We no longer add these. If you use Emacs, configure it yourself.

Also, due to our "smart-tab" usage the editor anyway does a subpar
job handling our tabs. However, on the upside every user can choose
whatever tab-width he/she prefers. If "smart-tabs" are used properly
(like we do), every tab-width will work.

No manual changes, just ran commands:

    F=($(git grep -l -e '-\*-'))
    sed '1 { /\/\* *-\*-  *[mM]ode.*\*\/$/d }'     -i "${F[@]}"
    sed '1,4 { /^\(#\|--\|dnl\) *-\*- [mM]ode/d }' -i "${F[@]}"

Check remaining lines with:

    git grep -e '-\*-'

The ultimate purpose of this is to cleanup our files and eventually use
SPDX license identifiers. For that, first get rid of the boilerplate lines.

clang on CentOS 7.6 (3.4.2-9.el7) warns:

      CC       clients/tui/newt/clients_tui_newt_libnmt_newt_a-nmt-newt-button.o
    In file included from ../clients/tui/newt/nmt-newt-button.c:26:
    In file included from ../shared/nm-default.h:280:
    ../shared/nm-glib-aux/nm-macros-internal.h:1617:2: error: unknown warning group -Wstringop-truncation, ignored [-Werror,-Wunknown-pragmas]
            NM_PRAGMA_WARNING_DISABLE ("-Wstringop-truncation");
            ^
    ../shared/nm-glib-aux/nm-macros-internal.h:419:9: note: expanded from macro NM_PRAGMA_WARNING_DISABLE
            _Pragma(_NM_PRAGMA_WARNING_DO(warning))
            ^
    <scratch space>:109:25: note: expanded from here
     GCC diagnostic ignored "-Wstringop-truncation"
                            ^

This warning totally defeats the purpose of why we use the pragma in the
first place.

[default=meh] instead of (default is meh) or (default: meh).

https://github.com/NetworkManager/NetworkManager/pull/344

We should always get the nesting in struct initializers right.
Everyhing else is error-prone, and the warning is good.

Enable it.

Building with link-time optimization requires some tricks explained
in [1].

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=48200#c28

If configure.ac automatically adds compiler flags to CFLAGS, it
becomes hard to override one of them for a specific target because
CFLAGS is added last. It is better to use AM_CFLAGS. See [1].

[1] https://www.gnu.org/software/automake/manual/html_node/Flag-Variables-Ordering.html

Some warnings depends on others: -Wformat-security won't work without
-Wformat. With -Wall we're confident enough that we have important
warnings enabled and in any case we're going to enable it anyway.

https://github.com/NetworkManager/NetworkManager/pull/175

g-ir-scanner uses distutils that have an unfortunate misfeature of
inheriting the compiler flags it itself was built with.

This includes the hardening flags that don't work with without
redhat-rpm-build and break with clang every full moon.

A configure check makes it clear about what went wrong in case
introspection is desired, otherwise turns it off.

(Taken from network-manager commit 678890ed0347849990787e8893122a39f95cb708)

With --enable-more-warnings, we already used -std=gnu99, see
commit ba2b2de3.

Compilation may behave differently depending on the selected
C standard that we choose. It seems wrong, with more-warnings,
to build against a C standard, while otherwise leaving it undefind.

Indeed, one might argue, that our build system should not use
such compiler specific options. At least, not without detecting
support for the compiler option during ./configure.

However:

- we already did this for --enable-more-warnings.

- we should not program against a theoretical compiler. In practice,
  only gcc and clang works to build NetworkManager. Both these compilers
  support this option, so there is no reason to not use it. If we ever
  come into the situation to support another compiler, adjusting -std=gnu99
  will be the smallest problem. Until that happens (and that's far from
  imminent), don't pretend to be portable to non-existing compilers and
  use the flag that in practice is available.

See-also: https://gcc.gnu.org/onlinedocs/gcc/Standards.html

Make it possible to add compiler options to a different variable than
CFLAGS. This is useful to conditionally disable a compiler warning for a
subpart of a tree.

We commonly only allow tabs at the beginning of a line, not
afterwards. The reason for this style is so that the code
looks formated right with tabstop=4 and tabstop=8.

This fixes the GCC 8 build. It disables the warning conditionally so that we
get the warning back if glib gets fixed.

It was disabled for shady reasons (not checking write() return value)
that are long gone. Worse even, it hid some real bugs.

We don't use them, so add a compiler warning about their use.
I think they are annoying, because sizeof(x) and typeof(x) might
evaluate at runtime. Especially the typeof() extension is useful
for macros, but behaves badly with variable-length arrays due to
running code at runtime.

But the worst is, G_STATIC_ASSERT() is implemented by declaring
an array of negative length. Usually, the checked condition should
be a compile time constant, but with VLAs the compiler would not evaluate
the static-assert at compile time and instead accept it silently. It's easy
to mess up static asserts to wrongly have a non-constant condition,
especially when the static-assert is used inside a macro.

Just say no.

Ideally we should switch to the standard macro AX_CODE_COVERAGE for
code coverage, but infortunately it's not supported on older distros
(e.g. on Travis).

Keep using the current macro, but remove the lcov version check as
it's not clear why it's needed in the first place (see [1]). The
latest version of lcov is now 1.13.

[1] http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=commit;h=dedd290bdb647704d74c13992bd04275d9cb648e

  src/NetworkManagerUtils.c:347:18: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
          NMIPAddr a1 = { 0 }, a2 = { 0 };
                          ^
                          {}

Should we initialize unions this way? I think it's all right -- the initializer
works well and { { { 0 } } } is probably not what we'd like to see.

(cherry picked from commit 43012156)

  src/NetworkManagerUtils.c:347:18: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
          NMIPAddr a1 = { 0 }, a2 = { 0 };
                          ^
                          {}

Should we initialize unions this way? I think it's all right -- the initializer
works well and { { { 0 } } } is probably not what we'd like to see.

... and prepend the $ld_gc_flags instead of appending to the $CFLAGS.

Mostly sort alphabetically, but
  - keep -Wextra first
  - move "-Wno-*" flags to the end

The warning seems questionable and overly strict.
For now, just disable it to allow building with gcc7.

    src/systemd/src/basic/time-util.c: In function ‘format_timespan’:
    src/systemd/src/basic/time-util.c:509:46: error: ‘%0*lu’ directive output between 1 and 2147483648 bytes may cause result to exceed ‘INT_MAX’ [-Werror=format-truncation=]
                                                  "%s"USEC_FMT".%0*"PRI_USEC"%s",
                                                  ^~~~
    src/systemd/src/basic/time-util.c:509:60: note: format string is defined here
                                                  "%s"USEC_FMT".%0*"PRI_USEC"%s",
    src/systemd/src/basic/time-util.c:509:46: note: directive argument in the range [0, 18446744073709551614]
                                                  "%s"USEC_FMT".%0*"PRI_USEC"%s",
                                                  ^~~~

https://mail.gnome.org/archives/networkmanager-list/2017-February/msg00001.html

No change in behavior.

It will make it easier to policy the default.

(cherry picked from commit 8647be37)

It will make it easier to policy the default.

We already use several GCC extenions, like typeof() and
__attribute__((cleanup)). They are too convinient to miss
and every supported compiler must support these.
Currently, gcc and clang does. Maybe other compilers would
support that too, but who knows, nobody seems to test that.

We also already use stdbool.h (C99) and the imported systemd
code is mostly gnu99 too (it's not clear to me, because I don't
find it precisely documented. Certainly it makes use of C99 features
too).

C99/gnu99 has some nice improvements that we no longer should miss
out. For example "flexible array members" or "variable declaration
in init-part of for loop".

It doesn't mean we have to use every obscure (badly supported?)
feature, it means we don't have to forgo features that are well
supported. C99 is 17 years old, I mean, really...

If somebody comes along and ports NM to non-gcc/clang, we can address
bugs about unsupported language features as they surface.
But let's not restrict us to some hypothetical compiler (or language
specification).

Also, NetworkManager is not ported on environment beside Linux.
We don't have to be so considerate about the required build environment.
Gcc is probably the most portable compiler out there. I doubt porting
NetworkManager to *BSD fails due to missing gnu99 features. And if that
causes issues, we should fix them after they happen in practice.

We want to embed the current commit-id in the ./configure script.
That way the generated ./configure file in the source tarball
references the commit-id from which the tarball was created.

Then, in a second step, a script can check ./configure to find
the parent commit. This is for example done by the 'makerepo.sh'
script.

This is generally useful, and also done by network-manager-applet
and libnl3 projects. Move the function to a separate m4 macro
to reuse it. It should also be re-used in NetworkManager's VPN plugins.

https://bugzilla.gnome.org/show_bug.cgi?id=767207

We break the aliasing rules in the code, and thus the flag should
always be enabled to prevent wrong optimizations, even without
--enable-more-warnings.

It contains useful macros for determining compiler support for
flags/attributes. We already similar macros in compiler_options.m4,
but the plan is to replace them.

New with gcc 6.0.

Also, fold duplicate chunks together.

We'll use that for more compiler feature-checking macros.

Some of the checks include glib headers.

Duplicated const specifiers are allowed by C99 and can easily
happen in macros. Also, systemd's interal code will use them.

Disable this warning, it doesn't seem useful.

Originally m4/introspection.m4 was copied from gobject-introspection
repository. We however modified it in commit f6272144.

Reimport the file with latest changes, but still preserving our
workaround.