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author | Ben Pfaff <blp@cs.stanford.edu> | 2010-06-09 20:53:13 -0700 |
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committer | Ben Pfaff <blp@cs.stanford.edu> | 2010-06-09 20:53:13 -0700 |
commit | 47e899ad11a04647942b39dd501bfc2381e9b2f0 (patch) | |
tree | da1aada3072a79d9d424c09a1cd5e97e0ef8c1bc /doc | |
parent | 1629006348e1f66f07ce3ddcf3ebd2d14556cfce (diff) | |
download | gnulib-47e899ad11a04647942b39dd501bfc2381e9b2f0.tar.gz |
Add "Extending Gnulib" chapter to manual.
* doc/gnulib.texi (Writing Modules): Add cross-reference to new chapter.
(Extending Gnulib): New chapter.
* doc/gnulib-intro.texi (Openness): Add cross-reference to new chapter.
Diffstat (limited to 'doc')
-rw-r--r-- | doc/gnulib-intro.texi | 4 | ||||
-rw-r--r-- | doc/gnulib.texi | 83 |
2 files changed, 83 insertions, 4 deletions
diff --git a/doc/gnulib-intro.texi b/doc/gnulib-intro.texi index 4cb86b865f..52191ec26e 100644 --- a/doc/gnulib-intro.texi +++ b/doc/gnulib-intro.texi @@ -346,5 +346,5 @@ locally add modules that are treated like Gnulib modules by @code{gnulib-tool}. @end enumerate -This is achieved by the @samp{--local-dir} option of @code{gnulib-tool}. - +This is achieved by the @samp{--local-dir} option of @code{gnulib-tool} +(@pxref{Extending Gnulib}). diff --git a/doc/gnulib.texi b/doc/gnulib.texi index 4cbc9e74b7..a1f54461cf 100644 --- a/doc/gnulib.texi +++ b/doc/gnulib.texi @@ -54,6 +54,7 @@ Documentation License''. * Introduction:: * Invoking gnulib-tool:: * Writing modules:: +* Extending Gnulib:: * Miscellaneous Notes:: * POSIX Substitutes Library:: Building as a separate substitutes library. * Header File Substitutes:: Overriding system headers. @@ -117,8 +118,8 @@ Resources: @node Writing modules @chapter Writing modules -This chapter explains how to write modules of your own, either for your own -package (to be used with gnulib-tool's @samp{--local-dir} option), or for +This chapter explains how to write modules of your own, either to +extend Gnulib for your own package (@pxref{Extending Gnulib}), or for inclusion in gnulib proper. The guidelines in this chapter do not necessarily need to be followed for @@ -608,6 +609,84 @@ before every release. @end enumerate +@node Extending Gnulib +@chapter Extending Gnulib + +Gnulib modules are intended to be suitable for widespread use. Most +problems with Gnulib can and should be fixed in a generic way, so that +all of Gnulib's users can benefit from the change. But occasionally a +problem arises that is difficult or undesirable to fix generically, or +a project that uses Gnulib may need to work around an issue before the +Gnulib maintainers commit a final fix. Maintainers may also want to +add their own pools of modules to projects as Gnulib ``staging +areas.'' + +The obvious way to make local changes to Gnulib modules is to use +@command{gnulib-tool} to check out pristine modules, then to modify +the results in-place. This works well enough for short-lived +experiments. It is harder to keep modified versions of Gnulib modules +for a long time, even though Git (or another distributed version +control systems) can help out a lot with this during the development +process. + +Git, however, doesn't address the distribution issue. When a package +``foobar'' needs a modified version of, say, @file{stdint.in.h}, it +either has to put a comment into @file{foobar/autogen.sh} saying +``Attention! This doesn't work with a pristine Gnulib, you need this +and that patch after checking out Gnulib,'' or it has to use the +@samp{--avoid=stdint} option and provide the modified @code{stdint} +module in a different directory. + +The @option{--local-dir} option to @command{gnulib-tool} solves this +problem. It allows the package to override or augment Gnulib. This +means: + +@itemize @bullet +@item +You can store files that are to override Gnulib files or modules. + +@item +You can store context diffs to be applied to Gnulib files. + +@item +You can add modules of your own, that are not (yet) in Gnulib. + +@item +You can also add unstructured amounts of code to the library, by +grouping the non-Gnulib files of the library in a single kitchen-sink +``module.'' (This kind of kitchen-sink module is not needed when you +use the @command{gnulib-tool} option @samp{--makefile-name}.) +@end itemize + +In a release tarball, you can distribute the contents of this +@option{--local-dir} directory that will be combinable with newer +versions of Gnulib, barring incompatible changes to Gnulib. + +If the @samp{--local-dir=@var{directory}} option is specified, then +@command{gnulib-tool} looks in @file{@var{directory}} whenever it +reads a file from the Gnulib directory. Suppose @command{gnulib-tool} +is looking for @var{file}. Then: + +@itemize @bullet +@item +If @file{@var{directory}/@var{file}} exists, then @samp{gnulib-tool} uses +it instead of the file included in Gnulib. + +@item +Otherwise, if @file{@var{directory}/@var{file}.diff} exists, then +@command{gnulib-tool} uses the file from Gnulib after applying the diff +using the @command{patch} program. + +@item +Otherwise, @command{gnulib-tool} uses the file included in Gnulib. +@end itemize + +Please make wise use of this option. It also allows you to easily +hold back modifications you make to Gnulib macros in cases it may be +better to share them. + + + @node Miscellaneous Notes @chapter Miscellaneous Notes |