Doxygen Internals


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 course the main() function.

Configuration options

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 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 will also create the documentation for the configuration items, creating the file config.doc.

Gathering Input files

After the configuration is known, the input files are searched using searchInputFiles() and any tag files are read using readTagFile()

Parsing Input files

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.

Resolving relations

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

For doxygen specific concepts the following subclasses are available

Finally the data for members of classes, namespaces, and files is stored in the subclass MemberDef.

Producing debug output

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.

Producing output


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