+@node Extra tests modules
+@section Extra tests modules
+
+@cindex Extra tests modules
+@cindex C++ tests modules
+@cindex tests modules, C++
+@cindex long-running tests modules
+@cindex tests modules, long-running
+@cindex privileged tests modules
+@cindex tests modules, privileged
+@cindex unportable tests modules
+@cindex tests modules, unportable
+Test modules can be marked with some special status attributes. When a
+test module has such an attribute, @code{gnulib-tool --import} will not
+include it by default.
+
+The supported status attributes are:
+
+@table @code
+@item c++-test
+Indicates that the test is testing C++ interoperability. Such a test is
+useful in a C++ or mixed C/C++ package, but is useless in a C package.
+
+@item longrunning-test
+Indicates that the test takes a long time to compile or execute (more
+than five minutes or so). Such a test is better avoided in a release
+that is made for the general public.
+
+@item privileged-test
+Indicates that the test will request special privileges, for example,
+ask for the superuser password. Such a test may hang when run
+non-interactively and is therefore better avoided in a release that is
+made for the general public.
+
+@item unportable-test
+Indicates that the test is known to fail on some systems, and that
+there is no workaround about it. Such a test is better avoided in a
+release that is made for the general public.
+@end table
+
+@code{gnulib-tool --import} will not include tests marked with these
+attributes by default. When @code{gnulib-tool} is invoked with one
+of the options @code{--with-c++-tests}, @code{--with-longrunning-tests},
+@code{--with-privileged-tests}, @code{--with-unportable-tests}, it
+will include tests despite the corresponding special status attribute.
+When @code{gnulib-tool} receives the option @code{--with-all-tests},
+it will include all tests regardless of their status attributes.
+
+@code{gnulib-tool --create-testdir} and
+@code{gnulib-tool --create-megatestdir} by default include all tests of
+modules specified on the command line, regardless of their status
+attributes. Tests of modules occurring as dependencies are not included
+by default if they have one of these status attributes. The options
+@code{--with-c++-tests}, @code{--with-longrunning-tests},
+@code{--with-privileged-tests}, @code{--with-unportable-tests} are
+recognized here as well. Additionally, @code{gnulib-tool} also
+understands the options @code{--without-c++-tests},
+@code{--without-longrunning-tests}, @code{--without-privileged-tests},
+@code{--without-unportable-tests}.
+
+In order to mark a module with a status attribute, you need to add it
+to the module description, like this:
+
+@example
+Status:
+longrunning-test
+@end example
+
+If only a part of a test deserves a particular status attribute, you
+can split the module into a primary and a secondary test module,
+say @code{foo-tests} and @code{foo-extra-tests}. Then add a dependency
+from @code{foo-tests} to @code{foo-extra-tests}, and mark the
+@code{foo-extra-tests} with the particular status attribute.
+
+
+@node A C++ namespace for gnulib
+@section A C++ namespace for gnulib
+
+The function definitions provided by Gnulib (@code{.c} code) are meant
+to be compiled by a C compiler. The header files (@code{.h} files),
+on the other hand, can be used in either C or C++.
+
+By default, when used in a C++ compilation unit, the @code{.h} files
+declare the same symbols and overrides as in C mode, except that functions
+defined by Gnulib or by the system are declared as @samp{extern "C"}.
+
+It is also possible to indicate to Gnulib to provide many of its symbols
+in a dedicated C++ namespace. If you define the macro
+@code{GNULIB_NAMESPACE} to an identifier, many functions will be defined
+in the namespace specified by the identifier instead of the global
+namespace. For example, after you have defined
+@smallexample
+#define GNULIB_NAMESPACE gnulib
+@end smallexample
+@noindent
+at the beginning of a compilation unit, Gnulib's @code{<fcntl.h>} header
+file will make available the @code{open} function as @code{gnulib::open}.
+The symbol @code{open} will still refer to the system's @code{open} function,
+with its platform specific bugs and limitations.
+
+The symbols provided in the Gnulib namespace are those for which the
+corresponding header file contains a @code{_GL_CXXALIAS_RPL} or
+@code{_GL_CXXALIAS_SYS} macro invocation.
+
+The benefits of this namespace mode are:
+@itemize
+@item
+Gnulib defines fewer symbols as preprocessor macros. For example, on a
+platform where @code{open} has to be overridden, Gnulib normally does
+@code{#define open rpl_open}. If your package has a class with a member
+@code{open}, for example a class @code{foo} with a method @code{foo::open},
+then if you define this member in a compilation unit that includes
+@code{<fcntl.h>} and use it in a compilation unit that does not include
+@code{<fcntl.h>}, or vice versa, you will get a link error. Worse: You
+will not notice this problem on the platform where the system's @code{open}
+function works fine. This problem goes away in namespace mode.
+
+@item
+It provides a safety check whether the set of modules your package requests
+from Gnulib is sufficient. For example, if you use the function
+@code{gnulib::open} in your code, and you forgot to request the module
+@samp{open} from Gnulib, you will get a compilation error (regardless of
+the platform).
+@end itemize
+
+The drawback of this namespace mode is that the system provided symbols in
+the global namespace are still present, even when they contain bugs that
+Gnulib fixes. For example, if you call @code{open (...)} in your code,
+it will invoke the possibly buggy system function, even if you have
+requested the module @samp{open} from gnulib-tool.
+
+You can turn on the namespace mode in some compilation units and keep it
+turned off in others. This can be useful if your package consists of
+an application layer that does not need to invoke POSIX functions and
+an operating system interface layer that contains all the OS function
+calls. In such a situation, you will want to turn on the namespace mode
+for the application layer --- to avoid many preprocessor macro
+definitions --- and turn it off for the OS interface layer --- to avoid
+the drawback of the namespace mode, mentioned above.
+
+
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