From: Eric Botcazou <[email protected]>
A change made a long time ago has introduced a leak of the secondary stack
at run time for unconstrained limited non-controlled arrays in anonymous
contexts, because of the lack of a transient scope in these contexts.
The large comment preceding the call to Establish_Transient_Scope in the
Resolve_Call procedure explains the strategy for build-in-place functions,
so the best course of action is probably to revert the commit and to fix
the original problem along the lines of the comment.
gcc/ada/ChangeLog:
* exp_ch3.adb (Expand_N_Object_Declaration): Delete ancient comment.
* exp_ch6.adb (Expand_Call_Helper): Do not establish a transient
scope for build-in-place functions in anonymous contexts here...
(Make_Build_In_Place_Call_In_Anonymous_Context): ...but here instead.
* sem_attr.adb (Resolve_Attribute) <Attribute_Range>: Remove obsolete
code dealing with transient scopes.
* sem_res.adb (Resolve_Actuals): Likewise.
(Resolve_Call): Adjust comment on the strategy for transient scopes.
Tested on x86_64-pc-linux-gnu, committed on master.
---
gcc/ada/exp_ch3.adb | 5 +---
gcc/ada/exp_ch6.adb | 57 ++++++++++++++++----------------------------
gcc/ada/sem_attr.adb | 10 --------
gcc/ada/sem_res.adb | 24 ++++---------------
4 files changed, 26 insertions(+), 70 deletions(-)
diff --git a/gcc/ada/exp_ch3.adb b/gcc/ada/exp_ch3.adb
index db41ab75d3e..fbc7060a744 100644
--- a/gcc/ada/exp_ch3.adb
+++ b/gcc/ada/exp_ch3.adb
@@ -7858,10 +7858,7 @@ package body Exp_Ch3 is
-- Ada 2005 (AI-318-02): If the initialization expression is a call
-- to a build-in-place function, then access to the declared object
- -- must be passed to the function. Currently we limit such functions
- -- to those with constrained limited result subtypes, but eventually
- -- plan to expand the allowed forms of functions that are treated as
- -- build-in-place.
+ -- must be passed to the function.
elsif Is_Build_In_Place_Function_Call (Expr_Q) then
Make_Build_In_Place_Call_In_Object_Declaration (N, Expr_Q);
diff --git a/gcc/ada/exp_ch6.adb b/gcc/ada/exp_ch6.adb
index eb141839a3e..f41dca311d1 100644
--- a/gcc/ada/exp_ch6.adb
+++ b/gcc/ada/exp_ch6.adb
@@ -5713,38 +5713,13 @@ package body Exp_Ch6 is
if Nkind (Call_Node) = N_Function_Call
and then Needs_Finalization (Etype (Call_Node))
+ and then not Is_Build_In_Place_Function_Call (Call_Node)
+ and then (No (First_Formal (Subp))
+ or else not
+ Is_Concurrent_Record_Type (Etype (First_Formal (Subp))))
then
- if not Is_Build_In_Place_Function_Call (Call_Node)
- and then
- (No (First_Formal (Subp))
- or else
- not Is_Concurrent_Record_Type (Etype (First_Formal (Subp))))
- then
- Expand_Ctrl_Function_Call
- (Call_Node, Needs_Secondary_Stack (Etype (Call_Node)));
-
- -- Build-in-place function calls which appear in anonymous contexts
- -- need a transient scope to ensure the proper finalization of the
- -- intermediate result after its use.
-
- elsif Is_Build_In_Place_Function_Call (Call_Node)
- and then Nkind (Parent (Unqual_Conv (Call_Node))) in
- N_Attribute_Reference
- | N_Function_Call
- | N_Indexed_Component
- | N_Object_Renaming_Declaration
- | N_Procedure_Call_Statement
- | N_Selected_Component
- | N_Slice
- and then
- (Ekind (Current_Scope) /= E_Loop
- or else Nkind (Parent (Call_Node)) /= N_Function_Call
- or else not
- Is_Build_In_Place_Function_Call (Parent (Call_Node)))
- then
- Establish_Transient_Scope
- (Call_Node, Needs_Secondary_Stack (Etype (Call_Node)));
- end if;
+ Expand_Ctrl_Function_Call
+ (Call_Node, Needs_Secondary_Stack (Etype (Call_Node)));
-- Functions returning noncontrolled objects that may be subject to
-- user-defined indexing also need special attention. The problem
@@ -9313,6 +9288,8 @@ package body Exp_Ch6 is
Loc : constant Source_Ptr := Sloc (Function_Call);
Func_Call : constant Node_Id := Unqual_Conv (Function_Call);
Function_Id : Entity_Id;
+ Known_Size : Boolean;
+ Needs_Fin : Boolean;
Result_Subt : Entity_Id;
begin
@@ -9339,11 +9316,12 @@ package body Exp_Ch6 is
Warn_BIP (Func_Call);
Result_Subt := Etype (Function_Id);
+ Known_Size := Caller_Known_Size (Func_Call, Result_Subt);
+ Needs_Fin := Needs_Finalization (Result_Subt);
-- If the build-in-place function returns a controlled object, then the
- -- object needs to be finalized immediately after the context. Since
- -- this case produces a transient scope, the servicing finalizer needs
- -- to name the returned object.
+ -- object needs to be finalized immediately after the context is exited,
+ -- which requires the creation of a transient scope and a named object.
-- If the build-in-place function returns a definite subtype, then an
-- object also needs to be created and an access value designating it
@@ -9357,9 +9335,12 @@ package body Exp_Ch6 is
-- the expander using the appropriate mechanism in Make_Build_In_Place_
-- Call_In_Object_Declaration.
- if Needs_Finalization (Result_Subt)
- or else Caller_Known_Size (Func_Call, Result_Subt)
- then
+ if Needs_Fin or else Known_Size then
+ if Needs_Fin then
+ Establish_Transient_Scope
+ (Func_Call, Manage_Sec_Stack => not Known_Size);
+ end if;
+
declare
Temp_Id : constant Entity_Id := Make_Temporary (Loc, 'R');
Temp_Decl : constant Node_Id :=
@@ -9400,6 +9381,8 @@ package body Exp_Ch6 is
Add_Access_Actual_To_Build_In_Place_Call
(Func_Call, Function_Id, Empty);
+ Establish_Transient_Scope (Func_Call, Manage_Sec_Stack => True);
+
-- Mark the call as processed as a build-in-place call
Set_Is_Expanded_Build_In_Place_Call (Func_Call);
diff --git a/gcc/ada/sem_attr.adb b/gcc/ada/sem_attr.adb
index 20270c20fe1..95f1466968a 100644
--- a/gcc/ada/sem_attr.adb
+++ b/gcc/ada/sem_attr.adb
@@ -12631,16 +12631,6 @@ package body Sem_Attr is
begin
if not Is_Entity_Name (P) or else not Is_Type (Entity (P)) then
Resolve (P);
-
- -- If the prefix is a function call returning on the secondary
- -- stack, we must make sure to mark/release the stack.
-
- if Nkind (P) = N_Function_Call
- and then Nkind (Parent (N)) = N_Loop_Parameter_Specification
- and then Requires_Transient_Scope (Etype (P))
- then
- Set_Uses_Sec_Stack (Scope (Current_Scope));
- end if;
end if;
Dims := Expressions (N);
diff --git a/gcc/ada/sem_res.adb b/gcc/ada/sem_res.adb
index a0287f1abe5..a44016c8012 100644
--- a/gcc/ada/sem_res.adb
+++ b/gcc/ada/sem_res.adb
@@ -4486,21 +4486,6 @@ package body Sem_Res is
Set_Do_Range_Check (Expression (A));
end if;
- -- If the actual is a function call that returns a limited
- -- unconstrained object that needs finalization, create a
- -- transient scope for it, so that it can receive the proper
- -- finalization list.
-
- elsif Expander_Active
- and then Nkind (A) = N_Function_Call
- and then Is_Limited_Record (Etype (F))
- and then not Is_Constrained (Etype (F))
- and then (Needs_Finalization (Etype (F))
- or else Has_Task (Etype (F)))
- then
- Establish_Transient_Scope (A, Manage_Sec_Stack => False);
- Resolve (A, Etype (F));
-
-- A small optimization: if one of the actuals is a concatenation
-- create a block around a procedure call to recover stack space.
-- This alleviates stack usage when several procedure calls in
@@ -7063,10 +7048,11 @@ package body Sem_Res is
-- b) Subprograms that are ignored ghost entities do not return anything
- -- c) Calls to a build-in-place function, since such functions may
- -- allocate their result directly in a target object, and cases where
- -- the result does get allocated in the secondary stack are checked for
- -- within the specialized Exp_Ch6 procedures for expanding those
+ -- c) Calls to a build-in-place function, since such functions allocate
+ -- their result directly in the target object or on the secondary stack,
+ -- and cases where the target object needs to be created and destroyed
+ -- on exit to the context, or the secondary stack is used, are checked
+ -- for within the specialized Exp_Ch6 procedures for expanding those
-- build-in-place calls.
-- d) Calls to inlinable expression functions do not use the secondary
--
2.51.0
