This page provides a high-level overview of the internals of doxygen, with links to the relevant parts of the code. This document is intended for developers who want to work on doxygen. Users of doxygen are referred to the User Manual.
The generic starting point of the application is of cource the main() function.
Configuration file data is stored in singleton class Config and can be accessed using wrapper macros Config_getString(), Config_getInt(), Config_getList(), Config_getEnum(), and Config_getBool() depending on the type of the option.
The format of the configuration file (options and types) is defined
by the file config.xml. As part of the build process,
the python script configgen.py will create a file configoptions.cpp
from this, which serves as the input for the configuration file parser
that is invoked using Config::parse(). The script configgen.py will also
create the documentation for the configuration items, creating the file
config.doc.
After the configuration is known, the input files are searched using searchInputFiles() and any tag files are read using readTagFile()
The function parseFiles() takes care of parsing all files. It uses the ParserManager singleton factory to create a suitable parser object for each file. Each parser implements the abstract interface ParserInterface.
If the parser indicates it needs preprocessing via ParserInterface::needsPreprocessing(), doxygen will call preprocessFile() on the file.
A second step is to convert multiline C++-style comments into C style comments for easier processing later on. As side effect of this step also aliases (ALIASES option) are resolved. The function that performs these 2 tasks is called convertCppComments().
Note: Alias resolution should better be done in a separate step as it is now coupled to C/C++ code and does not work automatically for other languages!
The third step is the actual language parsing and is done by calling ParserInterface::parseInput() on the parser interface returned by the ParserManager.
The result of parsing is a tree of Entry objects. These Entry objects are wrapped in a EntryNav object and stored on disk using Entry::createNavigationIndex() on the root node of the tree.
Each Entry object roughly contains the raw data for a symbol and is later converted into a Definition object.
When a parser finds a special comment block in the input, it will do a first pass parsing via parseCommentBlock(). During this pass the comment block is split into multiple parts if needed. Some data that is later needed is extracted like section labels, xref items, and formulas. Also Markdown markup is processed using processMarkdown() during this pass.
The Entry objects created and filled during parsing are stored on disk (to keep memory needs low). The name, parent/child relation, and location on disk of each Entry is stored as a tree of EntryNav nodes, which is kept in memory.
Doxygen does a number of tree walks over the EntryNav nodes in the tree to build up the data structures needed to produce the output.
The resulting data structures are all children of the generic base class called Definition which holds all non-specific data for a symbol definition.
Definition is an abstract base class. Concrete subclasses are - ClassDef: for storing class/struct/union related data - NamespaceDef: for storing namespace related data - FileDef: for storing file related data - DirDef: for storing directory related data
For doxygen specific concepts the following subclasses are available - GroupDef: for storing grouping related data - PageDef: for storing page related data
Finally the data for members of classes, namespaces, and files is stored in the subclass MemberDef.
Within doxygen there are a number of ways to obtain debug output. Besides the invasive method of putting print statements in the code there are a number of easy ways to get debug information.
.l filesflex / lex command. The result is that of each input line the (lex) rule(s)
that are applied on it are shown..l fileProperties of this fileWrite used lex rules to Yes.l file is newer than the corresponding .cpp file
or remove the corresponding .cpp fileperl script is given to toggle the
possibility of having the rules debug information.LEX="flex -d" with the make command on the
command line. In this case the .l that are converted to the corresponding
.cpp files during this make get the rules debug information.make..l files that are rebuild to .cpp
files so be sure that only the .l files(s) of which you want to have the
rules debug information is (are) newer than the corresponding .cpp
file(s).-d option with the
following possibilities (each option has to be preceded by -d):EXPAND_ONLY_PREDEF, PREDEFINED and MACRO_EXPANSION. MULTILINE_CPP_IS_BRIEF is set to NO).ALIASES)"." (dot).lex files used. When a lexer is started and when a lexer
ends the name of the lex file is given so it is possible to see in which lexer the
problem occurs. This makes it easier to select the file to be compiled in lex debug mode.TODO