29d21088bb
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@52339 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
145 lines
5.6 KiB
C
145 lines
5.6 KiB
C
/////////////////////////////////////////////////////////////////////////////
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// Name: debugging.h
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// Purpose: topic overview
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// Author: wxWidgets team
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// RCS-ID: $Id$
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// Licence: wxWindows license
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/////////////////////////////////////////////////////////////////////////////
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/*!
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@page overview_debugging Debugging overview
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Classes, functions and macros: wxDebugContext, wxObject, wxLog,
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@ref page_func_cat_log, @ref page_macro_cat_debugging
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Various classes, functions and macros are provided in wxWidgets to help you debug
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your application. Most of these are only available if you compile both wxWidgets,
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your application and @e all libraries that use wxWidgets with the __WXDEBUG__ symbol
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defined. You can also test the __WXDEBUG__ symbol in your own applications to execute
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code that should be active only in debug mode.
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@li @ref overview_debugging_dbgctx
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@li @ref overview_debugging_dbgmacros
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@li @ref overview_debugging_logging
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@li @ref overview_debugging_dbgctx2
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<hr>
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@section overview_debugging_dbgctx wxDebugContext
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wxDebugContext is a class that never gets instantiated, but ties together
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various static functions and variables. It allows you to dump all objects to that stream,
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write statistics about object allocation, and check memory for errors.
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It is good practice to define a wxObject::Dump member function for each class you derive
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from a wxWidgets class, so that wxDebugContext::Dump can call it and
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give valuable information about the state of the application.
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If you have difficulty tracking down a memory leak, recompile
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in debugging mode and call wxDebugContext::Dump and wxDebugContext::PrintStatistics at
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appropriate places. They will tell you what objects have not yet been
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deleted, and what kinds of object they are. In fact, in debug mode wxWidgets will automatically
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detect memory leaks when your application is about to exit, and if there are any leaks,
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will give you information about the problem. (How much information depends on the operating system
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and compiler -- some systems don't allow all memory logging to be enabled). See the
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memcheck sample for example of usage.
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For wxDebugContext to do its work, the @e new and @e delete operators for wxObject
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have been redefined to store extra information about dynamically allocated objects
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(but not statically declared objects).
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This slows down a debugging version of an application, but can
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find difficult-to-detect memory leaks (objects are not
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deallocated), overwrites (writing past the end of your object) and
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underwrites (writing to memory in front of the object).
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If debugging mode is on and the symbols wxUSE_GLOBAL_MEMORY_OPERATORS and
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wxUSE_DEBUG_NEW_ALWAYS are set to 1 in setup.h, 'new' is defined to be:
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@code
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#define new new(__FILE__,__LINE__)
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@endcode
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All occurrences of 'new' in wxWidgets and your own application will use
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the overridden form of the operator with two extra arguments. This means that
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the debugging output (and error messages reporting memory problems) will tell you what
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file and on what line you allocated the object. Unfortunately not all
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compilers allow this definition to work properly, but most do.
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@section overview_debugging_dbgmacros Debug macros
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You should also use @ref page_macro_cat_debugging as part of a 'defensive programming'
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strategy, scattering wxASSERTs liberally to test for problems in your code as early as
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possible.
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Forward thinking will save a surprising amount of time in the long run.
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#wxASSERT is used to pop up an error message box when a condition
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is not @true. You can also use #wxASSERT_MSG to supply your
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own helpful error message. For example:
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@code
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void MyClass::MyFunction(wxObject* object)
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{
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wxASSERT_MSG( (object != NULL), "object should not be NULL in MyFunction!" );
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...
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};
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@endcode
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The message box allows you to continue execution or abort the program. If you are running
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the application inside a debugger, you will be able to see exactly where the problem was.
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@section overview_debugging_logging Logging functions
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You can use the wxLogDebug and wxLogTrace functions to output debugging information in
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debug mode; it will do nothing for non-debugging code.
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@section overview_debugging_dbgctx2 wxDebugContext overview
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Class: wxDebugContext
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wxDebugContext is a class for performing various debugging and memory tracing operations.
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This class has only static data and function members, and there should be
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no instances. Probably the most useful members are SetFile (for directing output
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to a file, instead of the default standard error or debugger output);
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Dump (for dumping the dynamically allocated objects) and PrintStatistics
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(for dumping information about allocation of objects). You can also call
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Check to check memory blocks for integrity.
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Here's an example of use. The SetCheckpoint ensures that only the
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allocations done after the checkpoint will be dumped.
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@code
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wxDebugContext::SetCheckpoint();
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wxDebugContext::SetFile("c:\\temp\\debug.log");
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wxString *thing = new wxString;
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char *ordinaryNonObject = new char[1000];
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wxDebugContext::Dump();
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wxDebugContext::PrintStatistics();
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@endcode
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You can use wxDebugContext if __WXDEBUG__ is defined, or you can use it
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at any other time (if wxUSE_DEBUG_CONTEXT is set to 1 in setup.h). It is not disabled
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in non-debug mode because you may not wish to recompile wxWidgets and your entire application
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just to make use of the error logging facility.
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@note wxDebugContext::SetFile has a problem at present, so use the default stream instead.
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Eventually the logging will be done through the wxLog facilities instead.
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*/
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