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------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- G N A T . D E B U G _ P O O L S -- -- -- -- S p e c -- -- -- -- Copyright (C) 1992-2011, 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 3, 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. -- -- -- -- As a special exception under Section 7 of GPL version 3, you are granted -- -- additional permissions described in the GCC Runtime Library Exception, -- -- version 3.1, as published by the Free Software Foundation. -- -- -- -- You should have received a copy of the GNU General Public License and -- -- a copy of the GCC Runtime Library Exception along with this program; -- -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- -- <http://www.gnu.org/licenses/>. -- -- -- -- 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 Ada 95 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 or standard error. -- 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; Default_Errors_To_Stdout : constant Boolean := True; Default_Low_Level_Traces : constant Boolean := False; -- 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; Errors_To_Stdout : Boolean := Default_Errors_To_Stdout; Low_Level_Traces : Boolean := Default_Low_Level_Traces); -- 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 or standard output, depending -- on Errors_To_Stdout, 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. -- -- Errors_To_Stdout: Errors messages will be displayed on stdout if -- this parameter is True, or to stderr otherwise. -- -- Low_Level_Traces: Traces all allocation and deallocations on the -- stream specified by Errors_To_Stdout. This can be used for -- post-processing by your own application, or to debug the -- debug_pool itself. The output indicates the size of the allocated -- block both as requested by the application and as physically -- allocated to fit the additional information needed by the debug -- pool. -- -- 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. generic 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 chunk, its current status (allocated or -- logically freed), etc. private -- 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); -- Allocate a new chunk of memory, and set it up so that the debug pool -- can check accesses to its data, and report incorrect access later on. -- The parameters have the same semantics as defined in the ARM95. procedure Deallocate (Pool : in out Debug_Pool; Storage_Address : Address; Size_In_Storage_Elements : Storage_Count; Alignment : Storage_Count); -- Mark a block of memory as invalid. It might not be physically removed -- immediately, depending on the setup of the debug pool, so that checks -- are still possible. The parameters have the same semantics as defined -- in the RM. function Storage_Size (Pool : Debug_Pool) return SSC; -- Return the maximal size of data that can be allocated through Pool. -- Since Pool uses the malloc() system call, all the memory is accessible -- through the pool procedure Dereference (Pool : in out Debug_Pool; Storage_Address : System.Address; Size_In_Storage_Elements : Storage_Count; Alignment : Storage_Count); -- Check whether a dereference statement is valid, i.e. whether the pointer -- was allocated through Pool. As documented above, errors will be -- reported either by a special error message or an exception, depending -- on the setup of the storage pool. -- The parameters have the same semantics as defined in the ARM95. type Byte_Count is mod System.Max_Binary_Modulus; -- Type used for maintaining byte counts, needs to be large enough -- to accommodate 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; Errors_To_Stdout : Boolean := Default_Errors_To_Stdout; Low_Level_Traces : Boolean := Default_Low_Level_Traces; 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 -- accessed 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 dangerous, 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;
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