\section{Debugging overview}\label{debuggingoverview}
-Classes: \helpref{wxDebugContext}{wxdebugcontext}, \helpref{wxDebugStreamBuf}{wxdebugstreambuf},
-\rtfsp\helpref{wxObject}{wxobject}
+Classes, functions and macros: \helpref{wxDebugContext}{wxdebugcontext}, \helpref{wxObject}{wxobject}, \helpref{wxLog}{wxlog},
+\rtfsp\helpref{Log functions}{logfunctions}, \helpref{Debug macros}{debugmacros}
-Various classes, functions and macros are provided in wxWindows to help you debug
-your application. Most of these are only available if you compile both wxWindows,
-your application and {\it all} libraries that use wxWindows with the DEBUG flag
-set to 1 or more.
+Various classes, functions and macros are provided in wxWidgets to help you debug
+your application. Most of these are only available if you compile both wxWidgets,
+your application and {\it all} libraries that use wxWidgets with the \_\_WXDEBUG\_\_ symbol
+defined. You can also test the \_\_WXDEBUG\_\_ symbol in your own applications to execute
+code that should be active only in debug mode.
-wxDebugContext is a class that never gets instantiated, but ties together
-various functions and variables. It allows you to set the debugging stream, dump
-all objects to that stream, write statistics about object allocation, and
-check memory for errors.
+\wxheading{wxDebugContext}
-You can use the \helpref{WXTRACE}{trace} macro to output debugging information in DEBUG mode;
-it will be defined to nothing for non-debugging code.
+\helpref{wxDebugContext}{wxdebugcontext} is a class that never gets instantiated, but ties together
+various static functions and variables. It allows you to dump all objects to that stream, write statistics about object allocation, and
+check memory for errors.
-It is good practice to define a Dump member function for each class you derive
-from a wxWindows class, so that wxDebugContext::Dump can call it and
+It is good practice to define a \helpref{wxObject::Dump}{wxobjectdump} member function for each class you derive
+from a wxWidgets class, so that \helpref{wxDebugContext::Dump}{wxdebugcontextdump} can call it and
give valuable information about the state of the application.
+If you have difficulty tracking down a memory leak, recompile
+in debugging mode and call \helpref{wxDebugContext::Dump}{wxdebugcontextdump} and \helpref{wxDebugContext::PrintStatistics}{wxdebugcontextprintstatistics} at
+appropriate places. They will tell you what objects have not yet been
+deleted, and what kinds of object they are. In fact, in debug mode wxWidgets will automatically
+detect memory leaks when your application is about to exit, and if there are any leaks,
+will give you information about the problem. (How much information depends on the operating system
+and compiler -- some systems don't allow all memory logging to be enabled). See the
+memcheck sample for example of usage.
+
For wxDebugContext to do its work, the {\it new} and {\it delete}\rtfsp
operators for wxObject have been redefined to store extra information
about dynamically allocated objects (but not statically declared
objects). This slows down a debugging version of an application, but can
-in theory find difficult-to-detect memory leaks (objects are not
+find difficult-to-detect memory leaks (objects are not
deallocated), overwrites (writing past the end of your object) and
underwrites (writing to memory in front of the object).
-If you have difficulty tracking down a memory leak, recompile
-in debugging mode and call wxDebugContext::Dump and wxDebugContext::Statistics
-at appropriate places. They will tell you what objects have not yet been
-deleted, and what kinds of object they are.
+If debugging mode is on and the symbols wxUSE\_GLOBAL\_MEMORY\_OPERATORS and
+wxUSE\_DEBUG\_NEW\_ALWAYS are set to 1 in setup.h, 'new' is defined to be:
+
+{\small
+\begin{verbatim}
+#define new new(__FILE__,__LINE__)
+\end{verbatim}
+}%
-If you use the macro WXDEBUG\_NEW instead of the normal 'new', the debugging
-output (and error messages reporting memory problems) will also tell you what
-file and on what line you allocated the object.
+All occurrences of 'new' in wxWidgets and your own application will use
+the overridden form of the operator with two extra arguments. This means that the debugging
+output (and error messages reporting memory problems) will tell you what
+file and on what line you allocated the object. Unfortunately not all
+compilers allow this definition to work properly, but most do.
-To avoid the need for replacing existing new operators with WXDEBUG\_NEW, you
-can write this at the top of each application file:
+\wxheading{Debug macros}
+You should also use \helpref{debug macros}{debugmacros} as part of a `defensive programming' strategy,
+scattering wxASSERTs liberally to test for problems in your code as early as possible. Forward thinking
+will save a surprising amount of time in the long run.
+
+\helpref{wxASSERT}{wxassert} is used to pop up an error message box when a condition
+is not true. You can also use \helpref{wxASSERT\_MSG}{wxassertmsg} to supply your
+own helpful error message. For example:
+
+{\small
\begin{verbatim}
-#define new WXDEBUG\_NEW
+ void MyClass::MyFunction(wxObject* object)
+ {
+ wxASSERT_MSG( (object != NULL), "object should not be NULL in MyFunction!" );
+
+ ...
+ };
\end{verbatim}
+}
+
+The message box allows you to continue execution or abort the program. If you are running
+the application inside a debugger, you will be able to see exactly where the problem was.
-In non-debugging mode, this will revert to the usual interpretation
-of new. Note that for this not to mess up new-based allocation of non-wxObject derived classes and
-built-in types, there are global definitions of new and delete which match
-the syntax required for storing filename and line numbers. These merely
-call malloc and free, and so do not do anything interesting. The definitions
-may possibly cause multiple symbol problems for some compilers and so might
-need to be omitted by setting the USE\_GLOBAL\_MEMORY\_OPERATORS to 0 in wx\_setup.h
+\wxheading{Logging functions}
+
+You can use the \helpref{wxLogDebug}{wxlogdebug} and \helpref{wxLogTrace}{wxlogtrace} functions to output debugging information in debug mode;
+it will do nothing for non-debugging code.
\subsection{wxDebugContext overview}\label{wxdebugcontextoverview}
Class: \helpref{wxDebugContext}{wxdebugcontext}
wxDebugContext is a class for performing various debugging and memory tracing
-operations. wxDebugContext, and the related macros and function WXTRACE and
-wxTrace, are only present if USE\_DEBUG\_CONTEXT is used.
+operations.
This class has only static data and function members, and there should be
no instances. Probably the most useful members are SetFile (for directing output
Check to check memory blocks for integrity.
Here's an example of use. The SetCheckpoint ensures that only the
-allocations done after the checkpoint will be dumped. Unfortunately
-the define of new to WXDEBUG\_NEW does not work for Borland C++ (and
-perhaps other compilers) because it fails to find the correct overloaded
-operator for non-object usage of new. Instead, you need to use WXDEBUG\_NEW
-explicitly if there are any examples of non-object new usage in the file.
+allocations done after the checkpoint will be dumped.
\begin{verbatim}
-#define new WXDEBUG_NEW
-
wxDebugContext::SetCheckpoint();
wxDebugContext::SetFile("c:\\temp\\debug.log");
wxString *thing = new wxString;
- // Proves that defining 'new' to be 'WXDEBUG_NEW' doesn't mess up
- // non-object allocation. Doesn't work for Borland C++.
char *ordinaryNonObject = new char[1000];
wxDebugContext::Dump();
wxDebugContext::PrintStatistics();
\end{verbatim}
-You can use wxDebugContext if DEBUG is 1 or more, or you can use it
-at any other time (if USE\_DEBUG\_CONTEXT is 1). It is not disabled
-for DEBUG = 1 (as in earlier versions of wxWindows) because you
-may not wish to recompile wxWindows and your entire application
-just to make use of the error logging facility. This is especially
-true in a Windows NT or Windows 95 environment, where you cannot
-easily output to a debug window: wxDebugContext can be used to
-write to log files instead.
+You can use wxDebugContext if \_\_WXDEBUG\_\_ is defined, or you can use it
+at any other time (if wxUSE\_DEBUG\_CONTEXT is set to 1 in setup.h). It is not disabled
+in non-debug mode because you may not wish to recompile wxWidgets and your entire application
+just to make use of the error logging facility.
+
+Note: wxDebugContext::SetFile has a problem at present, so use the default stream instead.
+Eventually the logging will be done through the wxLog facilities instead.
projects / wxWidgets.git / blobdiff