| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT COMPILER COMPONENTS -- |
| -- -- |
| -- S Y S T E M . S E C O N D A R Y _ S T A C K -- |
| -- -- |
| -- B o d y -- |
| -- -- |
| -- Copyright (C) 1992-2005, Free Software Foundation, Inc. -- |
| -- -- |
| -- GNAT is free software; you can redistribute it and/or modify it under -- |
| -- terms of the GNU General Public License as published by the Free Soft- -- |
| -- ware Foundation; either version 2, or (at your option) any later ver- -- |
| -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- |
| -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- |
| -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- |
| -- for more details. You should have received a copy of the GNU General -- |
| -- Public License distributed with GNAT; see file COPYING. If not, write -- |
| -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, -- |
| -- Boston, MA 02110-1301, USA. -- |
| -- -- |
| -- As a special exception, if other files instantiate generics from this -- |
| -- unit, or you link this unit with other files to produce an executable, -- |
| -- this unit does not by itself cause the resulting executable to be -- |
| -- covered by the GNU General Public License. This exception does not -- |
| -- however invalidate any other reasons why the executable file might be -- |
| -- covered by the GNU Public License. -- |
| -- -- |
| -- GNAT was originally developed by the GNAT team at New York University. -- |
| -- Extensive contributions were provided by Ada Core Technologies Inc. -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| with System.Soft_Links; |
| with System.Parameters; |
| with Unchecked_Conversion; |
| with Unchecked_Deallocation; |
| |
| package body System.Secondary_Stack is |
| |
| package SSL renames System.Soft_Links; |
| |
| use type SSE.Storage_Offset; |
| use type System.Parameters.Size_Type; |
| |
| SS_Ratio_Dynamic : constant Boolean := |
| Parameters.Sec_Stack_Ratio = Parameters.Dynamic; |
| -- There are two entirely different implementations of the secondary |
| -- stack mechanism in this unit, and this Boolean is used to select |
| -- between them (at compile time, so the generated code will contain |
| -- only the code for the desired variant). If SS_Ratio_Dynamic is |
| -- True, then the secondary stack is dynamically allocated from the |
| -- heap in a linked list of chunks. If SS_Ration_Dynamic is False, |
| -- then the secondary stack is allocated statically by grabbing a |
| -- section of the primary stack and using it for this purpose. |
| |
| type Memory is array (SS_Ptr range <>) of SSE.Storage_Element; |
| for Memory'Alignment use Standard'Maximum_Alignment; |
| -- This is the type used for actual allocation of secondary stack |
| -- areas. We require maximum alignment for all such allocations. |
| |
| --------------------------------------------------------------- |
| -- Data Structures for Dynamically Allocated Secondary Stack -- |
| --------------------------------------------------------------- |
| |
| -- The following is a diagram of the data structures used for the |
| -- case of a dynamically allocated secondary stack, where the stack |
| -- is allocated as a linked list of chunks allocated from the heap. |
| |
| -- +------------------+ |
| -- | Next | |
| -- +------------------+ |
| -- | | Last (200) |
| -- | | |
| -- | | |
| -- | | |
| -- | | |
| -- | | |
| -- | | First (101) |
| -- +------------------+ |
| -- +----------> | | | |
| -- | +----------+-------+ |
| -- | | | |
| -- | ^ V |
| -- | | | |
| -- | +-------+----------+ |
| -- | | | | |
| -- | +------------------+ |
| -- | | | Last (100) |
| -- | | C | |
| -- | | H | |
| -- +-----------------+ | +-------->| U | |
| -- | Current_Chunk -|--+ | | N | |
| -- +-----------------+ | | K | |
| -- | Top -|-----+ | | First (1) |
| -- +-----------------+ +------------------+ |
| -- | Default_Size | | Prev | |
| -- +-----------------+ +------------------+ |
| -- |
| |
| type Chunk_Id (First, Last : SS_Ptr); |
| type Chunk_Ptr is access all Chunk_Id; |
| |
| type Chunk_Id (First, Last : SS_Ptr) is record |
| Prev, Next : Chunk_Ptr; |
| Mem : Memory (First .. Last); |
| end record; |
| |
| type Stack_Id is record |
| Top : SS_Ptr; |
| Default_Size : SSE.Storage_Count; |
| Current_Chunk : Chunk_Ptr; |
| end record; |
| |
| type Stack_Ptr is access Stack_Id; |
| -- Pointer to record used to represent a dynamically allocated secondary |
| -- stack descriptor for a secondary stack chunk. |
| |
| procedure Free is new Unchecked_Deallocation (Chunk_Id, Chunk_Ptr); |
| -- Free a dynamically allocated chunk |
| |
| function To_Stack_Ptr is new |
| Unchecked_Conversion (Address, Stack_Ptr); |
| function To_Addr is new |
| Unchecked_Conversion (Stack_Ptr, Address); |
| -- Convert to and from address stored in task data structures |
| |
| -------------------------------------------------------------- |
| -- Data Structures for Statically Allocated Secondary Stack -- |
| -------------------------------------------------------------- |
| |
| -- For the static case, the secondary stack is a single contiguous |
| -- chunk of storage, carved out of the primary stack, and represented |
| -- by the following data strcuture |
| |
| type Fixed_Stack_Id is record |
| Top : SS_Ptr; |
| -- Index of next available location in Mem. This is initialized to |
| -- 0, and then incremented on Allocate, and Decremented on Release. |
| |
| Last : SS_Ptr; |
| -- Length of usable Mem array, which is thus the index past the |
| -- last available location in Mem. Mem (Last-1) can be used. This |
| -- is used to check that the stack does not overflow. |
| |
| Max : SS_Ptr; |
| -- Maximum value of Top. Initialized to 0, and then may be incremented |
| -- on Allocate, but is never Decremented. The last used location will |
| -- be Mem (Max - 1), so Max is the maximum count of used stack space. |
| |
| Mem : Memory (0 .. 0); |
| -- This is the area that is actually used for the secondary stack. |
| -- Note that the upper bound is a dummy value properly defined by |
| -- the value of Last. We never actually allocate objects of type |
| -- Fixed_Stack_Id, so the bounds declared here do not matter. |
| end record; |
| |
| Dummy_Fixed_Stack : Fixed_Stack_Id; |
| pragma Warnings (Off, Dummy_Fixed_Stack); |
| -- Well it is not quite true that we never allocate an object of the |
| -- type. This dummy object is allocated for the purpose of getting the |
| -- offset of the Mem field via the 'Position attribute (such a nuisance |
| -- that we cannot apply this to a field of a type!) |
| |
| type Fixed_Stack_Ptr is access Fixed_Stack_Id; |
| -- Pointer to record used to describe statically allocated sec stack |
| |
| function To_Fixed_Stack_Ptr is new |
| Unchecked_Conversion (Address, Fixed_Stack_Ptr); |
| -- Convert from address stored in task data structures |
| |
| -------------- |
| -- Allocate -- |
| -------------- |
| |
| procedure SS_Allocate |
| (Addr : out Address; |
| Storage_Size : SSE.Storage_Count) |
| is |
| Max_Align : constant SS_Ptr := SS_Ptr (Standard'Maximum_Alignment); |
| Max_Size : constant SS_Ptr := |
| ((SS_Ptr (Storage_Size) + Max_Align - 1) / Max_Align) |
| * Max_Align; |
| |
| begin |
| -- Case of fixed allocation secondary stack |
| |
| if not SS_Ratio_Dynamic then |
| declare |
| Fixed_Stack : constant Fixed_Stack_Ptr := |
| To_Fixed_Stack_Ptr (SSL.Get_Sec_Stack_Addr.all); |
| |
| begin |
| -- Check if max stack usage is increasing |
| |
| if Fixed_Stack.Top + Max_Size > Fixed_Stack.Max then |
| |
| -- If so, check if max size is exceeded |
| |
| if Fixed_Stack.Top + Max_Size > Fixed_Stack.Last then |
| raise Storage_Error; |
| end if; |
| |
| -- Record new max usage |
| |
| Fixed_Stack.Max := Fixed_Stack.Top + Max_Size; |
| end if; |
| |
| -- Set resulting address and update top of stack pointer |
| |
| Addr := Fixed_Stack.Mem (Fixed_Stack.Top)'Address; |
| Fixed_Stack.Top := Fixed_Stack.Top + Max_Size; |
| end; |
| |
| -- Case of dynamically allocated secondary stack |
| |
| else |
| declare |
| Stack : constant Stack_Ptr := |
| To_Stack_Ptr (SSL.Get_Sec_Stack_Addr.all); |
| Chunk : Chunk_Ptr; |
| |
| To_Be_Released_Chunk : Chunk_Ptr; |
| |
| begin |
| Chunk := Stack.Current_Chunk; |
| |
| -- The Current_Chunk may not be the good one if a lot of release |
| -- operations have taken place. So go down the stack if necessary |
| |
| while Chunk.First > Stack.Top loop |
| Chunk := Chunk.Prev; |
| end loop; |
| |
| -- Find out if the available memory in the current chunk is |
| -- sufficient, if not, go to the next one and eventally create |
| -- the necessary room. |
| |
| while Chunk.Last - Stack.Top + 1 < Max_Size loop |
| if Chunk.Next /= null then |
| |
| -- Release unused non-first empty chunk |
| |
| if Chunk.Prev /= null and then Chunk.First = Stack.Top then |
| To_Be_Released_Chunk := Chunk; |
| Chunk := Chunk.Prev; |
| Chunk.Next := To_Be_Released_Chunk.Next; |
| To_Be_Released_Chunk.Next.Prev := Chunk; |
| Free (To_Be_Released_Chunk); |
| end if; |
| |
| -- Create new chunk of default size unless it is not |
| -- sufficient to satisfy the current request. |
| |
| elsif SSE.Storage_Count (Max_Size) <= Stack.Default_Size then |
| Chunk.Next := |
| new Chunk_Id |
| (First => Chunk.Last + 1, |
| Last => Chunk.Last + SS_Ptr (Stack.Default_Size)); |
| |
| Chunk.Next.Prev := Chunk; |
| |
| -- Otherwise create new chunk of requested size |
| |
| else |
| Chunk.Next := |
| new Chunk_Id |
| (First => Chunk.Last + 1, |
| Last => Chunk.Last + Max_Size); |
| |
| Chunk.Next.Prev := Chunk; |
| end if; |
| |
| Chunk := Chunk.Next; |
| Stack.Top := Chunk.First; |
| end loop; |
| |
| -- Resulting address is the address pointed by Stack.Top |
| |
| Addr := Chunk.Mem (Stack.Top)'Address; |
| Stack.Top := Stack.Top + Max_Size; |
| Stack.Current_Chunk := Chunk; |
| end; |
| end if; |
| end SS_Allocate; |
| |
| ------------- |
| -- SS_Free -- |
| ------------- |
| |
| procedure SS_Free (Stk : in out Address) is |
| begin |
| -- Case of statically allocated secondary stack, nothing to free |
| |
| if not SS_Ratio_Dynamic then |
| return; |
| |
| -- Case of dynamically allocated secondary stack |
| |
| else |
| declare |
| Stack : Stack_Ptr := To_Stack_Ptr (Stk); |
| Chunk : Chunk_Ptr; |
| |
| procedure Free is new Unchecked_Deallocation (Stack_Id, Stack_Ptr); |
| |
| begin |
| Chunk := Stack.Current_Chunk; |
| |
| while Chunk.Prev /= null loop |
| Chunk := Chunk.Prev; |
| end loop; |
| |
| while Chunk.Next /= null loop |
| Chunk := Chunk.Next; |
| Free (Chunk.Prev); |
| end loop; |
| |
| Free (Chunk); |
| Free (Stack); |
| Stk := Null_Address; |
| end; |
| end if; |
| end SS_Free; |
| |
| ---------------- |
| -- SS_Get_Max -- |
| ---------------- |
| |
| function SS_Get_Max return Long_Long_Integer is |
| begin |
| if SS_Ratio_Dynamic then |
| return -1; |
| else |
| declare |
| Fixed_Stack : constant Fixed_Stack_Ptr := |
| To_Fixed_Stack_Ptr (SSL.Get_Sec_Stack_Addr.all); |
| begin |
| return Long_Long_Integer (Fixed_Stack.Max); |
| end; |
| end if; |
| end SS_Get_Max; |
| |
| ------------- |
| -- SS_Info -- |
| ------------- |
| |
| procedure SS_Info is |
| begin |
| Put_Line ("Secondary Stack information:"); |
| |
| -- Case of fixed secondary stack |
| |
| if not SS_Ratio_Dynamic then |
| declare |
| Fixed_Stack : constant Fixed_Stack_Ptr := |
| To_Fixed_Stack_Ptr (SSL.Get_Sec_Stack_Addr.all); |
| |
| begin |
| Put_Line ( |
| " Total size : " |
| & SS_Ptr'Image (Fixed_Stack.Last) |
| & " bytes"); |
| |
| Put_Line ( |
| " Current allocated space : " |
| & SS_Ptr'Image (Fixed_Stack.Top - 1) |
| & " bytes"); |
| end; |
| |
| -- Case of dynamically allocated secondary stack |
| |
| else |
| declare |
| Stack : constant Stack_Ptr := |
| To_Stack_Ptr (SSL.Get_Sec_Stack_Addr.all); |
| Nb_Chunks : Integer := 1; |
| Chunk : Chunk_Ptr := Stack.Current_Chunk; |
| |
| begin |
| while Chunk.Prev /= null loop |
| Chunk := Chunk.Prev; |
| end loop; |
| |
| while Chunk.Next /= null loop |
| Nb_Chunks := Nb_Chunks + 1; |
| Chunk := Chunk.Next; |
| end loop; |
| |
| -- Current Chunk information |
| |
| Put_Line ( |
| " Total size : " |
| & SS_Ptr'Image (Chunk.Last) |
| & " bytes"); |
| |
| Put_Line ( |
| " Current allocated space : " |
| & SS_Ptr'Image (Stack.Top - 1) |
| & " bytes"); |
| |
| Put_Line ( |
| " Number of Chunks : " |
| & Integer'Image (Nb_Chunks)); |
| |
| Put_Line ( |
| " Default size of Chunks : " |
| & SSE.Storage_Count'Image (Stack.Default_Size)); |
| end; |
| end if; |
| end SS_Info; |
| |
| ------------- |
| -- SS_Init -- |
| ------------- |
| |
| procedure SS_Init |
| (Stk : in out Address; |
| Size : Natural := Default_Secondary_Stack_Size) |
| is |
| begin |
| -- Case of fixed size secondary stack |
| |
| if not SS_Ratio_Dynamic then |
| declare |
| Fixed_Stack : constant Fixed_Stack_Ptr := |
| To_Fixed_Stack_Ptr (Stk); |
| |
| begin |
| Fixed_Stack.Top := 0; |
| Fixed_Stack.Max := 0; |
| |
| if Size < Dummy_Fixed_Stack.Mem'Position then |
| Fixed_Stack.Last := 0; |
| else |
| Fixed_Stack.Last := |
| SS_Ptr (Size) - Dummy_Fixed_Stack.Mem'Position; |
| end if; |
| end; |
| |
| -- Case of dynamically allocated secondary stack |
| |
| else |
| declare |
| Stack : Stack_Ptr; |
| begin |
| Stack := new Stack_Id; |
| Stack.Current_Chunk := new Chunk_Id (1, SS_Ptr (Size)); |
| Stack.Top := 1; |
| Stack.Default_Size := SSE.Storage_Count (Size); |
| Stk := To_Addr (Stack); |
| end; |
| end if; |
| end SS_Init; |
| |
| ------------- |
| -- SS_Mark -- |
| ------------- |
| |
| function SS_Mark return Mark_Id is |
| Sstk : constant System.Address := SSL.Get_Sec_Stack_Addr.all; |
| begin |
| if SS_Ratio_Dynamic then |
| return (Sstk => Sstk, Sptr => To_Stack_Ptr (Sstk).Top); |
| else |
| return (Sstk => Sstk, Sptr => To_Fixed_Stack_Ptr (Sstk).Top); |
| end if; |
| end SS_Mark; |
| |
| ---------------- |
| -- SS_Release -- |
| ---------------- |
| |
| procedure SS_Release (M : Mark_Id) is |
| begin |
| if SS_Ratio_Dynamic then |
| To_Stack_Ptr (M.Sstk).Top := M.Sptr; |
| else |
| To_Fixed_Stack_Ptr (M.Sstk).Top := M.Sptr; |
| end if; |
| end SS_Release; |
| |
| ------------------------- |
| -- Package Elaboration -- |
| ------------------------- |
| |
| -- Allocate a secondary stack for the main program to use |
| |
| -- We make sure that the stack has maximum alignment. Some systems require |
| -- this (e.g. Sun), and in any case it is a good idea for efficiency. |
| |
| Stack : aliased Stack_Id; |
| for Stack'Alignment use Standard'Maximum_Alignment; |
| |
| Chunk : aliased Chunk_Id (1, SS_Ptr (Default_Secondary_Stack_Size)); |
| for Chunk'Alignment use Standard'Maximum_Alignment; |
| |
| Chunk_Address : Address; |
| |
| begin |
| if SS_Ratio_Dynamic then |
| Stack.Top := 1; |
| Stack.Current_Chunk := Chunk'Access; |
| Stack.Default_Size := SSE.Storage_Offset (Default_Secondary_Stack_Size); |
| System.Soft_Links.Set_Sec_Stack_Addr_NT (Stack'Address); |
| |
| else |
| Chunk_Address := Chunk'Address; |
| SS_Init (Chunk_Address, Default_Secondary_Stack_Size); |
| System.Soft_Links.Set_Sec_Stack_Addr_NT (Chunk_Address); |
| end if; |
| end System.Secondary_Stack; |
