build: optionally build and install with meson

This commit adds several meson.build, which successfully build and
install Lix executables, libraries, and headers. Meson does not yet
build docs, Perl bindings, or run tests, which will be added in
following commits. As such, this commit does not remove the existing
build system, or make it the default, and also as such, this commit has
several FIXMEs and TODOs as notes for what should be done before the
existing autoconf + make buildsystem can be removed and Meson made the
default. This commit does not modify any source files.

A Meson-enabled build is also added as a Hydra job, and to
`nix flake check`.

Change-Id: I667c8685b13b7bab91e281053f807a11616ae3d4

1 files changed, 287 insertions, 0 deletions

diff --git a/meson.build b/meson.build
new file mode 100644
index 000000000..73c13582b
--- /dev/null
+++ b/meson.build
@@ -0,0 +1,287 @@
+#
+# OUTLINE:
+#
+# The top-level meson.build file (this file) handles general logic for build options,
+# generation of config.h (which is put in the build directory, not the source root
+# like the previous, autoconf-based build system did), the mechanism for header
+# generation, and the few global C++ compiler arguments that are added to all targets in Lix.
+#
+# src/meson.build coordinates each of Lix's subcomponents (the lib dirs in ./src),
+# which each have their own meson.build. Lix's components depend on each other,
+# so each of `src/lib{util,store,fetchers,expr,main,cmd}/meson.build` rely on variables
+# set in earlier `meson.build` files. Each of these also defines the install targets for
+# their headers.
+#
+# src/meson.build also collects the miscellaneous source files that are in further subdirectories
+# that become part of the final Nix command (things like `src/nix-build/*.cc`).
+#
+# Finally, src/nix/meson.build defines the Nix command itself, relying on all prior meson files.
+
+project('lix', 'cpp',
+  version : run_command('bash', '-c', 'echo -n $(cat ./.version)$VERSION_SUFFIX', check : true).stdout().strip(),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+  ],
+)
+
+fs = import('fs')
+
+prefix = get_option('prefix')
+# For each of these paths, assume that it is relative to the prefix unless
+# it is already an absolute path (which is the default for store-dir, state-dir, and log-dir).
+path_opts = [
+  # Meson built-ins.
+  'datadir',
+  'sysconfdir',
+  'bindir',
+  'mandir',
+  'libdir',
+  'includedir',
+  # Homecooked Lix directories.
+  'store-dir',
+  'state-dir',
+  'log-dir',
+]
+foreach optname : path_opts
+  varname = optname.replace('-', '_')
+  path = get_option(optname)
+  if fs.is_absolute(path)
+    set_variable(varname, path)
+  else
+    set_variable(varname, prefix / path)
+  endif
+endforeach
+
+cxx = meson.get_compiler('cpp')
+
+host_system = host_machine.cpu_family() + '-' + host_machine.system()
+message('canonical Nix system name:', host_system)
+
+is_linux = host_machine.system() == 'linux'
+is_x64 = host_machine.cpu_family() == 'x86_64'
+
+deps = [ ]
+configdata = { }
+
+#
+# Dependencies
+#
+
+boehm = dependency('bdw-gc', required : get_option('gc'))
+if boehm.found()
+  deps += boehm
+endif
+configdata += {
+  'HAVE_BOEHMGC': boehm.found().to_int(),
+}
+
+boost = dependency('boost', required : true, modules : ['context', 'coroutine', 'container'])
+deps += boost
+
+# cpuid only makes sense on x86_64
+cpuid_required = is_x64 ? get_option('cpuid') : false
+cpuid = dependency('libcpuid', 'cpuid', required : cpuid_required)
+configdata += {
+  'HAVE_LIBCPUID': cpuid.found().to_int(),
+}
+deps += cpuid
+
+# seccomp only makes sense on Linux
+seccomp_required = is_linux ? get_option('seccomp-sandboxing') : false
+seccomp = dependency('libseccomp', 'seccomp', required : seccomp_required)
+configdata += {
+  'HAVE_SECCOMP': seccomp.found().to_int(),
+}
+
+libarchive = dependency('libarchive', required : true)
+deps += libarchive
+
+brotli = [
+  dependency('libbrotlicommon', required : true),
+  dependency('libbrotlidec', required : true),
+  dependency('libbrotlienc', required : true),
+]
+deps += brotli
+
+openssl = dependency('libcrypto', 'openssl', required : true)
+deps += openssl
+
+aws_sdk = dependency('aws-cpp-sdk-core', required : false)
+if aws_sdk.found()
+  # The AWS pkg-config adds -std=c++11.
+  # https://github.com/aws/aws-sdk-cpp/issues/2673
+  aws_sdk = aws_sdk.partial_dependency(
+    compile_args : false,
+    includes : true,
+    link_args : true,
+    links : true,
+    sources : true,
+  )
+  deps += aws_sdk
+  s = aws_sdk.version().split('.')
+  configdata += {
+    'AWS_VERSION_MAJOR': s[0].to_int(),
+    'AWS_VERSION_MINOR': s[1].to_int(),
+    'AWS_VERSION_PATCH': s[2].to_int(),
+  }
+  aws_sdk_transfer = dependency('aws-cpp-sdk-transfer', required : true).partial_dependency(
+    compile_args : false,
+    includes : true,
+    link_args : true,
+    links : true,
+    sources : true,
+  )
+endif
+
+aws_s3 = dependency('aws-cpp-sdk-s3', required : false)
+if aws_s3.found()
+  # The AWS pkg-config adds -std=c++11.
+  # https://github.com/aws/aws-sdk-cpp/issues/2673
+  aws_s3 = aws_s3.partial_dependency(
+    compile_args : false,
+    includes : true,
+    link_args : true,
+    links : true,
+    sources : true,
+  )
+  deps += aws_s3
+endif
+
+configdata += {
+  'ENABLE_S3': aws_s3.found().to_int(),
+}
+
+sqlite = dependency('sqlite3', 'sqlite', version : '>=3.6.19', required : true)
+deps += sqlite
+
+sodium = dependency('libsodium', 'sodium', required : true)
+deps += sodium
+
+curl = dependency('libcurl', 'curl', required : true)
+deps += curl
+
+editline = dependency('libeditline', 'editline', version : '>=1.14', required : true)
+deps += editline
+
+lowdown = dependency('lowdown', version : '>=0.9.0', required : true)
+deps += lowdown
+
+rapidcheck = dependency('rapidcheck', required : false)
+deps += rapidcheck
+
+gtest = dependency('gtest', required : false)
+deps += gtest
+
+#
+# Build-time tools
+#
+bash = find_program('bash')
+
+# Used to workaround https://github.com/mesonbuild/meson/issues/2320 in src/nix/meson.build.
+installcmd = find_program('install')
+
+sandbox_shell = get_option('sandbox-shell')
+# Consider it required if we're on Linux and the user explicitly specified a non-default value.
+sandbox_shell_required = sandbox_shell != 'busybox' and host_machine.system() == 'linux'
+# NOTE(Qyriad): package.nix puts busybox in buildInputs for Linux.
+# Most builds should not require setting this.
+busybox = find_program(sandbox_shell, required : sandbox_shell_required, native : false)
+if not busybox.found() and host_machine.system() == 'linux' and sandbox_shell_required
+  warning('busybox not found and other sandbox shell was specified')
+  warning('a sandbox shell is recommended on Linux -- configure with -Dsandbox-shell=/path/to/shell to set')
+endif
+# FIXME(Qyriad): the autoconf system checks that busybox has the "standalone" feature, indicating
+# that busybox sh won't run busybox applets as builtins (which would break our sandbox).
+
+lsof = find_program('lsof')
+bison = find_program('bison')
+flex = find_program('flex')
+
+# This is how Nix does generated headers...
+# FIXME(Qyriad): do we really need to use the shell for this?
+gen_header = generator(
+  bash,
+  arguments : [
+    '-c',
+    'echo \'R"__NIX_STR(\' | cat - @INPUT@ && echo \')__NIX_STR"\'',
+  ],
+  capture : true,
+  output : '@PLAINNAME@.gen.hh',
+)
+
+#
+# Configuration
+#
+
+run_command('ln', '-s',
+  meson.project_build_root() / '__nothing_link_target',
+  meson.project_build_root() / '__nothing_symlink',
+  check : true,
+)
+can_link_symlink = run_command('ln',
+  meson.project_build_root() / '__nothing_symlink',
+  meson.project_build_root() / '__nothing_hardlink',
+  check : false,
+).returncode() == 0
+run_command('rm', '-f',
+  meson.project_build_root() / '__nothing_symlink',
+  meson.project_build_root() / '__nothing_hardlink',
+  check : true,
+)
+summary('can hardlink to symlink', can_link_symlink, bool_yn : true)
+configdata += { 'CAN_LINK_SYMLINK': can_link_symlink.to_int() }
+
+
+# Check for each of these functions, and create a define like `#define HAVE_LCHOWN 1`.
+check_funcs = [
+  'lchown',
+  'lutimes',
+  'pipe2',
+  'posix_fallocate',
+  'statvfs',
+  'strsignal',
+  'sysconf',
+]
+foreach funcspec : check_funcs
+  define_name = 'HAVE_' + funcspec.underscorify().to_upper()
+  define_value = cxx.has_function(funcspec).to_int()
+  configdata += {
+    define_name: define_value,
+  }
+endforeach
+
+config_h = configure_file(
+  configuration : {
+    'PACKAGE_NAME': '"' + meson.project_name() + '"',
+    'PACKAGE_VERSION': '"' + meson.project_version() + '"',
+    'PACKAGE_TARNAME': '"' + meson.project_name() + '"',
+    'PACKAGE_STRING': '"' + meson.project_name() + ' ' + meson.project_version() + '"',
+    'HAVE_STRUCT_DIRENT_D_TYPE': 1, # FIXME: actually check this for solaris
+    'SYSTEM': '"' + host_system + '"',
+  } + configdata,
+  output : 'config.h',
+)
+
+install_headers(config_h, subdir : 'nix')
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config.h',
+  '-Wno-deprecated-declarations',
+  '-Wimplicit-fallthrough',
+  '-Werror=switch',
+  '-Werror=switch-enum',
+  language : 'cpp',
+)
+
+add_project_link_arguments('-pthread', language : 'cpp')
+if cxx.get_linker_id() in ['ld.bfd', 'ld.gold']
+  add_project_link_arguments('-Wl,--no-copy-dt-needed-entries', language : 'cpp')
+endif
+
+subdir('src')