Test if _Generic(3) is available.  Although we require GNU C11, some
old compilers, like the one in CentOS 7 still don't have full support
for C11, and _Generic(3) is not available there.

Cc: Andrew Clayton <a.clayton@nginx.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

Suggested-by: Andrew Clayton <a.clayton@nginx.com>
Signed-off-by: Alejandro Colomar <alx@nginx.com>

Future releases of GCC are planning to remove[0] default support for
some old features that were removed from C99 but GCC still accepts.

We can test for these changes by using the following -Werror=
directives

  -Werror=implicit-int
  -Werror=implicit-function-declaration
  -Werror=int-conversion
  -Werror=strict-prototypes
  -Werror=old-style-definition

Doing so revealed an issue with the auto/ tests in that the test
programs always define main as

  int main()

rather than

  int main(void)

which results in a bunch of errors like

build/autotest.c:3:23: error: function declaration isn't a prototype [-Werror=strict-prototypes]
    3 |                   int main() {
      |                       ^~~~
build/autotest.c: In function 'main':
build/autotest.c:3:23: error: old-style function definition [-Werror=old-style-definition]

The fix was easy, it only required fixing the main prototype with

  find -type f -exec sed -i 's/int main() {/int main(void) {/g' {} \;

Regardless of these upcoming GCC changes, this is probably a good thing
to do anyway for correctness.

[0]: https://fedoraproject.org/wiki/Changes/PortingToModernC

Link: <https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/message/CJXKTLXJUPZ4F2C2VQOTNMEA5JAUPMBD/>
Link: <https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/message/6SGHPHPAXKCVJ6PUZ57WVDQ5TDBVIRMF/>
Reviewed-by: Alejandro Colomar <alx@nginx.com>
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

'install -d' has an issue compared to 'mkdir -p':  it doesn't
respect existing directories.  It will set the ownership, file
mode, and SELinux contexts (and any other property that would be
set by install(1) to a newly-created directory), overwriting any
existing properties of the existing directory.

'mkdir -p' doesn't have this issue:  it is a no-op if the
directory exists.  However, it's not an ideal solution either,
since it can't be used to set the properties (owner, mode, ...) of
a newly-created directory.

Therefore, the best solution is to use install(1), but only after
making sure that the directory doesn't exist with test(1).

Reported-by: Andrew Clayton <a.clayton@nginx.com>
Reported-by: Alejandro Colomar <alx@nginx.com>
Closes: <https://github.com/nginx/unit/issues/769>
Signed-off-by: Alejandro Colomar <alx@nginx.com>
Tested-by: Andrew Clayton <a.clayton@nginx.com>
Reviewed-by: Andrew Clayton <a.clayton@nginx.com>

PHP 8.2 changed the prototype of the function, removing the last
parameter.

Signed-off-by: Remi Collet <remi@remirepo.net>
Cc: Timo Stark <t.stark@nginx.com>
Cc: George Peter Banyard <girgias@php.net>
Tested-by: Andy Postnikov <apostnikov@gmail.com>
Acked-by: Andy Postnikov <apostnikov@gmail.com>
Reviewed-by: Andrew Clayton <a.clayton@nginx.com>
Signed-off-by: Alejandro Colomar <alx@nginx.com>

@alejandro-colomar reported that the build was broken on MacOS

cc  -o build/unitd -pipe -fPIC -fvisibility=hidden -O -W -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -fstrict-aliasing -Wstrict-overflow=5 -Wmissing-prototypes -Werror -g   \
		build/src/nxt_main.o  build/libnxt.a \
		    \
                      \
                    -L/usr/local/Cellar/pcre2/10.40/lib -lpcre2-8
Undefined symbols for architecture x86_64:
  "_nxt_fs_mkdir_parent", referenced from:
      _nxt_runtime_pid_file_create in libnxt.a(nxt_runtime.o)
      _nxt_runtime_controller_socket in libnxt.a(nxt_controller.o)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [build/unitd] Error 1

This was due to commit 57fc920 ("Socket: Created control socket & pid file
directories.").

This happened because this commit introduced the usage of
nxt_fs_mkdir_parent() in core code which uses nxt_fs_mkdir(), both of
these are defined in src/nxt_fs.c. It turns out however that this file
doesn't get built on MacOS (or any system that isn't Linux or that
lacks a FreeBSD compatible nmount(2) system call) due to the following

In auto/sources we have

  if [ $NXT_HAVE_ROOTFS = YES ]; then
      NXT_LIB_SRCS="$NXT_LIB_SRCS src/nxt_fs.c"
  fi

NXT_HAVE_ROOTFS is set in auto/isolation

  If [ $NXT_HAVE_MOUNT = YES -a $NXT_HAVE_UNMOUNT = YES ]; then
      NXT_HAVE_ROOTFS=YES

      cat << END >> $NXT_AUTO_CONFIG_H
  #ifndef NXT_HAVE_ISOLATION_ROOTFS
  #define NXT_HAVE_ISOLATION_ROOTFS  1
  #endif
  END

  fi

While we do have a check for a generic umount(2) which is found on
MacOS, for mount(2) we currently only check for the Linux mount(2) and
FreeBSD nmount(2) system calls. So NXT_HAVE_ROOTFS is set to NO on MacOS
and we don't build src/nxt_fs.c

This fixes the immediate build issue by taking the mount/umount OS
support out of nxt_fs.c into a new nxt_fs_mount.c file which is guarded
by the above while we now build nxt_fs.c unconditionally.

This should fix the build on any _supported_ system.

Reported-by: Alejandro Colomar <alx@nginx.com>
Fixes: 57fc920 ("Socket: Created control socket & pid file directories.")
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

nxt_sockaddr_ntop() stopped being used in commit (git) 029942f4eb71.
It has been replaced mostly by nxt_sockaddr_text().

    commit 029942f4eb7196c2cff0d0e26bc6ff274138f7d8
    Author: Igor Sysoev <igor@sysoev.ru>
    Date:   Wed Feb 22 15:09:59 2017 +0300

        I/O operations refactoring.

nxt_job_sockaddr_parse() stopped being used in commit (git) 794248090a74.

    commit 794248090a74f31cbfcf24ea8c835df2d4d21073
    Author: Igor Sysoev <igor@sysoev.ru>
    Date:   Wed Mar 4 14:04:08 2020 +0300

        Legacy upstream code removed.

Also, remove functions and types used only by those two functions:

nxt_job_sockaddr_unix_parse()
nxt_job_sockaddr_inet6_parse()
nxt_job_sockaddr_inet_parse()
nxt_job_sockaddr_parse_t
nxt_job_resolve()
nxt_job_resolve_t

Some non-Linux systems implement pivot_root(2), even if they
don't document that.  An example is MacOS:

$ grepc pivot_root / 2>/dev/null
.../sys/sysproto.h:3012:
int pivot_root(struct proc *, struct pivot_root_args *, int *);

Since the prototype of the syscall differs from that of Linux, we
can't use that syscall.  Let's make sure the test only detects
pivot_root(2) under Linux.  Also, rename the feature macro to make
clear that it's only about Linux's pivot_root(2).

This closes #737 issue on GitHub.