X-Git-Url: https://git.saurik.com/wxWidgets.git/blobdiff_plain/a660d684eda27638bca0384b2058911a31c8e845..f7ba097de48a958039b18c9915d0191675c84314:/docs/latex/wx/tdebug.tex diff --git a/docs/latex/wx/tdebug.tex b/docs/latex/wx/tdebug.tex index e996ebdfb2..76ab37d3db 100644 --- a/docs/latex/wx/tdebug.tex +++ b/docs/latex/wx/tdebug.tex @@ -1,56 +1,84 @@ \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. +your application and {\it all} libraries that use wxWindows 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 wxWindows 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 wxWindows 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 symbol wxUSE\_GLOBAL\_MEMORY\_OPERATORS is 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 wxWindows 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} @@ -59,8 +87,7 @@ need to be omitted by setting the USE\_GLOBAL\_MEMORY\_OPERATORS to 0 in wx\_set 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 @@ -70,35 +97,26 @@ Dump (for dumping the dynamically allocated objects) and PrintStatistics 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 wxWindows 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.