Add a Meson build system

This allows bwrap to be built as a subproject in larger Meson projects.
When built as a subproject, we install into the --libexecdir and
require a program prefix to be specified: for example, Flatpak would use
program_prefix=flatpak- to get /usr/libexec/flatpak-bwrap. Verified to
be backwards-compatible as far as Meson 0.49.0 (Debian 9 backports).

Loosely based on previous work by Jussi Pakkanen (see #133).

Differences between the Autotools and Meson builds:

The Meson build requires a version of libcap that has pkg-config
metadata (introduced in libcap 2.23, in 2013).

The Meson build has no equivalent of --with-priv-mode=setuid. On
distributions like Debian <= 10 and RHEL <= 7 that require a setuid bwrap
executable, the sysadmin or distribution packaging will need to set the
correct permissions on the bwrap executable; Debian already did this via
packaging rather than the upstream build system.

The Meson build supports being used as a subproject, and there is CI
for this. It automatically disables shell completions and man pages,
moves the bubblewrap executable to ${libexecdir}, and renames the
bubblewrap executable according to a program_prefix option that the
caller must specify (for example, Flatpak would use
-Dprogram_prefix=flatpak- to get /usr/libexec/flatpak-bwrap). See the
tests/use-as-subproject/ directory for an example.

Signed-off-by: Simon McVittie <smcv@collabora.com>

1 files changed, 147 insertions, 0 deletions

diff --git a/meson.build b/meson.build
new file mode 100644
index 0000000..159ab2b
--- /dev/null
+++ b/meson.build
@@ -0,0 +1,147 @@
+project(
+  'bubblewrap',
+  'c',
+  version : '0.5.0',
+  meson_version : '>=0.49.0',
+  default_options : [
+    'warning_level=2',
+  ],
+)
+
+cc = meson.get_compiler('c')
+add_project_arguments('-D_GNU_SOURCE', language : 'c')
+
+# Keep this in sync with ostree, except remove -Wall (part of Meson
+# warning_level 2) and -Werror=declaration-after-statement
+add_project_arguments(
+  cc.get_supported_arguments([
+    '-Werror=shadow',
+    '-Werror=empty-body',
+    '-Werror=strict-prototypes',
+    '-Werror=missing-prototypes',
+    '-Werror=implicit-function-declaration',
+    '-Werror=pointer-arith',
+    '-Werror=init-self',
+    '-Werror=missing-declarations',
+    '-Werror=return-type',
+    '-Werror=overflow',
+    '-Werror=int-conversion',
+    '-Werror=parenthesis',
+    '-Werror=incompatible-pointer-types',
+    '-Werror=misleading-indentation',
+    '-Werror=missing-include-dirs',
+    '-Werror=aggregate-return',
+
+    # Extra warnings specific to bubblewrap
+    '-Werror=switch-default',
+    '-Wswitch-enum',
+
+    # Meson warning_level=2 would do this, but we are not fully
+    # signedness-safe yet
+    '-Wno-sign-compare',
+    '-Wno-error=sign-compare',
+
+    # Deliberately not warning about these, ability to zero-initialize
+    # a struct is a feature
+    '-Wno-missing-field-initializers',
+    '-Wno-error=missing-field-initializers',
+  ]),
+  language : 'c',
+)
+
+if (
+  cc.has_argument('-Werror=format=2')
+  and cc.has_argument('-Werror=format-security')
+  and cc.has_argument('-Werror=format-nonliteral')
+)
+  add_project_arguments([
+    '-Werror=format=2',
+    '-Werror=format-security',
+    '-Werror=format-nonliteral',
+  ], language : 'c')
+endif
+
+sh = find_program('sh', required : true)
+bash = find_program('bash', required : false)
+
+libcap_dep = dependency('libcap', required : true)
+
+selinux_dep = dependency(
+  'libselinux',
+  version : '>=2.1.9',
+  # if disabled, Meson will behave as though libselinux was not found
+  required : get_option('selinux'),
+)
+
+cdata = configuration_data()
+cdata.set_quoted(
+  'PACKAGE_STRING',
+  '@0@ @1@'.format(meson.project_name(), meson.project_version()),
+)
+
+if selinux_dep.found()
+  cdata.set('HAVE_SELINUX', 1)
+  if selinux_dep.version().version_compare('>=2.3')
+    cdata.set('HAVE_SELINUX_2_3', 1)
+  endif
+endif
+
+if get_option('require_userns')
+  cdata.set('ENABLE_REQUIRE_USERNS', 1)
+endif
+
+configure_file(
+  output : 'config.h',
+  configuration : cdata,
+)
+
+if meson.is_subproject()
+  bwrapdir = get_option('libexecdir')
+
+  if get_option('program_prefix') == ''
+    error('program_prefix option must be set when bwrap is a subproject')
+  endif
+else
+  bwrapdir = get_option('bindir')
+endif
+
+bwrap = executable(
+  get_option('program_prefix') + 'bwrap',
+  [
+    'bubblewrap.c',
+    'bind-mount.c',
+    'network.c',
+    'utils.c',
+  ],
+  install : true,
+  install_dir : bwrapdir,
+  dependencies : [selinux_dep, libcap_dep],
+)
+
+xsltproc = find_program('xsltproc', required : get_option('man'))
+
+if xsltproc.found() and not meson.is_subproject()
+  custom_target(
+    'bwrap.1',
+    output : 'bwrap.1',
+    input : 'bwrap.xml',
+    command : [
+      xsltproc,
+      '--nonet',
+      '--stringparam', 'man.output.quietly', '1',
+      '--stringparam', 'funcsynopsis.style', 'ansi',
+      '--stringparam', 'man.th.extra1.suppress', '1',
+      '--stringparam', 'man.authors.section.enabled', '0',
+      '--stringparam', 'man.copyright.section.enabled', '0',
+      '-o', '@OUTPUT@',
+      'http://docbook.sourceforge.net/release/xsl/current/manpages/docbook.xsl',
+      '@INPUT@',
+    ],
+    install : true,
+    install_dir : get_option('mandir') / 'man1',
+  )
+endif
+
+if not meson.is_subproject()
+  subdir('completions')
+endif