8f8d58d193
Change {DECLARE,IMPLEMENT}_*CLASS and {DECLARE,BEGIN,END}_EVENT_TABLE
occurrences to use the wx-prefixed version of the macros.
113 lines
5.2 KiB
C
113 lines
5.2 KiB
C
/////////////////////////////////////////////////////////////////////////////
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// Name: debugging.h
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// Purpose: topic overview
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// Author: Vadim Zeitlin
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// Copyright: (c) 2009 Vadim Zeitlin <vadim@wxwidgets.org>
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// Licence: wxWindows licence
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/////////////////////////////////////////////////////////////////////////////
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/**
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@page overview_debugging Debugging
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@tableofcontents
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Various classes, functions and macros are provided in wxWidgets to help you
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debug your application. Assertion macros allow you to insert various checks in
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your application which can be compiled out or disabled in release builds but
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are extremely useful while developing. Logging functions are also provided
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which are useful for inserting traces into your application code as well as
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debugging. Both assertions and debug logging are also used by wxWidgets itself
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so you may encounter them even if you don't use either of these features
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yourself.
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@see wxLog, @ref group_funcmacro_log, @ref group_funcmacro_debug
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@section overview_debugging_config Configuring Debug Support
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Starting with wxWidgets 2.9.1 debugging features are always available by
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default (and not only in a special "debug" build of the library) and you need
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to predefine wxDEBUG_LEVEL symbol as 0 when building both the library and your
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application to remove them completely from the generated object code. However
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the debugging features are disabled by default when the application itself is
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built with @c NDEBUG defined (i.e. in "release" or "production" mode) so there
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is no need to do this, unless the resources of the system your application will
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be running on are unusually constrained (notice that when asserts are disabled
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their condition is not even evaluated so the only run-time cost is a single
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condition check and the extra space taken by the asserts in the code).
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This automatic deactivation of debugging code is done by wxIMPLEMENT_APP()
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macro so if you don't use you may need to explicitly call
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wxDISABLE_DEBUG_SUPPORT() yourself.
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Also notice that it is possible to build your own application with a different
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value of wxDEBUG_LEVEL than the one which was used for wxWidgets itself. E.g.
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you may be using an official binary version of the library which will have been
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compiled with default @code wxDEBUG_LEVEL == 1 @endcode but still predefine
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wxDEBUG_LEVEL as 0 for your own code.
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On the other hand, if you do want to keep the asserts even in production
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builds, you will probably want to override the handling of assertion failures
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as the default behaviour which pops up a message box notifying the user about
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the problem is usually inappropriate. Use wxSetAssertHandler() to set up your
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own custom function which should be called instead of the standard assertion
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failure handler. Such function could log an appropriate message in the
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application log file or maybe notify the user about the problem in some more
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user-friendly way.
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@section overview_debugging_dbgmacros Assertion Macros
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wxASSERT(), wxFAIL(), wxCHECK() as well as their other variants (see @ref
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group_funcmacro_debug) are similar to the standard assert() macro but are more
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flexible and powerful. The first of them is equivalent to assert() itself, i.e.
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it simply checks a condition and does nothing if it is true. The second one is
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equivalent to checking an always false condition and is supposed to be used for
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code paths which are supposed to be inaccessible (e.g. @c default branch of a
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@c switch statement which should never be executed). Finally, the wxCHECK()
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family of macros verifies the condition just as wxASSERT() does and performs
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some action such returning from the function if it fails -- thus, it is useful
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for checking the functions preconditions.
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All of the above functions exist in @c _MSG variants which allow you to provide
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a custom message which will be shown (or, more generally, passed to the assert
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handler) if the assertion fails, in addition to the usual file and line number
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information and the condition itself.
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Example of using an assertion macro:
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@code
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void GetTheAnswer(int *p)
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{
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wxCHECK_RET( p, "pointer can't be NULL in GetTheAnswer()" );
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*p = 42;
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};
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@endcode
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If the condition is false, i.e. @c p is @NULL, the assertion handler is called
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and, in any case (even when wxDEBUG_LEVEL is 0), the function returns without
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dereferencing the NULL pointer on the next line thus avoiding a crash.
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The default assertion handler behaviour depends on whether the application
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using wxWidgets was compiled in release build (with @c NDEBUG defined) or debug
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one (without) but may be changed in either case as explained above. If it
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wasn't changed, then nothing will happen in the release build and a message box
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showing the information about the assert as well as allowing to stop the
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program, ignore future asserts or break into the debugger is shown. On the
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platforms where wxStackWalker is supported the message box will also show the
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stack trace at the moment when the assert failed often allowing you to diagnose
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the problem without using the debugger at all. You can see an example of such
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message box in the @ref page_samples_except.
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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
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information in debug mode; it will do nothing for non-debugging code.
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*/
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