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1 281 jeremybenn
------------------------------------------------------------------------------
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--                                                                          --
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--                         GNAT COMPILER COMPONENTS                         --
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--                                                                          --
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--                       G N A T . D E B U G _ P O O L S                    --
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--                                                                          --
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--                                 S p e c                                  --
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--                                                                          --
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--          Copyright (C) 1992-2009, Free Software Foundation, Inc.         --
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--                                                                          --
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-- GNAT is free software;  you can  redistribute it  and/or modify it under --
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-- terms of the  GNU General Public License as published  by the Free Soft- --
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-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
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-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
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--                                                                          --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception,   --
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-- version 3.1, as published by the Free Software Foundation.               --
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--                                                                          --
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-- You should have received a copy of the GNU General Public License and    --
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-- a copy of the GCC Runtime Library Exception along with this program;     --
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-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
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-- <http://www.gnu.org/licenses/>.                                          --
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--                                                                          --
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-- GNAT was originally developed  by the GNAT team at  New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc.      --
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--                                                                          --
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------------------------------------------------------------------------------
31
 
32
--  This packages provides a special implementation of the Ada95 storage pools
33
 
34
--  The goal of this debug pool is to detect incorrect uses of memory
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--  (multiple deallocations, access to invalid memory,...). Errors are reported
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--  in one of two ways: either by immediately raising an exception, or by
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--  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
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--  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
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--
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--      Pool : GNAT.Debug_Pools.Debug_Pool;
48
 
49
--  This package was designed to be as efficient as possible, but still has an
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--  impact on the performance of your code, which depends on the number of
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--  allocations, deallocations and, somewhat less, dereferences that your
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--  application performs.
53
 
54
--  For each faulty memory use, this debug pool will print several lines
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--  of information, including things like the location where the memory
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--  was initially allocated, the location where it was freed etc.
57
 
58
--  Physical allocations and deallocations are done through the usual system
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--  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
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--  kept around is configurable) so that it can distinguish between memory that
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--  has not been allocated and memory that has been allocated but freed. This
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--  also means that this memory cannot be reallocated, preventing what would
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--  otherwise be a false indication that freed memory is now allocated.
65
 
66
--  In addition, this package presents several subprograms that help analyze
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--  the behavior of your program, by reporting memory leaks, the total amount
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--  of memory that was allocated. The pool is also designed to work correctly
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--  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;
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   Default_Low_Level_Traces  : constant Boolean := False;
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   --  The above values are constants used for the parameters to Configure
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   --  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;
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      Stack_Trace_Depth              : Natural := Default_Stack_Trace_Depth;
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      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;

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