Move classes used by scripts to their own module

Those classes are used by wrapper scripts and we should not have to
import the rest of mesonlib, build.py, and all their dependencies for
that.

This renames mesonlib/ directory to utils/ and add a mesonlib.py module
that imports everything from utils/ to not have to change `import
mesonlib` everywhere. It allows to import utils.core without importing
the rest of mesonlib.

7 files changed, 2674 insertions, 0 deletions

diff --git a/mesonbuild/utils/__init__.py b/mesonbuild/utils/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/mesonbuild/utils/__init__.py
diff --git a/mesonbuild/utils/core.py b/mesonbuild/utils/core.py
new file mode 100644
index 0000000..ed413ca
--- /dev/null
+++ b/mesonbuild/utils/core.py
@@ -0,0 +1,160 @@
+# Copyright 2012-2022 The Meson development team
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Contains the strict minimum to run scripts.
+
+When the backend needs to call back into Meson during compilation for running
+scripts or wrapping commands, it is important to load as little python modules
+as possible for performance reasons.
+"""
+
+from __future__ import annotations
+from dataclasses import dataclass
+import os
+import abc
+import typing as T
+
+if T.TYPE_CHECKING:
+    from typing_extensions import Literal
+    from ..mparser import BaseNode
+    from . import programs
+
+
+__all__ = [
+    'MesonException',
+    'MesonBugException',
+    'HoldableObject',
+    'EnvInitValueType',
+    'EnvironmentVariables',
+    'ExecutableSerialisation',
+]
+
+
+class MesonException(Exception):
+    '''Exceptions thrown by Meson'''
+
+    def __init__(self, *args: object, file: T.Optional[str] = None,
+                 lineno: T.Optional[int] = None, colno: T.Optional[int] = None):
+        super().__init__(*args)
+        self.file = file
+        self.lineno = lineno
+        self.colno = colno
+
+    @classmethod
+    def from_node(cls, *args: object, node: BaseNode) -> MesonException:
+        """Create a MesonException with location data from a BaseNode
+
+        :param node: A BaseNode to set location data from
+        :return: A Meson Exception instance
+        """
+        return cls(*args, file=node.filename, lineno=node.lineno, colno=node.colno)
+
+class MesonBugException(MesonException):
+    '''Exceptions thrown when there is a clear Meson bug that should be reported'''
+
+    def __init__(self, msg: str, file: T.Optional[str] = None,
+                 lineno: T.Optional[int] = None, colno: T.Optional[int] = None):
+        super().__init__(msg + '\n\n    This is a Meson bug and should be reported!',
+                         file=file, lineno=lineno, colno=colno)
+
+class HoldableObject(metaclass=abc.ABCMeta):
+    ''' Dummy base class for all objects that can be
+        held by an interpreter.baseobjects.ObjectHolder '''
+
+EnvInitValueType = T.Dict[str, T.Union[str, T.List[str]]]
+
+class EnvironmentVariables(HoldableObject):
+    def __init__(self, values: T.Optional[EnvInitValueType] = None,
+                 init_method: Literal['set', 'prepend', 'append'] = 'set', separator: str = os.pathsep) -> None:
+        self.envvars: T.List[T.Tuple[T.Callable[[T.Dict[str, str], str, T.List[str], str], str], str, T.List[str], str]] = []
+        # The set of all env vars we have operations for. Only used for self.has_name()
+        self.varnames: T.Set[str] = set()
+
+        if values:
+            init_func = getattr(self, init_method)
+            for name, value in values.items():
+                v = value if isinstance(value, list) else [value]
+                init_func(name, v, separator)
+
+    def __repr__(self) -> str:
+        repr_str = "<{0}: {1}>"
+        return repr_str.format(self.__class__.__name__, self.envvars)
+
+    def hash(self, hasher: T.Any):
+        myenv = self.get_env({})
+        for key in sorted(myenv.keys()):
+            hasher.update(bytes(key, encoding='utf-8'))
+            hasher.update(b',')
+            hasher.update(bytes(myenv[key], encoding='utf-8'))
+            hasher.update(b';')
+
+    def has_name(self, name: str) -> bool:
+        return name in self.varnames
+
+    def get_names(self) -> T.Set[str]:
+        return self.varnames
+
+    def set(self, name: str, values: T.List[str], separator: str = os.pathsep) -> None:
+        self.varnames.add(name)
+        self.envvars.append((self._set, name, values, separator))
+
+    def append(self, name: str, values: T.List[str], separator: str = os.pathsep) -> None:
+        self.varnames.add(name)
+        self.envvars.append((self._append, name, values, separator))
+
+    def prepend(self, name: str, values: T.List[str], separator: str = os.pathsep) -> None:
+        self.varnames.add(name)
+        self.envvars.append((self._prepend, name, values, separator))
+
+    @staticmethod
+    def _set(env: T.Dict[str, str], name: str, values: T.List[str], separator: str) -> str:
+        return separator.join(values)
+
+    @staticmethod
+    def _append(env: T.Dict[str, str], name: str, values: T.List[str], separator: str) -> str:
+        curr = env.get(name)
+        return separator.join(values if curr is None else [curr] + values)
+
+    @staticmethod
+    def _prepend(env: T.Dict[str, str], name: str, values: T.List[str], separator: str) -> str:
+        curr = env.get(name)
+        return separator.join(values if curr is None else values + [curr])
+
+    def get_env(self, full_env: T.MutableMapping[str, str]) -> T.Dict[str, str]:
+        env = full_env.copy()
+        for method, name, values, separator in self.envvars:
+            env[name] = method(env, name, values, separator)
+        return env
+
+
+@dataclass(eq=False)
+class ExecutableSerialisation:
+
+    # XXX: should capture and feed default to False, instead of None?
+
+    cmd_args: T.List[str]
+    env: T.Optional[EnvironmentVariables] = None
+    exe_wrapper: T.Optional['programs.ExternalProgram'] = None
+    workdir: T.Optional[str] = None
+    extra_paths: T.Optional[T.List] = None
+    capture: T.Optional[bool] = None
+    feed: T.Optional[bool] = None
+    tag: T.Optional[str] = None
+    verbose: bool = False
+
+    def __post_init__(self) -> None:
+        self.pickled = False
+        self.skip_if_destdir = False
+        self.subproject = ''
diff --git a/mesonbuild/utils/platform.py b/mesonbuild/utils/platform.py
new file mode 100644
index 0000000..f0676a6
--- /dev/null
+++ b/mesonbuild/utils/platform.py
@@ -0,0 +1,37 @@
+# SPDX-license-identifier: Apache-2.0
+# Copyright 2012-2021 The Meson development team
+# Copyright © 2021 Intel Corporation
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""base classes providing no-op functionality.."""
+
+import os
+import typing as T
+
+from .. import mlog
+
+__all__ = ['BuildDirLock']
+
+# This needs to be inherited by the specific implementations to make type
+# checking happy
+class BuildDirLock:
+
+    def __init__(self, builddir: str) -> None:
+        self.lockfilename = os.path.join(builddir, 'meson-private/meson.lock')
+
+    def __enter__(self) -> None:
+        mlog.debug('Calling the no-op version of BuildDirLock')
+
+    def __exit__(self, *args: T.Any) -> None:
+        pass
diff --git a/mesonbuild/utils/posix.py b/mesonbuild/utils/posix.py
new file mode 100644
index 0000000..67f9a44
--- /dev/null
+++ b/mesonbuild/utils/posix.py
@@ -0,0 +1,39 @@
+# SPDX-license-identifier: Apache-2.0
+# Copyright 2012-2021 The Meson development team
+# Copyright © 2021 Intel Corporation
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Posix specific implementations of mesonlib functionality."""
+
+import fcntl
+import typing as T
+
+from .universal import MesonException
+from .platform import BuildDirLock as BuildDirLockBase
+
+__all__ = ['BuildDirLock']
+
+class BuildDirLock(BuildDirLockBase):
+
+    def __enter__(self) -> None:
+        self.lockfile = open(self.lockfilename, 'w', encoding='utf-8')
+        try:
+            fcntl.flock(self.lockfile, fcntl.LOCK_EX | fcntl.LOCK_NB)
+        except (BlockingIOError, PermissionError):
+            self.lockfile.close()
+            raise MesonException('Some other Meson process is already using this build directory. Exiting.')
+
+    def __exit__(self, *args: T.Any) -> None:
+        fcntl.flock(self.lockfile, fcntl.LOCK_UN)
+        self.lockfile.close()
diff --git a/mesonbuild/utils/universal.py b/mesonbuild/utils/universal.py
new file mode 100644
index 0000000..aaefbc5
--- /dev/null
+++ b/mesonbuild/utils/universal.py
@@ -0,0 +1,2279 @@
+# Copyright 2012-2020 The Meson development team
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""A library of random helper functionality."""
+
+from __future__ import annotations
+from pathlib import Path
+import argparse
+import enum
+import sys
+import stat
+import time
+import abc
+import platform, subprocess, operator, os, shlex, shutil, re
+import collections
+from functools import lru_cache, wraps, total_ordering
+from itertools import tee, filterfalse
+from tempfile import TemporaryDirectory, NamedTemporaryFile
+import typing as T
+import textwrap
+import copy
+import pickle
+
+from mesonbuild import mlog
+from .core import MesonException, HoldableObject
+
+if T.TYPE_CHECKING:
+    from typing_extensions import Literal
+
+    from .._typing import ImmutableListProtocol
+    from ..build import ConfigurationData
+    from ..coredata import KeyedOptionDictType, UserOption
+    from ..compilers.compilers import Compiler
+
+FileOrString = T.Union['File', str]
+
+_T = T.TypeVar('_T')
+_U = T.TypeVar('_U')
+
+__all__ = [
+    'GIT',
+    'python_command',
+    'project_meson_versions',
+    'SecondLevelHolder',
+    'File',
+    'FileMode',
+    'GitException',
+    'LibType',
+    'MachineChoice',
+    'EnvironmentException',
+    'FileOrString',
+    'GitException',
+    'OptionKey',
+    'dump_conf_header',
+    'OptionOverrideProxy',
+    'OptionType',
+    'OrderedSet',
+    'PerMachine',
+    'PerMachineDefaultable',
+    'PerThreeMachine',
+    'PerThreeMachineDefaultable',
+    'ProgressBar',
+    'RealPathAction',
+    'TemporaryDirectoryWinProof',
+    'Version',
+    'check_direntry_issues',
+    'classify_unity_sources',
+    'current_vs_supports_modules',
+    'darwin_get_object_archs',
+    'default_libdir',
+    'default_libexecdir',
+    'default_prefix',
+    'detect_subprojects',
+    'detect_vcs',
+    'do_conf_file',
+    'do_conf_str',
+    'do_replacement',
+    'exe_exists',
+    'expand_arguments',
+    'extract_as_list',
+    'first',
+    'generate_list',
+    'get_compiler_for_source',
+    'get_filenames_templates_dict',
+    'get_library_dirs',
+    'get_variable_regex',
+    'get_wine_shortpath',
+    'git',
+    'has_path_sep',
+    'is_aix',
+    'is_android',
+    'is_ascii_string',
+    'is_cygwin',
+    'is_debianlike',
+    'is_dragonflybsd',
+    'is_freebsd',
+    'is_haiku',
+    'is_hurd',
+    'is_irix',
+    'is_linux',
+    'is_netbsd',
+    'is_openbsd',
+    'is_osx',
+    'is_qnx',
+    'is_sunos',
+    'is_windows',
+    'is_wsl',
+    'iter_regexin_iter',
+    'join_args',
+    'listify',
+    'partition',
+    'path_is_in_root',
+    'pickle_load',
+    'Popen_safe',
+    'quiet_git',
+    'quote_arg',
+    'relative_to_if_possible',
+    'relpath',
+    'replace_if_different',
+    'run_once',
+    'get_meson_command',
+    'set_meson_command',
+    'split_args',
+    'stringlistify',
+    'substitute_values',
+    'substring_is_in_list',
+    'typeslistify',
+    'verbose_git',
+    'version_compare',
+    'version_compare_condition_with_min',
+    'version_compare_many',
+    'search_version',
+    'windows_proof_rm',
+    'windows_proof_rmtree',
+]
+
+
+# TODO: this is such a hack, this really should be either in coredata or in the
+# interpreter
+# {subproject: project_meson_version}
+project_meson_versions = collections.defaultdict(str)  # type: T.DefaultDict[str, str]
+
+
+from glob import glob
+
+if os.path.basename(sys.executable) == 'meson.exe':
+    # In Windows and using the MSI installed executable.
+    python_command = [sys.executable, 'runpython']
+else:
+    python_command = [sys.executable]
+_meson_command: T.Optional['ImmutableListProtocol[str]'] = None
+
+
+class EnvironmentException(MesonException):
+    '''Exceptions thrown while processing and creating the build environment'''
+
+class GitException(MesonException):
+    def __init__(self, msg: str, output: T.Optional[str] = None):
+        super().__init__(msg)
+        self.output = output.strip() if output else ''
+
+GIT = shutil.which('git')
+def git(cmd: T.List[str], workingdir: T.Union[str, bytes, os.PathLike], check: bool = False, **kwargs: T.Any) -> T.Tuple[subprocess.Popen, str, str]:
+    cmd = [GIT] + cmd
+    p, o, e = Popen_safe(cmd, cwd=workingdir, **kwargs)
+    if check and p.returncode != 0:
+        raise GitException('Git command failed: ' + str(cmd), e)
+    return p, o, e
+
+def quiet_git(cmd: T.List[str], workingdir: T.Union[str, bytes, os.PathLike], check: bool = False) -> T.Tuple[bool, str]:
+    if not GIT:
+        m = 'Git program not found.'
+        if check:
+            raise GitException(m)
+        return False, m
+    p, o, e = git(cmd, workingdir, check)
+    if p.returncode != 0:
+        return False, e
+    return True, o
+
+def verbose_git(cmd: T.List[str], workingdir: T.Union[str, bytes, os.PathLike], check: bool = False) -> bool:
+    if not GIT:
+        m = 'Git program not found.'
+        if check:
+            raise GitException(m)
+        return False
+    p, _, _ = git(cmd, workingdir, check, stdout=None, stderr=None)
+    return p.returncode == 0
+
+def set_meson_command(mainfile: str) -> None:
+    global _meson_command  # pylint: disable=global-statement
+    # On UNIX-like systems `meson` is a Python script
+    # On Windows `meson` and `meson.exe` are wrapper exes
+    if not mainfile.endswith('.py'):
+        _meson_command = [mainfile]
+    elif os.path.isabs(mainfile) and mainfile.endswith('mesonmain.py'):
+        # Can't actually run meson with an absolute path to mesonmain.py, it must be run as -m mesonbuild.mesonmain
+        _meson_command = python_command + ['-m', 'mesonbuild.mesonmain']
+    else:
+        # Either run uninstalled, or full path to meson-script.py
+        _meson_command = python_command + [mainfile]
+    # We print this value for unit tests.
+    if 'MESON_COMMAND_TESTS' in os.environ:
+        mlog.log(f'meson_command is {_meson_command!r}')
+
+
+def get_meson_command() -> T.Optional['ImmutableListProtocol[str]']:
+    return _meson_command
+
+
+def is_ascii_string(astring: T.Union[str, bytes]) -> bool:
+    try:
+        if isinstance(astring, str):
+            astring.encode('ascii')
+        elif isinstance(astring, bytes):
+            astring.decode('ascii')
+    except UnicodeDecodeError:
+        return False
+    return True
+
+
+def check_direntry_issues(direntry_array: T.Union[T.Iterable[T.Union[str, bytes]], str, bytes]) -> None:
+    import locale
+    # Warn if the locale is not UTF-8. This can cause various unfixable issues
+    # such as os.stat not being able to decode filenames with unicode in them.
+    # There is no way to reset both the preferred encoding and the filesystem
+    # encoding, so we can just warn about it.
+    e = locale.getpreferredencoding()
+    if e.upper() != 'UTF-8' and not is_windows():
+        if isinstance(direntry_array, (str, bytes)):
+            direntry_array = [direntry_array]
+        for de in direntry_array:
+            if is_ascii_string(de):
+                continue
+            mlog.warning(textwrap.dedent(f'''
+                You are using {e!r} which is not a Unicode-compatible
+                locale but you are trying to access a file system entry called {de!r} which is
+                not pure ASCII. This may cause problems.
+                '''), file=sys.stderr)
+
+class SecondLevelHolder(HoldableObject, metaclass=abc.ABCMeta):
+    ''' A second level object holder. The primary purpose
+        of such objects is to hold multiple objects with one
+        default option. '''
+
+    @abc.abstractmethod
+    def get_default_object(self) -> HoldableObject: ...
+
+class FileMode:
+    # The first triad is for owner permissions, the second for group permissions,
+    # and the third for others (everyone else).
+    # For the 1st character:
+    #  'r' means can read
+    #  '-' means not allowed
+    # For the 2nd character:
+    #  'w' means can write
+    #  '-' means not allowed
+    # For the 3rd character:
+    #  'x' means can execute
+    #  's' means can execute and setuid/setgid is set (owner/group triads only)
+    #  'S' means cannot execute and setuid/setgid is set (owner/group triads only)
+    #  't' means can execute and sticky bit is set ("others" triads only)
+    #  'T' means cannot execute and sticky bit is set ("others" triads only)
+    #  '-' means none of these are allowed
+    #
+    # The meanings of 'rwx' perms is not obvious for directories; see:
+    # https://www.hackinglinuxexposed.com/articles/20030424.html
+    #
+    # For information on this notation such as setuid/setgid/sticky bits, see:
+    # https://en.wikipedia.org/wiki/File_system_permissions#Symbolic_notation
+    symbolic_perms_regex = re.compile('[r-][w-][xsS-]' # Owner perms
+                                      '[r-][w-][xsS-]' # Group perms
+                                      '[r-][w-][xtT-]') # Others perms
+
+    def __init__(self, perms: T.Optional[str] = None, owner: T.Union[str, int, None] = None,
+                 group: T.Union[str, int, None] = None):
+        self.perms_s = perms
+        self.perms = self.perms_s_to_bits(perms)
+        self.owner = owner
+        self.group = group
+
+    def __repr__(self) -> str:
+        ret = '<FileMode: {!r} owner={} group={}'
+        return ret.format(self.perms_s, self.owner, self.group)
+
+    @classmethod
+    def perms_s_to_bits(cls, perms_s: T.Optional[str]) -> int:
+        '''
+        Does the opposite of stat.filemode(), converts strings of the form
+        'rwxr-xr-x' to st_mode enums which can be passed to os.chmod()
+        '''
+        if perms_s is None:
+            # No perms specified, we will not touch the permissions
+            return -1
+        eg = 'rwxr-xr-x'
+        if not isinstance(perms_s, str):
+            raise MesonException(f'Install perms must be a string. For example, {eg!r}')
+        if len(perms_s) != 9 or not cls.symbolic_perms_regex.match(perms_s):
+            raise MesonException(f'File perms {perms_s!r} must be exactly 9 chars. For example, {eg!r}')
+        perms = 0
+        # Owner perms
+        if perms_s[0] == 'r':
+            perms |= stat.S_IRUSR
+        if perms_s[1] == 'w':
+            perms |= stat.S_IWUSR
+        if perms_s[2] == 'x':
+            perms |= stat.S_IXUSR
+        elif perms_s[2] == 'S':
+            perms |= stat.S_ISUID
+        elif perms_s[2] == 's':
+            perms |= stat.S_IXUSR
+            perms |= stat.S_ISUID
+        # Group perms
+        if perms_s[3] == 'r':
+            perms |= stat.S_IRGRP
+        if perms_s[4] == 'w':
+            perms |= stat.S_IWGRP
+        if perms_s[5] == 'x':
+            perms |= stat.S_IXGRP
+        elif perms_s[5] == 'S':
+            perms |= stat.S_ISGID
+        elif perms_s[5] == 's':
+            perms |= stat.S_IXGRP
+            perms |= stat.S_ISGID
+        # Others perms
+        if perms_s[6] == 'r':
+            perms |= stat.S_IROTH
+        if perms_s[7] == 'w':
+            perms |= stat.S_IWOTH
+        if perms_s[8] == 'x':
+            perms |= stat.S_IXOTH
+        elif perms_s[8] == 'T':
+            perms |= stat.S_ISVTX
+        elif perms_s[8] == 't':
+            perms |= stat.S_IXOTH
+            perms |= stat.S_ISVTX
+        return perms
+
+dot_C_dot_H_warning = """You are using .C or .H files in your project. This is deprecated.
+         Currently, Meson treats this as C++ code, but they
+            used to be treated as C code.
+         Note that the situation is a bit more complex if you are using the
+         Visual Studio compiler, as it treats .C files as C code, unless you add
+         the /TP compiler flag, but this is unreliable.
+         See https://github.com/mesonbuild/meson/pull/8747 for the discussions."""
+class File(HoldableObject):
+    def __init__(self, is_built: bool, subdir: str, fname: str):
+        if fname.endswith(".C") or fname.endswith(".H"):
+            mlog.warning(dot_C_dot_H_warning, once=True)
+        self.is_built = is_built
+        self.subdir = subdir
+        self.fname = fname
+        self.hash = hash((is_built, subdir, fname))
+
+    def __str__(self) -> str:
+        return self.relative_name()
+
+    def __repr__(self) -> str:
+        ret = '<File: {0}'
+        if not self.is_built:
+            ret += ' (not built)'
+        ret += '>'
+        return ret.format(self.relative_name())
+
+    @staticmethod
+    @lru_cache(maxsize=None)
+    def from_source_file(source_root: str, subdir: str, fname: str) -> 'File':
+        if not os.path.isfile(os.path.join(source_root, subdir, fname)):
+            raise MesonException(f'File {fname} does not exist.')
+        return File(False, subdir, fname)
+
+    @staticmethod
+    def from_built_file(subdir: str, fname: str) -> 'File':
+        return File(True, subdir, fname)
+
+    @staticmethod
+    def from_built_relative(relative: str) -> 'File':
+        dirpart, fnamepart = os.path.split(relative)
+        return File(True, dirpart, fnamepart)
+
+    @staticmethod
+    def from_absolute_file(fname: str) -> 'File':
+        return File(False, '', fname)
+
+    @lru_cache(maxsize=None)
+    def rel_to_builddir(self, build_to_src: str) -> str:
+        if self.is_built:
+            return self.relative_name()
+        else:
+            return os.path.join(build_to_src, self.subdir, self.fname)
+
+    @lru_cache(maxsize=None)
+    def absolute_path(self, srcdir: str, builddir: str) -> str:
+        absdir = srcdir
+        if self.is_built:
+            absdir = builddir
+        return os.path.join(absdir, self.relative_name())
+
+    @property
+    def suffix(self) -> str:
+        return os.path.splitext(self.fname)[1][1:].lower()
+
+    def endswith(self, ending: T.Union[str, T.Tuple[str, ...]]) -> bool:
+        return self.fname.endswith(ending)
+
+    def split(self, s: str, maxsplit: int = -1) -> T.List[str]:
+        return self.fname.split(s, maxsplit=maxsplit)
+
+    def rsplit(self, s: str, maxsplit: int = -1) -> T.List[str]:
+        return self.fname.rsplit(s, maxsplit=maxsplit)
+
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, File):
+            return NotImplemented
+        if self.hash != other.hash:
+            return False
+        return (self.fname, self.subdir, self.is_built) == (other.fname, other.subdir, other.is_built)
+
+    def __hash__(self) -> int:
+        return self.hash
+
+    @lru_cache(maxsize=None)
+    def relative_name(self) -> str:
+        return os.path.join(self.subdir, self.fname)
+
+
+def get_compiler_for_source(compilers: T.Iterable['Compiler'], src: 'FileOrString') -> 'Compiler':
+    """Given a set of compilers and a source, find the compiler for that source type."""
+    for comp in compilers:
+        if comp.can_compile(src):
+            return comp
+    raise MesonException(f'No specified compiler can handle file {src!s}')
+
+
+def classify_unity_sources(compilers: T.Iterable['Compiler'], sources: T.Sequence['FileOrString']) -> T.Dict['Compiler', T.List['FileOrString']]:
+    compsrclist: T.Dict['Compiler', T.List['FileOrString']] = {}
+    for src in sources:
+        comp = get_compiler_for_source(compilers, src)
+        if comp not in compsrclist:
+            compsrclist[comp] = [src]
+        else:
+            compsrclist[comp].append(src)
+    return compsrclist
+
+
+class MachineChoice(enum.IntEnum):
+
+    """Enum class representing one of the two abstract machine names used in
+    most places: the build, and host, machines.
+    """
+
+    BUILD = 0
+    HOST = 1
+
+    def get_lower_case_name(self) -> str:
+        return PerMachine('build', 'host')[self]
+
+    def get_prefix(self) -> str:
+        return PerMachine('build.', '')[self]
+
+
+class PerMachine(T.Generic[_T]):
+    def __init__(self, build: _T, host: _T) -> None:
+        self.build = build
+        self.host = host
+
+    def __getitem__(self, machine: MachineChoice) -> _T:
+        return {
+            MachineChoice.BUILD:  self.build,
+            MachineChoice.HOST:   self.host,
+        }[machine]
+
+    def __setitem__(self, machine: MachineChoice, val: _T) -> None:
+        setattr(self, machine.get_lower_case_name(), val)
+
+    def miss_defaulting(self) -> "PerMachineDefaultable[T.Optional[_T]]":
+        """Unset definition duplicated from their previous to None
+
+        This is the inverse of ''default_missing''. By removing defaulted
+        machines, we can elaborate the original and then redefault them and thus
+        avoid repeating the elaboration explicitly.
+        """
+        unfreeze = PerMachineDefaultable() # type: PerMachineDefaultable[T.Optional[_T]]
+        unfreeze.build = self.build
+        unfreeze.host = self.host
+        if unfreeze.host == unfreeze.build:
+            unfreeze.host = None
+        return unfreeze
+
+    def __repr__(self) -> str:
+        return f'PerMachine({self.build!r}, {self.host!r})'
+
+
+class PerThreeMachine(PerMachine[_T]):
+    """Like `PerMachine` but includes `target` too.
+
+    It turns out just one thing do we need track the target machine. There's no
+    need to computer the `target` field so we don't bother overriding the
+    `__getitem__`/`__setitem__` methods.
+    """
+    def __init__(self, build: _T, host: _T, target: _T) -> None:
+        super().__init__(build, host)
+        self.target = target
+
+    def miss_defaulting(self) -> "PerThreeMachineDefaultable[T.Optional[_T]]":
+        """Unset definition duplicated from their previous to None
+
+        This is the inverse of ''default_missing''. By removing defaulted
+        machines, we can elaborate the original and then redefault them and thus
+        avoid repeating the elaboration explicitly.
+        """
+        unfreeze = PerThreeMachineDefaultable() # type: PerThreeMachineDefaultable[T.Optional[_T]]
+        unfreeze.build = self.build
+        unfreeze.host = self.host
+        unfreeze.target = self.target
+        if unfreeze.target == unfreeze.host:
+            unfreeze.target = None
+        if unfreeze.host == unfreeze.build:
+            unfreeze.host = None
+        return unfreeze
+
+    def matches_build_machine(self, machine: MachineChoice) -> bool:
+        return self.build == self[machine]
+
+    def __repr__(self) -> str:
+        return f'PerThreeMachine({self.build!r}, {self.host!r}, {self.target!r})'
+
+
+class PerMachineDefaultable(PerMachine[T.Optional[_T]]):
+    """Extends `PerMachine` with the ability to default from `None`s.
+    """
+    def __init__(self, build: T.Optional[_T] = None, host: T.Optional[_T] = None) -> None:
+        super().__init__(build, host)
+
+    def default_missing(self) -> "PerMachine[_T]":
+        """Default host to build
+
+        This allows just specifying nothing in the native case, and just host in the
+        cross non-compiler case.
+        """
+        freeze = PerMachine(self.build, self.host)
+        if freeze.host is None:
+            freeze.host = freeze.build
+        return freeze
+
+    def __repr__(self) -> str:
+        return f'PerMachineDefaultable({self.build!r}, {self.host!r})'
+
+    @classmethod
+    def default(cls, is_cross: bool, build: _T, host: _T) -> PerMachine[_T]:
+        """Easy way to get a defaulted value
+
+        This allows simplifying the case where you can control whether host and
+        build are separate or not with a boolean. If the is_cross value is set
+        to true then the optional host value will be used, otherwise the host
+        will be set to the build value.
+        """
+        m = cls(build)
+        if is_cross:
+            m.host = host
+        return m.default_missing()
+
+
+class PerThreeMachineDefaultable(PerMachineDefaultable, PerThreeMachine[T.Optional[_T]]):
+    """Extends `PerThreeMachine` with the ability to default from `None`s.
+    """
+    def __init__(self) -> None:
+        PerThreeMachine.__init__(self, None, None, None)
+
+    def default_missing(self) -> "PerThreeMachine[T.Optional[_T]]":
+        """Default host to build and target to host.
+
+        This allows just specifying nothing in the native case, just host in the
+        cross non-compiler case, and just target in the native-built
+        cross-compiler case.
+        """
+        freeze = PerThreeMachine(self.build, self.host, self.target)
+        if freeze.host is None:
+            freeze.host = freeze.build
+        if freeze.target is None:
+            freeze.target = freeze.host
+        return freeze
+
+    def __repr__(self) -> str:
+        return f'PerThreeMachineDefaultable({self.build!r}, {self.host!r}, {self.target!r})'
+
+
+def is_sunos() -> bool:
+    return platform.system().lower() == 'sunos'
+
+
+def is_osx() -> bool:
+    return platform.system().lower() == 'darwin'
+
+
+def is_linux() -> bool:
+    return platform.system().lower() == 'linux'
+
+
+def is_android() -> bool:
+    return platform.system().lower() == 'android'
+
+
+def is_haiku() -> bool:
+    return platform.system().lower() == 'haiku'
+
+
+def is_openbsd() -> bool:
+    return platform.system().lower() == 'openbsd'
+
+
+def is_windows() -> bool:
+    platname = platform.system().lower()
+    return platname == 'windows'
+
+def is_wsl() -> bool:
+    return is_linux() and 'microsoft' in platform.release().lower()
+
+def is_cygwin() -> bool:
+    return sys.platform == 'cygwin'
+
+
+def is_debianlike() -> bool:
+    return os.path.isfile('/etc/debian_version')
+
+
+def is_dragonflybsd() -> bool:
+    return platform.system().lower() == 'dragonfly'
+
+
+def is_netbsd() -> bool:
+    return platform.system().lower() == 'netbsd'
+
+
+def is_freebsd() -> bool:
+    return platform.system().lower() == 'freebsd'
+
+def is_irix() -> bool:
+    return platform.system().startswith('irix')
+
+def is_hurd() -> bool:
+    return platform.system().lower() == 'gnu'
+
+def is_qnx() -> bool:
+    return platform.system().lower() == 'qnx'
+
+def is_aix() -> bool:
+    return platform.system().lower() == 'aix'
+
+def exe_exists(arglist: T.List[str]) -> bool:
+    try:
+        if subprocess.run(arglist, timeout=10).returncode == 0:
+            return True
+    except (FileNotFoundError, subprocess.TimeoutExpired):
+        pass
+    return False
+
+
+@lru_cache(maxsize=None)
+def darwin_get_object_archs(objpath: str) -> 'ImmutableListProtocol[str]':
+    '''
+    For a specific object (executable, static library, dylib, etc), run `lipo`
+    to fetch the list of archs supported by it. Supports both thin objects and
+    'fat' objects.
+    '''
+    _, stdo, stderr = Popen_safe(['lipo', '-info', objpath])
+    if not stdo:
+        mlog.debug(f'lipo {objpath}: {stderr}')
+        return None
+    stdo = stdo.rsplit(': ', 1)[1]
+    # Convert from lipo-style archs to meson-style CPUs
+    stdo = stdo.replace('i386', 'x86')
+    stdo = stdo.replace('arm64', 'aarch64')
+    stdo = stdo.replace('ppc7400', 'ppc')
+    stdo = stdo.replace('ppc970', 'ppc')
+    # Add generic name for armv7 and armv7s
+    if 'armv7' in stdo:
+        stdo += ' arm'
+    return stdo.split()
+
+
+def detect_vcs(source_dir: T.Union[str, Path]) -> T.Optional[T.Dict[str, str]]:
+    vcs_systems = [
+        dict(name = 'git',        cmd = 'git', repo_dir = '.git', get_rev = 'git describe --dirty=+', rev_regex = '(.*)', dep = '.git/logs/HEAD'),
+        dict(name = 'mercurial',  cmd = 'hg',  repo_dir = '.hg',  get_rev = 'hg id -i',               rev_regex = '(.*)', dep = '.hg/dirstate'),
+        dict(name = 'subversion', cmd = 'svn', repo_dir = '.svn', get_rev = 'svn info',               rev_regex = 'Revision: (.*)', dep = '.svn/wc.db'),
+        dict(name = 'bazaar',     cmd = 'bzr', repo_dir = '.bzr', get_rev = 'bzr revno',              rev_regex = '(.*)', dep = '.bzr'),
+    ]
+    if isinstance(source_dir, str):
+        source_dir = Path(source_dir)
+
+    parent_paths_and_self = collections.deque(source_dir.parents)
+    # Prepend the source directory to the front so we can check it;
+    # source_dir.parents doesn't include source_dir
+    parent_paths_and_self.appendleft(source_dir)
+    for curdir in parent_paths_and_self:
+        for vcs in vcs_systems:
+            if Path.is_dir(curdir.joinpath(vcs['repo_dir'])) and shutil.which(vcs['cmd']):
+                vcs['wc_dir'] = str(curdir)
+                return vcs
+    return None
+
+def current_vs_supports_modules() -> bool:
+    vsver = os.environ.get('VSCMD_VER', '')
+    nums = vsver.split('.', 2)
+    major = int(nums[0])
+    if major >= 17:
+        return True
+    if major == 16 and int(nums[1]) >= 10:
+        return True
+    return vsver.startswith('16.9.0') and '-pre.' in vsver
+
+# a helper class which implements the same version ordering as RPM
+class Version:
+    def __init__(self, s: str) -> None:
+        self._s = s
+
+        # split into numeric, alphabetic and non-alphanumeric sequences
+        sequences1 = re.finditer(r'(\d+|[a-zA-Z]+|[^a-zA-Z\d]+)', s)
+
+        # non-alphanumeric separators are discarded
+        sequences2 = [m for m in sequences1 if not re.match(r'[^a-zA-Z\d]+', m.group(1))]
+
+        # numeric sequences are converted from strings to ints
+        sequences3 = [int(m.group(1)) if m.group(1).isdigit() else m.group(1) for m in sequences2]
+
+        self._v = sequences3
+
+    def __str__(self) -> str:
+        return '{} (V={})'.format(self._s, str(self._v))
+
+    def __repr__(self) -> str:
+        return f'<Version: {self._s}>'
+
+    def __lt__(self, other: object) -> bool:
+        if isinstance(other, Version):
+            return self.__cmp(other, operator.lt)
+        return NotImplemented
+
+    def __gt__(self, other: object) -> bool:
+        if isinstance(other, Version):
+            return self.__cmp(other, operator.gt)
+        return NotImplemented
+
+    def __le__(self, other: object) -> bool:
+        if isinstance(other, Version):
+            return self.__cmp(other, operator.le)
+        return NotImplemented
+
+    def __ge__(self, other: object) -> bool:
+        if isinstance(other, Version):
+            return self.__cmp(other, operator.ge)
+        return NotImplemented
+
+    def __eq__(self, other: object) -> bool:
+        if isinstance(other, Version):
+            return self._v == other._v
+        return NotImplemented
+
+    def __ne__(self, other: object) -> bool:
+        if isinstance(other, Version):
+            return self._v != other._v
+        return NotImplemented
+
+    def __cmp(self, other: 'Version', comparator: T.Callable[[T.Any, T.Any], bool]) -> bool:
+        # compare each sequence in order
+        for ours, theirs in zip(self._v, other._v):
+            # sort a non-digit sequence before a digit sequence
+            ours_is_int = isinstance(ours, int)
+            theirs_is_int = isinstance(theirs, int)
+            if ours_is_int != theirs_is_int:
+                return comparator(ours_is_int, theirs_is_int)
+
+            if ours != theirs:
+                return comparator(ours, theirs)
+
+        # if equal length, all components have matched, so equal
+        # otherwise, the version with a suffix remaining is greater
+        return comparator(len(self._v), len(other._v))
+
+
+def _version_extract_cmpop(vstr2: str) -> T.Tuple[T.Callable[[T.Any, T.Any], bool], str]:
+    if vstr2.startswith('>='):
+        cmpop = operator.ge
+        vstr2 = vstr2[2:]
+    elif vstr2.startswith('<='):
+        cmpop = operator.le
+        vstr2 = vstr2[2:]
+    elif vstr2.startswith('!='):
+        cmpop = operator.ne
+        vstr2 = vstr2[2:]
+    elif vstr2.startswith('=='):
+        cmpop = operator.eq
+        vstr2 = vstr2[2:]
+    elif vstr2.startswith('='):
+        cmpop = operator.eq
+        vstr2 = vstr2[1:]
+    elif vstr2.startswith('>'):
+        cmpop = operator.gt
+        vstr2 = vstr2[1:]
+    elif vstr2.startswith('<'):
+        cmpop = operator.lt
+        vstr2 = vstr2[1:]
+    else:
+        cmpop = operator.eq
+
+    return (cmpop, vstr2)
+
+
+def version_compare(vstr1: str, vstr2: str) -> bool:
+    (cmpop, vstr2) = _version_extract_cmpop(vstr2)
+    return cmpop(Version(vstr1), Version(vstr2))
+
+
+def version_compare_many(vstr1: str, conditions: T.Union[str, T.Iterable[str]]) -> T.Tuple[bool, T.List[str], T.List[str]]:
+    if isinstance(conditions, str):
+        conditions = [conditions]
+    found = []
+    not_found = []
+    for req in conditions:
+        if not version_compare(vstr1, req):
+            not_found.append(req)
+        else:
+            found.append(req)
+    return not_found == [], not_found, found
+
+
+# determine if the minimum version satisfying the condition |condition| exceeds
+# the minimum version for a feature |minimum|
+def version_compare_condition_with_min(condition: str, minimum: str) -> bool:
+    if condition.startswith('>='):
+        cmpop = operator.le
+        condition = condition[2:]
+    elif condition.startswith('<='):
+        return False
+    elif condition.startswith('!='):
+        return False
+    elif condition.startswith('=='):
+        cmpop = operator.le
+        condition = condition[2:]
+    elif condition.startswith('='):
+        cmpop = operator.le
+        condition = condition[1:]
+    elif condition.startswith('>'):
+        cmpop = operator.lt
+        condition = condition[1:]
+    elif condition.startswith('<'):
+        return False
+    else:
+        cmpop = operator.le
+
+    # Declaring a project(meson_version: '>=0.46') and then using features in
+    # 0.46.0 is valid, because (knowing the meson versioning scheme) '0.46.0' is
+    # the lowest version which satisfies the constraint '>=0.46'.
+    #
+    # But this will fail here, because the minimum version required by the
+    # version constraint ('0.46') is strictly less (in our version comparison)
+    # than the minimum version needed for the feature ('0.46.0').
+    #
+    # Map versions in the constraint of the form '0.46' to '0.46.0', to embed
+    # this knowledge of the meson versioning scheme.
+    condition = condition.strip()
+    if re.match(r'^\d+.\d+$', condition):
+        condition += '.0'
+
+    return T.cast('bool', cmpop(Version(minimum), Version(condition)))
+
+def search_version(text: str) -> str:
+    # Usually of the type 4.1.4 but compiler output may contain
+    # stuff like this:
+    # (Sourcery CodeBench Lite 2014.05-29) 4.8.3 20140320 (prerelease)
+    # Limiting major version number to two digits seems to work
+    # thus far. When we get to GCC 100, this will break, but
+    # if we are still relevant when that happens, it can be
+    # considered an achievement in itself.
+    #
+    # This regex is reaching magic levels. If it ever needs
+    # to be updated, do not complexify but convert to something
+    # saner instead.
+    # We'll demystify it a bit with a verbose definition.
+    version_regex = re.compile(r"""
+    (?<!                # Zero-width negative lookbehind assertion
+        (
+            \d          # One digit
+            | \.        # Or one period
+        )               # One occurrence
+    )
+    # Following pattern must not follow a digit or period
+    (
+        \d{1,2}         # One or two digits
+        (
+            \.\d+       # Period and one or more digits
+        )+              # One or more occurrences
+        (
+            -[a-zA-Z0-9]+   # Hyphen and one or more alphanumeric
+        )?              # Zero or one occurrence
+    )                   # One occurrence
+    """, re.VERBOSE)
+    match = version_regex.search(text)
+    if match:
+        return match.group(0)
+
+    # try a simpler regex that has like "blah 2020.01.100 foo" or "blah 2020.01 foo"
+    version_regex = re.compile(r"(\d{1,4}\.\d{1,4}\.?\d{0,4})")
+    match = version_regex.search(text)
+    if match:
+        return match.group(0)
+
+    return 'unknown version'
+
+
+def default_libdir() -> str:
+    if is_debianlike():
+        try:
+            pc = subprocess.Popen(['dpkg-architecture', '-qDEB_HOST_MULTIARCH'],
+                                  stdout=subprocess.PIPE,
+                                  stderr=subprocess.DEVNULL)
+            (stdo, _) = pc.communicate()
+            if pc.returncode == 0:
+                archpath = stdo.decode().strip()
+                return 'lib/' + archpath
+        except Exception:
+            pass
+    if is_freebsd() or is_irix():
+        return 'lib'
+    if os.path.isdir('/usr/lib64') and not os.path.islink('/usr/lib64'):
+        return 'lib64'
+    return 'lib'
+
+
+def default_libexecdir() -> str:
+    # There is no way to auto-detect this, so it must be set at build time
+    return 'libexec'
+
+
+def default_prefix() -> str:
+    return 'c:/' if is_windows() else '/usr/local'
+
+
+def get_library_dirs() -> T.List[str]:
+    if is_windows():
+        return ['C:/mingw/lib'] # TODO: get programmatically
+    if is_osx():
+        return ['/usr/lib'] # TODO: get programmatically
+    # The following is probably Debian/Ubuntu specific.
+    # /usr/local/lib is first because it contains stuff
+    # installed by the sysadmin and is probably more up-to-date
+    # than /usr/lib. If you feel that this search order is
+    # problematic, please raise the issue on the mailing list.
+    unixdirs = ['/usr/local/lib', '/usr/lib', '/lib']
+
+    if is_freebsd():
+        return unixdirs
+    # FIXME: this needs to be further genericized for aarch64 etc.
+    machine = platform.machine()
+    if machine in ('i386', 'i486', 'i586', 'i686'):
+        plat = 'i386'
+    elif machine.startswith('arm'):
+        plat = 'arm'
+    else:
+        plat = ''
+
+    # Solaris puts 32-bit libraries in the main /lib & /usr/lib directories
+    # and 64-bit libraries in platform specific subdirectories.
+    if is_sunos():
+        if machine == 'i86pc':
+            plat = 'amd64'
+        elif machine.startswith('sun4'):
+            plat = 'sparcv9'
+
+    usr_platdir = Path('/usr/lib/') / plat
+    if usr_platdir.is_dir():
+        unixdirs += [str(x) for x in (usr_platdir).iterdir() if x.is_dir()]
+    if os.path.exists('/usr/lib64'):
+        unixdirs.append('/usr/lib64')
+
+    lib_platdir = Path('/lib/') / plat
+    if lib_platdir.is_dir():
+        unixdirs += [str(x) for x in (lib_platdir).iterdir() if x.is_dir()]
+    if os.path.exists('/lib64'):
+        unixdirs.append('/lib64')
+
+    return unixdirs
+
+
+def has_path_sep(name: str, sep: str = '/\\') -> bool:
+    'Checks if any of the specified @sep path separators are in @name'
+    for each in sep:
+        if each in name:
+            return True
+    return False
+
+
+if is_windows():
+    # shlex.split is not suitable for splitting command line on Window (https://bugs.python.org/issue1724822);
+    # shlex.quote is similarly problematic. Below are "proper" implementations of these functions according to
+    # https://docs.microsoft.com/en-us/cpp/c-language/parsing-c-command-line-arguments and
+    # https://blogs.msdn.microsoft.com/twistylittlepassagesallalike/2011/04/23/everyone-quotes-command-line-arguments-the-wrong-way/
+
+    _whitespace = ' \t\n\r'
+    _find_unsafe_char = re.compile(fr'[{_whitespace}"]').search
+
+    def quote_arg(arg: str) -> str:
+        if arg and not _find_unsafe_char(arg):
+            return arg
+
+        result = '"'
+        num_backslashes = 0
+        for c in arg:
+            if c == '\\':
+                num_backslashes += 1
+            else:
+                if c == '"':
+                    # Escape all backslashes and the following double quotation mark
+                    num_backslashes = num_backslashes * 2 + 1
+
+                result += num_backslashes * '\\' + c
+                num_backslashes = 0
+
+        # Escape all backslashes, but let the terminating double quotation
+        # mark we add below be interpreted as a metacharacter
+        result += (num_backslashes * 2) * '\\' + '"'
+        return result
+
+    def split_args(cmd: str) -> T.List[str]:
+        result = []
+        arg = ''
+        num_backslashes = 0
+        num_quotes = 0
+        in_quotes = False
+        for c in cmd:
+            if c == '\\':
+                num_backslashes += 1
+            else:
+                if c == '"' and not num_backslashes % 2:
+                    # unescaped quote, eat it
+                    arg += (num_backslashes // 2) * '\\'
+                    num_quotes += 1
+                    in_quotes = not in_quotes
+                elif c in _whitespace and not in_quotes:
+                    if arg or num_quotes:
+                        # reached the end of the argument
+                        result.append(arg)
+                        arg = ''
+                        num_quotes = 0
+                else:
+                    if c == '"':
+                        # escaped quote
+                        num_backslashes = (num_backslashes - 1) // 2
+
+                    arg += num_backslashes * '\\' + c
+
+                num_backslashes = 0
+
+        if arg or num_quotes:
+            result.append(arg)
+
+        return result
+else:
+    def quote_arg(arg: str) -> str:
+        return shlex.quote(arg)
+
+    def split_args(cmd: str) -> T.List[str]:
+        return shlex.split(cmd)
+
+
+def join_args(args: T.Iterable[str]) -> str:
+    return ' '.join([quote_arg(x) for x in args])
+
+
+def do_replacement(regex: T.Pattern[str], line: str,
+                   variable_format: Literal['meson', 'cmake', 'cmake@'],
+                   confdata: T.Union[T.Dict[str, T.Tuple[str, T.Optional[str]]], 'ConfigurationData']) -> T.Tuple[str, T.Set[str]]:
+    missing_variables = set()  # type: T.Set[str]
+    if variable_format == 'cmake':
+        start_tag = '${'
+        backslash_tag = '\\${'
+    else:
+        start_tag = '@'
+        backslash_tag = '\\@'
+
+    def variable_replace(match: T.Match[str]) -> str:
+        # Pairs of escape characters before '@' or '\@'
+        if match.group(0).endswith('\\'):
+            num_escapes = match.end(0) - match.start(0)
+            return '\\' * (num_escapes // 2)
+        # Single escape character and '@'
+        elif match.group(0) == backslash_tag:
+            return start_tag
+        # Template variable to be replaced
+        else:
+            varname = match.group(1)
+            var_str = ''
+            if varname in confdata:
+                var, _ = confdata.get(varname)
+                if isinstance(var, str):
+                    var_str = var
+                elif isinstance(var, int):
+                    var_str = str(var)
+                else:
+                    msg = f'Tried to replace variable {varname!r} value with ' \
+                          f'something other than a string or int: {var!r}'
+                    raise MesonException(msg)
+            else:
+                missing_variables.add(varname)
+            return var_str
+    return re.sub(regex, variable_replace, line), missing_variables
+
+def do_define(regex: T.Pattern[str], line: str, confdata: 'ConfigurationData',
+              variable_format: Literal['meson', 'cmake', 'cmake@']) -> str:
+    def get_cmake_define(line: str, confdata: 'ConfigurationData') -> str:
+        arr = line.split()
+        define_value = []
+        for token in arr[2:]:
+            try:
+                (v, desc) = confdata.get(token)
+                define_value += [str(v)]
+            except KeyError:
+                define_value += [token]
+        return ' '.join(define_value)
+
+    arr = line.split()
+    if variable_format == 'meson' and len(arr) != 2:
+        raise MesonException('#mesondefine does not contain exactly two tokens: %s' % line.strip())
+
+    varname = arr[1]
+    try:
+        (v, desc) = confdata.get(varname)
+    except KeyError:
+        return '/* #undef %s */\n' % varname
+    if isinstance(v, bool):
+        if v:
+            return '#define %s\n' % varname
+        else:
+            return '#undef %s\n' % varname
+    elif isinstance(v, int):
+        return '#define %s %d\n' % (varname, v)
+    elif isinstance(v, str):
+        if variable_format == 'meson':
+            result = v
+        else:
+            result = get_cmake_define(line, confdata)
+        result = f'#define {varname} {result}\n'
+        (result, missing_variable) = do_replacement(regex, result, variable_format, confdata)
+        return result
+    else:
+        raise MesonException('#mesondefine argument "%s" is of unknown type.' % varname)
+
+def get_variable_regex(variable_format: Literal['meson', 'cmake', 'cmake@'] = 'meson') -> T.Pattern[str]:
+    # Only allow (a-z, A-Z, 0-9, _, -) as valid characters for a define
+    # Also allow escaping '@' with '\@'
+    if variable_format in {'meson', 'cmake@'}:
+        regex = re.compile(r'(?:\\\\)+(?=\\?@)|\\@|@([-a-zA-Z0-9_]+)@')
+    else:
+        regex = re.compile(r'(?:\\\\)+(?=\\?\$)|\\\${|\${([-a-zA-Z0-9_]+)}')
+    return regex
+
+def do_conf_str(src: str, data: list, confdata: 'ConfigurationData',
+                variable_format: Literal['meson', 'cmake', 'cmake@'],
+                encoding: str = 'utf-8') -> T.Tuple[T.List[str], T.Set[str], bool]:
+    def line_is_valid(line: str, variable_format: str) -> bool:
+        if variable_format == 'meson':
+            if '#cmakedefine' in line:
+                return False
+        else: # cmake format
+            if '#mesondefine' in line:
+                return False
+        return True
+
+    regex = get_variable_regex(variable_format)
+
+    search_token = '#mesondefine'
+    if variable_format != 'meson':
+        search_token = '#cmakedefine'
+
+    result = []
+    missing_variables = set()
+    # Detect when the configuration data is empty and no tokens were found
+    # during substitution so we can warn the user to use the `copy:` kwarg.
+    confdata_useless = not confdata.keys()
+    for line in data:
+        if line.startswith(search_token):
+            confdata_useless = False
+            line = do_define(regex, line, confdata, variable_format)
+        else:
+            if not line_is_valid(line, variable_format):
+                raise MesonException(f'Format error in {src}: saw "{line.strip()}" when format set to "{variable_format}"')
+            line, missing = do_replacement(regex, line, variable_format, confdata)
+            missing_variables.update(missing)
+            if missing:
+                confdata_useless = False
+        result.append(line)
+
+    return result, missing_variables, confdata_useless
+
+def do_conf_file(src: str, dst: str, confdata: 'ConfigurationData',
+                 variable_format: Literal['meson', 'cmake', 'cmake@'],
+                 encoding: str = 'utf-8') -> T.Tuple[T.Set[str], bool]:
+    try:
+        with open(src, encoding=encoding, newline='') as f:
+            data = f.readlines()
+    except Exception as e:
+        raise MesonException(f'Could not read input file {src}: {e!s}')
+
+    (result, missing_variables, confdata_useless) = do_conf_str(src, data, confdata, variable_format, encoding)
+    dst_tmp = dst + '~'
+    try:
+        with open(dst_tmp, 'w', encoding=encoding, newline='') as f:
+            f.writelines(result)
+    except Exception as e:
+        raise MesonException(f'Could not write output file {dst}: {e!s}')
+    shutil.copymode(src, dst_tmp)
+    replace_if_different(dst, dst_tmp)
+    return missing_variables, confdata_useless
+
+CONF_C_PRELUDE = '''/*
+ * Autogenerated by the Meson build system.
+ * Do not edit, your changes will be lost.
+ */
+
+#pragma once
+
+'''
+
+CONF_NASM_PRELUDE = '''; Autogenerated by the Meson build system.
+; Do not edit, your changes will be lost.
+
+'''
+
+def dump_conf_header(ofilename: str, cdata: 'ConfigurationData', output_format: T.Literal['c', 'nasm']) -> None:
+    if output_format == 'c':
+        prelude = CONF_C_PRELUDE
+        prefix = '#'
+    else:
+        prelude = CONF_NASM_PRELUDE
+        prefix = '%'
+
+    ofilename_tmp = ofilename + '~'
+    with open(ofilename_tmp, 'w', encoding='utf-8') as ofile:
+        ofile.write(prelude)
+        for k in sorted(cdata.keys()):
+            (v, desc) = cdata.get(k)
+            if desc:
+                if output_format == 'c':
+                    ofile.write('/* %s */\n' % desc)
+                elif output_format == 'nasm':
+                    for line in desc.split('\n'):
+                        ofile.write('; %s\n' % line)
+            if isinstance(v, bool):
+                if v:
+                    ofile.write(f'{prefix}define {k}\n\n')
+                else:
+                    ofile.write(f'{prefix}undef {k}\n\n')
+            elif isinstance(v, (int, str)):
+                ofile.write(f'{prefix}define {k} {v}\n\n')
+            else:
+                raise MesonException('Unknown data type in configuration file entry: ' + k)
+    replace_if_different(ofilename, ofilename_tmp)
+
+
+def replace_if_different(dst: str, dst_tmp: str) -> None:
+    # If contents are identical, don't touch the file to prevent
+    # unnecessary rebuilds.
+    different = True
+    try:
+        with open(dst, 'rb') as f1, open(dst_tmp, 'rb') as f2:
+            if f1.read() == f2.read():
+                different = False
+    except FileNotFoundError:
+        pass
+    if different:
+        os.replace(dst_tmp, dst)
+    else:
+        os.unlink(dst_tmp)
+
+
+def listify(item: T.Any, flatten: bool = True) -> T.List[T.Any]:
+    '''
+    Returns a list with all args embedded in a list if they are not a list.
+    This function preserves order.
+    @flatten: Convert lists of lists to a flat list
+    '''
+    if not isinstance(item, list):
+        return [item]
+    result = []  # type: T.List[T.Any]
+    for i in item:
+        if flatten and isinstance(i, list):
+            result += listify(i, flatten=True)
+        else:
+            result.append(i)
+    return result
+
+
+def extract_as_list(dict_object: T.Dict[_T, _U], key: _T, pop: bool = False) -> T.List[_U]:
+    '''
+    Extracts all values from given dict_object and listifies them.
+    '''
+    fetch: T.Callable[[_T], _U] = dict_object.get
+    if pop:
+        fetch = dict_object.pop
+    # If there's only one key, we don't return a list with one element
+    return listify(fetch(key) or [], flatten=True)
+
+
+def typeslistify(item: 'T.Union[_T, T.Sequence[_T]]',
+                 types: 'T.Union[T.Type[_T], T.Tuple[T.Type[_T]]]') -> T.List[_T]:
+    '''
+    Ensure that type(@item) is one of @types or a
+    list of items all of which are of type @types
+    '''
+    if isinstance(item, types):
+        item = T.cast('T.List[_T]', [item])
+    if not isinstance(item, list):
+        raise MesonException('Item must be a list or one of {!r}, not {!r}'.format(types, type(item)))
+    for i in item:
+        if i is not None and not isinstance(i, types):
+            raise MesonException('List item must be one of {!r}, not {!r}'.format(types, type(i)))
+    return item
+
+
+def stringlistify(item: T.Union[T.Any, T.Sequence[T.Any]]) -> T.List[str]:
+    return typeslistify(item, str)
+
+
+def expand_arguments(args: T.Iterable[str]) -> T.Optional[T.List[str]]:
+    expended_args = []  # type: T.List[str]
+    for arg in args:
+        if not arg.startswith('@'):
+            expended_args.append(arg)
+            continue
+
+        args_file = arg[1:]
+        try:
+            with open(args_file, encoding='utf-8') as f:
+                extended_args = f.read().split()
+            expended_args += extended_args
+        except Exception as e:
+            mlog.error('Expanding command line arguments:',  args_file, 'not found')
+            mlog.exception(e)
+            return None
+    return expended_args
+
+
+def partition(pred: T.Callable[[_T], object], iterable: T.Iterable[_T]) -> T.Tuple[T.Iterator[_T], T.Iterator[_T]]:
+    """Use a predicate to partition entries into false entries and true
+    entries.
+
+    >>> x, y = partition(is_odd, range(10))
+    >>> (list(x), list(y))
+    ([0, 2, 4, 6, 8], [1, 3, 5, 7, 9])
+    """
+    t1, t2 = tee(iterable)
+    return filterfalse(pred, t1), filter(pred, t2)
+
+
+def Popen_safe(args: T.List[str], write: T.Optional[str] = None,
+               stdin: T.Union[T.TextIO, T.BinaryIO, int] = subprocess.DEVNULL,
+               stdout: T.Union[T.TextIO, T.BinaryIO, int] = subprocess.PIPE,
+               stderr: T.Union[T.TextIO, T.BinaryIO, int] = subprocess.PIPE,
+               **kwargs: T.Any) -> T.Tuple['subprocess.Popen[str]', str, str]:
+    import locale
+    encoding = locale.getpreferredencoding()
+    # Stdin defaults to DEVNULL otherwise the command run by us here might mess
+    # up the console and ANSI colors will stop working on Windows.
+    # If write is not None, set stdin to PIPE so data can be sent.
+    if write is not None:
+        stdin = subprocess.PIPE
+    if not sys.stdout.encoding or encoding.upper() != 'UTF-8':
+        p, o, e = Popen_safe_legacy(args, write=write, stdin=stdin, stdout=stdout, stderr=stderr, **kwargs)
+    else:
+        p = subprocess.Popen(args, universal_newlines=True, close_fds=False,
+                             stdin=stdin, stdout=stdout, stderr=stderr, **kwargs)
+        o, e = p.communicate(write)
+    # Sometimes the command that we run will call another command which will be
+    # without the above stdin workaround, so set the console mode again just in
+    # case.
+    mlog.setup_console()
+    return p, o, e
+
+
+def Popen_safe_legacy(args: T.List[str], write: T.Optional[str] = None,
+                      stdin: T.Union[T.TextIO, T.BinaryIO, int] = subprocess.DEVNULL,
+                      stdout: T.Union[T.TextIO, T.BinaryIO, int] = subprocess.PIPE,
+                      stderr: T.Union[T.TextIO, T.BinaryIO, int] = subprocess.PIPE,
+                      **kwargs: T.Any) -> T.Tuple['subprocess.Popen[str]', str, str]:
+    p = subprocess.Popen(args, universal_newlines=False, close_fds=False,
+                         stdin=stdin, stdout=stdout, stderr=stderr, **kwargs)
+    input_ = None  # type: T.Optional[bytes]
+    if write is not None:
+        input_ = write.encode('utf-8')
+    o, e = p.communicate(input_)
+    if o is not None:
+        if sys.stdout.encoding:
+            o = o.decode(encoding=sys.stdout.encoding, errors='replace').replace('\r\n', '\n')
+        else:
+            o = o.decode(errors='replace').replace('\r\n', '\n')
+    if e is not None:
+        if sys.stderr is not None and sys.stderr.encoding:
+            e = e.decode(encoding=sys.stderr.encoding, errors='replace').replace('\r\n', '\n')
+        else:
+            e = e.decode(errors='replace').replace('\r\n', '\n')
+    return p, o, e
+
+
+def iter_regexin_iter(regexiter: T.Iterable[str], initer: T.Iterable[str]) -> T.Optional[str]:
+    '''
+    Takes each regular expression in @regexiter and tries to search for it in
+    every item in @initer. If there is a match, returns that match.
+    Else returns False.
+    '''
+    for regex in regexiter:
+        for ii in initer:
+            if not isinstance(ii, str):
+                continue
+            match = re.search(regex, ii)
+            if match:
+                return match.group()
+    return None
+
+
+def _substitute_values_check_errors(command: T.List[str], values: T.Dict[str, T.Union[str, T.List[str]]]) -> None:
+    # Error checking
+    inregex = ['@INPUT([0-9]+)?@', '@PLAINNAME@', '@BASENAME@']  # type: T.List[str]
+    outregex = ['@OUTPUT([0-9]+)?@', '@OUTDIR@']                 # type: T.List[str]
+    if '@INPUT@' not in values:
+        # Error out if any input-derived templates are present in the command
+        match = iter_regexin_iter(inregex, command)
+        if match:
+            raise MesonException(f'Command cannot have {match!r}, since no input files were specified')
+    else:
+        if len(values['@INPUT@']) > 1:
+            # Error out if @PLAINNAME@ or @BASENAME@ is present in the command
+            match = iter_regexin_iter(inregex[1:], command)
+            if match:
+                raise MesonException(f'Command cannot have {match!r} when there is '
+                                     'more than one input file')
+        # Error out if an invalid @INPUTnn@ template was specified
+        for each in command:
+            if not isinstance(each, str):
+                continue
+            match2 = re.search(inregex[0], each)
+            if match2 and match2.group() not in values:
+                m = 'Command cannot have {!r} since there are only {!r} inputs'
+                raise MesonException(m.format(match2.group(), len(values['@INPUT@'])))
+    if '@OUTPUT@' not in values:
+        # Error out if any output-derived templates are present in the command
+        match = iter_regexin_iter(outregex, command)
+        if match:
+            raise MesonException(f'Command cannot have {match!r} since there are no outputs')
+    else:
+        # Error out if an invalid @OUTPUTnn@ template was specified
+        for each in command:
+            if not isinstance(each, str):
+                continue
+            match2 = re.search(outregex[0], each)
+            if match2 and match2.group() not in values:
+                m = 'Command cannot have {!r} since there are only {!r} outputs'
+                raise MesonException(m.format(match2.group(), len(values['@OUTPUT@'])))
+
+
+def substitute_values(command: T.List[str], values: T.Dict[str, T.Union[str, T.List[str]]]) -> T.List[str]:
+    '''
+    Substitute the template strings in the @values dict into the list of
+    strings @command and return a new list. For a full list of the templates,
+    see get_filenames_templates_dict()
+
+    If multiple inputs/outputs are given in the @values dictionary, we
+    substitute @INPUT@ and @OUTPUT@ only if they are the entire string, not
+    just a part of it, and in that case we substitute *all* of them.
+
+    The typing of this function is difficult, as only @OUTPUT@ and @INPUT@ can
+    be lists, everything else is a string. However, TypeDict cannot represent
+    this, as you can have optional keys, but not extra keys. We end up just
+    having to us asserts to convince type checkers that this is okay.
+
+    https://github.com/python/mypy/issues/4617
+    '''
+
+    def replace(m: T.Match[str]) -> str:
+        v = values[m.group(0)]
+        assert isinstance(v, str), 'for mypy'
+        return v
+
+    # Error checking
+    _substitute_values_check_errors(command, values)
+
+    # Substitution
+    outcmd = []  # type: T.List[str]
+    rx_keys = [re.escape(key) for key in values if key not in ('@INPUT@', '@OUTPUT@')]
+    value_rx = re.compile('|'.join(rx_keys)) if rx_keys else None
+    for vv in command:
+        more: T.Optional[str] = None
+        if not isinstance(vv, str):
+            outcmd.append(vv)
+        elif '@INPUT@' in vv:
+            inputs = values['@INPUT@']
+            if vv == '@INPUT@':
+                outcmd += inputs
+            elif len(inputs) == 1:
+                outcmd.append(vv.replace('@INPUT@', inputs[0]))
+            else:
+                raise MesonException("Command has '@INPUT@' as part of a "
+                                     "string and more than one input file")
+        elif '@OUTPUT@' in vv:
+            outputs = values['@OUTPUT@']
+            if vv == '@OUTPUT@':
+                outcmd += outputs
+            elif len(outputs) == 1:
+                outcmd.append(vv.replace('@OUTPUT@', outputs[0]))
+            else:
+                raise MesonException("Command has '@OUTPUT@' as part of a "
+                                     "string and more than one output file")
+
+        # Append values that are exactly a template string.
+        # This is faster than a string replace.
+        elif vv in values:
+            o = values[vv]
+            assert isinstance(o, str), 'for mypy'
+            more = o
+        # Substitute everything else with replacement
+        elif value_rx:
+            more = value_rx.sub(replace, vv)
+        else:
+            more = vv
+
+        if more is not None:
+            outcmd.append(more)
+
+    return outcmd
+
+
+def get_filenames_templates_dict(inputs: T.List[str], outputs: T.List[str]) -> T.Dict[str, T.Union[str, T.List[str]]]:
+    '''
+    Create a dictionary with template strings as keys and values as values for
+    the following templates:
+
+    @INPUT@  - the full path to one or more input files, from @inputs
+    @OUTPUT@ - the full path to one or more output files, from @outputs
+    @OUTDIR@ - the full path to the directory containing the output files
+
+    If there is only one input file, the following keys are also created:
+
+    @PLAINNAME@ - the filename of the input file
+    @BASENAME@ - the filename of the input file with the extension removed
+
+    If there is more than one input file, the following keys are also created:
+
+    @INPUT0@, @INPUT1@, ... one for each input file
+
+    If there is more than one output file, the following keys are also created:
+
+    @OUTPUT0@, @OUTPUT1@, ... one for each output file
+    '''
+    values = {}  # type: T.Dict[str, T.Union[str, T.List[str]]]
+    # Gather values derived from the input
+    if inputs:
+        # We want to substitute all the inputs.
+        values['@INPUT@'] = inputs
+        for (ii, vv) in enumerate(inputs):
+            # Write out @INPUT0@, @INPUT1@, ...
+            values[f'@INPUT{ii}@'] = vv
+        if len(inputs) == 1:
+            # Just one value, substitute @PLAINNAME@ and @BASENAME@
+            values['@PLAINNAME@'] = plain = os.path.basename(inputs[0])
+            values['@BASENAME@'] = os.path.splitext(plain)[0]
+    if outputs:
+        # Gather values derived from the outputs, similar to above.
+        values['@OUTPUT@'] = outputs
+        for (ii, vv) in enumerate(outputs):
+            values[f'@OUTPUT{ii}@'] = vv
+        # Outdir should be the same for all outputs
+        values['@OUTDIR@'] = os.path.dirname(outputs[0])
+        # Many external programs fail on empty arguments.
+        if values['@OUTDIR@'] == '':
+            values['@OUTDIR@'] = '.'
+    return values
+
+
+def _make_tree_writable(topdir: str) -> None:
+    # Ensure all files and directories under topdir are writable
+    # (and readable) by owner.
+    for d, _, files in os.walk(topdir):
+        os.chmod(d, os.stat(d).st_mode | stat.S_IWRITE | stat.S_IREAD)
+        for fname in files:
+            fpath = os.path.join(d, fname)
+            if os.path.isfile(fpath):
+                os.chmod(fpath, os.stat(fpath).st_mode | stat.S_IWRITE | stat.S_IREAD)
+
+
+def windows_proof_rmtree(f: str) -> None:
+    # On Windows if anyone is holding a file open you can't
+    # delete it. As an example an anti virus scanner might
+    # be scanning files you are trying to delete. The only
+    # way to fix this is to try again and again.
+    delays = [0.1, 0.1, 0.2, 0.2, 0.2, 0.5, 0.5, 1, 1, 1, 1, 2]
+    writable = False
+    for d in delays:
+        try:
+            # Start by making the tree writable.
+            if not writable:
+                _make_tree_writable(f)
+                writable = True
+        except PermissionError:
+            time.sleep(d)
+            continue
+        try:
+            shutil.rmtree(f)
+            return
+        except FileNotFoundError:
+            return
+        except OSError:
+            time.sleep(d)
+    # Try one last time and throw if it fails.
+    shutil.rmtree(f)
+
+
+def windows_proof_rm(fpath: str) -> None:
+    """Like windows_proof_rmtree, but for a single file."""
+    if os.path.isfile(fpath):
+        os.chmod(fpath, os.stat(fpath).st_mode | stat.S_IWRITE | stat.S_IREAD)
+    delays = [0.1, 0.1, 0.2, 0.2, 0.2, 0.5, 0.5, 1, 1, 1, 1, 2]
+    for d in delays:
+        try:
+            os.unlink(fpath)
+            return
+        except FileNotFoundError:
+            return
+        except OSError:
+            time.sleep(d)
+    os.unlink(fpath)
+
+
+class TemporaryDirectoryWinProof(TemporaryDirectory):
+    """
+    Like TemporaryDirectory, but cleans things up using
+    windows_proof_rmtree()
+    """
+
+    def __exit__(self, exc: T.Any, value: T.Any, tb: T.Any) -> None:
+        try:
+            super().__exit__(exc, value, tb)
+        except OSError:
+            windows_proof_rmtree(self.name)
+
+    def cleanup(self) -> None:
+        try:
+            super().cleanup()
+        except OSError:
+            windows_proof_rmtree(self.name)
+
+
+def detect_subprojects(spdir_name: str, current_dir: str = '',
+                       result: T.Optional[T.Dict[str, T.List[str]]] = None) -> T.Dict[str, T.List[str]]:
+    if result is None:
+        result = {}
+    spdir = os.path.join(current_dir, spdir_name)
+    if not os.path.exists(spdir):
+        return result
+    for trial in glob(os.path.join(spdir, '*')):
+        basename = os.path.basename(trial)
+        if trial == 'packagecache':
+            continue
+        append_this = True
+        if os.path.isdir(trial):
+            detect_subprojects(spdir_name, trial, result)
+        elif trial.endswith('.wrap') and os.path.isfile(trial):
+            basename = os.path.splitext(basename)[0]
+        else:
+            append_this = False
+        if append_this:
+            if basename in result:
+                result[basename].append(trial)
+            else:
+                result[basename] = [trial]
+    return result
+
+
+def substring_is_in_list(substr: str, strlist: T.List[str]) -> bool:
+    for s in strlist:
+        if substr in s:
+            return True
+    return False
+
+
+class OrderedSet(T.MutableSet[_T]):
+    """A set that preserves the order in which items are added, by first
+    insertion.
+    """
+    def __init__(self, iterable: T.Optional[T.Iterable[_T]] = None):
+        self.__container: T.OrderedDict[_T, None] = collections.OrderedDict()
+        if iterable:
+            self.update(iterable)
+
+    def __contains__(self, value: object) -> bool:
+        return value in self.__container
+
+    def __iter__(self) -> T.Iterator[_T]:
+        return iter(self.__container.keys())
+
+    def __len__(self) -> int:
+        return len(self.__container)
+
+    def __repr__(self) -> str:
+        # Don't print 'OrderedSet("")' for an empty set.
+        if self.__container:
+            return 'OrderedSet("{}")'.format(
+                '", "'.join(repr(e) for e in self.__container.keys()))
+        return 'OrderedSet()'
+
+    def __reversed__(self) -> T.Iterator[_T]:
+        return reversed(self.__container.keys())
+
+    def add(self, value: _T) -> None:
+        self.__container[value] = None
+
+    def discard(self, value: _T) -> None:
+        if value in self.__container:
+            del self.__container[value]
+
+    def move_to_end(self, value: _T, last: bool = True) -> None:
+        self.__container.move_to_end(value, last)
+
+    def pop(self, last: bool = True) -> _T:
+        item, _ = self.__container.popitem(last)
+        return item
+
+    def update(self, iterable: T.Iterable[_T]) -> None:
+        for item in iterable:
+            self.__container[item] = None
+
+    def difference(self, set_: T.Iterable[_T]) -> 'OrderedSet[_T]':
+        return type(self)(e for e in self if e not in set_)
+
+    def difference_update(self, iterable: T.Iterable[_T]) -> None:
+        for item in iterable:
+            self.discard(item)
+
+def relpath(path: str, start: str) -> str:
+    # On Windows a relative path can't be evaluated for paths on two different
+    # drives (i.e. c:\foo and f:\bar).  The only thing left to do is to use the
+    # original absolute path.
+    try:
+        return os.path.relpath(path, start)
+    except (TypeError, ValueError):
+        return path
+
+def path_is_in_root(path: Path, root: Path, resolve: bool = False) -> bool:
+    # Check whether a path is within the root directory root
+    try:
+        if resolve:
+            path.resolve().relative_to(root.resolve())
+        else:
+            path.relative_to(root)
+    except ValueError:
+        return False
+    return True
+
+def relative_to_if_possible(path: Path, root: Path, resolve: bool = False) -> Path:
+    try:
+        if resolve:
+            return path.resolve().relative_to(root.resolve())
+        else:
+            return path.relative_to(root)
+    except ValueError:
+        return path
+
+class LibType(enum.IntEnum):
+
+    """Enumeration for library types."""
+
+    SHARED = 0
+    STATIC = 1
+    PREFER_SHARED = 2
+    PREFER_STATIC = 3
+
+
+class ProgressBarFallback:  # lgtm [py/iter-returns-non-self]
+    '''
+    Fallback progress bar implementation when tqdm is not found
+
+    Since this class is not an actual iterator, but only provides a minimal
+    fallback, it is safe to ignore the 'Iterator does not return self from
+    __iter__ method' warning.
+    '''
+    def __init__(self, iterable: T.Optional[T.Iterable[str]] = None, total: T.Optional[int] = None,
+                 bar_type: T.Optional[str] = None, desc: T.Optional[str] = None):
+        if iterable is not None:
+            self.iterable = iter(iterable)
+            return
+        self.total = total
+        self.done = 0
+        self.printed_dots = 0
+        if self.total and bar_type == 'download':
+            print('Download size:', self.total)
+        if desc:
+            print(f'{desc}: ', end='')
+
+    # Pretend to be an iterator when called as one and don't print any
+    # progress
+    def __iter__(self) -> T.Iterator[str]:
+        return self.iterable
+
+    def __next__(self) -> str:
+        return next(self.iterable)
+
+    def print_dot(self) -> None:
+        print('.', end='')
+        sys.stdout.flush()
+        self.printed_dots += 1
+
+    def update(self, progress: int) -> None:
+        self.done += progress
+        if not self.total:
+            # Just print one dot per call if we don't have a total length
+            self.print_dot()
+            return
+        ratio = int(self.done / self.total * 10)
+        while self.printed_dots < ratio:
+            self.print_dot()
+
+    def close(self) -> None:
+        print('')
+
+try:
+    from tqdm import tqdm
+except ImportError:
+    # ideally we would use a typing.Protocol here, but it's part of typing_extensions until 3.8
+    ProgressBar = ProgressBarFallback  # type: T.Union[T.Type[ProgressBarFallback], T.Type[ProgressBarTqdm]]
+else:
+    class ProgressBarTqdm(tqdm):
+        def __init__(self, *args: T.Any, bar_type: T.Optional[str] = None, **kwargs: T.Any) -> None:
+            if bar_type == 'download':
+                kwargs.update({'unit': 'bytes', 'leave': True})
+            else:
+                kwargs.update({'leave': False})
+            kwargs['ncols'] = 100
+            super().__init__(*args, **kwargs)
+
+    ProgressBar = ProgressBarTqdm
+
+
+class RealPathAction(argparse.Action):
+    def __init__(self, option_strings: T.List[str], dest: str, default: str = '.', **kwargs: T.Any):
+        default = os.path.abspath(os.path.realpath(default))
+        super().__init__(option_strings, dest, nargs=None, default=default, **kwargs)
+
+    def __call__(self, parser: argparse.ArgumentParser, namespace: argparse.Namespace,
+                 values: T.Union[str, T.Sequence[T.Any], None], option_string: str = None) -> None:
+        assert isinstance(values, str)
+        setattr(namespace, self.dest, os.path.abspath(os.path.realpath(values)))
+
+
+def get_wine_shortpath(winecmd: T.List[str], wine_paths: T.Sequence[str],
+                       workdir: T.Optional[str] = None) -> str:
+    '''
+    WINEPATH size is limited to 1024 bytes which can easily be exceeded when
+    adding the path to every dll inside build directory. See
+    https://bugs.winehq.org/show_bug.cgi?id=45810.
+
+    To shorten it as much as possible we use path relative to `workdir`
+    where possible and convert absolute paths to Windows shortpath (e.g.
+    "/usr/x86_64-w64-mingw32/lib" to "Z:\\usr\\X86_~FWL\\lib").
+
+    This limitation reportedly has been fixed with wine >= 6.4
+    '''
+
+    # Remove duplicates
+    wine_paths = list(OrderedSet(wine_paths))
+
+    # Check if it's already short enough
+    wine_path = ';'.join(wine_paths)
+    if len(wine_path) <= 1024:
+        return wine_path
+
+    # Check if we have wine >= 6.4
+    from ..programs import ExternalProgram
+    wine = ExternalProgram('wine', winecmd, silent=True)
+    if version_compare(wine.get_version(), '>=6.4'):
+        return wine_path
+
+    # Check paths that can be reduced by making them relative to workdir.
+    rel_paths = []
+    if workdir:
+        abs_paths = []
+        for p in wine_paths:
+            try:
+                rel = Path(p).relative_to(workdir)
+                rel_paths.append(str(rel))
+            except ValueError:
+                abs_paths.append(p)
+        wine_paths = abs_paths
+
+    if wine_paths:
+        # BAT script that takes a list of paths in argv and prints semi-colon separated shortpaths
+        with NamedTemporaryFile('w', suffix='.bat', encoding='utf-8', delete=False) as bat_file:
+            bat_file.write('''
+            @ECHO OFF
+            for %%x in (%*) do (
+                echo|set /p=;%~sx
+            )
+            ''')
+        try:
+            stdout = subprocess.check_output(winecmd + ['cmd', '/C', bat_file.name] + wine_paths,
+                                             encoding='utf-8', stderr=subprocess.DEVNULL)
+            stdout = stdout.strip(';')
+            if stdout:
+                wine_paths = stdout.split(';')
+            else:
+                mlog.warning('Could not shorten WINEPATH: empty stdout')
+        except subprocess.CalledProcessError as e:
+            mlog.warning(f'Could not shorten WINEPATH: {str(e)}')
+        finally:
+            os.unlink(bat_file.name)
+    wine_path = ';'.join(rel_paths + wine_paths)
+    if len(wine_path) > 1024:
+        mlog.warning('WINEPATH exceeds 1024 characters which could cause issues')
+    return wine_path
+
+
+def run_once(func: T.Callable[..., _T]) -> T.Callable[..., _T]:
+    ret = []  # type: T.List[_T]
+
+    @wraps(func)
+    def wrapper(*args: T.Any, **kwargs: T.Any) -> _T:
+        if ret:
+            return ret[0]
+
+        val = func(*args, **kwargs)
+        ret.append(val)
+        return val
+
+    return wrapper
+
+
+def generate_list(func: T.Callable[..., T.Generator[_T, None, None]]) -> T.Callable[..., T.List[_T]]:
+    @wraps(func)
+    def wrapper(*args: T.Any, **kwargs: T.Any) -> T.List[_T]:
+        return list(func(*args, **kwargs))
+
+    return wrapper
+
+
+class OptionOverrideProxy(collections.abc.Mapping):
+    '''Mimic an option list but transparently override selected option
+    values.
+    '''
+
+    # TODO: the typing here could be made more explicit using a TypeDict from
+    # python 3.8 or typing_extensions
+
+    def __init__(self, overrides: T.Dict['OptionKey', T.Any], options: 'KeyedOptionDictType',
+                 subproject: T.Optional[str] = None):
+        self.overrides = overrides
+        self.options = options
+        self.subproject = subproject
+
+    def __getitem__(self, key: 'OptionKey') -> 'UserOption':
+        # FIXME: This is fundamentally the same algorithm than interpreter.get_option_internal().
+        # We should try to share the code somehow.
+        key = key.evolve(subproject=self.subproject)
+        if not key.is_project():
+            opt = self.options.get(key)
+            if opt is None or opt.yielding:
+                opt = self.options[key.as_root()]
+        else:
+            opt = self.options[key]
+            if opt.yielding:
+                opt = self.options.get(key.as_root(), opt)
+        override_value = self.overrides.get(key.as_root())
+        if override_value is not None:
+            opt = copy.copy(opt)
+            opt.set_value(override_value)
+        return opt
+
+    def __iter__(self) -> T.Iterator['OptionKey']:
+        return iter(self.options)
+
+    def __len__(self) -> int:
+        return len(self.options)
+
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, OptionOverrideProxy):
+            return NotImplemented
+        t1 = (self.overrides, self.subproject, self.options)
+        t2 = (other.overrides, other.subproject, other.options)
+        return t1 == t2
+
+
+class OptionType(enum.IntEnum):
+
+    """Enum used to specify what kind of argument a thing is."""
+
+    BUILTIN = 0
+    BACKEND = 1
+    BASE = 2
+    COMPILER = 3
+    PROJECT = 4
+
+# This is copied from coredata. There is no way to share this, because this
+# is used in the OptionKey constructor, and the coredata lists are
+# OptionKeys...
+_BUILTIN_NAMES = {
+    'prefix',
+    'bindir',
+    'datadir',
+    'includedir',
+    'infodir',
+    'libdir',
+    'libexecdir',
+    'localedir',
+    'localstatedir',
+    'mandir',
+    'sbindir',
+    'sharedstatedir',
+    'sysconfdir',
+    'auto_features',
+    'backend',
+    'buildtype',
+    'debug',
+    'default_library',
+    'errorlogs',
+    'install_umask',
+    'layout',
+    'optimization',
+    'prefer_static',
+    'stdsplit',
+    'strip',
+    'unity',
+    'unity_size',
+    'warning_level',
+    'werror',
+    'wrap_mode',
+    'force_fallback_for',
+    'pkg_config_path',
+    'cmake_prefix_path',
+}
+
+
+def _classify_argument(key: 'OptionKey') -> OptionType:
+    """Classify arguments into groups so we know which dict to assign them to."""
+
+    if key.name.startswith('b_'):
+        return OptionType.BASE
+    elif key.lang is not None:
+        return OptionType.COMPILER
+    elif key.name in _BUILTIN_NAMES or key.module:
+        return OptionType.BUILTIN
+    elif key.name.startswith('backend_'):
+        assert key.machine is MachineChoice.HOST, str(key)
+        return OptionType.BACKEND
+    else:
+        assert key.machine is MachineChoice.HOST, str(key)
+        return OptionType.PROJECT
+
+
+@total_ordering
+class OptionKey:
+
+    """Represents an option key in the various option dictionaries.
+
+    This provides a flexible, powerful way to map option names from their
+    external form (things like subproject:build.option) to something that
+    internally easier to reason about and produce.
+    """
+
+    __slots__ = ['name', 'subproject', 'machine', 'lang', '_hash', 'type', 'module']
+
+    name: str
+    subproject: str
+    machine: MachineChoice
+    lang: T.Optional[str]
+    _hash: int
+    type: OptionType
+    module: T.Optional[str]
+
+    def __init__(self, name: str, subproject: str = '',
+                 machine: MachineChoice = MachineChoice.HOST,
+                 lang: T.Optional[str] = None,
+                 module: T.Optional[str] = None,
+                 _type: T.Optional[OptionType] = None):
+        # the _type option to the constructor is kinda private. We want to be
+        # able tos ave the state and avoid the lookup function when
+        # pickling/unpickling, but we need to be able to calculate it when
+        # constructing a new OptionKey
+        object.__setattr__(self, 'name', name)
+        object.__setattr__(self, 'subproject', subproject)
+        object.__setattr__(self, 'machine', machine)
+        object.__setattr__(self, 'lang', lang)
+        object.__setattr__(self, 'module', module)
+        object.__setattr__(self, '_hash', hash((name, subproject, machine, lang, module)))
+        if _type is None:
+            _type = _classify_argument(self)
+        object.__setattr__(self, 'type', _type)
+
+    def __setattr__(self, key: str, value: T.Any) -> None:
+        raise AttributeError('OptionKey instances do not support mutation.')
+
+    def __getstate__(self) -> T.Dict[str, T.Any]:
+        return {
+            'name': self.name,
+            'subproject': self.subproject,
+            'machine': self.machine,
+            'lang': self.lang,
+            '_type': self.type,
+            'module': self.module,
+        }
+
+    def __setstate__(self, state: T.Dict[str, T.Any]) -> None:
+        """De-serialize the state of a pickle.
+
+        This is very clever. __init__ is not a constructor, it's an
+        initializer, therefore it's safe to call more than once. We create a
+        state in the custom __getstate__ method, which is valid to pass
+        splatted to the initializer.
+        """
+        # Mypy doesn't like this, because it's so clever.
+        self.__init__(**state)  # type: ignore
+
+    def __hash__(self) -> int:
+        return self._hash
+
+    def _to_tuple(self) -> T.Tuple[str, OptionType, str, str, MachineChoice, str]:
+        return (self.subproject, self.type, self.lang or '', self.module or '', self.machine, self.name)
+
+    def __eq__(self, other: object) -> bool:
+        if isinstance(other, OptionKey):
+            return self._to_tuple() == other._to_tuple()
+        return NotImplemented
+
+    def __lt__(self, other: object) -> bool:
+        if isinstance(other, OptionKey):
+            return self._to_tuple() < other._to_tuple()
+        return NotImplemented
+
+    def __str__(self) -> str:
+        out = self.name
+        if self.lang:
+            out = f'{self.lang}_{out}'
+        if self.machine is MachineChoice.BUILD:
+            out = f'build.{out}'
+        if self.module:
+            out = f'{self.module}.{out}'
+        if self.subproject:
+            out = f'{self.subproject}:{out}'
+        return out
+
+    def __repr__(self) -> str:
+        return f'OptionKey({self.name!r}, {self.subproject!r}, {self.machine!r}, {self.lang!r}, {self.module!r}, {self.type!r})'
+
+    @classmethod
+    def from_string(cls, raw: str) -> 'OptionKey':
+        """Parse the raw command line format into a three part tuple.
+
+        This takes strings like `mysubproject:build.myoption` and Creates an
+        OptionKey out of them.
+        """
+        try:
+            subproject, raw2 = raw.split(':')
+        except ValueError:
+            subproject, raw2 = '', raw
+
+        module = None
+        for_machine = MachineChoice.HOST
+        try:
+            prefix, raw3 = raw2.split('.')
+            if prefix == 'build':
+                for_machine = MachineChoice.BUILD
+            else:
+                module = prefix
+        except ValueError:
+            raw3 = raw2
+
+        from ..compilers import all_languages
+        if any(raw3.startswith(f'{l}_') for l in all_languages):
+            lang, opt = raw3.split('_', 1)
+        else:
+            lang, opt = None, raw3
+        assert ':' not in opt
+        assert '.' not in opt
+
+        return cls(opt, subproject, for_machine, lang, module)
+
+    def evolve(self, name: T.Optional[str] = None, subproject: T.Optional[str] = None,
+               machine: T.Optional[MachineChoice] = None, lang: T.Optional[str] = '',
+               module: T.Optional[str] = '') -> 'OptionKey':
+        """Create a new copy of this key, but with alterted members.
+
+        For example:
+        >>> a = OptionKey('foo', '', MachineChoice.Host)
+        >>> b = OptionKey('foo', 'bar', MachineChoice.Host)
+        >>> b == a.evolve(subproject='bar')
+        True
+        """
+        # We have to be a little clever with lang here, because lang is valid
+        # as None, for non-compiler options
+        return OptionKey(
+            name if name is not None else self.name,
+            subproject if subproject is not None else self.subproject,
+            machine if machine is not None else self.machine,
+            lang if lang != '' else self.lang,
+            module if module != '' else self.module
+        )
+
+    def as_root(self) -> 'OptionKey':
+        """Convenience method for key.evolve(subproject='')."""
+        return self.evolve(subproject='')
+
+    def as_build(self) -> 'OptionKey':
+        """Convenience method for key.evolve(machine=MachinceChoice.BUILD)."""
+        return self.evolve(machine=MachineChoice.BUILD)
+
+    def as_host(self) -> 'OptionKey':
+        """Convenience method for key.evolve(machine=MachinceChoice.HOST)."""
+        return self.evolve(machine=MachineChoice.HOST)
+
+    def is_backend(self) -> bool:
+        """Convenience method to check if this is a backend option."""
+        return self.type is OptionType.BACKEND
+
+    def is_builtin(self) -> bool:
+        """Convenience method to check if this is a builtin option."""
+        return self.type is OptionType.BUILTIN
+
+    def is_compiler(self) -> bool:
+        """Convenience method to check if this is a builtin option."""
+        return self.type is OptionType.COMPILER
+
+    def is_project(self) -> bool:
+        """Convenience method to check if this is a project option."""
+        return self.type is OptionType.PROJECT
+
+    def is_base(self) -> bool:
+        """Convenience method to check if this is a base option."""
+        return self.type is OptionType.BASE
+
+def pickle_load(filename: str, object_name: str, object_type: T.Type) -> T.Any:
+    load_fail_msg = f'{object_name} file {filename!r} is corrupted. Try with a fresh build tree.'
+    try:
+        with open(filename, 'rb') as f:
+            obj = pickle.load(f)
+    except (pickle.UnpicklingError, EOFError):
+        raise MesonException(load_fail_msg)
+    except (TypeError, ModuleNotFoundError, AttributeError):
+        raise MesonException(
+            f"{object_name} file {filename!r} references functions or classes that don't "
+            "exist. This probably means that it was generated with an old "
+            "version of meson.")
+    if not isinstance(obj, object_type):
+        raise MesonException(load_fail_msg)
+    from ..coredata import version as coredata_version
+    from ..coredata import major_versions_differ, MesonVersionMismatchException
+    if major_versions_differ(obj.version, coredata_version):
+        raise MesonVersionMismatchException(obj.version, coredata_version)
+    return obj
+
+
+def first(iter: T.Iterable[_T], predicate: T.Callable[[_T], bool]) -> T.Optional[_T]:
+    """Find the first entry in an iterable where the given predicate is true
+
+    :param iter: The iterable to search
+    :param predicate: A finding function that takes an element from the iterable
+        and returns True if found, otherwise False
+    :return: The first found element, or None if it is not found
+    """
+    for i in iter:
+        if predicate(i):
+            return i
+    return None
diff --git a/mesonbuild/utils/vsenv.py b/mesonbuild/utils/vsenv.py
new file mode 100644
index 0000000..5f32990
--- /dev/null
+++ b/mesonbuild/utils/vsenv.py
@@ -0,0 +1,120 @@
+import os
+import subprocess
+import json
+import pathlib
+import platform
+import shutil
+import tempfile
+
+from .. import mlog
+from .universal import MesonException, is_windows
+
+
+__all__ = [
+    'setup_vsenv',
+]
+
+
+bat_template = '''@ECHO OFF
+
+call "{}"
+
+ECHO {}
+SET
+'''
+
+# If on Windows and VS is installed but not set up in the environment,
+# set it to be runnable. In this way Meson can be directly invoked
+# from any shell, VS Code etc.
+def _setup_vsenv(force: bool) -> bool:
+    if not is_windows():
+        return False
+    if os.environ.get('OSTYPE') == 'cygwin':
+        return False
+    if 'MESON_FORCE_VSENV_FOR_UNITTEST' not in os.environ:
+        # VSINSTALL is set when running setvars from a Visual Studio installation
+        # Tested with Visual Studio 2012 and 2017
+        if 'VSINSTALLDIR' in os.environ:
+            return False
+        # Check explicitly for cl when on Windows
+        if shutil.which('cl.exe'):
+            return False
+    if not force:
+        if shutil.which('cc'):
+            return False
+        if shutil.which('gcc'):
+            return False
+        if shutil.which('clang'):
+            return False
+        if shutil.which('clang-cl'):
+            return False
+
+    root = os.environ.get("ProgramFiles(x86)") or os.environ.get("ProgramFiles")
+    bat_locator_bin = pathlib.Path(root, 'Microsoft Visual Studio/Installer/vswhere.exe')
+    if not bat_locator_bin.exists():
+        raise MesonException(f'Could not find {bat_locator_bin}')
+    bat_json = subprocess.check_output(
+        [
+            str(bat_locator_bin),
+            '-latest',
+            '-prerelease',
+            '-requiresAny',
+            '-requires', 'Microsoft.VisualStudio.Component.VC.Tools.x86.x64',
+            '-requires', 'Microsoft.VisualStudio.Workload.WDExpress',
+            '-products', '*',
+            '-utf8',
+            '-format',
+            'json'
+        ]
+    )
+    bat_info = json.loads(bat_json)
+    if not bat_info:
+        # VS installer instelled but not VS itself maybe?
+        raise MesonException('Could not parse vswhere.exe output')
+    bat_root = pathlib.Path(bat_info[0]['installationPath'])
+    if platform.machine() == 'ARM64':
+        bat_path = bat_root / 'VC/Auxiliary/Build/vcvarsx86_arm64.bat'
+    else:
+        bat_path = bat_root / 'VC/Auxiliary/Build/vcvars64.bat'
+        # if VS is not found try VS Express
+        if not bat_path.exists():
+            bat_path = bat_root / 'VC/Auxiliary/Build/vcvarsx86_amd64.bat'
+    if not bat_path.exists():
+        raise MesonException(f'Could not find {bat_path}')
+
+    mlog.log('Activating VS', bat_info[0]['catalog']['productDisplayVersion'])
+    bat_separator = '---SPLIT---'
+    bat_contents = bat_template.format(bat_path, bat_separator)
+    bat_file = tempfile.NamedTemporaryFile('w', suffix='.bat', encoding='utf-8', delete=False)
+    bat_file.write(bat_contents)
+    bat_file.flush()
+    bat_file.close()
+    bat_output = subprocess.check_output(bat_file.name, universal_newlines=True)
+    os.unlink(bat_file.name)
+    bat_lines = bat_output.split('\n')
+    bat_separator_seen = False
+    for bat_line in bat_lines:
+        if bat_line == bat_separator:
+            bat_separator_seen = True
+            continue
+        if not bat_separator_seen:
+            continue
+        if not bat_line:
+            continue
+        try:
+            k, v = bat_line.split('=', 1)
+        except ValueError:
+            # there is no "=", ignore junk data
+            pass
+        else:
+            os.environ[k] = v
+    return True
+
+def setup_vsenv(force: bool = False) -> bool:
+    try:
+        return _setup_vsenv(force)
+    except MesonException as e:
+        if force:
+            raise
+        mlog.warning('Failed to activate VS environment:', str(e))
+        return False
diff --git a/mesonbuild/utils/win32.py b/mesonbuild/utils/win32.py
new file mode 100644
index 0000000..bc0caec
--- /dev/null
+++ b/mesonbuild/utils/win32.py
@@ -0,0 +1,39 @@
+# SPDX-license-identifier: Apache-2.0
+# Copyright 2012-2021 The Meson development team
+# Copyright © 2021 Intel Corporation
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Windows specific implementations of mesonlib functionality."""
+
+import msvcrt
+import typing as T
+
+from .universal import MesonException
+from .platform import BuildDirLock as BuildDirLockBase
+
+__all__ = ['BuildDirLock']
+
+class BuildDirLock(BuildDirLockBase):
+
+    def __enter__(self) -> None:
+        self.lockfile = open(self.lockfilename, 'w', encoding='utf-8')
+        try:
+            msvcrt.locking(self.lockfile.fileno(), msvcrt.LK_NBLCK, 1)
+        except (BlockingIOError, PermissionError):
+            self.lockfile.close()
+            raise MesonException('Some other Meson process is already using this build directory. Exiting.')
+
+    def __exit__(self, *args: T.Any) -> None:
+        msvcrt.locking(self.lockfile.fileno(), msvcrt.LK_UNLCK, 1)
+        self.lockfile.close()