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-- --
-- --
-- G N A T . D E B U G _ P O O L S --
-- --
-- S p e c --
-- --
-- Copyright (C) 1992-2003 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, 59 Temple Place - Suite 330, Boston, --
-- MA 02111-1307, 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. --
-- --
-- This packages provides a special implementation of the Ada95 storage pools.
-- The goal of this debug pool is to detect incorrect uses of memory
-- (multiple deallocations, access to invalid memory,...). Errors are reported
-- in one of two ways: either by immediately raising an exception, or by
-- printing a message on standard output.
-- You need to instrument your code to use this package: for each access type
-- you want to monitor, you need to add a clause similar to:
-- type Integer_Access is access Integer;
-- for Integer_Access'Storage_Pool use Pool;
-- where Pool is a tagged object declared with
-- Pool : GNAT.Debug_Pools.Debug_Pool;
-- This package was designed to be as efficient as possible, but still has an
-- impact on the performance of your code, which depends on the number of
-- allocations, deallocations and, somewhat less, dereferences that your
-- application performs.
-- For each faulty memory use, this debug pool will print several lines
-- of information, including things like the location where the memory
-- was initially allocated, the location where it was freed etc.
-- Physical allocations and deallocations are done through the usual system
-- calls. However, in order to provide proper checks, the debug pool will not
-- release the memory immediately. It keeps released memory around (the amount
-- kept around is configurable) so that it can distinguish between memory that
-- has not been allocated and memory that has been allocated but freed. This
-- also means that this memory cannot be reallocated, preventing what would
-- otherwise be a false indication that freed memory is now allocated.
-- In addition, this package presents several subprograms that help analyze
-- the behavior of your program, by reporting memory leaks, the total amount
-- of memory that was allocated. The pool is also designed to work correctly
-- in conjunction with gnatmem.
-- Finally, a subprogram Print_Pool is provided for use from the debugger.
-- Limitations
-- ===========
-- Current limitation of this debug pool: if you use this debug pool for a
-- general access type ("access all"), the pool might report invalid
-- dereferences if the access object is pointing to another object on the
-- stack which was not allocated through a call to "new".
-- This debug pool will respect all alignments specified in your code, but
-- it does that by aligning all objects using Standard'Maximum_Alignment.
-- This allows faster checks, and limits the performance impact of using
-- this pool.
with System; use System;
with System.Storage_Elements; use System.Storage_Elements;
with System.Checked_Pools;
package GNAT.Debug_Pools is
type Debug_Pool is new System.Checked_Pools.Checked_Pool with private;
-- The new debug pool
subtype SSC is System.Storage_Elements.Storage_Count;
Default_Max_Freed : constant SSC := 50_000_000;
Default_Stack_Trace_Depth : constant Natural := 20;
Default_Reset_Content : constant Boolean := False;
Default_Raise_Exceptions : constant Boolean := True;
Default_Advanced_Scanning : constant Boolean := False;
Default_Min_Freed : constant SSC := 0;
-- The above values are constants used for the parameters to Configure
-- if not overridden in the call. See description of Configure for full
-- details on these parameters. If these defaults are not satisfactory,
-- then you need to call Configure to change the default values.
procedure Configure
(Pool : in out Debug_Pool;
Stack_Trace_Depth : Natural := Default_Stack_Trace_Depth;
Maximum_Logically_Freed_Memory : SSC := Default_Max_Freed;
Minimum_To_Free : SSC := Default_Min_Freed;
Reset_Content_On_Free : Boolean := Default_Reset_Content;
Raise_Exceptions : Boolean := Default_Raise_Exceptions;
Advanced_Scanning : Boolean := Default_Advanced_Scanning);
-- Subprogram used to configure the debug pool.
-- Stack_Trace_Depth. This parameter controls the maximum depth of stack
-- traces that are output to indicate locations of actions for error
-- conditions such as bad allocations. If set to zero, the debug pool
-- will not try to compute backtraces. This is more efficient but gives
-- less information on problem locations
-- Maximum_Logically_Freed_Memory: maximum amount of memory (bytes)
-- that should be kept before starting to physically deallocate some.
-- This value should be non-zero, since having memory that is logically
-- but not physically freed helps to detect invalid memory accesses.
-- Minimum_To_Free is the minimum amount of memory that should be freed
-- every time the pool starts physically releasing memory. The algorithm
-- to compute which block should be physically released needs some
-- expensive initialization (see Advanced_Scanning below), and this
-- parameter can be used to limit the performance impact by ensuring
-- that a reasonable amount of memory is freed each time. Even in the
-- advanced scanning mode, marked blocks may be released to match this
-- Minimum_To_Free parameter.
-- Reset_Content_On_Free: If true, then the contents of the freed memory
-- is reset to the pattern 16#DEADBEEF#, following an old IBM convention.
-- This helps in detecting invalid memory references from the debugger.
-- Raise_Exceptions: If true, the exceptions below will be raised every
-- time an error is detected. If you set this to False, then the action
-- is to generate output on standard error, noting the errors, but to
-- keep running if possible (of course if storage is badly damaged, this
-- attempt may fail. This helps to detect more than one error in a run.
-- Advanced_Scanning: If true, the pool will check the contents of all
-- allocated blocks before physically releasing memory. Any possible
-- reference to a logically free block will prevent its deallocation.
-- Note that this algorithm is approximate, and it is recommended
-- that you set Minimum_To_Free to a non-zero value to save time.
-- All instantiations of this pool use the same internal tables. However,
-- they do not store the same amount of information for the tracebacks,
-- and they have different counters for maximum logically freed memory.
Accessing_Not_Allocated_Storage : exception;
-- Exception raised if Raise_Exception is True, and an attempt is made
-- to access storage that was never allocated.
Accessing_Deallocated_Storage : exception;
-- Exception raised if Raise_Exception is True, and an attempt is made
-- to access storage that was allocated but has been deallocated.
Freeing_Not_Allocated_Storage : exception;
-- Exception raised if Raise_Exception is True, and an attempt is made
-- to free storage that had not been previously allocated.
Freeing_Deallocated_Storage : exception;
-- Exception raised if Raise_Exception is True, and an attempt is made
-- to free storage that had already been freed.
-- Note on the above exceptions. The distinction between not allocated
-- and deallocated storage is not guaranteed to be accurate in the case
-- where storage is allocated, and then physically freed. Larger values
-- of the parameter Maximum_Logically_Freed_Memory will help to guarantee
-- that this distinction is made more accurately.
with procedure Put_Line (S : String) is <>;
with procedure Put (S : String) is <>;
procedure Print_Info
(Pool : Debug_Pool;
Cumulate : Boolean := False;
Display_Slots : Boolean := False;
Display_Leaks : Boolean := False);
-- Print out information about the High Water Mark, the current and
-- total number of bytes allocated and the total number of bytes
-- deallocated.
-- If Display_Slots is true, this subprogram prints a list of all the
-- locations in the application that have done at least one allocation or
-- deallocation. The result might be used to detect places in the program
-- where lots of allocations are taking place. This output is not in any
-- defined order.
-- If Cumulate if True, then each stack trace will display the number of
-- allocations that were done either directly, or by the subprograms called
-- at that location (e.g: if there were two physical allocations at a->b->c
-- and a->b->d, then a->b would be reported as performing two allocations).
-- If Display_Leaks is true, then each block that has not been deallocated
-- (often called a "memory leak") will be listed, along with the traceback
-- showing where it was allocated. Not that no grouping of the blocks is
-- done, you should use the Dump_Gnatmem procedure below in conjunction
-- with the gnatmem utility.
procedure Print_Info_Stdout
(Pool : Debug_Pool;
Cumulate : Boolean := False;
Display_Slots : Boolean := False;
Display_Leaks : Boolean := False);
-- Standard instantiation of Print_Info to print on standard_output. More
-- convenient to use where this is the intended location, and in particular
-- easier to use from the debugger.
procedure Dump_Gnatmem (Pool : Debug_Pool; File_Name : String);
-- Create an external file on the disk, which can be processed by gnatmem
-- to display the location of memory leaks.
-- This provides a nicer output that Print_Info above, and groups similar
-- stack traces together. This also provides an easy way to save the memory
-- status of your program for post-mortem analysis.
-- To use this file, use the following command line:
-- gnatmem 5 -i <File_Name> <Executable_Name>
-- If you want all the stack traces to be displayed with 5 levels.
procedure Print_Pool (A : System.Address);
pragma Export (C, Print_Pool, "print_pool");
-- This subprogram is meant to be used from a debugger. Given an address in
-- memory, it will print on standard output the known information about
-- this address (provided, of course, the matching pointer is handled by
-- the Debug_Pool).
-- The information includes the stacktrace for the allocation or
-- deallocation of that memory chunck, its current status (allocated or
-- logically freed), etc.
-- The following are the standard primitive subprograms for a pool
procedure Allocate
(Pool : in out Debug_Pool;
Storage_Address : out Address;
Size_In_Storage_Elements : Storage_Count;
Alignment : Storage_Count);
procedure Deallocate
(Pool : in out Debug_Pool;
Storage_Address : Address;
Size_In_Storage_Elements : Storage_Count;
Alignment : Storage_Count);
function Storage_Size (Pool : Debug_Pool) return SSC;
procedure Dereference
(Pool : in out Debug_Pool;
Storage_Address : System.Address;
Size_In_Storage_Elements : Storage_Count;
Alignment : Storage_Count);
type Byte_Count is mod System.Max_Binary_Modulus;
-- Type used for maintaining byte counts, needs to be large enough
-- to accomodate counts allowing for repeated use of the same memory.
type Debug_Pool is new System.Checked_Pools.Checked_Pool with record
Stack_Trace_Depth : Natural := Default_Stack_Trace_Depth;
Maximum_Logically_Freed_Memory : SSC := Default_Max_Freed;
Reset_Content_On_Free : Boolean := Default_Reset_Content;
Raise_Exceptions : Boolean := Default_Raise_Exceptions;
Minimum_To_Free : SSC := Default_Min_Freed;
Advanced_Scanning : Boolean := Default_Advanced_Scanning;
Allocated : Byte_Count := 0;
-- Total number of bytes allocated in this pool
Logically_Deallocated : Byte_Count := 0;
-- Total number of bytes logically deallocated in this pool. This is the
-- memory that the application has released, but that the pool has not
-- yet physically released through a call to free(), to detect later
-- accesed to deallocated memory.
Physically_Deallocated : Byte_Count := 0;
-- Total number of bytes that were free()-ed.
Marked_Blocks_Deallocated : Boolean := False;
-- Set to true if some mark blocks had to be deallocated in the advanced
-- scanning scheme. Since this is potentially dangereous, this is
-- reported to the user, who might want to rerun his program with a
-- lower Minimum_To_Free value.
High_Water : Byte_Count := 0;
-- Maximum of Allocated - Logically_Deallocated - Physically_Deallocated
First_Free_Block : System.Address := System.Null_Address;
Last_Free_Block : System.Address := System.Null_Address;
-- Pointers to the first and last logically freed blocks.
First_Used_Block : System.Address := System.Null_Address;
-- Pointer to the list of currently allocated blocks. This list is
-- used to list the memory leaks in the application on exit, as well as
-- for the advanced freeing algorithms that needs to traverse all these
-- blocks to find possible references to the block being physically
-- freed.
end record;
end GNAT.Debug_Pools;