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   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                       G N A T . D E B U G _ P O O L S                    --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2011, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 --  This packages provides a special implementation of the Ada 95 storage pools
  33
  34 --  The goal of this debug pool is to detect incorrect uses of memory
  35 --  (multiple deallocations, access to invalid memory,...). Errors are reported
  36 --  in one of two ways: either by immediately raising an exception, or by
  37 --  printing a message on standard output or standard error.
  38
  39 --  You need to instrument your code to use this package: for each access type
  40 --  you want to monitor, you need to add a clause similar to:
  41
  42 --      type Integer_Access is access Integer;
  43 --      for Integer_Access'Storage_Pool use Pool;
  44
  45 --  where Pool is a tagged object declared with
  46 --
  47 --      Pool : GNAT.Debug_Pools.Debug_Pool;
  48
  49 --  This package was designed to be as efficient as possible, but still has an
  50 --  impact on the performance of your code, which depends on the number of
  51 --  allocations, deallocations and, somewhat less, dereferences that your
  52 --  application performs.
  53
  54 --  For each faulty memory use, this debug pool will print several lines
  55 --  of information, including things like the location where the memory
  56 --  was initially allocated, the location where it was freed etc.
  57
  58 --  Physical allocations and deallocations are done through the usual system
  59 --  calls. However, in order to provide proper checks, the debug pool will not
  60 --  release the memory immediately. It keeps released memory around (the amount
  61 --  kept around is configurable) so that it can distinguish between memory that
  62 --  has not been allocated and memory that has been allocated but freed. This
  63 --  also means that this memory cannot be reallocated, preventing what would
  64 --  otherwise be a false indication that freed memory is now allocated.
  65
  66 --  In addition, this package presents several subprograms that help analyze
  67 --  the behavior of your program, by reporting memory leaks, the total amount
  68 --  of memory that was allocated. The pool is also designed to work correctly
  69 --  in conjunction with gnatmem.
  70
  71 --  Finally, a subprogram Print_Pool is provided for use from the debugger
  72
  73 --  Limitations
  74 --  ===========
  75
  76 --  Current limitation of this debug pool: if you use this debug pool for a
  77 --  general access type ("access all"), the pool might report invalid
  78 --  dereferences if the access object is pointing to another object on the
  79 --  stack which was not allocated through a call to "new".
  80
  81 --  This debug pool will respect all alignments specified in your code, but
  82 --  it does that by aligning all objects using Standard'Maximum_Alignment.
  83 --  This allows faster checks, and limits the performance impact of using
  84 --  this pool.
  85
  86 with System;                  use System;
  87 with System.Storage_Elements; use System.Storage_Elements;
  88 with System.Checked_Pools;
  89
  90 package GNAT.Debug_Pools is
  91
  92    type Debug_Pool is new System.Checked_Pools.Checked_Pool with private;
  93    --  The new debug pool
  94
  95    subtype SSC is System.Storage_Elements.Storage_Count;
  96
  97    Default_Max_Freed         : constant SSC     := 50_000_000;
  98    Default_Stack_Trace_Depth : constant Natural := 20;
  99    Default_Reset_Content     : constant Boolean := False;
 100    Default_Raise_Exceptions  : constant Boolean := True;
 101    Default_Advanced_Scanning : constant Boolean := False;
 102    Default_Min_Freed         : constant SSC     := 0;
 103    Default_Errors_To_Stdout  : constant Boolean := True;
 104    Default_Low_Level_Traces  : constant Boolean := False;
 105    --  The above values are constants used for the parameters to Configure
 106    --  if not overridden in the call. See description of Configure for full
 107    --  details on these parameters. If these defaults are not satisfactory,
 108    --  then you need to call Configure to change the default values.
 109
 110    procedure Configure
 111      (Pool                           : in out Debug_Pool;
 112       Stack_Trace_Depth              : Natural := Default_Stack_Trace_Depth;
 113       Maximum_Logically_Freed_Memory : SSC     := Default_Max_Freed;
 114       Minimum_To_Free                : SSC     := Default_Min_Freed;
 115       Reset_Content_On_Free          : Boolean := Default_Reset_Content;
 116       Raise_Exceptions               : Boolean := Default_Raise_Exceptions;
 117       Advanced_Scanning              : Boolean := Default_Advanced_Scanning;
 118       Errors_To_Stdout               : Boolean := Default_Errors_To_Stdout;
 119       Low_Level_Traces               : Boolean := Default_Low_Level_Traces);
 120    --  Subprogram used to configure the debug pool.
 121    --
 122    --    Stack_Trace_Depth. This parameter controls the maximum depth of stack
 123    --    traces that are output to indicate locations of actions for error
 124    --    conditions such as bad allocations. If set to zero, the debug pool
 125    --    will not try to compute backtraces. This is more efficient but gives
 126    --    less information on problem locations
 127    --
 128    --    Maximum_Logically_Freed_Memory: maximum amount of memory (bytes)
 129    --    that should be kept before starting to physically deallocate some.
 130    --    This value should be non-zero, since having memory that is logically
 131    --    but not physically freed helps to detect invalid memory accesses.
 132    --
 133    --    Minimum_To_Free is the minimum amount of memory that should be freed
 134    --    every time the pool starts physically releasing memory. The algorithm
 135    --    to compute which block should be physically released needs some
 136    --    expensive initialization (see Advanced_Scanning below), and this
 137    --    parameter can be used to limit the performance impact by ensuring
 138    --    that a reasonable amount of memory is freed each time. Even in the
 139    --    advanced scanning mode, marked blocks may be released to match this
 140    --    Minimum_To_Free parameter.
 141    --
 142    --    Reset_Content_On_Free: If true, then the contents of the freed memory
 143    --    is reset to the pattern 16#DEADBEEF#, following an old IBM convention.
 144    --    This helps in detecting invalid memory references from the debugger.
 145    --
 146    --    Raise_Exceptions: If true, the exceptions below will be raised every
 147    --    time an error is detected. If you set this to False, then the action
 148    --    is to generate output on standard error or standard output, depending
 149    --    on Errors_To_Stdout, noting the errors, but to
 150    --    keep running if possible (of course if storage is badly damaged, this
 151    --    attempt may fail. This helps to detect more than one error in a run.
 152    --
 153    --    Advanced_Scanning: If true, the pool will check the contents of all
 154    --    allocated blocks before physically releasing memory. Any possible
 155    --    reference to a logically free block will prevent its deallocation.
 156    --    Note that this algorithm is approximate, and it is recommended
 157    --    that you set Minimum_To_Free to a non-zero value to save time.
 158    --
 159    --    Errors_To_Stdout: Errors messages will be displayed on stdout if
 160    --    this parameter is True, or to stderr otherwise.
 161    --
 162    --    Low_Level_Traces: Traces all allocation and deallocations on the
 163    --    stream specified by Errors_To_Stdout. This can be used for
 164    --    post-processing by your own application, or to debug the
 165    --    debug_pool itself. The output indicates the size of the allocated
 166    --    block both as requested by the application and as physically
 167    --    allocated to fit the additional information needed by the debug
 168    --    pool.
 169    --
 170    --  All instantiations of this pool use the same internal tables. However,
 171    --  they do not store the same amount of information for the tracebacks,
 172    --  and they have different counters for maximum logically freed memory.
 173
 174    Accessing_Not_Allocated_Storage : exception;
 175    --  Exception raised if Raise_Exception is True, and an attempt is made
 176    --  to access storage that was never allocated.
 177
 178    Accessing_Deallocated_Storage : exception;
 179    --  Exception raised if Raise_Exception is True, and an attempt is made
 180    --  to access storage that was allocated but has been deallocated.
 181
 182    Freeing_Not_Allocated_Storage : exception;
 183    --  Exception raised if Raise_Exception is True, and an attempt is made
 184    --  to free storage that had not been previously allocated.
 185
 186    Freeing_Deallocated_Storage : exception;
 187    --  Exception raised if Raise_Exception is True, and an attempt is made
 188    --  to free storage that had already been freed.
 189
 190    --  Note on the above exceptions. The distinction between not allocated
 191    --  and deallocated storage is not guaranteed to be accurate in the case
 192    --  where storage is allocated, and then physically freed. Larger values
 193    --  of the parameter Maximum_Logically_Freed_Memory will help to guarantee
 194    --  that this distinction is made more accurately.
 195
 196    generic
 197       with procedure Put_Line (S : String) is <>;
 198       with procedure Put      (S : String) is <>;
 199    procedure Print_Info
 200      (Pool          : Debug_Pool;
 201       Cumulate      : Boolean := False;
 202       Display_Slots : Boolean := False;
 203       Display_Leaks : Boolean := False);
 204    --  Print out information about the High Water Mark, the current and
 205    --  total number of bytes allocated and the total number of bytes
 206    --  deallocated.
 207    --
 208    --  If Display_Slots is true, this subprogram prints a list of all the
 209    --  locations in the application that have done at least one allocation or
 210    --  deallocation. The result might be used to detect places in the program
 211    --  where lots of allocations are taking place. This output is not in any
 212    --  defined order.
 213    --
 214    --  If Cumulate if True, then each stack trace will display the number of
 215    --  allocations that were done either directly, or by the subprograms called
 216    --  at that location (e.g: if there were two physical allocations at a->b->c
 217    --  and a->b->d, then a->b would be reported as performing two allocations).
 218    --
 219    --  If Display_Leaks is true, then each block that has not been deallocated
 220    --  (often called a "memory leak") will be listed, along with the traceback
 221    --  showing where it was allocated. Not that no grouping of the blocks is
 222    --  done, you should use the Dump_Gnatmem procedure below in conjunction
 223    --  with the gnatmem utility.
 224
 225    procedure Print_Info_Stdout
 226      (Pool          : Debug_Pool;
 227       Cumulate      : Boolean := False;
 228       Display_Slots : Boolean := False;
 229       Display_Leaks : Boolean := False);
 230    --  Standard instantiation of Print_Info to print on standard_output. More
 231    --  convenient to use where this is the intended location, and in particular
 232    --  easier to use from the debugger.
 233
 234    procedure Dump_Gnatmem (Pool : Debug_Pool; File_Name : String);
 235    --  Create an external file on the disk, which can be processed by gnatmem
 236    --  to display the location of memory leaks.
 237    --
 238    --  This provides a nicer output that Print_Info above, and groups similar
 239    --  stack traces together. This also provides an easy way to save the memory
 240    --  status of your program for post-mortem analysis.
 241    --
 242    --  To use this file, use the following command line:
 243    --     gnatmem 5 -i <File_Name> <Executable_Name>
 244    --  If you want all the stack traces to be displayed with 5 levels.
 245
 246    procedure Print_Pool (A : System.Address);
 247    pragma Export (C, Print_Pool, "print_pool");
 248    --  This subprogram is meant to be used from a debugger. Given an address in
 249    --  memory, it will print on standard output the known information about
 250    --  this address (provided, of course, the matching pointer is handled by
 251    --  the Debug_Pool).
 252    --
 253    --  The information includes the stacktrace for the allocation or
 254    --  deallocation of that memory chunk, its current status (allocated or
 255    --  logically freed), etc.
 256
 257 private
 258    --  The following are the standard primitive subprograms for a pool
 259
 260    procedure Allocate
 261      (Pool                     : in out Debug_Pool;
 262       Storage_Address          : out Address;
 263       Size_In_Storage_Elements : Storage_Count;
 264       Alignment                : Storage_Count);
 265    --  Allocate a new chunk of memory, and set it up so that the debug pool
 266    --  can check accesses to its data, and report incorrect access later on.
 267    --  The parameters have the same semantics as defined in the ARM95.
 268
 269    procedure Deallocate
 270      (Pool                     : in out Debug_Pool;
 271       Storage_Address          : Address;
 272       Size_In_Storage_Elements : Storage_Count;
 273       Alignment                : Storage_Count);
 274    --  Mark a block of memory as invalid. It might not be physically removed
 275    --  immediately, depending on the setup of the debug pool, so that checks
 276    --  are still possible. The parameters have the same semantics as defined
 277    --  in the RM.
 278
 279    function Storage_Size (Pool : Debug_Pool) return SSC;
 280    --  Return the maximal size of data that can be allocated through Pool.
 281    --  Since Pool uses the malloc() system call, all the memory is accessible
 282    --  through the pool
 283
 284    procedure Dereference
 285      (Pool                     : in out Debug_Pool;
 286       Storage_Address          : System.Address;
 287       Size_In_Storage_Elements : Storage_Count;
 288       Alignment                : Storage_Count);
 289    --  Check whether a dereference statement is valid, i.e. whether the pointer
 290    --  was allocated through Pool. As documented above, errors will be
 291    --  reported either by a special error message or an exception, depending
 292    --  on the setup of the storage pool.
 293    --  The parameters have the same semantics as defined in the ARM95.
 294
 295    type Byte_Count is mod System.Max_Binary_Modulus;
 296    --  Type used for maintaining byte counts, needs to be large enough
 297    --  to accommodate counts allowing for repeated use of the same memory.
 298
 299    type Debug_Pool is new System.Checked_Pools.Checked_Pool with record
 300       Stack_Trace_Depth              : Natural := Default_Stack_Trace_Depth;
 301       Maximum_Logically_Freed_Memory : SSC     := Default_Max_Freed;
 302       Reset_Content_On_Free          : Boolean := Default_Reset_Content;
 303       Raise_Exceptions               : Boolean := Default_Raise_Exceptions;
 304       Minimum_To_Free                : SSC     := Default_Min_Freed;
 305       Advanced_Scanning              : Boolean := Default_Advanced_Scanning;
 306       Errors_To_Stdout               : Boolean := Default_Errors_To_Stdout;
 307       Low_Level_Traces               : Boolean := Default_Low_Level_Traces;
 308
 309       Allocated : Byte_Count := 0;
 310       --  Total number of bytes allocated in this pool
 311
 312       Logically_Deallocated : Byte_Count := 0;
 313       --  Total number of bytes logically deallocated in this pool. This is the
 314       --  memory that the application has released, but that the pool has not
 315       --  yet physically released through a call to free(), to detect later
 316       --  accessed to deallocated memory.
 317
 318       Physically_Deallocated : Byte_Count := 0;
 319       --  Total number of bytes that were free()-ed
 320
 321       Marked_Blocks_Deallocated : Boolean := False;
 322       --  Set to true if some mark blocks had to be deallocated in the advanced
 323       --  scanning scheme. Since this is potentially dangerous, this is
 324       --  reported to the user, who might want to rerun his program with a
 325       --  lower Minimum_To_Free value.
 326
 327       High_Water : Byte_Count := 0;
 328       --  Maximum of Allocated - Logically_Deallocated - Physically_Deallocated
 329
 330       First_Free_Block : System.Address := System.Null_Address;
 331       Last_Free_Block  : System.Address := System.Null_Address;
 332       --  Pointers to the first and last logically freed blocks
 333
 334       First_Used_Block : System.Address := System.Null_Address;
 335       --  Pointer to the list of currently allocated blocks. This list is
 336       --  used to list the memory leaks in the application on exit, as well as
 337       --  for the advanced freeing algorithms that needs to traverse all these
 338       --  blocks to find possible references to the block being physically
 339       --  freed.
 340    end record;
 341 end GNAT.Debug_Pools;