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Debugging macros
Functions and Macros by Category

## Detailed Description

Useful macros and functions for error checking and defensive programming.

Starting with wxWidgets 2.9.1, debugging support in wxWidgets is always compiled in by default, you need to explicitly define wxDEBUG_LEVEL as 0 to disable it completely. However, by default debugging macros are dormant in the release builds, i.e. when the main program is compiled with the standard `NDEBUG` symbol being defined. You may explicitly activate the debugging checks in the release build by calling wxSetAssertHandler() with a custom function if needed.

When debugging support is active, failure of both wxASSERT() and wxCHECK() macros conditions result in a debug alert. When debugging support is inactive or turned off entirely at compilation time, wxASSERT() and wxFAIL() macros don't do anything while wxCHECK() still checks its condition and returns if it fails, even if no alerts are shown to the user.

Finally, the compile time assertions don't happen during the run-time but result in the compilation error messages if the condition they check fail. They are always enabled and are not affected by wxDEBUG_LEVEL.

Related class group: Debugging.

## Macros
#define | wxDISABLE_DEBUG_SUPPORT()
| Use this macro to disable all debugging code in release build when not using wxIMPLEMENT_APP().
#define | wxDEBUG_LEVEL
| Preprocessor symbol defining the level of debug support available.
#define | __WXDEBUG__
| Compatibility macro indicating presence of debug support.
#define | wxASSERT(condition)
| Assert macro.
#define | wxASSERT_LEVEL_2(condition)
| Assert macro for expensive run-time checks.
#define | wxASSERT_LEVEL_2_MSG(condition, msg)
| Assert macro with a custom message for expensive run-time checks.
#define | wxASSERT_MIN_BITSIZE(type, size)
| This macro results in a compile time assertion failure if the size of the given `type` is less than `size` bits.
#define | wxASSERT_MSG(condition, message)
| Assert macro with message.
#define | wxCHECK(condition, retValue)
| Checks that the condition is true, returns with the given return value if not (stops execution in debug mode).
#define | wxCHECK_MSG(condition, retValue, message)
| Checks that the condition is true, returns with the given return value if not (stops execution in debug mode).
#define | wxCHECK_RET(condition, message)
| Checks that the condition is true, and returns if not (stops execution with the given error message in debug mode).
#define | wxCHECK2(condition, operation)
| Checks that the condition is true, and if not, it will wxFAIL() and execute the given `operation` if it is not.
#define | wxCHECK2_MSG(condition, operation, message)
| This is the same as wxCHECK2(), but wxFAIL_MSG() with the specified `message` is called instead of wxFAIL() if the `condition` is false.
#define | wxCOMPILE_TIME_ASSERT(condition, message)
| Using wxCOMPILE_TIME_ASSERT() results in a compilation error if the specified `condition` is false.
#define | wxCOMPILE_TIME_ASSERT2(condition, message, name)
| This macro is identical to wxCOMPILE_TIME_ASSERT() except that it allows you to specify a unique `name` for the struct internally defined by this macro to avoid getting the compilation errors described for wxCOMPILE_TIME_ASSERT().
#define | wxDISABLE_ASSERTS_IN_RELEASE_BUILD() wxDisableAsserts()
| Use this macro to disable asserts in release build when not using wxIMPLEMENT_APP().
#define | wxFAIL
| Will always generate an assert error if this code is reached (in debug mode).
#define | wxFAIL_MSG(message)
| Will always generate an assert error with specified message if this code is reached (in debug mode).
#define | wxDISABLE_DEBUG_LOGGING_IN_RELEASE_BUILD()
| Use this macro to disable logging at debug and trace levels in release build when not using wxIMPLEMENT_APP().
#define | WXDEBUG_NEW(arg)
| This is defined in debug mode to be call the redefined new operator with filename and line number arguments.

## Typedefs
typedef void(* | wxAssertHandler_t )(const wxString &file, int line, const wxString &func, const wxString &cond, const wxString &msg)
| Type for the function called in case of assert failure.

## Functions
void | wxAbort ()
| Exits the program immediately.
void | wxDisableAsserts ()
| Disable the condition checks in the assertions.
bool | wxIsDebuggerRunning ()
| Returns true if the program is running under debugger, false otherwise.
wxAssertHandler_t | wxSetAssertHandler (wxAssertHandler_t handler)
| Sets the function to be called in case of assertion failure.
void | wxSetDefaultAssertHandler ()
| Reset the assert handler to default function which shows a message box when an assert happens.
void | wxTrap ()
| Generate a debugger exception meaning that the control is passed to the debugger if one is attached to the process.

## Macro Definition Documentation

#define __WXDEBUG__

Compatibility macro indicating presence of debug support.

This symbol is defined if wxDEBUG_LEVEL is greater than 0 and undefined otherwise.

Include file:

    #include <wx/debug.h>

#define wxASSERT | ( |  | condition | ) |

Assert macro.

An error message will be generated if the condition is false in debug mode, but nothing will be done in the release build.

Please note that the condition in wxASSERT() should have no side effects because it will not be executed in release mode at all.

This macro should be used to catch (in debug builds) logical errors done by the programmer.

See Also
  wxASSERT_MSG(), wxCOMPILE_TIME_ASSERT()

Include file:

    #include <wx/debug.h>

#define wxASSERT_LEVEL_2 | ( |  | condition | ) |

Assert macro for expensive run-time checks.

This macro does nothing unless wxDEBUG_LEVEL is 2 or more and is meant to be used for the assertions with noticeable performance impact and which, hence, should be disabled during run-time.

If wxDEBUG_LEVEL is 2 or more, it becomes the same as wxASSERT().

Include file:

    #include <wx/debug.h>

#define wxASSERT_LEVEL_2_MSG | ( |  | condition,
|  |  | msg
| ) |  |

Assert macro with a custom message for expensive run-time checks.

If wxDEBUG_LEVEL is 2 or more, this is the same as wxASSERT_MSG(), otherwise it doesn't do anything at all.

See Also
  wxASSERT_LEVEL_2()

Include file:

    #include <wx/debug.h>

#define wxASSERT_MIN_BITSIZE | ( |  | type,
|  |  | size
| ) |  |

This macro results in a compile time assertion failure if the size of the given `type` is less than `size` bits.

This macro should be used to catch (in debug builds) logical errors done by the programmer.

You may use it like this, for example:

// we rely on the int being able to hold values up to 2^32
wxASSERT_MIN_BITSIZE(int, 32);
// can't work with the platforms using UTF-8 for wchar_t
wxASSERT_MIN_BITSIZE(wchar_t, 16);

Include file:

    #include <wx/debug.h>

#define wxASSERT_MSG | ( |  | condition,
|  |  | message
| ) |  |

Assert macro with message.

An error message will be generated if the condition is false.

This macro should be used to catch (in debug builds) logical errors done by the programmer.

See Also
  wxASSERT(), wxCOMPILE_TIME_ASSERT()

Include file:

    #include <wx/debug.h>

#define wxCHECK | ( |  | condition,
|  |  | retValue
| ) |  |

Checks that the condition is true, returns with the given return value if not (stops execution in debug mode).

This check is done even in release mode.

This macro should be used to catch (both in debug and release builds) logical errors done by the programmer.

Include file:

    #include <wx/debug.h>

#define wxCHECK2 | ( |  | condition,
|  |  | operation
| ) |  |

Checks that the condition is true, and if not, it will wxFAIL() and execute the given `operation` if it is not.

This is a generalisation of wxCHECK() and may be used when something else than just returning from the function must be done when the `condition` is false. This check is done even in release mode.

This macro should be used to catch (both in debug and release builds) logical errors done by the programmer.

Include file:

    #include <wx/debug.h>

#define wxCHECK2_MSG | ( |  | condition,
|  |  | operation,
|  |  | message
| ) |  |

This is the same as wxCHECK2(), but wxFAIL_MSG() with the specified `message` is called instead of wxFAIL() if the `condition` is false.

This macro should be used to catch (both in debug and release builds) logical errors done by the programmer.

Include file:

    #include <wx/debug.h>

#define wxCHECK_MSG | ( |  | condition,
|  |  | retValue,
|  |  | message
| ) |  |

Checks that the condition is true, returns with the given return value if not (stops execution in debug mode).

This check is done even in release mode.

This macro may be only used in non-void functions, see also wxCHECK_RET().

This macro should be used to catch (both in debug and release builds) logical errors done by the programmer.

Include file:

    #include <wx/debug.h>

#define wxCHECK_RET | ( |  | condition,
|  |  | message
| ) |  |

Checks that the condition is true, and returns if not (stops execution with the given error message in debug mode).

This check is done even in release mode.

This macro should be used in void functions instead of wxCHECK_MSG().

This macro should be used to catch (both in debug and release builds) logical errors done by the programmer.

Include file:

    #include <wx/debug.h>

#define wxCOMPILE_TIME_ASSERT | ( |  | condition,
|  |  | message
| ) |  |

Using wxCOMPILE_TIME_ASSERT() results in a compilation error if the specified `condition` is false.

The compiler error message should include the `message` identifier - please note that it must be a valid C++ identifier and not a string unlike in the other cases.

This macro is mostly useful for testing the expressions involving the `sizeof` operator as they can't be tested by the preprocessor but it is sometimes desirable to test them at the compile time.

Note that this macro internally declares a struct whose name it tries to make unique by using the `LINE` in it but it may still not work if you use it on the same line in two different source files. In this case you may either change the line in which either of them appears on or use the wxCOMPILE_TIME_ASSERT2() macro.

Also note that Microsoft Visual C++ has a bug which results in compiler errors if you use this macro with 'Program Database For Edit And Continue' (`/ZI`) option, so you shouldn't use it ('Program Database' (`/Zi`) is ok though) for the code making use of this macro.

This macro should be used to catch misconfigurations at compile-time.

See Also
  wxASSERT_MSG(), wxASSERT_MIN_BITSIZE()

Include file:

    #include <wx/debug.h>

#define wxCOMPILE_TIME_ASSERT2 | ( |  | condition,
|  |  | message,
|  |  | name
| ) |  |

This macro is identical to wxCOMPILE_TIME_ASSERT() except that it allows you to specify a unique `name` for the struct internally defined by this macro to avoid getting the compilation errors described for wxCOMPILE_TIME_ASSERT().

This macro should be used to catch misconfigurations at compile-time.

Include file:

    #include <wx/debug.h>

#define wxDEBUG_LEVEL

Preprocessor symbol defining the level of debug support available.

This symbol is defined to 1 by default meaning that asserts are compiled in (although they may be disabled by a call to wxDisableAsserts()). You may predefine it as 0 prior to including any wxWidgets headers to omit the calls to wxASSERT() and related macros entirely in your own code and you may also predefine it as 0 when building wxWidgets to also avoid including any asserts in wxWidgets itself.

Alternatively, you may predefine it as 2 to include wxASSERT_LEVEL_2() and similar macros which are used for asserts which have non-trivial run-time costs and so are disabled by default.

Since
  2.9.1

Include file:

    #include <wx/debug.h>

#define WXDEBUG_NEW | ( |  | arg | ) |

This is defined in debug mode to be call the redefined new operator with filename and line number arguments.

The definition is:

#define WXDEBUG_NEW new(__FILE__,__LINE__)

In non-debug mode, this is defined as the normal new operator.

Include file:

    #include <wx/object.h>

#define wxDISABLE_ASSERTS_IN_RELEASE_BUILD | ( |  | ) | wxDisableAsserts()

Use this macro to disable asserts in release build when not using wxIMPLEMENT_APP().

By default, assert message boxes are suppressed in release build by wxIMPLEMENT_APP() which uses this macro. If you don't use wxIMPLEMENT_APP() because your application initializes wxWidgets directly (e.g. calls wxEntry() or wxEntryStart() itself) but still want to suppress assert notifications in release build you need to use this macro directly.

See Also
  wxDISABLE_DEBUG_SUPPORT()

Since
  2.9.1

Include file:

    #include <wx/debug.h>

#define wxDISABLE_DEBUG_LOGGING_IN_RELEASE_BUILD | ( |  | ) |

Use this macro to disable logging at debug and trace levels in release build when not using wxIMPLEMENT_APP().

See Also
  wxDISABLE_DEBUG_SUPPORT(), wxDISABLE_ASSERTS_IN_RELEASE_BUILD(), Debugging

Since
  2.9.1

Include file:

    #include <wx/log.h>

#define wxDISABLE_DEBUG_SUPPORT | ( |  | ) |

Value:
wxDISABLE_ASSERTS_IN_RELEASE_BUILD(); \
wxDISABLE_DEBUG_LOGGING_IN_RELEASE_BUILD()

Use this macro to disable all debugging code in release build when not using wxIMPLEMENT_APP().

Currently this macro disables assert checking and debug and trace level logging messages in release build (i.e. when `NDEBUG` is defined). It is used by wxIMPLEMENT_APP() macro so you only need to use it explicitly if you don't use this macro but initialize wxWidgets directly (e.g. calls wxEntry() or wxEntryStart() itself).

If you do not want to disable debugging code even in release build of your application, you can use wxSetDefaultAssertHandler() and wxLog::SetLogLevel() with `wxLOG_Max` parameter to enable assertions and debug logging respectively.

See Also
  wxDISABLE_ASSERTS_IN_RELEASE_BUILD(), wxDISABLE_DEBUG_LOGGING_IN_RELEASE_BUILD(), Debugging

Since
  2.9.1

Include file:

    #include <wx/app.h>

#define wxFAIL

Will always generate an assert error if this code is reached (in debug mode).

Note that you don't have to (and cannot) use brackets when invoking this macro:

if (...some condition...) {
wxFAIL;
}

This macro should be used to catch (in debug builds) logical errors done by the programmer.

See Also
  wxFAIL_MSG()

Include file:

    #include <wx/debug.h>

#define wxFAIL_MSG | ( |  | message | ) |

Will always generate an assert error with specified message if this code is reached (in debug mode).

This macro is useful for marking "unreachable" code areas, for example it may be used in the "default:" branch of a switch statement if all possible cases are processed above.

This macro should be used to catch (in debug builds) logical errors done by the programmer.

See Also
  wxFAIL()

Include file:

    #include <wx/debug.h>

## Typedef Documentation

typedef void(* wxAssertHandler_t)(const wxString &file, int line, const wxString &func, const wxString &cond, const wxString &msg)

Type for the function called in case of assert failure.

See Also
  wxSetAssertHandler()

## Function Documentation

void wxAbort | ( |  | ) |

Exits the program immediately.

This is a simple wrapper for the standard abort() function which is not available under all platforms (currently only Windows CE doesn't provide it).

Since
  2.9.4

void wxDisableAsserts | ( |  | ) |

Disable the condition checks in the assertions.

This is the same as calling wxSetAssertHandler() with NULL handler.

Since
  2.9.0

Include file:

    #include <wx/debug.h>

bool wxIsDebuggerRunning | ( |  | ) |

Returns true if the program is running under debugger, false otherwise.

Please note that this function is currently only implemented for Win32 and always returns false elsewhere.

Include file:

    #include <wx/debug.h>

wxAssertHandler_t wxSetAssertHandler | ( | wxAssertHandler_t | handler | ) |

Sets the function to be called in case of assertion failure.

The default assert handler forwards to wxApp::OnAssertFailure() whose default behaviour is, in turn, to show the standard assertion failure dialog if a wxApp object exists or shows the same dialog itself directly otherwise.

While usually it is enough – and more convenient – to just override OnAssertFailure(), to handle all assertion failures, including those occurring even before wxApp object creation of after its destruction you need to provide your assertion handler function.

This function also provides a simple way to disable all asserts: simply pass NULL pointer to it. Doing this will result in not even evaluating assert conditions at all, avoiding almost all run-time cost of asserts.

Notice that this function is not MT-safe, so you should call it before starting any other threads.

The return value of this function is the previous assertion handler. It can be called after any pre-processing by your handler and can also be restored later if you uninstall your handler.

Parameters

  handler | The function to call in case of assertion failure or NULL.

Returns
  The previous assert handler which is not NULL by default but could be NULL if it had been previously set to this value using this function.

Since
  2.9.0

Include file:

    #include <wx/debug.h>

void wxSetDefaultAssertHandler | ( |  | ) |

Reset the assert handler to default function which shows a message box when an assert happens.

This can be useful for the applications compiled in release build (with `NDEBUG` defined) for which the asserts are by default disabled: if you wish to enable them even in this case you need to call this function.

Since
  2.9.1

Include file:

    #include <wx/debug.h>

void wxTrap | ( |  | ) |

Generate a debugger exception meaning that the control is passed to the debugger if one is attached to the process.

Otherwise the program just terminates abnormally.

If `wxDEBUG_LEVEL` is 0 (which is not the default) this function does nothing.

Include file:

    #include <wx/debug.h>