When a loop iterator has a block declaration containing statements that invoke
functions whose result is returned on the secondary stack (such as a
string-returning function), the compiler fails to generate code to release the
allocated memory when the loop terminates.
After this patch the following test works fine.
with Ada.Text_IO; use Ada.Text_IO;
with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
pragma Warnings (Off);
with System.Secondary_Stack;
pragma Warnings (On);
procedure Small is
procedure Info is new System.Secondary_Stack.Ss_Info (Put_Line);
US : Unbounded_String;
begin
Info;
for J in 1 .. 100_000 loop
Leaky_Block : declare
begin
if (J mod 20000) = 0 then
Info;
end if;
Ada.Text_IO.Put_Line (To_String (US)); -- Test
if (J mod 20000) = 0 then
Info;
end if;
end Leaky_Block;
end loop;
Info;
end;
Command:
gnatmake small.adb; small | grep "Current allocated space :" | uniq
Output:
Current allocated space : 0 bytes
Tested on x86_64-pc-linux-gnu, committed on trunk
2018-07-17 Javier Miranda <mira...@adacore.com>
gcc/ada/
* exp_ch7.adb (Make_Transient_Block): When determining whether an
enclosing scope already handles the secondary stack, take into account
transient blocks nested in a block that do not manage the secondary
stack and are located within a loop.--- gcc/ada/exp_ch7.adb
+++ gcc/ada/exp_ch7.adb
@@ -8695,9 +8695,33 @@ package body Exp_Ch7 is
Action : Node_Id;
Par : Node_Id) return Node_Id
is
+ function Within_Loop_Statement (N : Node_Id) return Boolean;
+ -- Return True when N appears within a loop and no block is containing N
+
function Manages_Sec_Stack (Id : Entity_Id) return Boolean;
-- Determine whether scoping entity Id manages the secondary stack
+ ---------------------------
+ -- Within_Loop_Statement --
+ ---------------------------
+
+ function Within_Loop_Statement (N : Node_Id) return Boolean is
+ Par : Node_Id := Parent (N);
+
+ begin
+ while not (Nkind_In (Par,
+ N_Loop_Statement,
+ N_Handled_Sequence_Of_Statements,
+ N_Package_Specification)
+ or else Nkind (Par) in N_Proper_Body)
+ loop
+ pragma Assert (Present (Par));
+ Par := Parent (Par);
+ end loop;
+
+ return Nkind (Par) = N_Loop_Statement;
+ end Within_Loop_Statement;
+
-----------------------
-- Manages_Sec_Stack --
-----------------------
@@ -8780,6 +8804,16 @@ package body Exp_Ch7 is
elsif Ekind (Scop) = E_Loop then
exit;
+ -- Ditto when the block appears without a block that does not
+ -- manage the secondary stack and is located within a loop.
+
+ elsif Ekind (Scop) = E_Block
+ and then not Manages_Sec_Stack (Scop)
+ and then Present (Block_Node (Scop))
+ and then Within_Loop_Statement (Block_Node (Scop))
+ then
+ exit;
+
-- The transient block does not need to manage the secondary stack
-- when there is an enclosing construct which already does that.
-- This optimization saves on SS_Mark and SS_Release calls but may
