Documentation for the GNU C++ Library is created from three independent sources: a manual, a FAQ, and an API reference.
The sub-directory doc
within the main source directory contains
Makefile.am and
Makefile.in, which provide rules for
generating documentation, described in excruciating detail
below. The doc
sub-directory also contains three directories: doxygen, which contains scripts and
fragments for doxygen, html, which contains an html
version of the manual, and xml, which contains an xml version
of the manual.
Diverging from established documentation conventions in the rest of the GCC project, libstdc++ does not use Texinfo as a markup language. Instead, Docbook is used to create the manual and the FAQ, and Doxygen is used to construct the API reference. Although divergent, this conforms to the GNU Project recommendations as long as the output is of sufficient quality, as per GNU Manuals.
Certain Makefile rules are required by the GNU Coding
Standards. These standard rules generate HTML, PDF, XML, or man
files. For each of the generative rules, there is an additional
install rule that is used to install any generated documentation
files into the prescribed installation directory. Files are
installed into share/doc
or share/man directories.
The standard Makefile rules are conditionally supported, based on the results of examining the host environment for prerequisites at configuration time. If requirements are not found, the rule is aliased to a dummy rule that does nothing, and produces no documentation. If the requirements are found, the rule forwards to a private rule that produces the requested documentation.
For more details on what prerequisites were found and where,
please consult the file config.log in the
libstdc++ build directory. Compare this log to what is expected
for the relevant Makefile conditionals:
BUILD_INFO, BUILD_XML,
BUILD_HTML, BUILD_MAN,
BUILD_PDF, and BUILD_EPUB.
Supported Makefile rules:
Generates multi-page HTML documentation, and installs it in the following directories:
doc/libstdc++/libstdc++-api.html
doc/libstdc++/libstdc++-manual.html
Generates indexed PDF documentation, and installs it as the following files:
doc/libstdc++/libstdc++-api.pdf
doc/libstdc++/libstdc++-manual.pdf
Generates man pages, and installs it in the following directory:
man/man3/
The generated man pages are namespace-qualified, so to look at
the man page for vector, one would use
man std::vector.
Generates documentation in the ebook/portable electronic reader format called Epub, and installs it as the following file.
doc/libstdc++/libstdc++-manual.epub
Generates single-file XML documentation, and installs it as the following files:
doc/libstdc++/libstdc++-api-single.xml
doc/libstdc++/libstdc++-manual-single.xml
Makefile rules for several other formats are explicitly not supported, and are always aliased to dummy rules. These unsupported formats are: info, ps, and dvi.
Table B.1. Doxygen Prerequisites
| Tool | Version | Required By |
|---|---|---|
| coreutils | 8.5 | all |
| bash | 4.1 | all |
| doxygen | 1.7.6.1 | all |
| graphviz | 2.26 | graphical hierarchies |
| pdflatex | 2007-59 | pdf output |
Prerequisite tools are Bash 2.0 or later, Doxygen, and the GNU coreutils. (GNU versions of find, xargs, and possibly sed and grep are used, just because the GNU versions make things very easy.)
To generate the pretty pictures and hierarchy graphs, the Graphviz package will need to be installed. For PDF output, pdflatex is required.
Be warned the PDF file generated via doxygen is extremely
large. At last count, the PDF file is over three thousand
pages. Generating this document taxes the underlying TeX
formatting system, and will require the expansion of TeX's memory
capacity. Specifically, the pool_size
variable in the configuration file texmf.cnf may
need to be increased by a minimum factor of two.
The following Makefile rules run Doxygen to generate HTML docs, XML docs, XML docs as a single file, PDF docs, and the man pages. These rules are not conditional! If the required tools are not found, or are the wrong versions, the rule may end in an error.
make doc-html-doxygen
make doc-xml-doxygen
make doc-xml-single-doxygen
make doc-pdf-doxygen
make doc-man-doxygen
Generated files are output into separate sub directories of
doc/doxygen/ in the
build directory, based on the output format. For instance, the
HTML docs will be in doc/doxygen/html.
Careful observers will see that the Makefile rules simply call
a script from the source tree, run_doxygen, which
does the actual work of running Doxygen and then (most
importantly) massaging the output files. If for some reason
you prefer to not go through the Makefile, you can call this
script directly. (Start by passing --help.)
If you wish to tweak the Doxygen settings, do so by editing
doc/doxygen/user.cfg.in. Notes to fellow
library hackers are written in triple-# comments.
Sometimes, mis-configuration of the pre-requisite tools can lead to errors when attempting to build the documentation. Here are some of the obvious errors, and ways to fix some common issues that may appear quite cryptic.
First, if using a rule like make pdf, try to
narrow down the scope of the error to either docbook
(make doc-pdf-docbook) or doxygen (make
doc-pdf-doxygen).
Working on the doxygen path only, closely examine the
contents of the following build directory:
build/target/libstdc++-v3/doc/doxygen/latex.
Pay attention to three files enclosed within, annotated as follows.
refman.tex
The actual latex file, or partial latex file. This is generated
via doxygen, and is the LaTeX version of the
Doxygen XML file libstdc++-api.xml. Go to a specific
line, and look at the genrated LaTeX, and try to deduce what
markup in libstdc++-api.xml is causing it.
refman.out
A log of the compilation of the converted LaTeX form to pdf. This
is a linear list, from the beginning of the
refman.tex file: the last entry of this file
should be the end of the LaTeX file. If it is truncated, then you
know that the last entry is the last part of the generated LaTeX
source file that is valid. Often this file contains an error with
a specific line number of refman.tex that is
incorrect, or will have clues at the end of the file with the dump
of the memory usage of LaTeX.
If the error at hand is not obvious after examination, a
fall-back strategy is to start commenting out the doxygen
input sources, which can be found in
doc/doxygen/user.cfg.in, look for the
INPUT tag. Start by commenting out whole
directories of header files, until the offending header is
identified. Then, read the latex log files to try and find
surround text, and look for that in the offending header.
In general, libstdc++ files should be formatted according to the rules found in the Coding Standard. Before any doxygen-specific formatting tweaks are made, please try to make sure that the initial formatting is sound.
Adding Doxygen markup to a file (informally called “doxygenating”) is very simple. The Doxygen manual can be found here. We try to use a very-recent version of Doxygen.
For classes, use
deque/vector/list
and std::pair as examples. For
functions, see their member functions, and the free functions
in stl_algobase.h. Member functions of
other container-like types should read similarly to these
member functions.
Some commentary to accompany the first list in the Special Documentation Blocks section of the Doxygen manual:
For longer comments, use the Javadoc style...
...not the Qt style. The intermediate *'s are preferred.
Use the triple-slash style only for one-line comments (the “brief” mode).
This is disgusting. Don't do this.
Some specific guidelines:
Use the @@-style of commands, not the !-style. Please be careful about whitespace in your markup comments. Most of the time it doesn't matter; doxygen absorbs most whitespace, and both HTML and *roff are agnostic about whitespace. However, in <pre> blocks and @@code/@@endcode sections, spacing can have “interesting” effects.
Use either kind of grouping, as
appropriate. doxygroups.cc exists for this
purpose. See stl_iterator.h for a good example
of the “other” kind of grouping.
Please use markup tags like @@p and @@a when referring to things such as the names of function parameters. Use @@e for emphasis when necessary. Use @@c to refer to other standard names. (Examples of all these abound in the present code.)
Complicated math functions should use the multi-line
format. An example from random.h:
/**
* @@brief A model of a linear congruential random number generator.
*
* @@f[
* x_{i+1}\leftarrow(ax_{i} + c) \bmod m
* @@f]
*/
One area of note is the markup required for
@@file markup in header files. Two details
are important: for filenames that have the same name in
multiple directories, include part of the installed path to
disambiguate. For example:
/** @@file debug/vector
* This file is a GNU debug extension to the Standard C++ Library.
*/
The other relevant detail for header files is the use of a
libstdc++-specific doxygen alias that helps distinguish
between public header files (like random)
from implementation or private header files (like
bits/c++config.h.) This alias is spelled
@@headername and can take one or two
arguments that detail the public header file or files that
should be included to use the contents of the file. All header
files that are not intended for direct inclusion must use
headername in the file
block. An example:
/** @@file bits/basic_string.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @@headername{string}
*/
Be careful about using certain, special characters when writing Doxygen comments. Single and double quotes, and separators in filenames are two common trouble spots. When in doubt, consult the following table.
Table B.2. HTML to Doxygen Markup Comparison
| HTML | Doxygen |
|---|---|
| \ | \\ |
| " | \" |
| ' | \' |
| <i> | @@a word |
| <b> | @@b word |
| <code> | @@c word |
| <em> | @@a word |
| <em> | <em>two words or more</em> |
Table B.3. Docbook Prerequisites
| Tool | Version | Required By |
|---|---|---|
| docbook5-style-xsl | 1.76.1 | all |
| xsltproc | 1.1.26 | all |
| xmllint | 2.7.7 | validation |
| dblatex | 0.3 | pdf output |
| pdflatex | 2007-59 | pdf output |
| docbook2X | 0.8.8 | info output |
| epub3 stylesheets | b3 | epub output |
Editing the DocBook sources requires an XML editor. Many exist: some notable options include emacs, Kate, or Conglomerate.
Some editors support special “XML Validation” modes that can validate the file as it is produced. Recommended is the nXML Mode for emacs.
Besides an editor, additional DocBook files and XML tools are also required.
Access to the DocBook 5.0 stylesheets and schema is required. The
stylesheets are usually packaged by vendor, in something
like docbook5-style-xsl. To exactly match
generated output, please use a version of the stylesheets
equivalent
to docbook5-style-xsl-1.75.2-3. The
installation directory for this package corresponds to
the XSL_STYLE_DIR
in doc/Makefile.am and defaults
to /usr/share/sgml/docbook/xsl-ns-stylesheets.
For processing XML, an XSLT processor and some style
sheets are necessary. Defaults are xsltproc
provided by libxslt.
For validating the XML document, you'll need
something like xmllint and access to the
relevant DocBook schema. These are provided
by a vendor package like libxml2 and docbook5-schemas-5.0-4
For PDF output, something that transforms valid Docbook XML to PDF is
required. Possible solutions include dblatex,
xmlto, or prince. Of
these, dblatex is the default. Other
options are listed on the DocBook web pages. Please
consult the <libstdc++@@gcc.gnu.org> list when
preparing printed manuals for current best practice and
suggestions.
For Texinfo output, something that transforms valid Docbook XML to Texinfo is required. The default choice is docbook2X.
For epub output, the stylesheets for EPUB3 are required. These stylesheets are still in development. To validate the created file, epubcheck is necessary.
The following Makefile rules generate (in order): an HTML version of all the DocBook documentation, a PDF version of the same, and a single XML document. These rules are not conditional! If the required tools are not found, or are the wrong versions, the rule may end in an error.
make doc-html-docbook
make doc-pdf-docbook
make doc-xml-single-docbook
Generated files are output into separate sub directores of
doc/docbook/ in the
build directory, based on the output format. For instance, the
HTML docs will be in doc/docbook/html.
If the Docbook stylesheets are installed in a custom location,
one can use the variable XSL_STYLE_DIR to
override the Makefile defaults. For example:
make XSL_STYLE_DIR="/usr/share/xml/docbook/stylesheet/nwalsh" doc-html-docbook
Sometimes, mis-configuration of the pre-requisite tools can lead to errors when attempting to build the documentation. Here are some of the obvious errors, and ways to fix some common issues that may appear quite cryptic.
First, if using a rule like make pdf, try to
narrow down the scope of the error to either docbook
(make doc-pdf-docbook) or doxygen (make
doc-pdf-doxygen).
Working on the docbook path only, closely examine the
contents of the following build directory:
build/target/libstdc++-v3/doc/docbook/latex.
Pay attention to three files enclosed within, annotated as follows.
spine.tex
The actual latex file, or partial latex file. This is generated
via dblatex, and is the LaTeX version of the
DocBook XML file spine.xml. Go to a specific
line, and look at the genrated LaTeX, and try to deduce what
markup in spine.xml is causing it.
spine.out
A log of the conversion from the XML form to the LaTeX form. This
is a linear list, from the beginning of the
spine.xml file: the last entry of this file
should be the end of the DocBook file. If it is truncated, then
you know that the last entry is the last part of the XML source
file that is valid. The error is after this point.
spine.log
A log of the compilation of the converted LaTeX form to pdf. This
is a linear list, from the beginning of the
spine.tex file: the last entry of this file
should be the end of the LaTeX file. If it is truncated, then you
know that the last entry is the last part of the generated LaTeX
source file that is valid. Often this file contains an error with
a specific line number of spine.tex that is
incorrect.
If the error at hand is not obvious after examination, or if one
encounters the inscruitable “Incomplete
\ifmmode” error, a fall-back strategy is to start
commenting out parts of the XML document (regardless of what
this does to over-all document validity). Start by
commenting out each of the largest parts of the
spine.xml file, section by section,
until the offending section is identified.
After editing the xml sources, please make sure that the XML documentation and markup is still valid. This can be done easily, with the following validation rule:
make doc-xml-validate-docbook
This is equivalent to doing:
xmllint --noout --valid xml/index.xml
Please note that individual sections and chapters of the
manual can be validated by substituting the file desired for
xml/index.xml in the command
above. Reducing scope in this manner can be helpful when
validation on the entire manual fails.
All Docbook xml sources should always validate. No excuses!
Which files are important
All Docbook files are in the directory
libstdc++-v3/doc/xml
Inside this directory, the files of importance:
spine.xml - index to documentation set
manual/spine.xml - index to manual
manual/*.xml - individual chapters and sections of the manual
faq.xml - index to FAQ
api.xml - index to source level / API
All *.txml files are template xml files, i.e., otherwise empty files with
the correct structure, suitable for filling in with new information.
Canonical Writing Style
class template
function template
member function template
(via C++ Templates, Vandevoorde)
class in namespace std: allocator, not std::allocator
header file: iostream, not <iostream>
General structure
<set>
<book>
</book>
<book>
<chapter>
</chapter>
</book>
<book>
<part>
<chapter>
<section>
</section>
<sect1>
</sect1>
<sect1>
<sect2>
</sect2>
</sect1>
</chapter>
<chapter>
</chapter>
</part>
</book>
</set>
Complete details on Docbook markup can be found in the DocBook Element Reference, online. An incomplete reference for HTML to Docbook conversion is detailed in the table below.
Table B.4. HTML to Docbook XML Markup Comparison
| HTML | Docbook |
|---|---|
| <p> | <para> |
| <pre> | <computeroutput>, <programlisting>, <literallayout> |
| <ul> | <itemizedlist> |
| <ol> | <orderedlist> |
| <il> | <listitem> |
| <dl> | <variablelist> |
| <dt> | <term> |
| <dd> | <listitem> |
| <a href=""> | <ulink url=""> |
| <code> | <literal>, <programlisting> |
| <strong> | <emphasis> |
| <em> | <emphasis> |
| " | <quote> |
And examples of detailed markup for which there are no real HTML equivalents are listed in the table below.
Table B.5. Docbook XML Element Use
| Element | Use |
|---|---|
| <structname> | <structname>char_traits</structname> |
| <classname> | <classname>string</classname> |
| <function> |
<function>clear()</function> <function>fs.clear()</function> |
| <type> | <type>long long</type> |
| <varname> | <varname>fs</varname> |
| <literal> |
<literal>-Weffc++</literal> <literal>rel_ops</literal> |
| <constant> |
<constant>_GNU_SOURCE</constant> <constant>3.0</constant> |
| <command> | <command>g++</command> |
| <errortext> | <errortext>In instantiation of</errortext> |
| <filename> |
<filename class="headerfile">ctype.h</filename> <filename class="directory">/home/gcc/build</filename> <filename class="libraryfile">libstdc++.so</filename> |
Table B.1. Doxygen Prerequisites
| Tool | Version | Required By |
|---|---|---|
| coreutils | 8.5 | all |
| bash | 4.1 | all |
| doxygen | 1.7.6.1 | all |
| graphviz | 2.26 | graphical hierarchies |
| pdflatex | 2007-59 | pdf output |
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pdflatex is required as well as a number of TeX packages
such as texlive-xtab and
texlive-tocloft.
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contents of the following build directory: build/target/libstdc++-v3/doc/doxygen/latex.
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line, and look at the generated LaTeX, and try to deduce what
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refman.log
A log created by latex as it processes the
refman.tex file. If generating the PDF fails
look at the end of this file for errors such as:
! LaTeX Error: File `xtab.sty' not found.
This indicates a required TeX package is missing. For the example above the texlive-xtab package needs to be installed.
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A log of the compilation of the converted LaTeX form to PDF. This
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in stl_algobase.h. Member
functions of other container-like types should read similarly to
these member functions.
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purpose. See stl_iterator.h
for a good example of the “other” kind of grouping.
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Complicated math functions should use the multi-line format.
An example from random.h:
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Table B.2. HTML to Doxygen Markup Comparison
| HTML | Doxygen |
|---|---|
| \ | \\ |
| " | \" |
| ' | \' |
| <i> | @@a word |
| <b> | @@b word |
| <code> | @@c word |
| <em> | @@a word |
| <em> | <em>two words or more</em> |
Table B.3. Docbook Prerequisites
| Tool | Version | Required By |
|---|---|---|
| docbook5-style-xsl | 1.76.1 | all |
| xsltproc | 1.1.26 | all |
| xmllint | 2.7.7 | validation |
| dblatex | 0.3 | pdf output |
| pdflatex | 2007-59 | pdf output |
| docbook2X | 0.8.8 | info output |
| epub3 stylesheets | b3 | epub output |
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