1) the command line gets shorter. I frequently run `make V=1` to see
the command line arguments for the compiler, and there is a lot
of noise.
2) define each of these variables at one place. This makes it easy
to verify that for all compilation units, a particular
define has the same value. Previously that was not obvious or
even not the case (see commit e5d1a71396
and commit d63cf1ef2f).
The point is to avoid redundancy.
3) not all compilation units need all defines. In fact, most modules
would only need a few of these defines. We aimed to pass the necessary
minium of defines to each compilation unit, but that was non-obvious
to get right and often we set a define that wasn't used. See for example
"src_settings_plugins_ibft_cppflags" which needlessly had "-DSYSCONFDIR".
This question is now entirely avoided by just defining all variables in
a header. We don't care to find the minimum, because every component
gets anyway all defines from the header.
4) this also avoids the situation, where a module that previously did
not use a particular define gets modified to require it. Previously,
that would have required to identify the missing define, and add
it to the CFLAGS of the complation unit. Since every compilation
now includes "config-extra.h", all defines are available everywhere.
5) the fact that each define is now available in all compilation units
could be perceived as a downside. But it isn't, because these defines
should have a unique name and one specific value. Defining the same
name with different values, or refer to the same value by different
names is a bug, not a desirable feature. Since these defines should
be unique accross the entire tree, there is no problem in providing
them to every compilation unit.
6) the reason why we generate "config-extra.h" this way, instead of using
AC_DEFINE() in configure.ac, is due to the particular handling of
autoconf for directory variables. See [1].
With meson, it would be trivial to put them into "config.h.meson".
While that is not easy with autoconf, the "config-extra.h" workaround
seems still preferable to me.
[1] https://www.gnu.org/software/autoconf/manual/autoconf-2.63/html_node/Installation-Directory-Variables.html
The present version of the specification is somewhat unclear at times,
Unclear points were discussed with the maintainers [1] and probably
some new version will address those.
https://www.spinics.net/lists/util-linux-ng/msg15222.html
Until then here's how the implementation copes with ambiguities
(after the discussion with util-linux maintainers):
1.) It is unclear whether multiple .schem files should override each
other or be merged. We use the overriding behavior -- take the
highest priority one and ignore the rest.
2.) We assume "name.schem" is more specific than "@term.schem".
3.) We assume the "Color name" are to be used as aliases for the color
sequences and translate them to ANSI escape sequences.
4.) The "Escape sequences" are of no use since the specification
pretty much assumes an ANSI terminal and none of the sequences make
any sense in ANSI color codes. We don't support them.
accept that.
5.) We don't implement TERMINAL_COLORS_DEBUG because it's unspecified
what should it do.
We also unconditionally use them with autotools.
Also, the detection for have_version_script does
not seem correct to me. At least, it didn't work
with clang.
The strings holding the names used for libraries have also been
moved to different variables. This way they would be less error
as these variables can be reused easily and any typing error
would be quickly detected.
Some targets are missing dependencies on some generated sources in
the meson port. These makes the build to fail due to missing source
files on a highly parallelized build.
These dependencies have been resolved by taking advantage of meson's
internal dependencies which can be used to pass source files,
include directories, libraries and compiler flags.
One of such internal dependencies called `core_dep` was already in
use. However, in order to avoid any confusion with another new
internal dependency called `nm_core_dep`, which is used to include
directories and source files from the `libnm-core` directory, the
`core_dep` dependency has been renamed to `nm_dep`.
These changes have allowed minimizing the build details which are
inherited by using those dependencies. The parallelized build has
also been improved.
Note that:
- we compile some source files multiple times. Most notably those
under "shared/".
- we include a default header "shared/nm-default.h" in every source
file. This header is supposed to setup a common environment by defining
and including parts that are commonly used. As we always include the
same header, the header must behave differently depending
one whether the compilation is for libnm-core, NetworkManager or
libnm-glib. E.g. it must include <glib/gi18n.h> or <glib/gi18n-lib.h>
depending on whether we compile a library or an application.
For that, the source files need the NETWORKMANAGER_COMPILATION #define
to behave accordingly.
Extend the define to be composed of flags. These flags are all named
NM_NETWORKMANAGER_COMPILATION_WITH_*, they indicate which part of the
build are available. E.g. when building libnm-core.la itself, then
WITH_LIBNM_CORE, WITH_LIBNM_CORE_INTERNAL, and WITH_LIBNM_CORE_PRIVATE
are available. When building NetworkManager, WITH_LIBNM_CORE_PRIVATE
is not available but the internal parts are still accessible. When
building nmcli, only WITH_LIBNM_CORE (the public part) is available.
This granularily controls the build.
Source files for enum types are generated by passing segments of the
source code of the files to the `glib-mkenums` command.
This patch removes those parameters where source code is used from
meson build files by moving those segmeents to template files.
https://mail.gnome.org/archives/networkmanager-list/2017-December/msg00057.html
