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Editing File: /usr/share/doc/util-linux/howto-build-sys.txt

util-linux build system
=======================

- the build system is non-recursive, individual subdirectories use
   Makemodule.am files. These files are merged together by automake
   into one global Makefile in the top-level directory

- all final build results (binaries, libtool scripts) are stored in top-level
   source directory

- all Makemodule.am files have to be designed as top-level makefiles, it
   means with full paths (e.g. foo_SOURCES = subdir/foo.c)

- always use '+=' operator for global variables (e.g. bin_PROGRAMS += foo)

- use libcommon.la (without path!) for lib/ stuff (e.g. foo_LDADD = libcommon.la)

- for libblkid, libuuid and libmount use lib<name>.la in _LDADD and
   -I$(ul_lib<name>_incdir) in _CFLAGS, for example

foo_LDADD = libmount.la
	foo_CFLAGS = -I$(ul_libmount_incdir)

- always use suffixes for hooks, for example

install-exec-hook-foo:
		ln -sf foo foooo

INSTALL_EXEC_HOOKS += install-exec-hook-foo

- all util-linux specific autoconf macros use UL_ prefix

- utils in Makefile.am files are enabled/disabled according to BUILD_<NAME>
   conditions (AM_CONDITIONAL), for example:

if BUILD_HWCLOCK
	...
	endif

- "if BUILD_<NAME>" blocks are never nested within another "if BUILD_<NAME>",
   all dependencies have to be resolved in configure.ac (see UL_REQUIRES_BUILD())

- all BUILD_<NAME> in configure.am are always based on build_<name> variables,
   for example:

AM_CONDITIONAL([BUILD_HWCLOCK], test "x$build_hwclock" = xyes)

the $build_<name> should be available in whole configure script

- AC_ARG_ENABLE() status is always stored in $enable_<name> variable, possible
   setting:

"check" - util/feature is optional, if any subcomponent (function, lib,
                  ...) is missing a warning is printed and the util/feature is
                  disabled

"yes"	- util/feature is required, if any subcomponent (function, lib,
                  ...) is missing an error is printed and ./configure aborted

"no"	- the util/feature is unwanted

The default status is always defined by UL_DEFAULT_ENABLE() and it might be
   globally modified by $ul_default_estate (see AC_ARG_ENABLE([all-programs])).

- it's possible to disable all programs, but enable just one (or more)
   explicitly specified, for example:

./configure --disable-all-programs --enable-hwclock

- some basic scenarios for the ./configure script are defined in the
   tools/config-gen.d/ directory. If you want to use these predefined scenarios
   then call

./tools/config-gen [<scenario> ...]

for example

./tools/config-gen all selinux

will build all utils with enabled selinux support. You can also define some
   CFLAGS, for example:

CFLAGS=$(rpm --eval '%optflags') ./tools/config-gen all

will use the default distro flags.

WARNING: config-gen is not designed for end-user or downstream distributions!
            It's for development purpose only. All end-users and downstream have
            to use standard ./configure script only.

- the tools/config-gen script is also used for build system regression tests,
   the test is not enabled by default, you have to use

tests/run.sh build-sys --force

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