/****************************************************************************** * * * * Copyright (C) 1997-2001 by Dimitri van Heesch. * * Permission to use, copy, modify, and distribute this software and its * documentation under the terms of the GNU General Public License is hereby * granted. No representations are made about the suitability of this software * for any purpose. It is provided "as is" without express or implied warranty. * See the GNU General Public License for more details. * * Documents produced by Doxygen are derivative works derived from the * input used in their production; they are not affected by this license. * */ /*! \page preprocessing Preprocessing Source files that are used as input to doxygen can be parsed by doxygen's built-in C-preprocessor. By default doxygen does only partial preprocessing. That is, it evaluates conditional compilation statements (like \#if) and evaluates macro definitions, but it does not perform macro expansion. So if you have the following code fragment \verbatim #define VERSION 200 #define CONST_STRING const char * #if VERSION >= 200 static CONST_STRING version = "2.xx"; #else static CONST_STRING version = "1.xx"; #endif \endverbatim Then by default doxygen will feed the following to its parser: \verbatim #define VERSION #define CONST_STRING static CONST_STRING version = "2.xx"; \endverbatim You can disable all preprocessing by setting \ref cfg_enable_preprocessing "ENABLE_PREPROCESSING" to \c NO in the configuation file. In the case above doxygen will then reads both statements! In case you want to expand the \c CONST_STRING macro, you should set the \ref cfg_macro_expansion "MACRO_EXPANSION" tag in the config file to \c YES. Then the result after preprocessing becomes: \verbatim #define VERSION #define CONST_STRING static const char * version = "1.xx"; \endverbatim Note that doxygen will now expand \e all macro definitions (recursively if needed). This is often too much. Therefore, doxygen also allows you to expand only those defines that you explicitly specify. For this you have to set the \ref cfg_expand_only_predef "EXPAND_ONLY_PREDEF" tag to \c YES and specify the macro definitions after the \ref cfg_predefined "PREDEFINED" or \ref cfg_expand_as_defined "EXPAND_AS_DEFINED" tag. As an example, suppose you have the following obfuscated code fragment of an abstract base class called \c IUnknown: \verbatim /*! A reference to an IID */ #ifdef __cplusplus #define REFIID const IID & #else #define REFIID const IID * #endif /*! The IUnknown interface */ DECLARE_INTERFACE(IUnknown) { STDMETHOD(HRESULT,QueryInterface) (THIS_ REFIID iid, void **ppv) PURE; STDMETHOD(ULONG,AddRef) (THIS) PURE; STDMETHOD(ULONG,Release) (THIS) PURE; }; \endverbatim without macro expansion doxygen will get confused, but we may not want to expand the REFIID macro, because it is documented and the user that reads the documentation should use it when implementing the interface. By setting the following in the config file: \verbatim ENABLE_PREPROCESSING = YES MACRO_EXPANSION = YES EXPAND_ONLY_PREDEF = YES PREDEFINED = "DECLARE_INTERFACE(name)=class name" \ "STDMETHOD(result,name)=virtual result name" \ "PURE= = 0" \ THIS_= \ THIS= \ __cplusplus \endverbatim we can make sure that the proper result is fed to doxygen's parser: \verbatim /*! A reference to an IID */ #define REFIID /*! The IUnknown interface */ class IUnknown { virtual HRESULT QueryInterface ( REFIID iid, void **ppv) = 0; virtual ULONG AddRef () = 0; virtual ULONG Release () = 0; }; \endverbatim Note that the \ref cfg_predefined "PREDEFINED" tag accepts function like macro definitions (like \c DECLARE_INTERFACE ), normal macro substitutions (like \c PURE and \c THIS) and plain defines (like \c __cplusplus). Note also that preprocessor definitions that are normally defined automatically by the preprocessor (like \c __cplusplus), have to be defined by hand with doxygen's parser (this is done because these defines are often platform/compiler specific). In some cases you may want to substitute a macro name or function by something else without exposing the result to further macro substitution. You can do this but using the := operator instead of = As an example suppose we have the following piece of code: \verbatim #define QList QListT class QListT { }; \endverbatim Then the only way to get doxygen interpret this as a class definition for class QList is to define: \verbatim PREDEFINED = QListT:=QList \endverbatim Here is example provided by Valter Minute that helps doxygen to wade through the boilerplate code in Microsoft's ATL library: \verbatim PREDEFINED = DECLARE_REGISTRY_RESOURCEID=// \ DECLARE_PROTECT_FINAL_CONSTRUCT=// \ BEGIN_COM_MAP=/* \ END_COM_MAP=*/// \ BEGIN_PROP_MAP=/* \ END_PROP_MAP=*/// \ BEGIN_MSG_MAP=/* \ END_MSG_MAP=*/// \ DECLARE_VIEW_STATUS=// \ "STDMETHOD(a)=HRESULT a" \ "ATL_NO_VTABLE= "\ "__declspec(a)= "\ BEGIN_CONNECTION_POINT_MAP=/* \ END_CONNECTION_POINT_MAP=*/// \ "DECLARE_AGGREGATABLE(Class)= " \ "DECLARE_REGISTRY_RESOURCEID(id)= " \endverbatim As you can see doxygen's preprocessor is quite powerful, but if you want even more flexibility you can always write an input filter and specify it after the \ref cfg_input_filter "INPUT_FILTER" tag. If you are unsure what the effect of doxygen's preprocessing will be you can run doxygen as follows: \verbatim doxygen -d Preprocessor \endverbatim This will instruct doxygen to dump the input sources to standard output after preprocessing has been done (Hint: set QUIET = YES and WARNINGS = NO in the configuration file to disable any other output). \htmlonly Go to the next section or return to the index. \endhtmlonly */