WIP: line-for-line rewrite of build system in Meson

meson.build

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+#
+# Old configure.ac
+#
+
+project(
+  'nix',
+  'cpp',
+  default_options : [
+    'cpp_std=c++14',
+    #'localstatedir=/nix/var',
+  ],
+)
+
+sed = find_program('sed')
+
+conf_data = configuration_data()
+
+system = get_option('with-system')
+if system == ''
+  system = host_machine.cpu() + '-' + host_machine.system()
+endif
+conf_data.set_quoted('SYSTEM', system, description : 'platform identifier (`cpu-os\')')
+
+# State should be stored in /nix/var, unless the user overrides it explicitly.
+if get_option('normal-var')
+  nixstatedir = '/nix/var'
+else
+  nixstatedir = get_option('localstatedir')
+endif
+
+global_libs = []
+# Solaris-specific stuff.
+if host_machine.cpu() == 'sunos'
+  global_libs += [
+    dependency('socket'),
+    dependency('nsl'),
+  ]
+endif
+
+# Use 64-bit file system calls so that we can support files > 2 GiB.
+
+# Note vs configure.ac: Meson always does large file support.
+
+# Check for pubsetbuf.
+want_pubsetbuf = get_option('have-pubsetbuf')
+if want_pubsetbuf.disabled()
+  have_pubsetbuf = false
+else
+  have_pubsetbuf = meson.get_compiler('cpp').compiles(
+    '''
+      #include <iostream>
+      using namespace std;
+      static char buf[1024];
+      void func() {
+        cerr.rdbuf()->pubsetbuf(buf, sizeof(buf));
+      }
+    ''',
+    name : 'pubsetbuf'
+  )
+  if want_pubsetbuf.enabled() and not have_pubsetbuf
+    error('you required the `pubsetbuf` function, but we do not have it.')
+  endif
+endif
+if have_pubsetbuf
+  conf_data.set('HAVE_PUBSETBUF', 1, description : 'Whether pubsetbuf is available.')
+endif
+
+foreach f : [
+  'statvfs',
+  'pipe2',
+  # Check for lutimes, optionally used for changing the mtime of symlinks.
+  'lutimes',
+]
+  if meson.get_compiler('cpp').has_function(f)
+    conf_data.set('HAVE_' + f.to_upper(), 1)
+  endif
+endforeach
+
+# Check whether the store optimiser can optimise symlinks.
+want_link_symlink = get_option('can-link-symlink')
+if want_link_symlink.disabled()
+  can_link_symlink = true
+else
+  link_text_script = '''
+    ln -s bla tmp_link;
+    ln tmp_link tmp_link2 2> /dev/null;
+    rm -f tmp_link tmp_link2
+  '''
+  can_link_symlink = run_command('sh', '-c', link_text_script).returncode() == 0
+  if want_link_symlink.enabled() and not can_link_symlink
+    error('you required that we hard link symlinks, but we cannot.')
+  endif
+endif
+if can_link_symlink
+  conf_data.set('CAN_LINK_SYMLINK', 1, description : 'Whether link() works on symlinks.')
+endif
+
+# Check for <locale>.
+meson.get_compiler('cpp').check_header('locale')
+
+foreach prog : [
+  'bash',
+  'patch',
+  'sed',
+  'tar',
+  'bzip2',
+  'gzip',
+  'xz',
+  'cat',
+  'tr',
+]
+  find_program(prog)
+endforeach
+
+false_ = find_program('false')
+foreach prog : [
+  'xmllint',
+  'xsltproc',
+  'flex',
+  'bison',
+]
+  find_program(prog, required: false)
+endforeach
+
+find_program('dot', required: false)
+lsof = find_program('lsof', required: false)
+
+conf_data.set_quoted('coreutils', get_option('with-coreutils-bin'))
+storedir = get_option('with-store-dir')
+
+# Special case
+pthread = dependency('threads')
+
+# Look for OpenSSL, a required dependency.
+openssl = [
+  dependency('openssl'),
+  dependency('libcrypto'),
+]
+
+# Look for libbz2, a required dependency.
+bz2 = meson.get_compiler('cpp').find_library('bz2')
+
+# Look for SQLite, a required dependency.
+sqlite3 = dependency('sqlite3', version : '>= 3.6.19')
+
+# Look for libcurl, a required dependency.
+libcurl = dependency('libcurl')
+
+# Look for editline, a required dependency.
+editline = dependency('libeditline')
+
+# Look for libsodium, an optional dependency.
+libsodium = dependency('sodium', required : false)
+if libsodium.found()
+  conf_data.set('HAVE_SODIUM', 1, description : 'Whether to use libsodium for cryptography.')
+endif
+
+# Look for libbrotli{enc,dec}.
+libbrotli = [
+  dependency('libbrotlienc'),
+  dependency('libbrotlidec'),
+]
+
+# Look for liblzma, a required dependency.
+liblzma = dependency('liblzma')
+if meson.get_compiler('cpp').has_function('lzma_stream_encoder_mt', dependencies : liblzma)
+  conf_data.set('HAVE_LSMA_MT', 1, description : 'xz multithreaded compression support')
+endif
+
+# Look for libseccomp, required for Linux sandboxing.
+want_seccomp = get_option('enable-seccomp-sandboxing')
+if want_seccomp.disabled() or (want_seccomp.auto() and host_machine.system() != 'linux')
+  seccomp = dependency('', required : false)
+else # enabled or auto on linux
+  seccomp = dependency('libseccomp')
+  if want_seccomp.enabled() and not seccomp.found()
+    error('you required `libseccomp`, but we do not have it.')
+  endif
+endif
+if seccomp.found()
+  conf_data.set('HAVE_SECCOMP', 1, description : 'Whether seccomp is available and should be used for sandboxing.')
+endif
+
+# Look for aws-cpp-sdk-s3.
+want_s3 = get_option('enable-s3')
+if want_s3.disabled()
+  enable_s3 = false
+else
+  enable_s3 = meson.get_compiler('cpp').check_header('aws/s3/S3Client.h')
+endif
+if enable_s3
+  conf_data.set('ENABLE_S3', 1, description : 'Whether to enable S3 support via aws-sdk-cpp.')
+endif
+
+if enable_s3
+  aws_version = meson.get_compiler('cpp').get_define(
+    'AWS_SDK_VERSION_STRING',
+    prefix : '#include <aws/core/VersionConfig.h>'
+  ).strip('"').split('.')
+  conf_data.set('AWS_VERSION_MAJOR', aws_version[0], description : 'Major version of aws-sdk-cpp.')
+  conf_data.set('AWS_VERSION_MINOR', aws_version[1], description : 'Minor version of aws-sdk-cpp.')
+endif
+
+# Whether to use the Boehm garbage collector.
+want_gc = get_option('enable-gc')
+if want_gc.disabled()
+  bdw_gc = false
+else
+  bdw_gc = dependency('bdw-gc', required : false)
+  if want_gc.enabled() and not bdw_gc.found()
+    error('you required garbage collection, but we do not have the library to support it.')
+  endif
+endif
+if libsodium.found()
+  conf_data.set('HAVE_BOEHMGC', 1, description : 'Whether to use the Boehm garbage collector.')
+endif
+
+# documentation generation switch
+conf_data.set('doc_generate', not get_option('disable-doc-gen'))
+
+
+foreach f : [
+  # Setuid installations.
+  'setresuid',
+  'setreuid',
+  'lchown',
+  # Nice to have, but not essential.
+  'strsignal',
+  'posix_fallocate',
+  'sysconf',
+]
+  if meson.get_compiler('cpp').has_function(f)
+    conf_data.set('HAVE_' + f.to_upper(), 1)
+  endif
+endforeach
+
+# This is needed if bzip2 is a static library, and the Nix libraries
+# are dynamic.
+if bz2.found() and host_machine.system() == 'darwin'
+  add_project_link_arguments('-all_load')
+endif
+
+# Do we have GNU tar?
+tar_script = '''
+  if @t0@ --version 2> /dev/null | grep -q GNU && tar cvf /dev/null --warning=no-timestamp ./config.log > /dev/null
+'''.format(find_program('tar').path())
+tar_flags = ''
+if run_command('sh', '-c', link_text_script).returncode() == 0
+  tar_flags += '--warning=no-timestamp'
+endif
+conf_data.set_quoted('tarFlags', tar_flags)
+
+sandbox_shell = get_option('with-sandbox-shell')
+
+#
+# Extra Configure
+#
+
+boost_context = dependency('boost', modules : ['context'])
+
+# Done by default by autoconf
+conf_data.set_quoted('PACKAGE_VERSION', meson.project_version())
+
+if enable_s3
+  aws_cpp_sdk_transfer = meson.get_compiler('cpp').find_library('aws-cpp-sdk-transfer')
+  aws_cpp_sdk_s3 = meson.get_compiler('cpp').find_library('aws-cpp-sdk-s3')
+  aws_cpp_sdk_core = meson.get_compiler('cpp').find_library('aws-cpp-sdk-core')
+else
+  aws_cpp_sdk_transfer = dependency('', required : false)
+  aws_cpp_sdk_s3 = dependency('', required : false)
+  aws_cpp_sdk_core = dependency('', required : false)
+endif
+
+#
+# original Configure.ac, but much go last
+#
+
+configure_file(
+  output : 'config.h',
+  configuration : conf_data
+)
+
+#
+# Old Makefile
+#
+
+global_subdirs = include_directories([
+  '.',
+  'src',
+  'src/libutil',
+  'src/libstore',
+  'src/libmain',
+  'src/libexpr',
+  'src/nix',
+])
+
+add_project_arguments('-g', '-Wall', '-include', 'config.h', language : 'cpp')
+
+subdir('src/libutil')
+subdir('src/libstore')
+subdir('src/libmain')
+subdir('src/libexpr')
+subdir('src/nix')
+subdir('src/resolve-system-dependencies')

meson_options.txt

@@ -0,0 +1,68 @@
+#
+# Original
+#
+
+option(
+  'with-system',
+  type : 'string',
+  description : '''
+    The identifier for the type of machine this build of Nix will try to perform builds for.
+    Typically a two-component config like that produced by `uname`.
+  ''',
+)
+option(
+  'normal-var',
+  type : 'boolean',
+  value : 'true',
+  description : 'Whether to use `/nix/var` or the user-overridable `localstatedir`.'
+)
+
+option(
+  'with-coreutils-bin',
+  type : 'string',
+  description : 'path of cat, mkdir, etc.'
+)
+
+option(
+  'with-store-dir',
+  type : 'string',
+  value : '/nix/store',
+  description : 'path of the Nix store (defaults to /nix/store)'
+)
+
+option(
+  'enable-seccomp-sandboxing',
+  type : 'feature',
+  description : '''
+    Don't build support for seccomp sandboxing (only recommended if your arch doesn't support libseccomp yet!
+  ''',
+)
+
+option(
+  'enable-gc',
+  type : 'feature',
+  description : '''
+    enable garbage collection in the Nix expression evaluator (requires Boehm GC) [default=no]
+  ''',
+)
+
+option(
+  'disable-doc-gen',
+  type : 'boolean',
+  value : false,
+  description : 'disable documentation generation',
+)
+
+option(
+  'with-sandbox-shell',
+  type : 'string',
+  description : 'path of a statically-linked shell to use as /bin/sh in sandboxes',
+)
+
+#
+# New for declarative config
+#
+
+option('have-pubsetbuf', type : 'feature')
+option('can-link-symlink', type : 'feature')
+option('enable-s3', type : 'feature')