meson/mesonbuild/build.py

# Copyright 2012-2017 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.

import copy, os, re
from collections import OrderedDict
import itertools, pathlib

from . import environment
from . import dependencies
from . import mlog
from .mesonlib import File, MesonException, listify, extract_as_list
from .mesonlib import typeslistify, stringlistify, classify_unity_sources
from .mesonlib import get_filenames_templates_dict, substitute_values
from .mesonlib import for_windows, for_darwin, for_cygwin
from .compilers import is_object, clike_langs, sort_clike, lang_suffixes

known_basic_kwargs = {'install': True,
                      'c_pch': True,
                      'cpp_pch': True,
                      'c_args': True,
                      'objc_args': True,
                      'objcpp_args': True,
                      'cpp_args': True,
                      'cs_args': True,
                      'vala_args': True,
                      'fortran_args': True,
                      'd_args': True,
                      'd_import_dirs': True,
                      'd_unittest': True,
                      'd_module_versions': True,
                      'java_args': True,
                      'rust_args': True,
                      'link_args': True,
                      'link_depends': True,
                      'link_with': True,
                      'link_whole': True,
                      'implicit_include_directories': True,
                      'include_directories': True,
                      'dependencies': True,
                      'install_dir': True,
                      'main_class': True,
                      'name_suffix': True,
                      'gui_app': True,
                      'extra_files': True,
                      'install_rpath': True,
                      'build_rpath': True,
                      'resources': True,
                      'sources': True,
                      'objects': True,
                      'native': True,
                      'build_by_default': True,
                      'override_options': True,
                      }

# These contain kwargs supported by both static and shared libraries. These are
# combined here because a library() call might be shared_library() or
# static_library() at runtime based on the configuration.
# FIXME: Find a way to pass that info down here so we can have proper target
# kwargs checking when specifically using shared_library() or static_library().
known_lib_kwargs = known_basic_kwargs.copy()
known_lib_kwargs.update({'version': True, # Only for shared libs
                         'soversion': True, # Only for shared libs
                         'name_prefix': True,
                         'vs_module_defs': True, # Only for shared libs
                         'vala_header': True,
                         'vala_vapi': True,
                         'vala_gir': True,
                         'pic': True, # Only for static libs
                         'rust_crate_type': True, # Only for Rust libs
                         })

known_exe_kwargs = known_basic_kwargs.copy()
known_exe_kwargs.update({'implib': True,
                         'export_dynamic': True
                         })

class InvalidArguments(MesonException):
    pass

class Build:
    """A class that holds the status of one build including
    all dependencies and so on.
    """

    def __init__(self, environment):
        self.project_name = 'name of master project'
        self.project_version = None
        self.environment = environment
        self.projects = {}
        self.targets = OrderedDict()
        self.compilers = OrderedDict()
        self.cross_compilers = OrderedDict()
        self.global_args = {}
        self.projects_args = {}
        self.global_link_args = {}
        self.projects_link_args = {}
        self.tests = []
        self.benchmarks = []
        self.headers = []
        self.man = []
        self.data = []
        self.static_linker = None
        self.static_cross_linker = None
        self.subprojects = {}
        self.install_scripts = []
        self.postconf_scripts = []
        self.install_dirs = []
        self.dep_manifest_name = None
        self.dep_manifest = {}
        self.cross_stdlibs = {}
        self.test_setups = {}

    def add_compiler(self, compiler):
        if self.static_linker is None and compiler.needs_static_linker():
            self.static_linker = self.environment.detect_static_linker(compiler)
        lang = compiler.get_language()
        if lang not in self.compilers:
            self.compilers[lang] = compiler

    def add_cross_compiler(self, compiler):
        if not self.cross_compilers:
            self.static_cross_linker = self.environment.detect_static_linker(compiler)
        lang = compiler.get_language()
        if lang not in self.cross_compilers:
            self.cross_compilers[lang] = compiler

    def get_project(self):
        return self.projects['']

    def get_targets(self):
        return self.targets

    def get_tests(self):
        return self.tests

    def get_benchmarks(self):
        return self.benchmarks

    def get_headers(self):
        return self.headers

    def get_man(self):
        return self.man

    def get_data(self):
        return self.data

    def get_install_subdirs(self):
        return self.install_dirs

    def get_global_args(self, compiler):
        return self.global_args.get(compiler.get_language(), [])

    def get_project_args(self, compiler, project):
        args = self.projects_args.get(project)
        if not args:
            return []
        return args.get(compiler.get_language(), [])

    def get_global_link_args(self, compiler):
        return self.global_link_args.get(compiler.get_language(), [])

    def get_project_link_args(self, compiler, project):
        link_args = self.projects_link_args.get(project)
        if not link_args:
            return []

        return link_args.get(compiler.get_language(), [])

class IncludeDirs:
    def __init__(self, curdir, dirs, is_system, extra_build_dirs=None):
        self.curdir = curdir
        self.incdirs = dirs
        self.is_system = is_system
        # Interpreter has validated that all given directories
        # actually exist.
        if extra_build_dirs is None:
            self.extra_build_dirs = []
        else:
            self.extra_build_dirs = extra_build_dirs

    def __repr__(self):
        r = '<{} {}/{}>'
        return r.format(self.__class__.__name__, self.curdir, self.incdirs)

    def get_curdir(self):
        return self.curdir

    def get_incdirs(self):
        return self.incdirs

    def get_extra_build_dirs(self):
        return self.extra_build_dirs

class ExtractedObjects:
    '''
    Holds a list of sources for which the objects must be extracted
    '''
    def __init__(self, target, srclist, is_unity):
        self.target = target
        self.srclist = srclist
        if is_unity:
            self.check_unity_compatible()

    def __repr__(self):
        r = '<{0} {1!r}: {2}>'
        return r.format(self.__class__.__name__, self.target.name, self.srclist)

    def check_unity_compatible(self):
        # Figure out if the extracted object list is compatible with a Unity
        # build. When we're doing a Unified build, we go through the sources,
        # and create a single source file from each subset of the sources that
        # can be compiled with a specific compiler. Then we create one object
        # from each unified source file.
        # If the list of sources for which we want objects is the same as the
        # list of sources that go into each unified build, we're good.
        srclist_set = set(self.srclist)
        # Objects for all the sources are required, so we're compatible
        if srclist_set == set(self.target.sources):
            return
        # Check if the srclist is a subset (of the target's sources) that is
        # going to form a unified source file and a single object
        compsrcs = classify_unity_sources(self.target.compilers.values(),
                                          self.target.sources)
        for srcs in compsrcs.values():
            if srclist_set == set(srcs):
                return
        msg = 'Single object files can not be extracted in Unity builds. ' \
              'You can only extract all the object files at once.'
        raise MesonException(msg)


class EnvironmentVariables:
    def __init__(self):
        self.envvars = []

    def __repr__(self):
        repr_str = "<{0}: {1}>"
        return repr_str.format(self.__class__.__name__, self.envvars)

    def get_value(self, values, kwargs):
        separator = kwargs.get('separator', os.pathsep)

        value = ''
        for var in values:
            value += separator + var
        return separator, value.strip(separator)

    def set(self, env, name, values, kwargs):
        return self.get_value(values, kwargs)[1]

    def append(self, env, name, values, kwargs):
        sep, value = self.get_value(values, kwargs)
        if name in env:
            return env[name] + sep + value
        return value

    def prepend(self, env, name, values, kwargs):
        sep, value = self.get_value(values, kwargs)
        if name in env:
            return value + sep + env[name]

        return value

    def get_env(self, full_env):
        env = {}
        for method, name, values, kwargs in self.envvars:
            env[name] = method(full_env, name, values, kwargs)
        return env

class Target:
    def __init__(self, name, subdir, subproject, build_by_default):
        if '/' in name or '\\' in name:
            # Fix failing test 53 when this becomes an error.
            mlog.warning('''Target "%s" has a path separator in its name.
This is not supported, it can cause unexpected failures and will become
a hard error in the future.''' % name)
        self.name = name
        self.subdir = subdir
        self.subproject = subproject
        self.build_by_default = build_by_default
        self.install = False
        self.build_always = False
        self.option_overrides = {}

    def get_basename(self):
        return self.name

    def get_subdir(self):
        return self.subdir

    def get_id(self):
        # This ID must also be a valid file name on all OSs.
        # It should also avoid shell metacharacters for obvious
        # reasons.
        base = self.name + self.type_suffix()
        if self.subproject == '':
            return base
        return self.subproject + '@@' + base

    def process_kwargs(self, kwargs):
        if 'build_by_default' in kwargs:
            self.build_by_default = kwargs['build_by_default']
            if not isinstance(self.build_by_default, bool):
                raise InvalidArguments('build_by_default must be a boolean value.')
        self.option_overrides = self.parse_overrides(kwargs)

    def parse_overrides(self, kwargs):
        result = {}
        overrides = stringlistify(kwargs.get('override_options', []))
        for o in overrides:
            if '=' not in o:
                raise InvalidArguments('Overrides must be of form "key=value"')
            k, v = o.split('=', 1)
            k = k.strip()
            v = v.strip()
            result[k] = v
        return result


class BuildTarget(Target):
    def __init__(self, name, subdir, subproject, is_cross, sources, objects, environment, kwargs):
        super().__init__(name, subdir, subproject, True)
        self.is_cross = is_cross
        unity_opt = environment.coredata.get_builtin_option('unity')
        self.is_unity = unity_opt == 'on' or (unity_opt == 'subprojects' and subproject != '')
        self.environment = environment
        self.sources = []
        self.compilers = OrderedDict()
        self.objects = []
        self.external_deps = []
        self.include_dirs = []
        self.link_targets = []
        self.link_whole_targets = []
        self.link_depends = []
        self.name_prefix_set = False
        self.name_suffix_set = False
        self.filename = 'no_name'
        # The list of all files outputted by this target. Useful in cases such
        # as Vala which generates .vapi and .h besides the compiled output.
        self.outputs = [self.filename]
        self.need_install = False
        self.pch = {}
        self.extra_args = {}
        self.generated = []
        self.extra_files = []
        # Sources can be:
        # 1. Pre-existing source files in the source tree
        # 2. Pre-existing sources generated by configure_file in the build tree
        # 3. Sources files generated by another target or a Generator
        self.process_sourcelist(sources)
        # Objects can be:
        # 1. Pre-existing objects provided by the user with the `objects:` kwarg
        # 2. Compiled objects created by and extracted from another target
        self.process_objectlist(objects)
        self.process_compilers()
        self.process_kwargs(kwargs, environment)
        self.check_unknown_kwargs(kwargs)
        if not any([self.sources, self.generated, self.objects, self.link_whole]):
            raise InvalidArguments('Build target %s has no sources.' % name)
        self.process_compilers_late()
        self.validate_sources()
        self.validate_cross_install(environment)

    def __lt__(self, other):
        return self.get_id() < other.get_id()

    def __repr__(self):
        repr_str = "<{0} {1}: {2}>"
        return repr_str.format(self.__class__.__name__, self.get_id(), self.filename)

    def validate_cross_install(self, environment):
        if environment.is_cross_build() and not self.is_cross and self.install:
            raise InvalidArguments('Tried to install a natively built target in a cross build.')

    def check_unknown_kwargs(self, kwargs):
        # Override this method in derived classes that have more
        # keywords.
        self.check_unknown_kwargs_int(kwargs, known_basic_kwargs)

    def check_unknown_kwargs_int(self, kwargs, known_kwargs):
        unknowns = []
        for k in kwargs:
            if k not in known_kwargs:
                unknowns.append(k)
        if len(unknowns) > 0:
            mlog.warning('Unknown keyword argument(s) in target %s: %s.' %
                         (self.name, ', '.join(unknowns)))

    def process_objectlist(self, objects):
        assert(isinstance(objects, list))
        for s in objects:
            if hasattr(s, 'held_object'):
                s = s.held_object
            if isinstance(s, (str, File, ExtractedObjects)):
                self.objects.append(s)
            elif isinstance(s, (GeneratedList, CustomTarget)):
                msg = 'Generated files are not allowed in the \'objects\' kwarg ' + \
                    'for target {!r}.\nIt is meant only for '.format(self.name) + \
                    'pre-built object files that are shipped with the\nsource ' + \
                    'tree. Try adding it in the list of sources.'
                raise InvalidArguments(msg)
            else:
                msg = 'Bad object of type {!r} in target {!r}.'.format(type(s).__name__, self.name)
                raise InvalidArguments(msg)

    def process_sourcelist(self, sources):
        sources = listify(sources)
        added_sources = {} # If the same source is defined multiple times, use it only once.
        for s in sources:
            # Holder unpacking. Ugly.
            if hasattr(s, 'held_object'):
                s = s.held_object
            if isinstance(s, File):
                if s not in added_sources:
                    self.sources.append(s)
                    added_sources[s] = True
            elif isinstance(s, (GeneratedList, CustomTarget, CustomTargetIndex)):
                self.generated.append(s)
            else:
                msg = 'Bad source of type {!r} in target {!r}.'.format(type(s).__name__, self.name)
                raise InvalidArguments(msg)

    @staticmethod
    def can_compile_remove_sources(compiler, sources):
        removed = False
        for s in sources[:]:
            if compiler.can_compile(s):
                sources.remove(s)
                removed = True
        return removed

    def process_compilers_late(self):
        """Processes additional compilers after kwargs have been evaluated.

        This can add extra compilers that might be required by keyword
        arguments, such as link_with or dependencies. It will also try to guess
        which compiler to use if one hasn't been selected already.
        """
        # Populate list of compilers
        if self.is_cross:
            compilers = self.environment.coredata.cross_compilers
        else:
            compilers = self.environment.coredata.compilers

        # If this library is linked against another library we need to consider
        # the languages of those libraries as well.
        if self.link_targets or self.link_whole_targets:
            extra = set()
            for t in itertools.chain(self.link_targets, self.link_whole_targets):
                for name, compiler in t.compilers.items():
                    if name in clike_langs:
                        extra.add((name, compiler))
            for name, compiler in sorted(extra, key=lambda p: sort_clike(p[0])):
                self.compilers[name] = compiler

        if not self.compilers:
            # No source files or parent targets, target consists of only object
            # files of unknown origin. Just add the first clike compiler
            # that we have and hope that it can link these objects
            for lang in clike_langs:
                if lang in compilers:
                    self.compilers[lang] = compilers[lang]
                    break

    def process_compilers(self):
        '''
        Populate self.compilers, which is the list of compilers that this
        target will use for compiling all its sources.
        We also add compilers that were used by extracted objects to simplify
        dynamic linker determination.
        '''
        if not self.sources and not self.generated and not self.objects:
            return
        # Populate list of compilers
        if self.is_cross:
            compilers = self.environment.coredata.cross_compilers
        else:
            compilers = self.environment.coredata.compilers
        # Pre-existing sources
        sources = list(self.sources)
        # All generated sources
        for gensrc in self.generated:
            for s in gensrc.get_outputs():
                # Generated objects can't be compiled, so don't use them for
                # compiler detection. If our target only has generated objects,
                # we will fall back to using the first c-like compiler we find,
                # which is what we need.
                if not is_object(s):
                    sources.append(s)
        # Sources that were used to create our extracted objects
        for o in self.objects:
            if not isinstance(o, ExtractedObjects):
                continue
            for s in o.srclist:
                # Don't add Vala sources since that will pull in the Vala
                # compiler even though we will never use it since we are
                # dealing with compiled C code.
                if not s.endswith(lang_suffixes['vala']):
                    sources.append(s)
        if sources:
            # For each source, try to add one compiler that can compile it.
            # It's ok if no compilers can do so, because users are expected to
            # be able to add arbitrary non-source files to the sources list.
            for s in sources:
                for lang, compiler in compilers.items():
                    if compiler.can_compile(s):
                        if lang not in self.compilers:
                            self.compilers[lang] = compiler
                        break
            # Re-sort according to clike_langs
            self.compilers = OrderedDict(sorted(self.compilers.items(),
                                                key=lambda t: sort_clike(t[0])))

        # If all our sources are Vala, our target also needs the C compiler but
        # it won't get added above.
        if 'vala' in self.compilers and 'c' not in self.compilers:
            self.compilers['c'] = compilers['c']

    def validate_sources(self):
        if not self.sources:
            return
        for lang in ('cs', 'java'):
            if lang in self.compilers:
                check_sources = list(self.sources)
                compiler = self.compilers[lang]
                if not self.can_compile_remove_sources(compiler, check_sources):
                    m = 'No {} sources found in target {!r}'.format(lang, self.name)
                    raise InvalidArguments(m)
                if check_sources:
                    m = '{0} targets can only contain {0} files:\n'.format(lang.capitalize())
                    m += '\n'.join([repr(c) for c in check_sources])
                    raise InvalidArguments(m)
                # CSharp and Java targets can't contain any other file types
                assert(len(self.compilers) == 1)
                return

    def process_link_depends(self, sources, environment):
        """Process the link_depends keyword argument.

        This is designed to handle strings, Files, and the output of Custom
        Targets. Notably it doesn't handle generator() returned objects, since
        adding them as a link depends would inherently cause them to be
        generated twice, since the output needs to be passed to the ld_args and
        link_depends.
        """
        sources = listify(sources)
        for s in sources:
            if hasattr(s, 'held_object'):
                s = s.held_object

            if isinstance(s, File):
                self.link_depends.append(s)
            elif isinstance(s, str):
                self.link_depends.append(
                    File.from_source_file(environment.source_dir, self.subdir, s))
            elif hasattr(s, 'get_outputs'):
                self.link_depends.extend(
                    [File.from_built_file(s.subdir, p) for p in s.get_outputs()])
            else:
                raise InvalidArguments(
                    'Link_depends arguments must be strings, Files, '
                    'or a Custom Target, or lists thereof.')

    def get_original_kwargs(self):
        return self.kwargs

    def unpack_holder(self, d):
        d = listify(d)
        newd = []
        for i in d:
            if isinstance(i, list):
                i = self.unpack_holder(i)
            elif hasattr(i, 'held_object'):
                i = i.held_object
            for t in ['dependencies', 'link_with', 'include_directories', 'sources']:
                if hasattr(i, t):
                    setattr(i, t, self.unpack_holder(getattr(i, t)))
            newd.append(i)
        return newd

    def copy_kwargs(self, kwargs):
        self.kwargs = copy.copy(kwargs)
        # This sucks quite badly. Arguments
        # are holders but they can't be pickled
        # so unpack those known.
        for k, v in self.kwargs.items():
            if isinstance(v, list):
                self.kwargs[k] = self.unpack_holder(v)
            if hasattr(v, 'held_object'):
                self.kwargs[k] = v.held_object
        for t in ['dependencies', 'link_with', 'include_directories', 'sources']:
            if t in self.kwargs:
                self.kwargs[t] = self.unpack_holder(self.kwargs[t])

    def extract_objects(self, srclist):
        obj_src = []
        for src in srclist:
            if not isinstance(src, str):
                raise MesonException('Object extraction arguments must be strings.')
            src = File(False, self.subdir, src)
            if src not in self.sources:
                raise MesonException('Tried to extract unknown source %s.' % src)
            obj_src.append(src)
        return ExtractedObjects(self, obj_src, self.is_unity)

    def extract_all_objects(self):
        return ExtractedObjects(self, self.sources, self.is_unity)

    def get_all_link_deps(self):
        return self.get_transitive_link_deps()

    def get_transitive_link_deps(self):
        result = []
        for i in self.link_targets:
            result += i.get_all_link_deps()
        return result

    def get_custom_install_dir(self):
        return self.install_dir

    def process_kwargs(self, kwargs, environment):
        super().process_kwargs(kwargs)
        self.copy_kwargs(kwargs)
        kwargs.get('modules', [])
        self.need_install = kwargs.get('install', self.need_install)
        llist = extract_as_list(kwargs, 'link_with')
        for linktarget in llist:
            # Sorry for this hack. Keyword targets are kept in holders
            # in kwargs. Unpack here without looking at the exact type.
            if hasattr(linktarget, "held_object"):
                linktarget = linktarget.held_object
            if isinstance(linktarget, dependencies.ExternalLibrary):
                raise MesonException('''An external library was used in link_with keyword argument, which
is reserved for libraries built as part of this project. External
libraries must be passed using the dependencies keyword argument
instead, because they are conceptually "external dependencies",
just like those detected with the dependency() function.''')
            self.link(linktarget)
        lwhole = extract_as_list(kwargs, 'link_whole')
        for linktarget in lwhole:
            # Sorry for this hack. Keyword targets are kept in holders
            # in kwargs. Unpack here without looking at the exact type.
            if hasattr(linktarget, "held_object"):
                linktarget = linktarget.held_object
            self.link_whole(linktarget)

        c_pchlist, cpp_pchlist, clist, cpplist, cslist, valalist,  objclist, objcpplist, fortranlist, rustlist \
            = extract_as_list(kwargs, 'c_pch', 'cpp_pch', 'c_args', 'cpp_args', 'cs_args', 'vala_args', 'objc_args',
                              'objcpp_args', 'fortran_args', 'rust_args')

        self.add_pch('c', c_pchlist)
        self.add_pch('cpp', cpp_pchlist)
        compiler_args = {'c': clist, 'cpp': cpplist, 'cs': cslist, 'vala': valalist, 'objc': objclist, 'objcpp': objcpplist,
                         'fortran': fortranlist, 'rust': rustlist
                         }
        for key, value in compiler_args.items():
            self.add_compiler_args(key, value)

        if not isinstance(self, Executable):
            self.vala_header = kwargs.get('vala_header', self.name + '.h')
            self.vala_vapi = kwargs.get('vala_vapi', self.name + '.vapi')
            self.vala_gir = kwargs.get('vala_gir', None)

        dlist = stringlistify(kwargs.get('d_args', []))
        self.add_compiler_args('d', dlist)
        dfeatures = dict()
        dfeature_unittest = kwargs.get('d_unittest', False)
        if dfeature_unittest:
            dfeatures['unittest'] = dfeature_unittest
        dfeature_versions = kwargs.get('d_module_versions', None)
        if dfeature_versions:
            dfeatures['versions'] = dfeature_versions
        dfeature_import_dirs = kwargs.get('d_import_dirs', None)
        if dfeature_import_dirs:
            dfeatures['import_dirs'] = dfeature_import_dirs
        if dfeatures:
            if 'd' in self.compilers:
                self.add_compiler_args('d', self.compilers['d'].get_feature_args(dfeatures))

        self.link_args = extract_as_list(kwargs, 'link_args')
        for i in self.link_args:
            if not isinstance(i, str):
                raise InvalidArguments('Link_args arguments must be strings.')
        for l in self.link_args:
            if '-Wl,-rpath' in l or l.startswith('-rpath'):
                mlog.warning('''Please do not define rpath with a linker argument, use install_rpath or build_rpath properties instead.
This will become a hard error in a future Meson release.''')
        self.process_link_depends(kwargs.get('link_depends', []), environment)
        # Target-specific include dirs must be added BEFORE include dirs from
        # internal deps (added inside self.add_deps()) to override them.
        inclist = extract_as_list(kwargs, 'include_directories')
        self.add_include_dirs(inclist)
        # Add dependencies (which also have include_directories)
        deplist = extract_as_list(kwargs, 'dependencies')
        self.add_deps(deplist)
        # If an item in this list is False, the output corresponding to
        # the list index of that item will not be installed
        self.install_dir = typeslistify(kwargs.get('install_dir', [None]),
                                        (str, bool))
        main_class = kwargs.get('main_class', '')
        if not isinstance(main_class, str):
            raise InvalidArguments('Main class must be a string')
        self.main_class = main_class
        if isinstance(self, Executable):
            self.gui_app = kwargs.get('gui_app', False)
            if not isinstance(self.gui_app, bool):
                raise InvalidArguments('Argument gui_app must be boolean.')
        elif 'gui_app' in kwargs:
            raise InvalidArguments('Argument gui_app can only be used on executables.')
        extra_files = extract_as_list(kwargs, 'extra_files')
        for i in extra_files:
            assert(isinstance(i, File))
            trial = os.path.join(environment.get_source_dir(), i.subdir, i.fname)
            if not(os.path.isfile(trial)):
                raise InvalidArguments('Tried to add non-existing extra file %s.' % i)
        self.extra_files = extra_files
        self.install_rpath = kwargs.get('install_rpath', '')
        if not isinstance(self.install_rpath, str):
            raise InvalidArguments('Install_rpath is not a string.')
        self.build_rpath = kwargs.get('build_rpath', '')
        if not isinstance(self.build_rpath, str):
            raise InvalidArguments('Build_rpath is not a string.')
        resources = extract_as_list(kwargs, 'resources')
        for r in resources:
            if not isinstance(r, str):
                raise InvalidArguments('Resource argument is not a string.')
            trial = os.path.join(environment.get_source_dir(), self.subdir, r)
            if not os.path.isfile(trial):
                raise InvalidArguments('Tried to add non-existing resource %s.' % r)
        self.resources = resources
        if 'name_prefix' in kwargs:
            name_prefix = kwargs['name_prefix']
            if isinstance(name_prefix, list):
                if name_prefix:
                    raise InvalidArguments('name_prefix array must be empty to signify null.')
            elif not isinstance(name_prefix, str):
                raise InvalidArguments('name_prefix must be a string.')
            self.prefix = name_prefix
            self.name_prefix_set = True
        if 'name_suffix' in kwargs:
            name_suffix = kwargs['name_suffix']
            if isinstance(name_suffix, list):
                if name_suffix:
                    raise InvalidArguments('name_suffix array must be empty to signify null.')
            else:
                if not isinstance(name_suffix, str):
                    raise InvalidArguments('name_suffix must be a string.')
                self.suffix = name_suffix
                self.name_suffix_set = True
        if isinstance(self, StaticLibrary):
            # You can't disable PIC on OS X. The compiler ignores -fno-PIC.
            # PIC is always on for Windows (all code is position-independent
            # since library loading is done differently)
            if for_darwin(self.is_cross, self.environment) or for_windows(self.is_cross, self.environment):
                self.pic = True
            elif '-fPIC' in clist + cpplist:
                mlog.warning("Use the 'pic' kwarg instead of passing -fPIC manually to static library {!r}".format(self.name))
                self.pic = True
            else:
                self.pic = kwargs.get('pic', False)
                if not isinstance(self.pic, bool):
                    raise InvalidArguments('Argument pic to static library {!r} must be boolean'.format(self.name))
        self.implicit_include_directories = kwargs.get('implicit_include_directories', True)
        if not isinstance(self.implicit_include_directories, bool):
            raise InvalidArguments('Implicit_include_directories must be a boolean.')

    def get_filename(self):
        return self.filename

    def get_outputs(self):
        return self.outputs

    def get_extra_args(self, language):
        return self.extra_args.get(language, [])

    def get_dependencies(self):
        transitive_deps = []
        for t in self.link_targets + self.link_whole_targets:
            transitive_deps.append(t)
            if isinstance(t, StaticLibrary):
                transitive_deps += t.get_dependencies()
        return transitive_deps

    def get_source_subdir(self):
        return self.subdir

    def get_sources(self):
        return self.sources

    def get_objects(self):
        return self.objects

    def get_generated_sources(self):
        return self.generated

    def should_install(self):
        return self.need_install

    def has_pch(self):
        return len(self.pch) > 0

    def get_pch(self, language):
        try:
            return self.pch[language]
        except KeyError:
            return[]

    def get_include_dirs(self):
        return self.include_dirs

    def add_deps(self, deps):
        deps = listify(deps)
        for dep in deps:
            if hasattr(dep, 'held_object'):
                dep = dep.held_object
            if isinstance(dep, dependencies.InternalDependency):
                # Those parts that are internal.
                self.process_sourcelist(dep.sources)
                self.add_include_dirs(dep.include_directories)
                for l in dep.libraries:
                    self.link(l)
                # Those parts that are external.
                extpart = dependencies.InternalDependency('undefined',
                                                          [],
                                                          dep.compile_args,
                                                          dep.link_args,
                                                          [], [], [])
                self.external_deps.append(extpart)
                # Deps of deps.
                self.add_deps(dep.ext_deps)
            elif isinstance(dep, dependencies.Dependency):
                self.external_deps.append(dep)
                self.process_sourcelist(dep.get_sources())
            elif isinstance(dep, BuildTarget):
                raise InvalidArguments('''Tried to use a build target as a dependency.
You probably should put it in link_with instead.''')
            else:
                # This is a bit of a hack. We do not want Build to know anything
                # about the interpreter so we can't import it and use isinstance.
                # This should be reliable enough.
                if hasattr(dep, 'project_args_frozen') or hasattr(dep, 'global_args_frozen'):
                    raise InvalidArguments('Tried to use subproject object as a dependency.\n'
                                           'You probably wanted to use a dependency declared in it instead.\n'
                                           'Access it by calling get_variable() on the subproject object.')
                raise InvalidArguments('Argument is of an unacceptable type {!r}.\nMust be '
                                       'either an external dependency (returned by find_library() or '
                                       'dependency()) or an internal dependency (returned by '
                                       'declare_dependency()).'.format(type(dep).__name__))

    def get_external_deps(self):
        return self.external_deps

    def link(self, target):
        for t in listify(target, unholder=True):
            if not isinstance(t, Target):
                raise InvalidArguments('{!r} is not a target.'.format(t))
            if not t.is_linkable_target():
                raise InvalidArguments('Link target {!r} is not linkable.'.format(t))
            if isinstance(self, SharedLibrary) and isinstance(t, StaticLibrary) and not t.pic:
                msg = "Can't link non-PIC static library {!r} into shared library {!r}. ".format(t.name, self.name)
                msg += "Use the 'pic' option to static_library to build with PIC."
                raise InvalidArguments(msg)
            if self.is_cross != t.is_cross:
                raise InvalidArguments('Tried to mix cross built and native libraries in target {!r}'.format(self.name))
            self.link_targets.append(t)

    def link_whole(self, target):
        for t in listify(target, unholder=True):
            if not isinstance(t, StaticLibrary):
                raise InvalidArguments('{!r} is not a static library.'.format(t))
            if isinstance(self, SharedLibrary) and not t.pic:
                msg = "Can't link non-PIC static library {!r} into shared library {!r}. ".format(t.name, self.name)
                msg += "Use the 'pic' option to static_library to build with PIC."
                raise InvalidArguments(msg)
            if self.is_cross != t.is_cross:
                raise InvalidArguments('Tried to mix cross built and native libraries in target {!r}'.format(self.name))
            self.link_whole_targets.append(t)

    def add_pch(self, language, pchlist):
        if not pchlist:
            return
        elif len(pchlist) == 1:
            if not environment.is_header(pchlist[0]):
                raise InvalidArguments('PCH argument %s is not a header.' % pchlist[0])
        elif len(pchlist) == 2:
            if environment.is_header(pchlist[0]):
                if not environment.is_source(pchlist[1]):
                    raise InvalidArguments('PCH definition must contain one header and at most one source.')
            elif environment.is_source(pchlist[0]):
                if not environment.is_header(pchlist[1]):
                    raise InvalidArguments('PCH definition must contain one header and at most one source.')
                pchlist = [pchlist[1], pchlist[0]]
            else:
                raise InvalidArguments('PCH argument %s is of unknown type.' % pchlist[0])
        elif len(pchlist) > 2:
            raise InvalidArguments('PCH definition may have a maximum of 2 files.')
        self.pch[language] = pchlist

    def add_include_dirs(self, args):
        ids = []
        for a in args:
            # FIXME same hack, forcibly unpack from holder.
            if hasattr(a, 'held_object'):
                a = a.held_object
            if not isinstance(a, IncludeDirs):
                raise InvalidArguments('Include directory to be added is not an include directory object.')
            ids.append(a)
        self.include_dirs += ids

    def add_compiler_args(self, language, args):
        args = listify(args)
        for a in args:
            if not isinstance(a, (str, File)):
                raise InvalidArguments('A non-string passed to compiler args.')
        if language in self.extra_args:
            self.extra_args[language] += args
        else:
            self.extra_args[language] = args

    def get_aliases(self):
        return {}

    def get_langs_used_by_deps(self):
        '''
        Sometimes you want to link to a C++ library that exports C API, which
        means the linker must link in the C++ stdlib, and we must use a C++
        compiler for linking. The same is also applicable for objc/objc++, etc,
        so we can keep using clike_langs for the priority order.

        See: https://github.com/mesonbuild/meson/issues/1653
        '''
        langs = []
        # Check if any of the external libraries were written in this language
        for dep in self.external_deps:
            if dep.language not in langs:
                langs.append(dep.language)
        # Check if any of the internal libraries this target links to were
        # written in this language
        for link_target in itertools.chain(self.link_targets, self.link_whole_targets):
            for language in link_target.compilers:
                if language not in langs:
                    langs.append(language)
        return langs

    def get_clike_dynamic_linker(self):
        '''
        We use the order of languages in `clike_langs` to determine which
        linker to use in case the target has sources compiled with multiple
        compilers. All languages other than those in this list have their own
        linker.
        Note that Vala outputs C code, so Vala sources can use any linker
        that can link compiled C. We don't actually need to add an exception
        for Vala here because of that.
        '''
        # Populate list of all compilers, not just those being used to compile
        # sources in this target
        if self.is_cross:
            all_compilers = self.environment.coredata.cross_compilers
        else:
            all_compilers = self.environment.coredata.compilers
        # Languages used by dependencies
        dep_langs = self.get_langs_used_by_deps()
        # Pick a compiler based on the language priority-order
        for l in clike_langs:
            if l in self.compilers or l in dep_langs:
                try:
                    return all_compilers[l]
                except KeyError:
                    raise MesonException(
                        'Could not get a dynamic linker for build target {!r}. '
                        'Requires a linker for language "{}", but that is not '
                        'a project language.'.format(self.name, l))

        m = 'Could not get a dynamic linker for build target {!r}'
        raise AssertionError(m.format(self.name))

    def get_using_msvc(self):
        '''
        Check if the dynamic linker is MSVC. Used by Executable, StaticLibrary,
        and SharedLibrary for deciding when to use MSVC-specific file naming
        and debug filenames.

        If at least some code is built with MSVC and the final library is
        linked with MSVC, we can be sure that some debug info will be
        generated. We only check the dynamic linker here because the static
        linker is guaranteed to be of the same type.

        Interesting cases:
        1. The Vala compiler outputs C code to be compiled by whatever
           C compiler we're using, so all objects will still be created by the
           MSVC compiler.
        2. If the target contains only objects, process_compilers guesses and
           picks the first compiler that smells right.
        '''
        linker = self.get_clike_dynamic_linker()
        if linker and linker.get_id() == 'msvc':
            return True
        return False

    def is_linkable_target(self):
        return False


class Generator:
    def __init__(self, args, kwargs):
        if len(args) != 1:
            raise InvalidArguments('Generator requires exactly one positional argument: the executable')
        exe = args[0]
        if hasattr(exe, 'held_object'):
            exe = exe.held_object
        if not isinstance(exe, (Executable, dependencies.ExternalProgram)):
            raise InvalidArguments('First generator argument must be an executable.')
        self.exe = exe
        self.depfile = None
        self.capture = False
        self.process_kwargs(kwargs)

    def __repr__(self):
        repr_str = "<{0}: {1}>"
        return repr_str.format(self.__class__.__name__, self.exe)

    def get_exe(self):
        return self.exe

    def process_kwargs(self, kwargs):
        if 'arguments' not in kwargs:
            raise InvalidArguments('Generator must have "arguments" keyword argument.')
        args = kwargs['arguments']
        if isinstance(args, str):
            args = [args]
        if not isinstance(args, list):
            raise InvalidArguments('"Arguments" keyword argument must be a string or a list of strings.')
        for a in args:
            if not isinstance(a, str):
                raise InvalidArguments('A non-string object in "arguments" keyword argument.')
        self.arglist = args
        if 'output' not in kwargs:
            raise InvalidArguments('Generator must have "output" keyword argument.')
        outputs = listify(kwargs['output'])
        for rule in outputs:
            if not isinstance(rule, str):
                raise InvalidArguments('"output" may only contain strings.')
            if '@BASENAME@' not in rule and '@PLAINNAME@' not in rule:
                raise InvalidArguments('Every element of "output" must contain @BASENAME@ or @PLAINNAME@.')
            if '/' in rule or '\\' in rule:
                raise InvalidArguments('"outputs" must not contain a directory separator.')
        if len(outputs) > 1:
            for o in outputs:
                if '@OUTPUT@' in o:
                    raise InvalidArguments('Tried to use @OUTPUT@ in a rule with more than one output.')
        self.outputs = outputs
        if 'depfile' in kwargs:
            depfile = kwargs['depfile']
            if not isinstance(depfile, str):
                raise InvalidArguments('Depfile must be a string.')
            if os.path.split(depfile)[1] != depfile:
                raise InvalidArguments('Depfile must be a plain filename without a subdirectory.')
            self.depfile = depfile
        if 'capture' in kwargs:
            capture = kwargs['capture']
            if not isinstance(capture, bool):
                raise InvalidArguments('Capture must be boolean.')
            self.capture = capture

    def get_base_outnames(self, inname):
        plainname = os.path.split(inname)[1]
        basename = os.path.splitext(plainname)[0]
        bases = [x.replace('@BASENAME@', basename).replace('@PLAINNAME@', plainname) for x in self.outputs]
        return bases

    def get_dep_outname(self, inname):
        if self.depfile is None:
            raise InvalidArguments('Tried to get dep name for rule that does not have dependency file defined.')
        plainname = os.path.split(inname)[1]
        basename = os.path.splitext(plainname)[0]
        return self.depfile.replace('@BASENAME@', basename).replace('@PLAINNAME@', plainname)

    def get_arglist(self, inname):
        plainname = os.path.split(inname)[1]
        basename = os.path.splitext(plainname)[0]
        return [x.replace('@BASENAME@', basename).replace('@PLAINNAME@', plainname) for x in self.arglist]

    def is_parent_path(self, parent, trial):
        relpath = pathlib.PurePath(trial).relative_to(parent)
        return relpath.parts[0] != '..' # For subdirs we can only go "down".

    def process_files(self, name, files, state, preserve_path_from=None, extra_args=[]):
        output = GeneratedList(self, state.subdir, preserve_path_from, extra_args=extra_args)
        for f in files:
            if isinstance(f, str):
                f = File.from_source_file(state.environment.source_dir, state.subdir, f)
            elif not isinstance(f, File):
                raise InvalidArguments('{} arguments must be strings or files not {!r}.'.format(name, f))
            if preserve_path_from:
                abs_f = f.absolute_path(state.environment.source_dir, state.environment.build_dir)
                if not self.is_parent_path(preserve_path_from, abs_f):
                    raise InvalidArguments('When using preserve_path_from, all input files must be in a subdirectory of the given dir.')
            output.add_file(f, state)
        return output


class GeneratedList:
    def __init__(self, generator, subdir, preserve_path_from=None, extra_args=[]):
        if hasattr(generator, 'held_object'):
            generator = generator.held_object
        self.generator = generator
        self.name = self.generator.exe
        self.subdir = subdir
        self.infilelist = []
        self.outfilelist = []
        self.outmap = {}
        self.extra_depends = []
        self.preserve_path_from = preserve_path_from
        self.extra_args = extra_args

    def add_preserved_path_segment(self, infile, outfiles, state):
        result = []
        in_abs = infile.absolute_path(state.environment.source_dir, state.environment.build_dir)
        assert(os.path.isabs(self.preserve_path_from))
        rel = os.path.relpath(in_abs, self.preserve_path_from)
        path_segment = os.path.split(rel)[0]
        for of in outfiles:
            result.append(os.path.join(path_segment, of))
        return result

    def add_file(self, newfile, state):
        self.infilelist.append(newfile)
        outfiles = self.generator.get_base_outnames(newfile.fname)
        if self.preserve_path_from:
            outfiles = self.add_preserved_path_segment(newfile, outfiles, state)
        self.outfilelist += outfiles
        self.outmap[newfile] = outfiles

    def get_inputs(self):
        return self.infilelist

    def get_outputs(self):
        return self.outfilelist

    def get_outputs_for(self, filename):
        return self.outmap[filename]

    def get_generator(self):
        return self.generator

    def get_extra_args(self):
        return self.extra_args

class Executable(BuildTarget):
    def __init__(self, name, subdir, subproject, is_cross, sources, objects, environment, kwargs):
        super().__init__(name, subdir, subproject, is_cross, sources, objects, environment, kwargs)
        # Unless overridden, executables have no suffix or prefix. Except on
        # Windows and with C#/Mono executables where the suffix is 'exe'
        if not hasattr(self, 'prefix'):
            self.prefix = ''
        if not hasattr(self, 'suffix'):
            # Executable for Windows or C#/Mono
            if (for_windows(is_cross, environment) or
                    for_cygwin(is_cross, environment) or 'cs' in self.compilers):
                self.suffix = 'exe'
            else:
                self.suffix = ''
        self.filename = self.name
        if self.suffix:
            self.filename += '.' + self.suffix
        self.outputs = [self.filename]

        # The import library this target will generate
        self.import_filename = None
        # The import library that Visual Studio would generate (and accept)
        self.vs_import_filename = None
        # The import library that GCC would generate (and prefer)
        self.gcc_import_filename = None

        # Check for export_dynamic
        self.export_dynamic = False
        if kwargs.get('export_dynamic'):
            if not isinstance(kwargs['export_dynamic'], bool):
                raise InvalidArguments('"export_dynamic" keyword argument must be a boolean')
            self.export_dynamic = True
        if kwargs.get('implib'):
            self.export_dynamic = True
        if self.export_dynamic and kwargs.get('implib') is False:
            raise InvalidArguments('"implib" keyword argument must not be false for if "export_dynamic" is true')

        # If using export_dynamic, set the import library name
        if self.export_dynamic:
            implib_basename = self.name + '.exe'
            if not isinstance(kwargs.get('implib', False), bool):
                implib_basename = kwargs['implib']
            if for_windows(is_cross, environment) or for_cygwin(is_cross, environment):
                self.vs_import_filename = '{0}.lib'.format(implib_basename)
                self.gcc_import_filename = 'lib{0}.a'.format(implib_basename)
                if self.get_using_msvc():
                    self.import_filename = self.vs_import_filename
                else:
                    self.import_filename = self.gcc_import_filename

        # Only linkwithable if using export_dynamic
        self.is_linkwithable = self.export_dynamic

    def type_suffix(self):
        return "@exe"

    def check_unknown_kwargs(self, kwargs):
        self.check_unknown_kwargs_int(kwargs, known_exe_kwargs)

    def get_import_filename(self):
        """
        The name of the import library that will be outputted by the compiler

        Returns None if there is no import library required for this platform
        """
        return self.import_filename

    def get_import_filenameslist(self):
        if self.import_filename:
            return [self.vs_import_filename, self.gcc_import_filename]
        return []

    def is_linkable_target(self):
        return self.is_linkwithable

class StaticLibrary(BuildTarget):
    def __init__(self, name, subdir, subproject, is_cross, sources, objects, environment, kwargs):
        if 'pic' not in kwargs and 'b_staticpic' in environment.coredata.base_options:
            kwargs['pic'] = environment.coredata.base_options['b_staticpic'].value
        super().__init__(name, subdir, subproject, is_cross, sources, objects, environment, kwargs)
        if 'cs' in self.compilers:
            raise InvalidArguments('Static libraries not supported for C#.')
        if 'rust' in self.compilers:
            # If no crate type is specified, or it's the generic lib type, use rlib
            if not hasattr(self, 'rust_crate_type') or self.rust_crate_type == 'lib':
                mlog.debug('Defaulting Rust static library target crate type to rlib')
                self.rust_crate_type = 'rlib'
            # Don't let configuration proceed with a non-static crate type
            elif self.rust_crate_type not in ['rlib', 'staticlib']:
                raise InvalidArguments('Crate type "{0}" invalid for static libraries; must be "rlib" or "staticlib"'.format(self.rust_crate_type))
        # By default a static library is named libfoo.a even on Windows because
        # MSVC does not have a consistent convention for what static libraries
        # are called. The MSVC CRT uses libfoo.lib syntax but nothing else uses
        # it and GCC only looks for static libraries called foo.lib and
        # libfoo.a. However, we cannot use foo.lib because that's the same as
        # the import library. Using libfoo.a is ok because people using MSVC
        # always pass the library filename while linking anyway.
        if not hasattr(self, 'prefix'):
            self.prefix = 'lib'
        if not hasattr(self, 'suffix'):
            if 'rust' in self.compilers:
                if not hasattr(self, 'rust_crate_type') or self.rust_crate_type == 'rlib':
                    # default Rust static library suffix
                    self.suffix = 'rlib'
                elif self.rust_crate_type == 'staticlib':
                    self.suffix = 'a'
            else:
                self.suffix = 'a'
        self.filename = self.prefix + self.name + '.' + self.suffix
        self.outputs = [self.filename]

    def type_suffix(self):
        return "@sta"

    def check_unknown_kwargs(self, kwargs):
        self.check_unknown_kwargs_int(kwargs, known_lib_kwargs)

    def process_kwargs(self, kwargs, environment):
        super().process_kwargs(kwargs, environment)
        if 'rust_crate_type' in kwargs:
            rust_crate_type = kwargs['rust_crate_type']
            if isinstance(rust_crate_type, str):
                self.rust_crate_type = rust_crate_type
            else:
                raise InvalidArguments('Invalid rust_crate_type "{0}": must be a string.'.format(rust_crate_type))

    def is_linkable_target(self):
        return True

class SharedLibrary(BuildTarget):
    def __init__(self, name, subdir, subproject, is_cross, sources, objects, environment, kwargs):
        self.soversion = None
        self.ltversion = None
        self.vs_module_defs = None
        # The import library this target will generate
        self.import_filename = None
        # The import library that Visual Studio would generate (and accept)
        self.vs_import_filename = None
        # The import library that GCC would generate (and prefer)
        self.gcc_import_filename = None
        super().__init__(name, subdir, subproject, is_cross, sources, objects, environment, kwargs)
        if 'rust' in self.compilers:
            # If no crate type is specified, or it's the generic lib type, use dylib
            if not hasattr(self, 'rust_crate_type') or self.rust_crate_type == 'lib':
                mlog.debug('Defaulting Rust dynamic library target crate type to "dylib"')
                self.rust_crate_type = 'dylib'
            # Don't let configuration proceed with a non-dynamic crate type
            elif self.rust_crate_type not in ['dylib', 'cdylib']:
                raise InvalidArguments('Crate type "{0}" invalid for dynamic libraries; must be "dylib" or "cdylib"'.format(self.rust_crate_type))
        if not hasattr(self, 'prefix'):
            self.prefix = None
        if not hasattr(self, 'suffix'):
            self.suffix = None
        self.basic_filename_tpl = '{0.prefix}{0.name}.{0.suffix}'
        self.determine_filenames(is_cross, environment)

    def determine_filenames(self, is_cross, env):
        """
        See https://github.com/mesonbuild/meson/pull/417 for details.

        First we determine the filename template (self.filename_tpl), then we
        set the output filename (self.filename).

        The template is needed while creating aliases (self.get_aliases),
        which are needed while generating .so shared libraries for Linux.

        Besides this, there's also the import library name, which is only used
        on Windows since on that platform the linker uses a separate library
        called the "import library" during linking instead of the shared
        library (DLL). The toolchain will output an import library in one of
        two formats: GCC or Visual Studio.

        When we're building with Visual Studio, the import library that will be
        generated by the toolchain is self.vs_import_filename, and with
        MinGW/GCC, it's self.gcc_import_filename. self.import_filename will
        always contain the import library name this target will generate.
        """
        prefix = ''
        suffix = ''
        self.filename_tpl = self.basic_filename_tpl
        # If the user already provided the prefix and suffix to us, we don't
        # need to do any filename suffix/prefix detection.
        # NOTE: manual prefix/suffix override is currently only tested for C/C++
        if self.prefix is not None and self.suffix is not None:
            pass
        # C# and Mono
        elif 'cs' in self.compilers:
            prefix = ''
            suffix = 'dll'
            self.filename_tpl = '{0.prefix}{0.name}.{0.suffix}'
        # C, C++, Swift, Vala
        # Only Windows uses a separate import library for linking
        # For all other targets/platforms import_filename stays None
        elif for_windows(is_cross, env):
            suffix = 'dll'
            self.vs_import_filename = '{0}.lib'.format(self.name)
            self.gcc_import_filename = 'lib{0}.dll.a'.format(self.name)
            if self.get_using_msvc():
                # Shared library is of the form foo.dll
                prefix = ''
                # Import library is called foo.lib
                self.import_filename = self.vs_import_filename
            # Assume GCC-compatible naming
            else:
                # Shared library is of the form libfoo.dll
                prefix = 'lib'
                # Import library is called libfoo.dll.a
                self.import_filename = self.gcc_import_filename
            # Shared library has the soversion if it is defined
            if self.soversion:
                self.filename_tpl = '{0.prefix}{0.name}-{0.soversion}.{0.suffix}'
            else:
                self.filename_tpl = '{0.prefix}{0.name}.{0.suffix}'
        elif for_cygwin(is_cross, env):
            suffix = 'dll'
            self.gcc_import_filename = 'lib{0}.dll.a'.format(self.name)
            # Shared library is of the form cygfoo.dll
            # (ld --dll-search-prefix=cyg is the default)
            prefix = 'cyg'
            # Import library is called libfoo.dll.a
            self.import_filename = self.gcc_import_filename
            if self.soversion:
                self.filename_tpl = '{0.prefix}{0.name}-{0.soversion}.{0.suffix}'
            else:
                self.filename_tpl = '{0.prefix}{0.name}.{0.suffix}'
        elif for_darwin(is_cross, env):
            prefix = 'lib'
            suffix = 'dylib'
            # On macOS, the filename can only contain the major version
            if self.soversion:
                # libfoo.X.dylib
                self.filename_tpl = '{0.prefix}{0.name}.{0.soversion}.{0.suffix}'
            else:
                # libfoo.dylib
                self.filename_tpl = '{0.prefix}{0.name}.{0.suffix}'
        else:
            prefix = 'lib'
            suffix = 'so'
            if self.ltversion:
                # libfoo.so.X[.Y[.Z]] (.Y and .Z are optional)
                self.filename_tpl = '{0.prefix}{0.name}.{0.suffix}.{0.ltversion}'
            elif self.soversion:
                # libfoo.so.X
                self.filename_tpl = '{0.prefix}{0.name}.{0.suffix}.{0.soversion}'
            else:
                # No versioning, libfoo.so
                self.filename_tpl = '{0.prefix}{0.name}.{0.suffix}'
        if self.prefix is None:
            self.prefix = prefix
        if self.suffix is None:
            self.suffix = suffix
        self.filename = self.filename_tpl.format(self)
        self.outputs = [self.filename]

    def process_kwargs(self, kwargs, environment):
        super().process_kwargs(kwargs, environment)
        # Shared library version
        if 'version' in kwargs:
            self.ltversion = kwargs['version']
            if not isinstance(self.ltversion, str):
                raise InvalidArguments('Shared library version needs to be a string, not ' + type(self.ltversion).__name__)
            if not re.fullmatch(r'[0-9]+(\.[0-9]+){0,2}', self.ltversion):
                raise InvalidArguments('Invalid Shared library version "{0}". Must be of the form X.Y.Z where all three are numbers. Y and Z are optional.'.format(self.ltversion))
        # Try to extract/deduce the soversion
        if 'soversion' in kwargs:
            self.soversion = kwargs['soversion']
            if isinstance(self.soversion, int):
                self.soversion = str(self.soversion)
            if not isinstance(self.soversion, str):
                raise InvalidArguments('Shared library soversion is not a string or integer.')
        elif self.ltversion:
            # library version is defined, get the soversion from that
            # We replicate what Autotools does here and take the first
            # number of the version by default.
            self.soversion = self.ltversion.split('.')[0]
        # Visual Studio module-definitions file
        if 'vs_module_defs' in kwargs:
            path = kwargs['vs_module_defs']
            if hasattr(path, 'held_object'):
                path = path.held_object
            if isinstance(path, str):
                if os.path.isabs(path):
                    self.vs_module_defs = File.from_absolute_file(path)
                else:
                    self.vs_module_defs = File.from_source_file(environment.source_dir, self.subdir, path)
                self.link_depends.append(self.vs_module_defs)
            elif isinstance(path, File):
                # When passing a generated file.
                self.vs_module_defs = path
                self.link_depends.append(path)
            elif hasattr(path, 'get_filename'):
                # When passing output of a Custom Target
                path = File.from_built_file(path.subdir, path.get_filename())
                self.vs_module_defs = path
                self.link_depends.append(path)
            else:
                raise InvalidArguments(
                    'Shared library vs_module_defs must be either a string, '
                    'a file object or a Custom Target')
        if 'rust_crate_type' in kwargs:
            rust_crate_type = kwargs['rust_crate_type']
            if isinstance(rust_crate_type, str):
                self.rust_crate_type = rust_crate_type
            else:
                raise InvalidArguments('Invalid rust_crate_type "{0}": must be a string.'.format(rust_crate_type))

    def check_unknown_kwargs(self, kwargs):
        self.check_unknown_kwargs_int(kwargs, known_lib_kwargs)

    def get_import_filename(self):
        """
        The name of the import library that will be outputted by the compiler

        Returns None if there is no import library required for this platform
        """
        return self.import_filename

    def get_import_filenameslist(self):
        if self.import_filename:
            return [self.vs_import_filename, self.gcc_import_filename]
        return []

    def get_all_link_deps(self):
        return [self] + self.get_transitive_link_deps()

    def get_aliases(self):
        """
        If the versioned library name is libfoo.so.0.100.0, aliases are:
        * libfoo.so.0 (soversion) -> libfoo.so.0.100.0
        * libfoo.so (unversioned; for linking) -> libfoo.so.0
        Same for dylib:
        * libfoo.dylib (unversioned; for linking) -> libfoo.0.dylib
        """
        aliases = {}
        # Aliases are only useful with .so and .dylib libraries. Also if
        # there's no self.soversion (no versioning), we don't need aliases.
        if self.suffix not in ('so', 'dylib') or not self.soversion:
            return {}
        # With .so libraries, the minor and micro versions are also in the
        # filename. If ltversion != soversion we create an soversion alias:
        # libfoo.so.0 -> libfoo.so.0.100.0
        # Where libfoo.so.0.100.0 is the actual library
        if self.suffix == 'so' and self.ltversion and self.ltversion != self.soversion:
            alias_tpl = self.filename_tpl.replace('ltversion', 'soversion')
            ltversion_filename = alias_tpl.format(self)
            aliases[ltversion_filename] = self.filename
        # libfoo.so.0/libfoo.0.dylib is the actual library
        else:
            ltversion_filename = self.filename
        # Unversioned alias:
        #  libfoo.so -> libfoo.so.0
        #  libfoo.dylib -> libfoo.0.dylib
        aliases[self.basic_filename_tpl.format(self)] = ltversion_filename
        return aliases

    def type_suffix(self):
        return "@sha"

    def is_linkable_target(self):
        return True

# A shared library that is meant to be used with dlopen rather than linking
# into something else.
class SharedModule(SharedLibrary):
    def __init__(self, name, subdir, subproject, is_cross, sources, objects, environment, kwargs):
        if 'version' in kwargs:
            raise MesonException('Shared modules must not specify the version kwarg.')
        if 'soversion' in kwargs:
            raise MesonException('Shared modules must not specify the soversion kwarg.')
        super().__init__(name, subdir, subproject, is_cross, sources, objects, environment, kwargs)
        self.import_filename = None

class CustomTarget(Target):
    known_kwargs = {'input': True,
                    'output': True,
                    'command': True,
                    'capture': False,
                    'install': True,
                    'install_dir': True,
                    'build_always': True,
                    'depends': True,
                    'depend_files': True,
                    'depfile': True,
                    'build_by_default': True,
                    'override_options': True,
                    }

    def __init__(self, name, subdir, subproject, kwargs, absolute_paths=False):
        super().__init__(name, subdir, subproject, False)
        self.dependencies = []
        self.extra_depends = []
        self.depend_files = [] # Files that this target depends on but are not on the command line.
        self.depfile = None
        self.process_kwargs(kwargs)
        self.extra_files = []
        # Whether to use absolute paths for all files on the commandline
        self.absolute_paths = absolute_paths
        unknowns = []
        for k in kwargs:
            if k not in CustomTarget.known_kwargs:
                unknowns.append(k)
        if len(unknowns) > 0:
            mlog.warning('Unknown keyword arguments in target %s: %s' %
                         (self.name, ', '.join(unknowns)))

    def __lt__(self, other):
        return self.get_id() < other.get_id()

    def __repr__(self):
        repr_str = "<{0} {1}: {2}>"
        return repr_str.format(self.__class__.__name__, self.get_id(), self.command)

    def get_id(self):
        return self.name + self.type_suffix()

    def get_target_dependencies(self):
        deps = self.dependencies[:]
        deps += self.extra_depends
        for c in self.sources:
            if hasattr(c, 'held_object'):
                c = c.held_object
            if isinstance(c, (BuildTarget, CustomTarget)):
                deps.append(c)
        return deps

    def get_transitive_build_target_deps(self):
        '''
        Recursively fetch the build targets that this custom target depends on,
        whether through `command:`, `depends:`, or `sources:` The recursion is
        only performed on custom targets.
        This is useful for setting PATH on Windows for finding required DLLs.
        F.ex, if you have a python script that loads a C module that links to
        other DLLs in your project.
        '''
        bdeps = set()
        deps = self.get_target_dependencies()
        for d in deps:
            if isinstance(d, BuildTarget):
                bdeps.add(d)
            elif isinstance(d, CustomTarget):
                bdeps.update(d.get_transitive_build_target_deps())
        return bdeps

    def flatten_command(self, cmd):
        cmd = listify(cmd, unholder=True)
        final_cmd = []
        for c in cmd:
            if isinstance(c, str):
                final_cmd.append(c)
            elif isinstance(c, File):
                self.depend_files.append(c)
                final_cmd.append(c)
            elif isinstance(c, dependencies.ExternalProgram):
                if not c.found():
                    m = 'Tried to use not-found external program {!r} in "command"'
                    raise InvalidArguments(m.format(c.name))
                self.depend_files.append(File.from_absolute_file(c.get_path()))
                final_cmd += c.get_command()
            elif isinstance(c, (BuildTarget, CustomTarget)):
                self.dependencies.append(c)
                final_cmd.append(c)
            elif isinstance(c, list):
                final_cmd += self.flatten_command(c)
            else:
                raise InvalidArguments('Argument {!r} in "command" is invalid'.format(c))
        return final_cmd

    def process_kwargs(self, kwargs):
        super().process_kwargs(kwargs)
        self.sources = extract_as_list(kwargs, 'input', unholder=True)
        if 'output' not in kwargs:
            raise InvalidArguments('Missing keyword argument "output".')
        self.outputs = listify(kwargs['output'])
        # This will substitute values from the input into output and return it.
        inputs = get_sources_string_names(self.sources)
        values = get_filenames_templates_dict(inputs, [])
        for i in self.outputs:
            if not(isinstance(i, str)):
                raise InvalidArguments('Output argument not a string.')
            if '/' in i:
                raise InvalidArguments('Output must not contain a path segment.')
            if '@INPUT@' in i or '@INPUT0@' in i:
                m = 'Output cannot contain @INPUT@ or @INPUT0@, did you ' \
                    'mean @PLAINNAME@ or @BASENAME@?'
                raise InvalidArguments(m)
            # We already check this during substitution, but the error message
            # will be unclear/confusing, so check it here.
            if len(inputs) != 1 and ('@PLAINNAME@' in i or '@BASENAME@' in i):
                m = "Output cannot contain @PLAINNAME@ or @BASENAME@ when " \
                    "there is more than one input (we can't know which to use)"
                raise InvalidArguments(m)
        self.outputs = substitute_values(self.outputs, values)
        self.capture = kwargs.get('capture', False)
        if self.capture and len(self.outputs) != 1:
            raise InvalidArguments('Capturing can only output to a single file.')
        if 'command' not in kwargs:
            raise InvalidArguments('Missing keyword argument "command".')
        if 'depfile' in kwargs:
            depfile = kwargs['depfile']
            if not isinstance(depfile, str):
                raise InvalidArguments('Depfile must be a string.')
            if os.path.split(depfile)[1] != depfile:
                raise InvalidArguments('Depfile must be a plain filename without a subdirectory.')
            self.depfile = depfile
        self.command = self.flatten_command(kwargs['command'])
        if self.capture:
            for c in self.command:
                if isinstance(c, str) and '@OUTPUT@' in c:
                    raise InvalidArguments('@OUTPUT@ is not allowed when capturing output.')
        if 'install' in kwargs:
            self.install = kwargs['install']
            if not isinstance(self.install, bool):
                raise InvalidArguments('"install" must be boolean.')
            if self.install:
                if 'install_dir' not in kwargs:
                    raise InvalidArguments('"install_dir" must be specified '
                                           'when installing a target')
                # If an item in this list is False, the output corresponding to
                # the list index of that item will not be installed
                self.install_dir = typeslistify(kwargs['install_dir'], (str, bool))
        else:
            self.install = False
            self.install_dir = [None]
        self.build_always = kwargs.get('build_always', False)
        if not isinstance(self.build_always, bool):
            raise InvalidArguments('Argument build_always must be a boolean.')
        extra_deps, depend_files = extract_as_list(kwargs, 'depends', 'depend_files', pop = False)
        for ed in extra_deps:
            while hasattr(ed, 'held_object'):
                ed = ed.held_object
            if not isinstance(ed, (CustomTarget, BuildTarget)):
                raise InvalidArguments('Can only depend on toplevel targets: custom_target or build_target (executable or a library)')
            self.extra_depends.append(ed)
        for i in depend_files:
            if isinstance(i, (File, str)):
                self.depend_files.append(i)
            else:
                mlog.debug(i)
                raise InvalidArguments('Unknown type {!r} in depend_files.'.format(type(i).__name__))

    def get_dependencies(self):
        return self.dependencies

    def should_install(self):
        return self.install

    def get_custom_install_dir(self):
        return self.install_dir

    def get_outputs(self):
        return self.outputs

    def get_filename(self):
        return self.outputs[0]

    def get_sources(self):
        return self.sources

    def get_generated_lists(self):
        genlists = []
        for c in self.sources:
            if hasattr(c, 'held_object'):
                c = c.held_object
            if isinstance(c, GeneratedList):
                genlists.append(c)
        return genlists

    def get_generated_sources(self):
        return self.get_generated_lists()

    def type_suffix(self):
        return "@cus"

    def __getitem__(self, index):
        return CustomTargetIndex(self, self.outputs[index])

    def __setitem__(self, index, value):
        raise NotImplementedError

    def __delitem__(self, index):
        raise NotImplementedError

class RunTarget(Target):
    def __init__(self, name, command, args, dependencies, subdir, subproject):
        super().__init__(name, subdir, subproject, False)
        self.command = command
        self.args = args
        self.dependencies = dependencies

    def __lt__(self, other):
        return self.get_id() < other.get_id()

    def __repr__(self):
        repr_str = "<{0} {1}: {2}>"
        return repr_str.format(self.__class__.__name__, self.get_id(), self.command)

    def get_dependencies(self):
        return self.dependencies

    def get_generated_sources(self):
        return []

    def get_sources(self):
        return []

    def should_install(self):
        return False

    def get_filename(self):
        return self.name

    def type_suffix(self):
        return "@run"

class Jar(BuildTarget):
    def __init__(self, name, subdir, subproject, is_cross, sources, objects, environment, kwargs):
        super().__init__(name, subdir, subproject, is_cross, sources, objects, environment, kwargs)
        for s in self.sources:
            if not s.endswith('.java'):
                raise InvalidArguments('Jar source %s is not a java file.' % s)
        self.filename = self.name + '.jar'
        self.outputs = [self.filename]
        self.java_args = kwargs.get('java_args', [])

    def get_main_class(self):
        return self.main_class

    def type_suffix(self):
        return "@jar"

    def get_java_args(self):
        return self.java_args

    def validate_cross_install(self, environment):
        # All jar targets are installable.
        pass


class CustomTargetIndex:

    """A special opaque object returned by indexing a CustomTarget. This object
    exists in meson, but acts as a proxy in the backends, making targets depend
    on the CustomTarget it's derived from, but only adding one source file to
    the sources.
    """

    def __init__(self, target, output):
        self.target = target
        self.output = output

    def __repr__(self):
        return '<CustomTargetIndex: {!r}[{}]>'.format(
            self.target, self.target.get_outputs().index(self.output))

    def get_outputs(self):
        return [self.output]

    def get_subdir(self):
        return self.target.get_subdir()


class ConfigureFile:

    def __init__(self, subdir, sourcename, targetname, configuration_data):
        self.subdir = subdir
        self.sourcename = sourcename
        self.targetname = targetname
        self.configuration_data = configuration_data

    def __repr__(self):
        repr_str = "<{0}: {1} -> {2}>"
        src = os.path.join(self.subdir, self.sourcename)
        dst = os.path.join(self.subdir, self.targetname)
        return repr_str.format(self.__class__.__name__, src, dst)

    def get_configuration_data(self):
        return self.configuration_data

    def get_subdir(self):
        return self.subdir

    def get_source_name(self):
        return self.sourcename

    def get_target_name(self):
        return self.targetname

class ConfigurationData:
    def __init__(self):
        super().__init__()
        self.values = {}

    def __repr__(self):
        return repr(self.values)

    def __contains__(self, value):
        return value in self.values

    def get(self, name):
        return self.values[name] # (val, desc)

    def keys(self):
        return self.values.keys()

# A bit poorly named, but this represents plain data files to copy
# during install.
class Data:
    def __init__(self, sources, install_dir, install_mode=None):
        self.sources = sources
        self.install_dir = install_dir
        self.install_mode = install_mode
        self.sources = listify(self.sources)
        for s in self.sources:
            assert(isinstance(s, File))

class RunScript(dict):
    def __init__(self, script, args):
        super().__init__()
        assert(isinstance(script, list))
        assert(isinstance(args, list))
        self['exe'] = script
        self['args'] = args

class TestSetup:
    def __init__(self, *, exe_wrapper=None, gdb=None, timeout_multiplier=None, env=None):
        self.exe_wrapper = exe_wrapper
        self.gdb = gdb
        self.timeout_multiplier = timeout_multiplier
        self.env = env

def get_sources_string_names(sources):
    '''
    For the specified list of @sources which can be strings, Files, or targets,
    get all the output basenames.
    '''
    names = []
    for s in sources:
        if hasattr(s, 'held_object'):
            s = s.held_object
        if isinstance(s, str):
            names.append(s)
        elif isinstance(s, (BuildTarget, CustomTarget, GeneratedList)):
            names += s.get_outputs()
        elif isinstance(s, File):
            names.append(s.fname)
        else:
            raise AssertionError('Unknown source type: {!r}'.format(s))
    return names