The HEAPTRC unit can be used to debug your memory allocation/deallocation. It keeps track of the calls to getmem/freemem, and, implicitly, of New/Dispose statements.
When the program exits, or when you request it explicitly. It displays the total memory used, and then dumps a list of blocks that were allocated but not freed. It also displays where the memory was allocated.
If there are any inconsistencies, such as memory blocks being allocated or freed twice, or a memory block that is released but with wrong size, this will be displayed also.
The information that is stored/displayed can be customized using some constants.
All that you need to do is to include heaptrc in the uses clause of your program. Make sure that it is the first unit in the clause, otherwise memory allocated in initialization code of units that precede the heaptrc unit will not be accounted for, causing an incorrect memory usage report.
The following example shows how to use the heaptrc unit.
Program heapex; { Program used to demonstrate the usage of heaptrc unit } Uses heaptrc; Var P1 : ^Longint; P2 : Pointer; I : longint; begin New(P1); // causes previous allocation not to be de-allocated New(P1); Dispose(P1); For I:=1 to 10 do begin GetMem (P2,128); // When I is even, deallocate block. We loose 5 times 128 // bytes this way. If (I mod 2) = 0 Then FreeMem(P2,128); end; GetMem(P2,128); // This will provoke an error and a memory dump Freemem (P2,64); end.
Marked memory at 08052C48 invalid Wrong size : 128 allocated 64 freed 0x0804C29C 0x080509E2 0x080480A4 0x00000000 Heap dump by heaptrc unit 13 memory blocks allocated : 1416/1424 6 memory blocks freed : 708/712 7 unfreed memory blocks : 708 True heap size : 2097152 True free heap : 2096040 Should be : 2096104 Call trace for block 0x08052C48 size 128 0x080509D6 0x080480A4 Call trace for block 0x08052B98 size 128 0x08050992 0x080480A4 Call trace for block 0x08052AE8 size 128 0x08050992 0x080480A4 Call trace for block 0x08052A38 size 128 0x08050992 0x080480A4 Call trace for block 0x08052988 size 128 0x08050992 0x080480A4 Call trace for block 0x080528D8 size 128 0x08050992 0x080480A4 Call trace for block 0x080528A0 size 4 0x08050961 0x080480A4
The FillExtraInfoType is a procedural type used in the SetExtraInfo call.
The following typed constants allow to fine-tune the standard dump of the
memory usage by DumpHeap:
Tracesize specifies how many levels of calls are displayed of the call stack during the memory dump. If you specify keepreleased:=True then half the TraceSize is reserved for the GetMem call stack, and the other half is reserved for the FreeMem call stack. For example, the default value of 8 will cause eight levels of call frames to be dumped for the getmem call if keepreleased is False. If KeepReleased is true, then 4 levels of call frames will be dumped for the GetMem call and 4 frames wil be dumped for the FreeMem call. If you want to change this value, you must recode the heaptrc unit.
Quicktrace determines whether the memory manager checks whether a block that is about to be released is allocated correctly. This is a rather time consuming search, and slows program execution significantly, so by default it is set to False.
If HaltOnError is set to True then an illegal call to FreeMem will cause the memory manager to execute a halt(1) instruction, causing a memory dump. By Default it is set to True.
If keepreleased is set to true, then a list of freed memory blocks is kept. This is useful if you suspect that the same memory block is released twice. However, this option is very memory intensive, so use it sparingly, and only when it's really necessary.
When dumping the memory summary, the extra info is shown as Longint values.
Program heapex; { Program used to demonstrate the usage of heaptrc unit } Uses heaptrc; Var P1 : ^Longint; P2 : Pointer; I : longint; Marker : Longint; Procedure SetMarker (P : pointer); Type PLongint = ^Longint; begin PLongint(P)^:=Marker; end; Procedure Part1; begin // Blocks allocated here are marked with $FFAAFFAA = -5570646 Marker := $FFAAFFAA; New(P1); New(P1); Dispose(P1); For I:=1 to 10 do begin GetMem (P2,128); If (I mod 2) = 0 Then FreeMem(P2,128); end; GetMem(P2,128); end; Procedure Part2; begin // Blocks allocated here are marked with $FAFAFAFA = -84215046 Marker := $FAFAFAFA; New(P1); New(P1); Dispose(P1); For I:=1 to 10 do begin GetMem (P2,128); If (I mod 2) = 0 Then FreeMem(P2,128); end; GetMem(P2,128); end; begin SetExtraInfo(SizeOf(Marker),@SetMarker); Writeln ('Part 1'); part1; Writeln('Part 2'); part2; end.