Memory Allocation Markers: Memory Leak Checking

Collaboration diagram for Memory Allocation Markers: Memory Leak Checking:

Classes
class	libcwd::marker_ct
	A memory allocation marker. More...

Functions
void	libcwd::move_outside (marker_ct *marker, void const *void_ptr)
	Move memory allocation pointed to by ptr outside marker.

Detailed Description

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Detailed Description

Libcwd does a weak attempt to support debugging of memory leaks.  I hope to greatly improve this in the future.It is possible to mark allocations that are done till that moment, and then later check for memory leaks by expecting no other memory allocations than those that already existed before the mark.  This is done by creating a marker_ct object.  The check for memory leaks is done when the marker is removed again.  This can be done recursively.A marker is created by passing it a description:

#if CWDEBUG_MARKER
  libcwd::marker_ct* marker = new libcwd::marker_ct("Description of the marker");
#endif

Any allocation done after the creation of this marker will be reported as a leak at the moment the marker is deleted.Markers are clearly visible in the Allocated memory Overview.  They are labeled MARKER (see also the allocator type table).  All memory that is allocated after a marker, is displayed indented and below that marker in the Allocated memory Overview.Finally, it is possible to move specific memory blocks outside markers, so they will not cause a memory leak detection.  This is done with the function

namespace libcwd {
  void move_outside(marker_ct* marker, void const* ptr);
}

which would move the memory allocation pointed to by ptr outside the test region of marker.A complete example program with output is given here:

#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <libcwd/sys.h>
#include <libcwd/debug.h>

// A dummy class
class A {
  int i;
  int j;
  char k;
};

int main(int argc, char* argv[])
{
  // Don't show allocations that are allocated before main()
  Debug( make_all_allocations_invisible_except(NULL) );

  // Select channels
  ForAllDebugChannels( if (debugChannel.is_on()) debugChannel.off() );
  Debug( dc::notice.on() );
  Debug( dc::malloc.on() );
  Debug( dc::warning.on() );
  // Debug( dc::bfd.on() );

  // Write debug output to cout
  Debug( libcw_do.set_ostream(&cout) );

  // Turn debug object on
  Debug( libcw_do.on() ); 

  // Allocate new object
  A* a1 = new A;
  AllocTag(a1, "First created");

#if CWDEBUG_MARKER
  // Create marker
  libcwd::marker_ct* marker = new libcwd::marker_ct("A test marker");
#endif

  // Allocate more objects
  A* a2 = new A[10];
  AllocTag(a2, "Created after the marker");
  int* p = new int[30];
  AllocTag(p, "Created after the marker");

  // Show Memory Allocation Overview
  Debug( list_allocations_on(libcw_do) );

  Dout(dc::notice, "Moving the int array outside of the marker...");
#if CWDEBUG_MARKER
  Debug( move_outside(marker, p) );
#endif

  // Show Memory Allocation Overview
  Debug( list_allocations_on(libcw_do) );

#if CWDEBUG_MARKER
  // Delete the marker
  delete marker;
#endif

#if CWDEBUG_ALLOC
  Dout(dc::notice, "Finished successfully.");
#else
  DoutFatal(dc::fatal, "Please reconfigure libcwd with --enable-alloc.");
#endif
  return 0;
}