meson: use a convenience library for the sources shared between core/ and the outside

This avoids double compilation. Those files are tiny, so it doesn't save time,
but we avoid repeated warnings and errors, and it's generally cleaner to it
this way.

The number of commands in 'ninja -C build clean && ninja -C build' drops from
1462 to 1455 for me.

meson.build

@@ -1713,9 +1713,9 @@ executable('systemd-run-generator',
 
 executable('systemd-fstab-generator',
            'src/fstab-generator/fstab-generator.c',
-           'src/core/mount-setup.c',
            include_directories : includes,
-           link_with : [libshared],
+           link_with : [libcore_shared,
+                        libshared],
            install_rpath : rootlibexecdir,
            install : true,
            install_dir : systemgeneratordir)
@@ -2353,20 +2353,18 @@ endif
 
 executable('systemd-remount-fs',
            'src/remount-fs/remount-fs.c',
-           'src/core/mount-setup.c',
-           'src/core/mount-setup.h',
            include_directories : includes,
-           link_with : [libshared],
+           link_with : [libcore_shared,
+                        libshared],
            install_rpath : rootlibexecdir,
            install : true,
            install_dir : rootlibexecdir)
 
 executable('systemd-machine-id-setup',
            'src/machine-id-setup/machine-id-setup-main.c',
-           'src/core/machine-id-setup.c',
-           'src/core/machine-id-setup.h',
            include_directories : includes,
-           link_with : [libshared],
+           link_with : [libcore_shared,
+                        libshared],
            install_rpath : rootlibexecdir,
            install : true,
            install_dir : rootbindir)
@@ -2678,12 +2676,9 @@ public_programs += exe
 
 executable('systemd-shutdown',
            systemd_shutdown_sources,
-           'src/core/mount-setup.c',
-           'src/core/mount-setup.h',
-           'src/core/killall.c',
-           'src/core/killall.h',
            include_directories : includes,
-           link_with : [libshared],
+           link_with : [libcore_shared,
+                        libshared],
            dependencies : [libmount],
            install_rpath : rootlibexecdir,
            install : true,
@@ -2724,12 +2719,9 @@ endif
 
 exe = executable('systemd-nspawn',
                  systemd_nspawn_sources,
-                 'src/core/mount-setup.c', # FIXME: use a variable?
-                 'src/core/mount-setup.h',
-                 'src/core/loopback-setup.c',
-                 'src/core/loopback-setup.h',
                  include_directories : includes,
-                 link_with : [libnspawn_core,
+                 link_with : [libcore_shared,
+                              libnspawn_core,
                               libshared],
                  dependencies : [libblkid],
                  install_rpath : rootlibexecdir,

src/core/meson.build

@@ -1,5 +1,16 @@
 # SPDX-License-Identifier: LGPL-2.1+
 
+libcore_shared_sources = '''
+        killall.c
+        killall.h
+        loopback-setup.c
+        loopback-setup.h
+        machine-id-setup.c
+        machine-id-setup.h
+        mount-setup.c
+        mount-setup.h
+'''.split()
+
 libcore_la_sources = '''
         audit-fd.c
         audit-fd.h
@@ -69,8 +80,6 @@ libcore_la_sources = '''
         job.h
         kill.c
         kill.h
-        killall.c
-        killall.h
         kmod-setup.c
         kmod-setup.h
         load-dropin.c
@@ -79,14 +88,8 @@ libcore_la_sources = '''
         load-fragment.h
         locale-setup.c
         locale-setup.h
-        loopback-setup.c
-        loopback-setup.h
-        machine-id-setup.c
-        machine-id-setup.h
         manager.c
         manager.h
-        mount-setup.c
-        mount-setup.h
         mount.c
         mount.h
         namespace.c
@@ -144,12 +147,22 @@ load_fragment_gperf_nulstr_c = custom_target(
         command : [awk, '-f', '@INPUT0@', '@INPUT1@'],
         capture : true)
 
+# A convenience library to share code with other binaries:
+# systemd-shutdown, systemd-remount-fs, systemd-machine-id-setup, …
+libcore_shared = static_library(
+        'core-shared',
+        libcore_shared_sources,
+        include_directories : includes,
+        dependencies : [versiondep,
+                        libmount])
+
 libcore = static_library(
         'core',
         libcore_la_sources,
         load_fragment_gperf_c,
         load_fragment_gperf_nulstr_c,
         include_directories : includes,
+        link_whole : libcore_shared,
         dependencies : [versiondep,
                         threads,
                         librt,

src/test/meson.build

@@ -714,11 +714,10 @@ tests += [
          'ENABLE_NSS', 'manual'],
 
         [['src/test/test-umount.c',
-          'src/core/mount-setup.c',
-          'src/core/mount-setup.h',
           'src/shutdown/umount.c',
           'src/shutdown/umount.h'],
-         [],
+         [libcore_shared,
+          libshared],
          [libmount]],
 
         [['src/test/test-bus-util.c'],