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Diffstat (limited to 'gcc/ada/g-debpoo.ads')
| -rw-r--r-- | gcc/ada/g-debpoo.ads | 272 |
1 files changed, 240 insertions, 32 deletions
diff --git a/gcc/ada/g-debpoo.ads b/gcc/ada/g-debpoo.ads index 0da981d8b77..3cfe1bc270a 100644 --- a/gcc/ada/g-debpoo.ads +++ b/gcc/ada/g-debpoo.ads @@ -6,7 +6,7 @@ -- -- -- S p e c -- -- -- --- Copyright (C) 1992-2001 Free Software Foundation, Inc. -- +-- 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- -- @@ -31,34 +31,218 @@ -- -- ------------------------------------------------------------------------------ +-- 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 - -- The debug pool is used to track down memory corruption due to use of - -- deallocated memory or incorrect unchecked conversions. Allocation - -- strategy : + type Debug_Pool is new System.Checked_Pools.Checked_Pool with private; + -- The new debug pool - -- - allocation: . memory is normally allocated with malloc - -- . the allocated address is noted in a table + subtype SSC is System.Storage_Elements.Storage_Count; - -- - deallocation: . memory is filled with "DEAD_BEEF" patterns - -- . memory is not freed - -- . exceptions are raised if the memory was not - -- allocated or was already deallocated + 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. - -- - dereference: . exceptions are raised if the memory was not - -- allocated or was already deallocated + 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; - Accessing_Deallocated_Storage : exception; - Freeing_Not_Allocated_Storage : exception; - Freeing_Deallocated_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. - type Debug_Pool is - new System.Checked_Pools.Checked_Pool with private; + 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. + +private + -- The following are the standard primitive subprograms for a pool procedure Allocate (Pool : in out Debug_Pool; @@ -72,9 +256,7 @@ package GNAT.Debug_Pools is Size_In_Storage_Elements : Storage_Count; Alignment : Storage_Count); - function Storage_Size - (Pool : Debug_Pool) - return System.Storage_Elements.Storage_Count; + function Storage_Size (Pool : Debug_Pool) return SSC; procedure Dereference (Pool : in out Debug_Pool; @@ -82,22 +264,48 @@ package GNAT.Debug_Pools is Size_In_Storage_Elements : Storage_Count; Alignment : Storage_Count); - generic - with procedure Put_Line (S : String); - procedure Print_Info (Pool : Debug_Pool); - -- Print out information about the High Water Mark, the current and - -- total number of bytes allocated and the total number of bytes - -- deallocated. + 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. -private type Debug_Pool is new System.Checked_Pools.Checked_Pool with record - Allocated : Storage_Count := 0; + 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 - Deallocated : Storage_Count := 0; - -- Total number of bytes deallocated 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. - High_Water : Storage_Count := 0; - -- Maximum of during the time of Allocated - Deallocated + 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; |