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

flake.nix

@@ -204,6 +204,11 @@
         # Binary package for various platforms.
         build = forAllSystems (system: self.packages.${system}.nix);
 
+        # FIXME(Qyriad): remove this when the migration to Meson has been completed.
+        mesonBuild = forAllSystems (system: self.packages.${system}.nix.override {
+          buildWithMeson = true;
+        });
+
         # Perl bindings for various platforms.
         perlBindings = forAllSystems (system: nixpkgsFor.${system}.native.nix.perl-bindings);
 
@@ -262,6 +267,8 @@
       };
 
       checks = forAllSystems (system: {
+        # FIXME(Qyriad): remove this when the migration to Meson has been completed.
+        mesonBuild = self.hydraJobs.mesonBuild.${system};
         binaryTarball = self.hydraJobs.binaryTarball.${system};
         perlBindings = self.hydraJobs.perlBindings.${system};
         nixpkgsLibTests = self.hydraJobs.tests.nixpkgsLibTests.${system};
@@ -321,7 +328,12 @@
                 ++ lib.optional (stdenv.cc.isClang && !stdenv.buildPlatform.isDarwin) pkgs.buildPackages.bear
                 ++ lib.optional
                   (stdenv.cc.isClang && stdenv.hostPlatform == stdenv.buildPlatform)
-                  pkgs.buildPackages.clang-tools;
+                  pkgs.buildPackages.clang-tools
+                ++ [
+                  # FIXME(Qyriad): remove once the migration to Meson is complete.
+                  pkgs.buildPackages.meson
+                  pkgs.buildPackages.ninja
+                ];
 
               src = null;
 

meson.build

@@ -0,0 +1,294 @@
+#
+# 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++20',
+    # 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)
+
+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 = dependency('libcpuid', 'cpuid', required : get_option('cpuid'))
+configdata += {
+  'HAVE_LIBCPUID': cpuid.found().to_int(),
+  }
+deps += cpuid
+
+seccomp = dependency('libseccomp', 'seccomp', required : get_option('seccomp-sandboxing'))
+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 : true)
+if aws_sdk.found()
+  # The AWS pkg-config adds -std=c++11.
+  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 : true)
+if aws_s3.found()
+  # The AWS pkg-config adds -std=c++11.
+  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
+
+# extern "C++" functions can't be checked with the normal mechanism (much less member functions),
+# so we have to do this one ourselves.
+has_pubsetbuf = cxx.compiles('''
+  #include <iostream>
+  using namespace std;
+  static char buf[1024];
+  decltype(cerr.rdbuf()->pubsetbuf(buf, sizeof(buf))) _;
+''')
+summary('have std::basic_streambuf::pubsetbuf', has_pubsetbuf, bool_yn : true)
+configdata += {
+  'HAVE_PUBSETBUF': has_pubsetbuf.to_int(),
+}
+
+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',
+  # FIXME(Qyriad): autoconf did this only if not Darwin, Solaris, or FreeBSD
+  # (...so only if Linux?)
+  '-Wl,--no-copy-dt-needed-entries',
+  language : 'cpp',
+)
+
+subdir('src')

meson.options

@@ -0,0 +1,32 @@
+# vim: filetype=meson
+option('gc', type : 'feature',
+  description : 'enable garbage collection in the Nix expression evaluator (requires Boehm GC)',
+)
+# TODO(Qyriad): is this feature maintained?
+option('embedded-sandbox-shell', type : 'feature',
+  description : 'include the sandbox shell in the Nix bindary',
+)
+
+option('cpuid', type : 'feature',
+  description : 'determine microarchitecture levels with libcpuid (only relevant on x86_64)',
+)
+
+option('seccomp-sandboxing', type : 'feature',
+  description : 'build support for seccomp sandboxing (recommended unless your arch doesn\'t support libseccomp, only relevant on Linux)',
+)
+
+option('sandbox-shell', type : 'string', value : 'busybox',
+  description : 'path to a statically-linked shell to use as /bin/sh in sandboxes (usually busybox)',
+)
+
+option('store-dir', type : 'string', value : '/nix/store',
+  description : 'path of the Nix store',
+)
+
+option('state-dir', type : 'string', value : '/nix/var/nix',
+  description : 'path to store state in for Nix',
+)
+
+option('log-dir', type : 'string', value : '/nix/var/log',
+  description : 'path to store logs in for Nix',
+)

meson/cleanup-install.bash

@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+# Meson will call this with an absolute path to Bash.
+# The shebang is just for convenience.
+
+set -euo pipefail
+
+echo "cleanup-install: removing Meson-placed C++ sources from dest includedir"
+
+if [[ "${1/--help/}" != "$1" ]]; then
+	echo "cleanup-install: this script should only be called from the Meson build system"
+	exit 1
+fi
+
+# Ensure the includedir was passed as the first argument
+# (set -u will make this fail otherwise).
+includedir="$1"
+# And then ensure that first argument is a directory that exists.
+if ! [[ -d "$1" ]]; then
+	echo "cleanup-install: this script should only be called from the Meson build system"
+	echo "argv[1] (${1@Q}) is not a directory"
+	exit 2
+fi
+
+# If DESTDIR environment variable is set, prepend it to the include dir.
+# Unfortunately, we cannot do this on the Meson side. We do have an environment variable
+# `MESON_INSTALL_DESTDIR_PREFIX`, but that will not refer to the include directory if
+# includedir has been set separately, which Lix's split-output derivation does.
+# We also cannot simply do an inline bash conditional like "${DESTDIR:=}" or similar,
+# because we need to specifically *join* DESTDIR and includedir with a slash, and *not*
+# have a slash if DESTDIR isn't set at all, since $includedir could be a relative directory.
+# Finally, DESTDIR is only available to us as an environment variable in these install scripts,
+# not in Meson logic.
+# Therefore, our best option is to have Meson pass this script the configured includedir,
+# and perform this dance with it and $DESTDIR.
+if [[ -n "${DESTDIR:-}" ]]; then
+	includedir="$DESTDIR/$includedir"
+fi
+
+# Intentionally not using -f.
+# If these files don't exist then our assumptions have been violated and we should fail.
+rm -v "$includedir/nix/parser-tab.cc" "$includedir/nix/lexer-tab.cc"

package.nix

@@ -24,10 +24,13 @@
   libcpuid,
   libseccomp,
   libsodium,
+  lsof,
   lowdown,
   mdbook,
   mdbook-linkcheck,
   mercurial,
+  meson,
+  ninja,
   openssl,
   pkg-config,
   rapidcheck,
@@ -47,6 +50,10 @@
   # Avoid setting things that would interfere with a functioning devShell
   forDevShell ? false,
 
+  # FIXME(Qyriad): build Lix using Meson instead of autoconf and make.
+  # This flag will be removed when the migration to Meson is complete.
+  buildWithMeson ? false,
+
   # Not a real argument, just the only way to approximate let-binding some
   # stuff for argument defaults.
   __forDefaults ? {
@@ -86,12 +93,16 @@
     ./README.md
   ];
 
-  topLevelBuildFiles = fileset.unions [
+  topLevelBuildFiles = fileset.unions ([
     ./local.mk
     ./Makefile
     ./Makefile.config.in
     ./mk
-  ];
+  ] ++ lib.optionals buildWithMeson [
+    ./meson.build
+    ./meson.options
+    ./meson/cleanup-install.bash
+  ]);
 
  functionalTestFiles = fileset.unions [
     ./tests/functional
@@ -126,6 +137,11 @@ in stdenv.mkDerivation (finalAttrs: {
 
   dontBuild = false;
 
+  # FIXME(Qyriad): see if this is still needed once the migration to Meson is completed.
+  mesonFlags = lib.optionals (buildWithMeson && stdenv.hostPlatform.isLinux) [
+    "-Dsandbox-shell=${lib.getBin busybox-sandbox-shell}/bin/busybox"
+  ];
+
   nativeBuildInputs = [
     bison
     flex
@@ -134,17 +150,21 @@ in stdenv.mkDerivation (finalAttrs: {
     mdbook
     mdbook-linkcheck
     autoconf-archive
-    autoreconfHook
+  ] ++ lib.optional (!buildWithMeson) autoreconfHook ++ [
     pkg-config
 
     # Tests
     git
     mercurial
     jq
+    lsof
   ] ++ lib.optional stdenv.hostPlatform.isLinux util-linuxMinimal
     ++ lib.optional (!officialRelease && buildUnreleasedNotes) changelog-d
     ++ lib.optional internalApiDocs doxygen
-  ;
+    ++ lib.optionals buildWithMeson [
+      meson
+      ninja
+  ];
 
   buildInputs = [
     curl
@@ -159,7 +179,7 @@ in stdenv.mkDerivation (finalAttrs: {
     lowdown
     libsodium
   ]
-    ++ lib.optionals stdenv.isLinux [ libseccomp ]
+    ++ lib.optionals stdenv.hostPlatform.isLinux [ libseccomp busybox-sandbox-shell ]
     ++ lib.optional stdenv.hostPlatform.isx86_64 libcpuid
     # There have been issues building these dependencies
     ++ lib.optional (stdenv.hostPlatform == stdenv.buildPlatform) aws-sdk-cpp-nix
@@ -177,6 +197,13 @@ in stdenv.mkDerivation (finalAttrs: {
     boost
   ];
 
+  # Needed for Meson to find Boost.
+  # https://github.com/NixOS/nixpkgs/issues/86131.
+  env = lib.optionalAttrs (buildWithMeson || forDevShell) {
+    BOOST_INCLUDEDIR = "${lib.getDev boost}/include";
+    BOOST_LIBRARYDIR = "${lib.getLib boost}/lib";
+  };
+
   preConfigure = lib.optionalString (!finalAttrs.dontBuild && !stdenv.hostPlatform.isStatic) ''
     # Copy libboost_context so we don't get all of Boost in our closure.
     # https://github.com/NixOS/nixpkgs/issues/45462

src/libcmd/meson.build

@@ -0,0 +1,58 @@
+libcmd_sources = files(
+  'built-path.cc',
+  'command-installable-value.cc',
+  'command.cc',
+  'common-eval-args.cc',
+  'editor-for.cc',
+  'installable-attr-path.cc',
+  'installable-derived-path.cc',
+  'installable-flake.cc',
+  'installable-value.cc',
+  'installables.cc',
+  'legacy.cc',
+  'markdown.cc',
+  'repl.cc',
+  'repl-interacter.cc',
+)
+
+libcmd_headers = files(
+  'built-path.hh',
+  'command-installable-value.hh',
+  'command.hh',
+  'common-eval-args.hh',
+  'editor-for.hh',
+  'installable-attr-path.hh',
+  'installable-derived-path.hh',
+  'installable-flake.hh',
+  'installable-value.hh',
+  'installables.hh',
+  'legacy.hh',
+  'markdown.hh',
+  'repl-interacter.hh',
+  'repl.hh',
+)
+
+libcmd = library(
+  'nixcmd',
+  libcmd_sources,
+  dependencies : [
+    liblixutil,
+    liblixstore,
+    liblixexpr,
+    liblixfetchers,
+    liblixmain,
+    boehm,
+    editline,
+    lowdown,
+  ],
+  install : true,
+  # FIXME(Qyriad): is this right?
+  install_rpath : libdir,
+)
+
+install_headers(libcmd_headers, subdir : 'nix', preserve_path : true)
+
+liblixcmd = declare_dependency(
+  include_directories : '.',
+  link_with : libcmd,
+)

src/libexpr/meson.build

@@ -0,0 +1,157 @@
+parser_tab = custom_target(
+  input : 'parser.y',
+  output : [
+    'parser-tab.cc',
+    'parser-tab.hh',
+  ],
+  command : [
+    'bison',
+    '-v',
+    '-o',
+    '@OUTPUT0@',
+    '@INPUT@',
+    '-d',
+  ],
+  # NOTE(Qyriad): Meson doesn't support installing only part of a custom target, so we add
+  # an install script below which removes parser-tab.cc.
+  install : true,
+  install_dir : includedir / 'nix',
+)
+
+lexer_tab = custom_target(
+  input : [
+    'lexer.l',
+    parser_tab,
+  ],
+  output : [
+    'lexer-tab.cc',
+    'lexer-tab.hh',
+  ],
+  command : [
+    'flex',
+    '--outfile',
+    '@OUTPUT0@',
+    '--header-file=' + '@OUTPUT1@',
+    '@INPUT0@',
+  ],
+  # NOTE(Qyriad): Meson doesn't support installing only part of a custom target, so we add
+  # an install script below which removes lexer-tab.cc.
+  install : true,
+  install_dir : includedir / 'nix',
+)
+
+# TODO(Qyriad): When the parser and lexer are rewritten this should be removed.
+# NOTE(Qyriad): We do this this way instead of an inline bash or rm command
+# due to subtleties in Meson. Check the comments in cleanup-install.bash for details.
+meson.add_install_script(
+  bash,
+  meson.project_source_root() / 'meson/cleanup-install.bash',
+  '@0@'.format(includedir),
+)
+
+imported_drv_to_derivation_gen = gen_header.process('imported-drv-to-derivation.nix')
+fetchurl_gen = gen_header.process('fetchurl.nix')
+derivation_gen = gen_header.process('primops/derivation.nix', preserve_path_from : meson.current_source_dir())
+call_flake_gen = gen_header.process('flake/call-flake.nix')
+
+libexpr_sources = files(
+  'attr-path.cc',
+  'attr-set.cc',
+  'eval-cache.cc',
+  'eval-error.cc',
+  'eval-settings.cc',
+  'eval.cc',
+  'function-trace.cc',
+  'get-drvs.cc',
+  'json-to-value.cc',
+  'nixexpr.cc',
+  'paths.cc',
+  'primops.cc',
+  'print-ambiguous.cc',
+  'print.cc',
+  'search-path.cc',
+  'value-to-json.cc',
+  'value-to-xml.cc',
+  'flake/config.cc',
+  'flake/flake.cc',
+  'flake/flakeref.cc',
+  'flake/lockfile.cc',
+  'primops/context.cc',
+  'primops/fetchClosure.cc',
+  'primops/fetchMercurial.cc',
+  'primops/fetchTree.cc',
+  'primops/fromTOML.cc',
+  'value/context.cc',
+)
+
+libexpr_headers = files(
+  'attr-path.hh',
+  'attr-set.hh',
+  'eval-cache.hh',
+  'eval-error.hh',
+  'eval-inline.hh',
+  'eval-settings.hh',
+  'eval.hh',
+  'flake/flake.hh',
+  'flake/flakeref.hh',
+  'flake/lockfile.hh',
+  'function-trace.hh',
+  'gc-small-vector.hh',
+  'get-drvs.hh',
+  'json-to-value.hh',
+  'nixexpr.hh',
+  'parser-state.hh',
+  'pos-idx.hh',
+  'pos-table.hh',
+  'primops.hh',
+  'print-ambiguous.hh',
+  'print-options.hh',
+  'print.hh',
+  'repl-exit-status.hh',
+  'search-path.hh',
+  'symbol-table.hh',
+  'value/context.hh',
+  'value-to-json.hh',
+  'value-to-xml.hh',
+  'value.hh',
+)
+
+libexpr = library(
+  'nixexpr',
+  libexpr_sources,
+  parser_tab,
+  lexer_tab,
+  imported_drv_to_derivation_gen,
+  fetchurl_gen,
+  derivation_gen,
+  call_flake_gen,
+  dependencies : [
+    liblixutil,
+    liblixstore,
+    liblixfetchers,
+    boehm,
+    boost,
+  ],
+  # for shared.hh
+  include_directories : '../libmain',
+  cpp_args : [
+    # FIXME(Qyriad): can we please fix this. toml11 pls.
+    # Technically this only applies to fromTOML.cc, but, well
+    # https://github.com/mesonbuild/meson/issues/1367
+    '-Wno-error=switch-enum',
+  ],
+  install : true,
+  # FIXME(Qyriad): is this right?
+  install_rpath : libdir,
+)
+
+install_headers(
+  libexpr_headers,
+  subdir : 'nix',
+  preserve_path : true
+)
+
+liblixexpr = declare_dependency(
+  include_directories : include_directories('.'),
+  link_with : libexpr,
+)

src/libfetchers/meson.build

@@ -0,0 +1,42 @@
+libfetchers_sources = files(
+  'attrs.cc',
+  'cache.cc',
+  'fetch-settings.cc',
+  'fetch-to-store.cc',
+  'fetchers.cc',
+  'git.cc',
+  'github.cc',
+  'indirect.cc',
+  'mercurial.cc',
+  'path.cc',
+  'registry.cc',
+  'tarball.cc',
+)
+
+libfetchers_headers = files(
+  'attrs.hh',
+  'cache.hh',
+  'fetch-settings.hh',
+  'fetch-to-store.hh',
+  'fetchers.hh',
+  'registry.hh',
+)
+
+libfetchers = library(
+  'nixfetchers',
+  libfetchers_sources,
+  dependencies : [
+    liblixstore,
+    liblixutil,
+  ],
+  install : true,
+  # FIXME(Qyriad): is this right?
+  install_rpath : libdir,
+)
+
+install_headers(libfetchers_headers, subdir : 'nix', preserve_path : true)
+
+liblixfetchers = declare_dependency(
+  include_directories : include_directories('.'),
+  link_with : libfetchers,
+)

src/libmain/meson.build

@@ -0,0 +1,33 @@
+libmain_sources = files(
+  'common-args.cc',
+  'loggers.cc',
+  'progress-bar.cc',
+  'shared.cc',
+  'stack.cc',
+)
+
+libmain_headers = files(
+  'common-args.hh',
+  'loggers.hh',
+  'progress-bar.hh',
+  'shared.hh',
+)
+
+libmain = library(
+  'nixmain',
+  libmain_sources,
+  dependencies : [
+    liblixutil,
+    liblixstore,
+  ],
+  install : true,
+  # FIXME(Qyriad): is this right?
+  install_rpath : libdir,
+)
+
+install_headers(libmain_headers, subdir : 'nix', preserve_path : true)
+
+liblixmain = declare_dependency(
+  include_directories : include_directories('.'),
+  link_with : libmain,
+)

src/libstore/meson.build

@@ -0,0 +1,188 @@
+schema_sql_gen = gen_header.process('schema.sql')
+ca_specific_schema_gen = gen_header.process('ca-specific-schema.sql')
+
+libstore_sources = files(
+  'binary-cache-store.cc',
+  'build-result.cc',
+  'common-protocol.cc',
+  'content-address.cc',
+  'crypto.cc',
+  'daemon.cc',
+  'derivations.cc',
+  'derived-path-map.cc',
+  'derived-path.cc',
+  'downstream-placeholder.cc',
+  'dummy-store.cc',
+  'export-import.cc',
+  'filetransfer.cc',
+  'gc.cc',
+  'globals.cc',
+  'http-binary-cache-store.cc',
+  'legacy-ssh-store.cc',
+  'local-binary-cache-store.cc',
+  'local-fs-store.cc',
+  'local-store.cc',
+  'lock.cc',
+  'log-store.cc',
+  'machines.cc',
+  'make-content-addressed.cc',
+  'misc.cc',
+  'names.cc',
+  'nar-accessor.cc',
+  'nar-info-disk-cache.cc',
+  'nar-info.cc',
+  'optimise-store.cc',
+  'outputs-spec.cc',
+  'parsed-derivations.cc',
+  'path-info.cc',
+  'path-references.cc',
+  'path-with-outputs.cc',
+  'path.cc',
+  'pathlocks.cc',
+  'profiles.cc',
+  'realisation.cc',
+  'remote-fs-accessor.cc',
+  'remote-store.cc',
+  's3-binary-cache-store.cc',
+  'serve-protocol.cc',
+  'sqlite.cc',
+  'ssh-store.cc',
+  'ssh.cc',
+  'store-api.cc',
+  'uds-remote-store.cc',
+  'worker-protocol.cc',
+  'build/derivation-goal.cc',
+  'build/drv-output-substitution-goal.cc',
+  'build/entry-points.cc',
+  'build/goal.cc',
+  'build/hook-instance.cc',
+  'build/local-derivation-goal.cc',
+  'build/personality.cc',
+  'build/substitution-goal.cc',
+  'build/worker.cc',
+  'builtins/buildenv.cc',
+  'builtins/fetchurl.cc',
+  'builtins/unpack-channel.cc',
+)
+
+
+libstore_headers = files(
+  'binary-cache-store.hh',
+  'build/derivation-goal.hh',
+  'build/drv-output-substitution-goal.hh',
+  'build/goal.hh',
+  'build/hook-instance.hh',
+  'build/local-derivation-goal.hh',
+  'build/personality.hh',
+  'build/substitution-goal.hh',
+  'build/worker.hh',
+  'build-result.hh',
+  'builtins/buildenv.hh',
+  'builtins.hh',
+  'common-protocol-impl.hh',
+  'common-protocol.hh',
+  'content-address.hh',
+  'crypto.hh',
+  'daemon.hh',
+  'derivations.hh',
+  'derived-path-map.hh',
+  'derived-path.hh',
+  'downstream-placeholder.hh',
+  'filetransfer.hh',
+  'fs-accessor.hh',
+  'gc-store.hh',
+  'globals.hh',
+  'indirect-root-store.hh',
+  'length-prefixed-protocol-helper.hh',
+  'local-fs-store.hh',
+  'local-store.hh',
+  'lock.hh',
+  'log-store.hh',
+  'machines.hh',
+  'make-content-addressed.hh',
+  'names.hh',
+  'nar-accessor.hh',
+  'nar-info-disk-cache.hh',
+  'nar-info.hh',
+  'outputs-spec.hh',
+  'parsed-derivations.hh',
+  'path-info.hh',
+  'path-references.hh',
+  'path-regex.hh',
+  'path-with-outputs.hh',
+  'path.hh',
+  'pathlocks.hh',
+  'profiles.hh',
+  'realisation.hh',
+  'remote-fs-accessor.hh',
+  'remote-store-connection.hh',
+  'remote-store.hh',
+  's3-binary-cache-store.hh',
+  's3.hh',
+  'serve-protocol-impl.hh',
+  'serve-protocol.hh',
+  'sqlite.hh',
+  'ssh-store-config.hh',
+  'ssh.hh',
+  'store-api.hh',
+  'store-cast.hh',
+  'uds-remote-store.hh',
+  'worker-protocol-impl.hh',
+  'worker-protocol.hh',
+)
+
+# These variables (aside from LSOF) are created pseudo-dynamically, near the beginning of
+# the top-level meson.build. Aside from prefix itself, each of these was
+# made into an absolute path by joining it with prefix, unless it was already
+# an absolute path (which is the default for store-dir, state-dir, and log-dir).
+cpp_str_defines = {
+  'LSOF': lsof.full_path(),
+  'NIX_PREFIX':    prefix,
+  'NIX_STORE_DIR': store_dir,
+  'NIX_DATA_DIR':  datadir,
+  'NIX_STATE_DIR': state_dir,
+  'NIX_LOG_DIR':   log_dir,
+  'NIX_CONF_DIR':  sysconfdir,
+  'NIX_BIN_DIR':   bindir,
+  'NIX_MAN_DIR':   mandir,
+}
+
+cpp_args = []
+
+foreach name, value : cpp_str_defines
+  cpp_args += [
+    '-D' + name + '=' + '"' + value + '"'
+  ]
+endforeach
+
+libstore = library(
+  'nixstore',
+  schema_sql_gen,
+  ca_specific_schema_gen,
+  libstore_sources,
+  dependencies : [
+    libarchive,
+    liblixutil, # Internal.
+    seccomp,
+    sqlite,
+    sodium,
+    seccomp,
+    curl,
+    openssl,
+    aws_sdk,
+    aws_s3,
+    aws_sdk_transfer,
+  ],
+  cpp_args : cpp_args,
+  install : true,
+  # FIXME(Qyriad): is this right?
+  install_rpath : libdir,
+)
+
+install_headers(libstore_headers, subdir : 'nix', preserve_path : true)
+
+# Used by libfetchers.
+liblixstore = declare_dependency(
+  include_directories : include_directories('.'),
+  link_with : libstore,
+)

src/libutil/meson.build

@@ -0,0 +1,112 @@
+libutil_sources = files(
+  'archive.cc',
+  'args.cc',
+  'canon-path.cc',
+  'cgroup.cc',
+  'compression.cc',
+  'compute-levels.cc',
+  'config.cc',
+  'english.cc',
+  'error.cc',
+  'exit.cc',
+  'experimental-features.cc',
+  'filesystem.cc',
+  'git.cc',
+  'hash.cc',
+  'hilite.cc',
+  'json-utils.cc',
+  'logging.cc',
+  'namespaces.cc',
+  'position.cc',
+  'references.cc',
+  'serialise.cc',
+  'signals.cc',
+  'source-path.cc',
+  'suggestions.cc',
+  'tarfile.cc',
+  'thread-pool.cc',
+  'url.cc',
+  'util.cc',
+  'xml-writer.cc',
+)
+
+libutil_headers = files(
+  'abstract-setting-to-json.hh',
+  'ansicolor.hh',
+  'archive.hh',
+  'args.hh',
+  'box_ptr.hh',
+  'callback.hh',
+  'canon-path.hh',
+  'cgroup.hh',
+  'chunked-vector.hh',
+  'closure.hh',
+  'comparator.hh',
+  'compression.hh',
+  'compute-levels.hh',
+  'config-impl.hh',
+  'config.hh',
+  'english.hh',
+  'error.hh',
+  'exit.hh',
+  'experimental-features.hh',
+  'finally.hh',
+  'fmt.hh',
+  'git.hh',
+  'hash.hh',
+  'hilite.hh',
+  'input-accessor.hh',
+  'json-impls.hh',
+  'json-utils.hh',
+  'logging.hh',
+  'lru-cache.hh',
+  'monitor-fd.hh',
+  'namespaces.hh',
+  'pool.hh',
+  'position.hh',
+  'ref.hh',
+  'references.hh',
+  'regex-combinators.hh',
+  'repair-flag.hh',
+  'serialise.hh',
+  'signals.hh',
+  'source-path.hh',
+  'split.hh',
+  'suggestions.hh',
+  'sync.hh',
+  'tarfile.hh',
+  'thread-pool.hh',
+  'topo-sort.hh',
+  'types.hh',
+  'url-parts.hh',
+  'url.hh',
+  'util.hh',
+  'variant-wrapper.hh',
+  'xml-writer.hh',
+)
+
+libutil = library(
+  'nixutil',
+  libutil_sources,
+  dependencies : [
+    aws_sdk,
+    aws_s3,
+    boehm,
+    boost,
+    cpuid,
+    seccomp,
+    libarchive,
+    brotli,
+    openssl,
+  ],
+  implicit_include_directories : true,
+  install : true,
+)
+
+install_headers(libutil_headers, subdir : 'nix', preserve_path : true)
+
+# Used by libstore and libfetchers.
+liblixutil = declare_dependency(
+  include_directories : include_directories('.'),
+  link_with : libutil
+)

src/meson.build

@@ -0,0 +1,65 @@
+# Subcomponents: these link into artifacts themselves, and have interdependencies.
+
+subdir('libutil')
+# Load-bearing order. libstore depends on libutil.
+subdir('libstore')
+# libfetchers depends on libstore
+subdir('libfetchers')
+# libexpr depends on all of the above
+subdir('libexpr')
+# libmain depends on libutil and libstore
+subdir('libmain')
+# libcmd depends on everything
+subdir('libcmd')
+
+
+# The rest of the subdirectories aren't separate components,
+# just source files in another directory, so we process them here.
+
+build_remote_sources = files(
+  'build-remote/build-remote.cc',
+)
+nix_build_sources = files(
+  'nix-build/nix-build.cc',
+)
+nix_channel_sources = files(
+  'nix-channel/nix-channel.cc',
+)
+unpack_channel_gen = gen_header.process('nix-channel/unpack-channel.nix')
+nix_collect_garbage_sources = files(
+  'nix-collect-garbage/nix-collect-garbage.cc',
+)
+nix_copy_closure_sources = files(
+  'nix-copy-closure/nix-copy-closure.cc',
+)
+nix_env_buildenv_gen = gen_header.process('nix-env/buildenv.nix')
+nix_env_sources = files(
+  'nix-env/nix-env.cc',
+  'nix-env/user-env.cc',
+)
+nix_instantiate_sources = files(
+  'nix-instantiate/nix-instantiate.cc',
+)
+nix_store_sources = files(
+  'nix-store/dotgraph.cc',
+  'nix-store/graphml.cc',
+  'nix-store/nix-store.cc',
+)
+
+# Hurray for Meson list flattening!
+nix2_commands_sources = [
+  build_remote_sources,
+  nix_build_sources,
+  nix_channel_sources,
+  unpack_channel_gen,
+  nix_collect_garbage_sources,
+  nix_copy_closure_sources,
+  nix_env_buildenv_gen,
+  nix_env_sources,
+  nix_instantiate_sources,
+  nix_store_sources,
+]
+
+# Finally, the nix command itself, which all of the other commands are implmented in terms of
+# as a multicall binary.
+subdir('nix')

src/nix/meson.build

@@ -0,0 +1,119 @@
+generate_manpage_gen = gen_header.process(meson.project_source_root() / 'doc/manual/generate-manpage.nix')
+
+utils_gen = gen_header.process(meson.project_source_root() / 'doc/manual/utils.nix')
+
+get_env_gen = gen_header.process('get-env.sh')
+
+# src/nix/profile.cc includes src/nix/profile.md, which includes "doc/files/profiles.md.gen.hh".
+# Unfortunately, https://github.com/mesonbuild/meson/issues/2320.
+# "docs/files" isn't a directory hierarchy that already exists somewhere in this source tree,
+# and Meson refuses to create targets with specific directory paths.
+# So run_command() it is.
+# NOTE(Qyriad): This corresponds to the previous buildsystem's `src/nix/doc/files/%.md` rule,
+# which as far as I can tell was only used for this file.
+run_command(
+  installcmd,
+  '-D',
+  meson.project_source_root() / 'doc/manual/src/command-ref/files/profiles.md',
+  meson.current_build_dir() / 'doc/files/profiles.md',
+  check : true,
+)
+profiles_md_gen = gen_header.process(
+  meson.current_build_dir() / 'doc/files/profiles.md',
+  preserve_path_from : meson.current_build_dir(),
+)
+
+nix_sources = files(
+  'add-to-store.cc',
+  'app.cc',
+  'build.cc',
+  'bundle.cc',
+  'cat.cc',
+  'copy.cc',
+  'daemon.cc',
+  'derivation-add.cc',
+  'derivation-show.cc',
+  'derivation.cc',
+  'develop.cc',
+  'diff-closures.cc',
+  'doctor.cc',
+  'dump-path.cc',
+  'edit.cc',
+  'eval.cc',
+  'flake.cc',
+  'fmt.cc',
+  'hash.cc',
+  'log.cc',
+  'ls.cc',
+  'main.cc',
+  'make-content-addressed.cc',
+  'nar.cc',
+  'optimise-store.cc',
+  'path-from-hash-part.cc',
+  'path-info.cc',
+  'ping-store.cc',
+  'prefetch.cc',
+  'profile.cc',
+  'realisation.cc',
+  'registry.cc',
+  'repl.cc',
+  'run.cc',
+  'search.cc',
+  'show-config.cc',
+  'sigs.cc',
+  'store-copy-log.cc',
+  'store-delete.cc',
+  'store-gc.cc',
+  'store-repair.cc',
+  'store.cc',
+  'upgrade-nix.cc',
+  'verify.cc',
+  'why-depends.cc',
+)
+
+nix = executable(
+  'nix',
+  nix_sources,
+  generate_manpage_gen,
+  utils_gen,
+  get_env_gen,
+  profiles_md_gen,
+  nix2_commands_sources,
+  dependencies : [
+    liblixcmd,
+    liblixutil,
+    liblixstore,
+    liblixexpr,
+    liblixfetchers,
+    liblixmain,
+    boehm,
+  ],
+  install : true,
+  # FIXME(Qyriad): is this right?
+  install_rpath : libdir,
+)
+
+nix_symlinks = [
+  'nix-build',
+  'nix-channel',
+  'nix-collect-garbage',
+  'nix-copy-closure',
+  'nix-daemon',
+  'nix-env',
+  'nix-hash',
+  'nix-instantiate',
+  'nix-prefetch-url',
+  'nix-shell',
+  'nix-store',
+]
+
+foreach linkname : nix_symlinks
+  install_symlink(
+    linkname,
+    # TODO(Qyriad): should these continue to be relative symlinks?
+    pointing_to : 'nix',
+    install_dir : bindir,
+    # The 'runtime' tag is what executables default to, which we want to emulate here.
+    install_tag : 'runtime'
+  )
+endforeach