Re: [Patch, Fortran, PR58586, v3] ICE with derived type with allocatable component passed by value

[Andre Vehreschild <vehre at gmx dot de>]

Hi Mikael,

thanks for the review. I still have some questions/remarks before commiting:

On Thu, 07 May 2015 12:14:59 +0200
Mikael Morin <mikael.morin@sfr.fr> wrote:
<snip>
> > @@ -2158,6 +2158,8 @@ build_function_decl (gfc_symbol * sym, bool global)
> >      gfc_set_decl_assembler_name (fndecl, gfc_sym_mangled_function_id
> > (sym)); 
> >    sym->backend_decl = fndecl;
> > +  if (sym == sym->result && !sym->result->backend_decl)
> > +    sym->result->backend_decl = result_decl;
> 
> Something is seriously misbehaving if the condition is true, and setting
> sym->backend_decl to result_decl doesn't seem any better than keeping it
> NULL.
> So, please remove this change

Did that. I think this was a relic from the start of me trying to understand
what was the issue and how to fix it. Later I didn't check, if it was still
necessary. Sorry for that.

> > @@ -5898,8 +5900,21 @@ gfc_generate_function_code (gfc_namespace * ns)
> >  
> >    if (TREE_TYPE (DECL_RESULT (fndecl)) != void_type_node)
> >      {
> > +      bool artificial_result_decl = false;
> >        tree result = get_proc_result (sym);
> >  
> > +      /* Make sure that a function returning an object with
> > +	 alloc/pointer_components always has a result, where at least
> > +	 the allocatable/pointer components are set to zero.  */
> > +      if (result == NULL_TREE && sym->attr.function
> > +	  && sym->ts.type == BT_DERIVED
> > +	  && (sym->ts.u.derived->attr.alloc_comp
> > +	      || sym->ts.u.derived->attr.pointer_comp))
> > +	{
> > +	  artificial_result_decl = true;
> > +	  result = gfc_get_fake_result_decl (sym, 0);
> > +	}
> 
> I expect the "fake" result decl to be needed in more cases.
> For example, if type is BT_CLASS.
> Here is a variant of alloc_comp_class_4.f03:c_init for such a case.
> 
>   class(c) function c_init2()
>     allocatable :: c_init2
>   end function
> 
> or even without class:
> 
>   type(t) function t_init()
>     allocatable :: t_init
>   end function
> 
> for some any type t.
> 
> So, remove the check for alloc_comp/pointer_comp and permit BT_CLASS.
> One minor thing, check sym->result's type and attribute instead of sym's
> here.  It should not make a difference, but I think it's more correct.

I am d'accord with checking sym->result, but I am not happy with removing the
checks for alloc_comp|pointer_comp. When I got you right there, you propose the
if to be like this:

      if (result == NULL_TREE && sym->attr.function
	  && (sym->result->ts.type == BT_DERIVED
	      || sym->result->ts.type == BT_CLASS))

Removing the attribute checks means to initialize every derived/class type
result, which may change the semantics of the code more than intented. Look for
example at this code

  type t
    integer :: i = 5
  end type

  type(t) function static_t_init()
  end function

When one compiles this code with -Wreturn-type, then the warning of an
uninitialized return value is issued at the function declaration. Nevertheless
the result of static_t_init is validly initialized and i is 5. This may
confuse users.

I therefore came to the very ugly solution to make this:

      if (result == NULL_TREE && sym->attr.function
	  && ((sym->result->ts.type == BT_DERIVED
	       && (sym->results->attr.allocatable
		   || sym->result->ts.u.derived->attr.alloc_comp
		   || sym->result->ts.u.derived->attr.pointer_comp))
	      || (sym->result->ts.type == BT_CLASS
		  && (CLASS_DATA (sym->result)->attr.allocatable
		      || CLASS_DATA (sym->result)->attr.alloc_comp
		      || CLASS_DATA (sym->result)->attr.pointer_comp))))

(I am not yet sure, whether the pointer attribute needs to be added to.) With
the code above the result of static_t_init is not initialized with all the
consequences. 

So what do you propose to do here?

Btw, I think I found an additional bug during testing: 
  type(t) function t_init()
    allocatable :: t_init
  end function
 
when called by:
  type(t), allocatable :: temp
  temp = t_init()

a segfault occurs, because the result of t_init() is NULL, which is
dereferenced by the caller in this pseudo-code:

  if (temp != 0B) goto L.12;
  temp = (struct t *) __builtin_malloc (4);
L.12:;
  *temp = *t_init (); <-- This obviously is problematic.

> The rest looks good.
> The patch is OK with the suggested changes above.  Thanks.
> I don't think the test functions above work well enough to be
> incorporated in a testcase for now.

?? I don't get you there? What do you mean? Do you think the
alloc_comp_class_3/4.* are not correctly testing the issue? Any idea of how to
test this better? I mean the pr is about this artificial constructs. I merely
struck it in search of a pr about allocatable components. 

Attached is a version of the patch that I currently use. Note the testcase
alloc_comp_class_4.f03 fails currently, because of the error noted above in
line 94.

Regards,
	Andre
-- 
Andre Vehreschild * Email: vehre ad gmx dot de 

diff --git a/gcc/fortran/resolve.c b/gcc/fortran/resolve.c
index 2ac4689..72df35e 100644
--- a/gcc/fortran/resolve.c
+++ b/gcc/fortran/resolve.c
@@ -14093,10 +14093,15 @@ resolve_symbol (gfc_symbol *sym)
 
       if ((!a->save && !a->dummy && !a->pointer
 	   && !a->in_common && !a->use_assoc
-	   && (a->referenced || a->result)
-	   && !(a->function && sym != sym->result))
+	   && !a->result && !a->function)
 	  || (a->dummy && a->intent == INTENT_OUT && !a->pointer))
 	apply_default_init (sym);
+      else if (a->function && sym->result && a->access != ACCESS_PRIVATE
+	       && (sym->ts.u.derived->attr.alloc_comp
+		   || sym->ts.u.derived->attr.pointer_comp))
+	/* Mark the result symbol to be referenced, when it has allocatable
+	   components.  */
+	sym->result->attr.referenced = 1;
     }
 
   if (sym->ts.type == BT_CLASS && sym->ns == gfc_current_ns
diff --git a/gcc/fortran/trans-decl.c b/gcc/fortran/trans-decl.c
index 4c18920..bcafd8c5 100644
--- a/gcc/fortran/trans-decl.c
+++ b/gcc/fortran/trans-decl.c
@@ -5898,8 +5898,26 @@ gfc_generate_function_code (gfc_namespace * ns)
 
   if (TREE_TYPE (DECL_RESULT (fndecl)) != void_type_node)
     {
+      bool artificial_result_decl = false;
       tree result = get_proc_result (sym);
 
+      /* Make sure that a function returning an object with
+	 alloc/pointer_components always has a result, where at least
+	 the allocatable/pointer components are set to zero.  */
+      if (result == NULL_TREE && sym->attr.function
+	  && ((sym->result->ts.type == BT_DERIVED
+	       && (sym->result->attr.allocatable
+		   || sym->result->ts.u.derived->attr.alloc_comp
+		   || sym->result->ts.u.derived->attr.pointer_comp))
+	      || (sym->result->ts.type == BT_CLASS
+		  && (CLASS_DATA (sym->result)->attr.allocatable
+		      || CLASS_DATA (sym->result)->attr.alloc_comp
+		      || CLASS_DATA (sym->result)->attr.pointer_comp))))
+	{
+	  artificial_result_decl = true;
+	  result = gfc_get_fake_result_decl (sym, 0);
+	}
+
       if (result != NULL_TREE && sym->attr.function && !sym->attr.pointer)
 	{
 	  if (sym->attr.allocatable && sym->attr.dimension == 0
@@ -5918,16 +5936,26 @@ gfc_generate_function_code (gfc_namespace * ns)
 							null_pointer_node));
 	    }
 	  else if (sym->ts.type == BT_DERIVED
-		   && sym->ts.u.derived->attr.alloc_comp
 		   && !sym->attr.allocatable)
 	    {
-	      rank = sym->as ? sym->as->rank : 0;
-	      tmp = gfc_nullify_alloc_comp (sym->ts.u.derived, result, rank);
-	      gfc_add_expr_to_block (&init, tmp);
+	      gfc_expr *init_exp;
+	      init_exp = gfc_default_initializer (&sym->ts);
+	      if (init_exp)
+		{
+		  tmp = gfc_trans_structure_assign (result, init_exp, 0);
+		  gfc_free_expr (init_exp);
+		  gfc_add_expr_to_block (&init, tmp);
+		}
+	      else if (sym->ts.u.derived->attr.alloc_comp)
+		{
+		  rank = sym->as ? sym->as->rank : 0;
+		  tmp = gfc_nullify_alloc_comp (sym->ts.u.derived, result, rank);
+		  gfc_add_expr_to_block (&init, tmp);
+		}
 	    }
 	}
 
-      if (result == NULL_TREE)
+      if (result == NULL_TREE || artificial_result_decl)
 	{
 	  /* TODO: move to the appropriate place in resolve.c.  */
 	  if (warn_return_type && sym == sym->result)
@@ -5937,7 +5965,7 @@ gfc_generate_function_code (gfc_namespace * ns)
 	  if (warn_return_type)
 	    TREE_NO_WARNING(sym->backend_decl) = 1;
 	}
-      else
+      if (result != NULL_TREE)
 	gfc_add_expr_to_block (&body, gfc_generate_return ());
     }
 
diff --git a/gcc/fortran/trans-expr.c b/gcc/fortran/trans-expr.c
index 4bbd685..16e584a 100644
--- a/gcc/fortran/trans-expr.c
+++ b/gcc/fortran/trans-expr.c
@@ -1472,7 +1472,6 @@ realloc_lhs_warning (bt type, bool array, locus *where)
 }
 
 
-static tree gfc_trans_structure_assign (tree dest, gfc_expr * expr, bool init);
 static void gfc_apply_interface_mapping_to_expr (gfc_interface_mapping *,
 						 gfc_expr *);
 
@@ -5341,12 +5340,22 @@ gfc_conv_procedure_call (gfc_se * se, gfc_symbol * sym,
       if (e && (e->ts.type == BT_DERIVED || e->ts.type == BT_CLASS)
 	    && e->ts.u.derived->attr.alloc_comp
 	    && !(e->symtree && e->symtree->n.sym->attr.pointer)
-	    && e->expr_type != EXPR_VARIABLE && !e->rank
-	    && e->expr_type != EXPR_STRUCTURE)
+	    && e->expr_type != EXPR_VARIABLE && !e->rank)
         {
 	  int parm_rank;
-	  tmp = build_fold_indirect_ref_loc (input_location,
-					 parmse.expr);
+	  /* It is known the e returns a structure type with at least one
+	     allocatable component.  When e is a function, ensure that the
+	     function is called once only by using a temporary variable.  */
+	  if (!DECL_P (parmse.expr))
+	    parmse.expr = gfc_evaluate_now_loc (input_location,
+						parmse.expr, &se->pre);
+
+	  if (fsym && fsym->attr.value)
+	    tmp = parmse.expr;
+	  else
+	    tmp = build_fold_indirect_ref_loc (input_location,
+					       parmse.expr);
+
 	  parm_rank = e->rank;
 	  switch (parm_kind)
 	    {
@@ -7137,7 +7146,7 @@ gfc_trans_subcomponent_assign (tree dest, gfc_component * cm, gfc_expr * expr,
 
 /* Assign a derived type constructor to a variable.  */
 
-static tree
+tree
 gfc_trans_structure_assign (tree dest, gfc_expr * expr, bool init)
 {
   gfc_constructor *c;
diff --git a/gcc/fortran/trans.h b/gcc/fortran/trans.h
index e2a1fea..3198c55 100644
--- a/gcc/fortran/trans.h
+++ b/gcc/fortran/trans.h
@@ -666,6 +666,9 @@ tree gfc_deallocate_scalar_with_status (tree, tree, bool, gfc_expr*, gfc_typespe
 /* Generate code to call realloc().  */
 tree gfc_call_realloc (stmtblock_t *, tree, tree);
 
+/* Assign a derived type constructor to a variable.  */
+tree gfc_trans_structure_assign (tree, gfc_expr *, bool);
+
 /* Generate code for an assignment, includes scalarization.  */
 tree gfc_trans_assignment (gfc_expr *, gfc_expr *, bool, bool);
 
diff --git a/gcc/testsuite/gfortran.dg/alloc_comp_class_3.f03 b/gcc/testsuite/gfortran.dg/alloc_comp_class_3.f03
new file mode 100644
index 0000000..0753e33
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/alloc_comp_class_3.f03
@@ -0,0 +1,55 @@
+! { dg-do run }
+! { dg-options "-Wreturn-type" }
+!
+! Check that pr58586 is fixed now.
+! Based on a contribution by Vladimir Fuka
+! Contibuted by Andre Vehreschild
+
+program test_pr58586
+  implicit none
+
+  type :: a
+  end type
+
+  type :: c
+     type(a), allocatable :: a
+  end type
+
+  type :: b
+     integer, allocatable :: a
+  end type
+
+  type :: t
+    integer, allocatable :: comp
+  end type
+  type :: u
+    type(t), allocatable :: comp
+  end type
+
+
+  ! These two are merely to check, if compilation works
+  call add(b())
+  call add(b(null()))
+
+  ! This needs to execute, to see whether the segfault at runtime is resolved
+  call add_c(c_init())
+
+  call sub(u())
+contains
+
+  subroutine add (d)
+    type(b), value :: d
+  end subroutine
+
+  subroutine add_c (d)
+    type(c), value :: d
+  end subroutine
+
+  type(c) function c_init()  ! { dg-warning "not set" }
+  end function
+
+  subroutine sub(d)
+    type(u), value :: d
+  end subroutine
+end program test_pr58586
+
diff --git a/gcc/testsuite/gfortran.dg/alloc_comp_class_4.f03 b/gcc/testsuite/gfortran.dg/alloc_comp_class_4.f03
new file mode 100644
index 0000000..e4c796e
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/alloc_comp_class_4.f03
@@ -0,0 +1,104 @@
+! { dg-do run }
+! { dg-options "-Wreturn-type" }
+!
+! Check that pr58586 is fixed now.
+! Based on a contribution by Vladimir Fuka
+! Contibuted by Andre Vehreschild
+
+module test_pr58586_mod
+  implicit none
+
+  type :: a
+  end type
+
+  type :: c
+     type(a), allocatable :: a
+  end type
+
+  type :: d
+  contains
+     procedure :: init => d_init
+  end type
+
+  type, extends(d) :: e
+  contains
+     procedure :: init => e_init
+  end type
+
+  type :: b
+     integer, allocatable :: a
+  end type
+
+  type t
+    integer :: i = 5
+  end type
+
+contains
+
+  subroutine add (d)
+    type(b), value :: d
+  end subroutine
+
+  subroutine add_c (d)
+    type(c), value :: d
+  end subroutine
+
+  subroutine add_class_c (d)
+    class(c), value :: d
+  end subroutine
+
+  subroutine add_t (d)
+    type(t), value :: d
+  end subroutine
+
+  type(c) function c_init() ! { dg-warning "not set" }
+  end function
+
+  class(c) function c_init2() ! { dg-warning "not set" }
+    allocatable :: c_init2
+  end function
+
+  type(c) function d_init(this) ! { dg-warning "not set" }
+    class(d) :: this
+  end function
+
+  type(c) function e_init(this)
+    class(e) :: this
+    allocate (e_init%a)
+  end function
+
+  type(t) function t_init() ! { dg-warning "not set" }
+    allocatable :: t_init
+  end function
+
+  type(t) function static_t_init() ! { dg-warning "not set" }
+  end function
+end module test_pr58586_mod
+
+program test_pr58586
+  use test_pr58586_mod
+
+  class(d), allocatable :: od
+  class(e), allocatable :: oe
+  type(t), allocatable :: temp
+
+  ! These two are merely to check, if compilation works
+  call add(b())
+  call add(b(null()))
+
+  ! This needs to execute, to see whether the segfault at runtime is resolved
+  call add_c(c_init())
+  call add_class_c(c_init2())
+
+  call add_t(static_t_init())
+  temp = t_init() ! <-- This derefs a null-pointer currently
+  if (allocated (temp)) call abort()
+
+  allocate(od)
+  call add_c(od%init())
+  deallocate(od)
+  allocate(oe)
+  call add_c(oe%init())
+  deallocate(oe)
+end program
+