ada: Restore fix for controlled dynamic allocation with BIP function call

The resolution made some time ago had been that a dynamic allocation for
a limited type that needs finalization with a function call as expression
always needs to be done in the called function, even if the limited type
has a known size.  But the fix implementing this resolution was dropped
inadvertently at some point.

The change also contains a small tweak for Expand_N_Object_Declaration
and a small related cleanup in the finalization machinery.

gcc/ada/

	* exp_ch3.adb (Expand_N_Object_Declaration): In the case of a
	return object of a BIP function that needs finalization, save
	the assignment statement made to initialize it, if any.
	* exp_ch6.ads (BIP_Formal_Kind): Adjust description.
	* exp_ch6.adb (Make_Build_In_Place_Call_In_Allocator): Make a
	couple of adjustments to the commentary.
	(Needs_BIP_Alloc_Form): Also return true if the function needs
	a BIP_Finalization_Master parameter.
	* exp_ch7.adb (Build_BIP_Cleanup_Stmts): Remove now always true
	test on Needs_BIP_Alloc_Form.
	(Attach_Object_To_Master_Node): Remove duplication in comment.

1 files changed, 18 insertions, 16 deletions

diff --git a/gcc/ada/exp_ch6.adb b/gcc/ada/exp_ch6.adb
index a89c9af..9e1844a 100644
--- a/gcc/ada/exp_ch6.adb
+++ b/gcc/ada/exp_ch6.adb
@@ -158,9 +158,9 @@ package body Exp_Ch6 is
       Alloc_Form     : BIP_Allocation_Form := Unspecified;
       Alloc_Form_Exp : Node_Id             := Empty;
       Pool_Actual    : Node_Id             := Make_Null (No_Location));
-   --  Ada 2005 (AI-318-02): Add the actuals needed for a build-in-place
-   --  function call that returns a caller-unknown-size result (BIP_Alloc_Form
-   --  and BIP_Storage_Pool). If Alloc_Form_Exp is present, then use it,
+   --  Ada 2005 (AI-318-02): If the result type of a build-in-place call needs
+   --  them, add the actuals parameters BIP_Alloc_Form and BIP_Storage_Pool.
+   --  If Alloc_Form_Exp is present, then pass it for the first parameter,
    --  otherwise pass a literal corresponding to the Alloc_Form parameter
    --  (which must not be Unspecified in that case). Pool_Actual is the
    --  parameter to pass to BIP_Storage_Pool.
@@ -8328,9 +8328,11 @@ package body Exp_Ch6 is
       Set_Can_Never_Be_Null (Acc_Type, False);
       --  It gets initialized to null, so we can't have that
 
-      --  When the result subtype is constrained, the return object is created
-      --  on the caller side, and access to it is passed to the function. This
-      --  optimization is disabled when the result subtype needs finalization
+      --  When the result subtype is returned on the secondary stack or is
+      --  tagged, the called function itself must perform the allocation of
+      --  the return object, so we pass parameters indicating that.
+
+      --  But that's also the case when the result subtype needs finalization
       --  actions because the caller side allocation may result in undesirable
       --  finalization. Consider the following example:
       --
@@ -8351,11 +8353,6 @@ package body Exp_Ch6 is
       --  will be finalized when access type Lim_Ctrl_Ptr goes out of scope
       --  since it is already attached on the related finalization master.
 
-      --  Here and in related routines, we must examine the full view of the
-      --  type, because the view at the point of call may differ from the
-      --  one in the function body, and the expansion mechanism depends on
-      --  the characteristics of the full view.
-
       if Needs_BIP_Alloc_Form (Function_Id) then
          Temp_Init := Empty;
 
@@ -8386,6 +8383,10 @@ package body Exp_Ch6 is
 
          Return_Obj_Actual := Empty;
 
+      --  When the result subtype neither is returned on the secondary stack
+      --  nor is tagged, the return object is created on the caller side, and
+      --  access to it is passed to the function.
+
       else
          --  Replace the initialized allocator of form "new T'(Func (...))"
          --  with an uninitialized allocator of form "new T", where T is the
@@ -8428,11 +8429,6 @@ package body Exp_Ch6 is
            (Result_Subt,
             Make_Explicit_Dereference (Loc,
               Prefix => New_Occurrence_Of (Return_Obj_Access, Loc)));
-
-      --  When the result subtype is unconstrained, the function itself must
-      --  perform the allocation of the return object, so we pass parameters
-      --  indicating that.
-
       end if;
 
       --  Declare the temp object
@@ -9636,6 +9632,12 @@ package body Exp_Ch6 is
       Typ : constant Entity_Id := Underlying_Type (Etype (Func_Id));
 
    begin
+      --  See Make_Build_In_Place_Call_In_Allocator for the rationale
+
+      if Needs_BIP_Finalization_Master (Func_Id) then
+         return True;
+      end if;
+
       --  A formal giving the allocation method is needed for build-in-place
       --  functions whose result type is returned on the secondary stack or
       --  is a tagged type. Tagged primitive build-in-place functions need