese

From f1ee9fb07728f69631f9795ba01b590d2277b6f3 Mon Sep 17 00:00:00 2001
From: Fritz O. Reese <fritzoreese@gmail.com>
Date: Thu, 12 May 2016 18:04:15 -0400
Subject: [PATCH] Remove extraneous component refs from derived type constructors.

gcc/fortran/
	PR fortran/71047
	* expr.c (gfc_default_initializer): Avoid extra component refs in
	constructors for derived types and classes.

gcc/testsuite/gfortran.dg/
	PR fortran/71047
	* pr71047.f08: New test.
---
 gcc/fortran/expr.c                    |    5 +++-
 gcc/testsuite/gfortran.dg/pr71047.f08 |   48 +++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+), 1 deletions(-)
 create mode 100644 gcc/testsuite/gfortran.dg/pr71047.f08

diff --git a/gcc/fortran/expr.c b/gcc/fortran/expr.c
index 6ebe08b..816ef01 100644
--- a/gcc/fortran/expr.c
+++ b/gcc/fortran/expr.c
@@ -3975,7 +3975,10 @@ gfc_default_initializer (gfc_typespec *ts)
 
       if (comp->initializer)
 	{
-          ctor->n.component = comp;
+          // Save the component ref for STRUCTUREs and UNIONs.
+          if (ts->u.derived->attr.flavor == FL_STRUCT
+              || ts->u.derived->attr.flavor == FL_UNION)
+            ctor->n.component = comp;
 	  ctor->expr = gfc_copy_expr (comp->initializer);
 	  if ((comp->ts.type != comp->initializer->ts.type
 	       || comp->ts.kind != comp->initializer->ts.kind)
diff --git a/gcc/testsuite/gfortran.dg/pr71047.f08 b/gcc/testsuite/gfortran.dg/pr71047.f08
new file mode 100644
index 0000000..61a0ad4
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr71047.f08
@@ -0,0 +1,48 @@
+! { dg-do compile }
+! { dg-options "-fdump-tree-original" }
+!
+! Fortran/PR71047
+!
+
+module m
+ implicit none
+
+ type, abstract :: c_abstr
+  integer :: i = 0
+ end type c_abstr
+
+ type, extends(c_abstr) :: t_a
+  class(c_abstr), allocatable :: f
+ end type t_a
+ 
+ type, extends(c_abstr) :: t_b
+ end type t_b
+
+contains
+
+ subroutine set(y,x)
+  class(c_abstr), intent(in)  :: x
+  type(t_a),      intent(out) :: y
+   allocate( y%f , source=x )
+ end subroutine set
+
+end module m
+
+
+program p
+ use m
+ implicit none
+
+ type(t_a) :: res
+ type(t_b) :: var
+
+  call set( res , var )
+  write(*,*) res%i
+
+end program p
+
+!
+! Check to ensure the vtable is actually initialized.
+!
+! { dg-final { scan-tree-dump "t_a\\.\\d+\\.f\\._vptr =" "original" } }
+!
-- 
1.7.1