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---
short-description: Enabling thread support
...

# Threads

Meson has a very simple notational shorthand for enabling thread support on your build targets. First you obtain the thread dependency object like this:

```meson
thread_dep = dependency('threads')
```

And then you just use it in a target like this:

```meson
executable('threadedprogram', ...
  dependencies : thread_dep)
```
# 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 typing as T
import os
import re
import pickle
import shlex
import subprocess
from collections import OrderedDict
from enum import Enum, unique
import itertools
from pathlib import PurePath, Path
from functools import lru_cache

from . import backends
from .. import modules
from .. import environment, mesonlib
from .. import build
from .. import mlog
from .. import dependencies
from .. import compilers
from ..arglist import CompilerArgs
from ..compilers import (
    Compiler, CCompiler,
    DmdDCompiler,
    FortranCompiler, PGICCompiler,
    VisualStudioCsCompiler,
    VisualStudioLikeCompiler,
)
from ..linkers import ArLinker, VisualStudioLinker
from ..mesonlib import (
    File, LibType, MachineChoice, MesonException, OrderedSet, PerMachine,
    ProgressBar, quote_arg, unholder,
)
from ..mesonlib import get_compiler_for_source, has_path_sep, OptionKey
from .backends import CleanTrees
from ..build import GeneratedList, InvalidArguments
from ..interpreter import Interpreter

if T.TYPE_CHECKING:
    from ..linkers import StaticLinker

FORTRAN_INCLUDE_PAT = r"^\s*#?include\s*['\"](\w+\.\w+)['\"]"
FORTRAN_MODULE_PAT = r"^\s*\bmodule\b\s+(\w+)\s*(?:!+.*)*$"
FORTRAN_SUBMOD_PAT = r"^\s*\bsubmodule\b\s*\((\w+:?\w+)\)\s*(\w+)"
FORTRAN_USE_PAT = r"^\s*use,?\s*(?:non_intrinsic)?\s*(?:::)?\s*(\w+)"

def cmd_quote(s):
    # see: https://docs.microsoft.com/en-us/windows/desktop/api/shellapi/nf-shellapi-commandlinetoargvw#remarks

    # backslash escape any existing double quotes
    # any existing backslashes preceding a quote are doubled
    s = re.sub(r'(\\*)"', lambda m: '\\' * (len(m.group(1)) * 2 + 1) + '"', s)
    # any terminal backslashes likewise need doubling
    s = re.sub(r'(\\*)$', lambda m: '\\' * (len(m.group(1)) * 2), s)
    # and double quote
    s = '"{}"'.format(s)

    return s

def gcc_rsp_quote(s):
    # see: the function buildargv() in libiberty
    #
    # this differs from sh-quoting in that a backslash *always* escapes the
    # following character, even inside single quotes.

    s = s.replace('\\', '\\\\')

    return shlex.quote(s)

# How ninja executes command lines differs between Unix and Windows
# (see https://ninja-build.org/manual.html#ref_rule_command)
if mesonlib.is_windows():
    quote_func = cmd_quote
    execute_wrapper = ['cmd', '/c']  # unused
    rmfile_prefix = ['del', '/f', '/s', '/q', '{}', '&&']
else:
    quote_func = quote_arg
    execute_wrapper = []
    rmfile_prefix = ['rm', '-f', '{}', '&&']

def get_rsp_threshold():
    '''Return a conservative estimate of the commandline size in bytes
    above which a response file should be used.  May be overridden for
    debugging by setting environment variable MESON_RSP_THRESHOLD.'''

    if mesonlib.is_windows():
        # Usually 32k, but some projects might use cmd.exe,
        # and that has a limit of 8k.
        limit = 8192
    else:
        # On Linux, ninja always passes the commandline as a single
        # big string to /bin/sh, and the kernel limits the size of a
        # single argument; see MAX_ARG_STRLEN
        limit = 131072
    # Be conservative
    limit = limit / 2
    return int(os.environ.get('MESON_RSP_THRESHOLD', limit))

# a conservative estimate of the command-line length limit
rsp_threshold = get_rsp_threshold()

# ninja variables whose value should remain unquoted. The value of these ninja
# variables (or variables we use them in) is interpreted directly by ninja
# (e.g. the value of the depfile variable is a pathname that ninja will read
# from, etc.), so it must not be shell quoted.
raw_names = {'DEPFILE_UNQUOTED', 'DESC', 'pool', 'description', 'targetdep', 'dyndep'}

NINJA_QUOTE_BUILD_PAT = re.compile(r"[$ :\n]")
NINJA_QUOTE_VAR_PAT = re.compile(r"[$ \n]")

def ninja_quote(text: str, is_build_line=False) -> str:
    if is_build_line:
        quote_re = NINJA_QUOTE_BUILD_PAT
    else:
        quote_re = NINJA_QUOTE_VAR_PAT
    # Fast path for when no quoting is necessary
    if not quote_re.search(text):
        return text
    if '\n' in text:
        errmsg = '''Ninja does not support newlines in rules. The content was:

{}

Please report this error with a test case to the Meson bug tracker.'''.format(text)
        raise MesonException(errmsg)
    return quote_re.sub(r'$\g<0>', text)

class TargetDependencyScannerInfo:
    def __init__(self, private_dir: str, source2object: T.Dict[str, str]):
        self.private_dir = private_dir
        self.source2object = source2object

@unique
class Quoting(Enum):
    both = 0
    notShell = 1
    notNinja = 2
    none = 3

class NinjaCommandArg:
    def __init__(self, s, quoting = Quoting.both):
        self.s = s
        self.quoting = quoting

    def __str__(self):
        return self.s

    @staticmethod
    def list(l, q):
        return [NinjaCommandArg(i, q) for i in l]

class NinjaComment:
    def __init__(self, comment):
        self.comment = comment

    def write(self, outfile):
        for l in self.comment.split('\n'):
            outfile.write('# ')
            outfile.write(l)
            outfile.write('\n')
        outfile.write('\n')

class NinjaRule:
    def __init__(self, rule, command, args, description,
                 rspable = False, deps = None, depfile = None, extra = None,
                 rspfile_quote_style = 'gcc'):

        def strToCommandArg(c):
            if isinstance(c, NinjaCommandArg):
                return c

            # deal with common cases here, so we don't have to explicitly
            # annotate the required quoting everywhere
            if c == '&&':
                # shell constructs shouldn't be shell quoted
                return NinjaCommandArg(c, Quoting.notShell)
            if c.startswith('$'):
                var = re.search(r'\$\{?(\w*)\}?', c).group(1)
                if var not in raw_names:
                    # ninja variables shouldn't be ninja quoted, and their value
                    # is already shell quoted
                    return NinjaCommandArg(c, Quoting.none)
                else:
                    # shell quote the use of ninja variables whose value must
                    # not be shell quoted (as it also used by ninja)
                    return NinjaCommandArg(c, Quoting.notNinja)

            return NinjaCommandArg(c)

        self.name = rule
        self.command = list(map(strToCommandArg, command))  # includes args which never go into a rspfile
        self.args = list(map(strToCommandArg, args))  # args which will go into a rspfile, if used
        self.description = description
        self.deps = deps  # depstyle 'gcc' or 'msvc'
        self.depfile = depfile
        self.extra = extra
        self.rspable = rspable  # if a rspfile can be used
        self.refcount = 0
        self.rsprefcount = 0
        self.rspfile_quote_style = rspfile_quote_style  # rspfile quoting style is 'gcc' or 'cl'

        if self.depfile == '$DEPFILE':
            self.depfile += '_UNQUOTED'

    @staticmethod
    def _quoter(x, qf = quote_func):
        if isinstance(x, NinjaCommandArg):
            if x.quoting == Quoting.none:
                return x.s
            elif x.quoting == Quoting.notNinja:
                return qf(x.s)
            elif x.quoting == Quoting.notShell:
                return ninja_quote(x.s)
            # fallthrough
        return ninja_quote(qf(str(x)))

    def write(self, outfile):
        if self.rspfile_quote_style == 'cl':
            rspfile_quote_func = cmd_quote
        else:
            rspfile_quote_func = gcc_rsp_quote

        def rule_iter():
            if self.refcount:
                yield ''
            if self.rsprefcount:
                yield '_RSP'

        for rsp in rule_iter():
            outfile.write('rule {}{}\n'.format(self.name, rsp))
            if rsp == '_RSP':
                outfile.write(' command = {} @$out.rsp\n'.format(' '.join([self._quoter(x) for x in self.command])))
                outfile.write(' rspfile = $out.rsp\n')
                outfile.write(' rspfile_content = {}\n'.format(' '.join([self._quoter(x, rspfile_quote_func) for x in self.args])))
            else:
                outfile.write(' command = {}\n'.format(' '.join([self._quoter(x) for x in (self.command + self.args)])))
            if self.deps:
                outfile.write(' deps = {}\n'.format(self.deps))
            if self.depfile:
                outfile.write(' depfile = {}\n'.format(self.depfile))
            outfile.write(' description = {}\n'.format(self.description))
            if self.extra:
                for l in self.extra.split('\n'):
                    outfile.write(' ')
                    outfile.write(l)
                    outfile.write('\n')
            outfile.write('\n')

    def length_estimate(self, infiles, outfiles, elems):
        # determine variables
        # this order of actions only approximates ninja's scoping rules, as
        # documented at: https://ninja-build.org/manual.html#ref_scope
        ninja_vars = {}
        for e in elems:
            (name, value) = e
            ninja_vars[name] = value
        ninja_vars['deps'] = self.deps
        ninja_vars['depfile'] = self.depfile
        ninja_vars['in'] = infiles
        ninja_vars['out'] = outfiles

        # expand variables in command
        command = ' '.join([self._quoter(x) for x in self.command + self.args])
        estimate = len(command)
        for m in re.finditer(r'(\${\w+}|\$\w+)?[^$]*', command):
            if m.start(1) != -1:
                estimate -= m.end(1) - m.start(1) + 1
                chunk = m.group(1)
                if chunk[1] == '{':
                    chunk = chunk[2:-1]
                else:
                    chunk = chunk[1:]
                chunk = ninja_vars.get(chunk, []) # undefined ninja variables are empty
                estimate += len(' '.join(chunk))

        # determine command length
        return estimate

class NinjaBuildElement:
    def __init__(self, all_outputs, outfilenames, rulename, infilenames, implicit_outs=None):
        self.implicit_outfilenames = implicit_outs or []
        if isinstance(outfilenames, str):
            self.outfilenames = [outfilenames]
        else:
            self.outfilenames = outfilenames
        assert(isinstance(rulename, str))
        self.rulename = rulename
        if isinstance(infilenames, str):
            self.infilenames = [infilenames]
        else:
            self.infilenames = infilenames
        self.deps = OrderedSet()
        self.orderdeps = OrderedSet()
        self.elems = []
        self.all_outputs = all_outputs

    def add_dep(self, dep):
        if isinstance(dep, list):
            self.deps.update(dep)
        else:
            self.deps.add(dep)

    def add_orderdep(self, dep):
        if isinstance(dep, list):
            self.orderdeps.update(dep)
        else:
            self.orderdeps.add(dep)

    def add_item(self, name, elems):
        # Always convert from GCC-style argument naming to the naming used by the
        # current compiler. Also filter system include paths, deduplicate, etc.
        if isinstance(elems, CompilerArgs):
            elems = elems.to_native()
        if isinstance(elems, str):
            elems = [elems]
        self.elems.append((name, elems))

        if name == 'DEPFILE':
            self.elems.append((name + '_UNQUOTED', elems))

    def _should_use_rspfile(self):
        # 'phony' is a rule built-in to ninja
        if self.rulename == 'phony':
            return False

        if not self.rule.rspable:
            return False

        infilenames = ' '.join([ninja_quote(i, True) for i in self.infilenames])
        outfilenames = ' '.join([ninja_quote(i, True) for i in self.outfilenames])

        return self.rule.length_estimate(infilenames,
                                         outfilenames,
                                         self.elems) >= rsp_threshold

    def count_rule_references(self):
        if self.rulename != 'phony':
            if self._should_use_rspfile():
                self.rule.rsprefcount += 1
            else:
                self.rule.refcount += 1

    def write(self, outfile):
        self.check_outputs()
        ins = ' '.join([ninja_quote(i, True) for i in self.infilenames])
        outs = ' '.join([ninja_quote(i, True) for i in self.outfilenames])
        implicit_outs = ' '.join([ninja_quote(i, True) for i in self.implicit_outfilenames])
        if implicit_outs:
            implicit_outs = ' | ' + implicit_outs
        use_rspfile = self._should_use_rspfile()
        if use_rspfile:
            rulename = self.rulename + '_RSP'
            mlog.debug("Command line for building %s is long, using a response file" % self.outfilenames)
        else:
            rulename = self.rulename
        line = 'build {}{}: {} {}'.format(outs, implicit_outs, rulename, ins)
        if len(self.deps) > 0:
            line += ' | ' + ' '.join([ninja_quote(x, True) for x in sorted(self.deps)])
        if len(self.orderdeps) > 0:
            line += ' || ' + ' '.join([ninja_quote(x, True) for x in sorted(self.orderdeps)])
        line += '\n'
        # This is the only way I could find to make this work on all
        # platforms including Windows command shell. Slash is a dir separator
        # on Windows, too, so all characters are unambiguous and, more importantly,
        # do not require quoting, unless explicitly specified, which is necessary for
        # the csc compiler.
        line = line.replace('\\', '/')
        if mesonlib.is_windows():
            # Support network paths as backslash, otherwise they are interpreted as
            # arguments for compile/link commands when using MSVC
            line = ' '.join(
                (l.replace('//', '\\\\', 1) if l.startswith('//') else l)
                for l in line.split(' ')
            )
        outfile.write(line)

        if use_rspfile:
            if self.rule.rspfile_quote_style == 'cl':
                qf = cmd_quote
            else:
                qf = gcc_rsp_quote
        else:
            qf = quote_func

        for e in self.elems:
            (name, elems) = e
            should_quote = name not in raw_names
            line = ' {} = '.format(name)
            newelems = []
            for i in elems:
                if not should_quote or i == '&&': # Hackety hack hack
                    newelems.append(ninja_quote(i))
                else:
                    newelems.append(ninja_quote(qf(i)))
            line += ' '.join(newelems)
            line += '\n'
            outfile.write(line)
        outfile.write('\n')

    def check_outputs(self):
        for n in self.outfilenames:
            if n in self.all_outputs:
                raise MesonException('Multiple producers for Ninja target "{}". Please rename your targets.'.format(n))
            self.all_outputs[n] = True

class NinjaBackend(backends.Backend):

    def __init__(self, build: T.Optional[build.Build], interpreter: T.Optional[Interpreter]):
        super().__init__(build, interpreter)
        self.name = 'ninja'
        self.ninja_filename = 'build.ninja'
        self.fortran_deps = {}
        self.all_outputs = {}
        self.introspection_data = {}
        self.created_llvm_ir_rule = PerMachine(False, False)

    def create_target_alias(self, to_target):
        # We need to use aliases for targets that might be used as directory
        # names to workaround a Ninja bug that breaks `ninja -t clean`.
        # This is used for 'reserved' targets such as 'test', 'install',
        # 'benchmark', etc, and also for RunTargets.
        # https://github.com/mesonbuild/meson/issues/1644
        if not to_target.startswith('meson-'):
            m = 'Invalid usage of create_target_alias with {!r}'
            raise AssertionError(m.format(to_target))
        from_target = to_target[len('meson-'):]
        elem = NinjaBuildElement(self.all_outputs, from_target, 'phony', to_target)
        self.add_build(elem)

    def detect_vs_dep_prefix(self, tempfilename):
        '''VS writes its dependency in a locale dependent format.
        Detect the search prefix to use.'''
        # TODO don't hard-code host
        for compiler in self.environment.coredata.compilers.host.values():
            # Have to detect the dependency format

            # IFort on windows is MSVC like, but doesn't have /showincludes
            if isinstance(compiler, FortranCompiler):
                continue
            if isinstance(compiler, PGICCompiler) and mesonlib.is_windows():
                # for the purpose of this function, PGI doesn't act enough like MSVC
                return open(tempfilename, 'a', encoding='utf-8')
            if isinstance(compiler, VisualStudioLikeCompiler):
                break
        else:
            # None of our compilers are MSVC, we're done.
            return open(tempfilename, 'a', encoding='utf-8')
        filename = os.path.join(self.environment.get_scratch_dir(),
                                'incdetect.c')
        with open(filename, 'w') as f:
            f.write('''#include<stdio.h>
int dummy;
''')

        # The output of cl dependency information is language
        # and locale dependent. Any attempt at converting it to
        # Python strings leads to failure. We _must_ do this detection
        # in raw byte mode and write the result in raw bytes.
        pc = subprocess.Popen(compiler.get_exelist() +
                              ['/showIncludes', '/c', 'incdetect.c'],
                              cwd=self.environment.get_scratch_dir(),
                              stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        (stdout, stderr) = pc.communicate()

        # We want to match 'Note: including file: ' in the line
        # 'Note: including file: d:\MyDir\include\stdio.h', however
        # different locales have different messages with a different
        # number of colons. Match up to the the drive name 'd:\'.
        # When used in cross compilation, the path separator is a
        # forward slash rather than a backslash so handle both; i.e.
        # the path is /MyDir/include/stdio.h.
        # With certain cross compilation wrappings of MSVC, the paths
        # use backslashes, but without the leading drive name, so
        # allow the path to start with any path separator, i.e.
        # \MyDir\include\stdio.h.
        matchre = re.compile(rb"^(.*\s)([a-zA-Z]:\\|[\\\/]).*stdio.h$")

        def detect_prefix(out):
            for line in re.split(rb'\r?\n', out):
                match = matchre.match(line)
                if match:
                    with open(tempfilename, 'ab') as binfile:
                        binfile.write(b'msvc_deps_prefix = ' + match.group(1) + b'\n')
                    return open(tempfilename, 'a', encoding='utf-8')
            return None

        # Some cl wrappers (e.g. Squish Coco) output dependency info
        # to stderr rather than stdout
        result = detect_prefix(stdout) or detect_prefix(stderr)
        if result:
            return result

        raise MesonException('Could not determine vs dep dependency prefix string.')

    def generate(self):
        ninja = environment.detect_ninja_command_and_version(log=True)
        if ninja is None:
            raise MesonException('Could not detect Ninja v1.8.2 or newer')
        (self.ninja_command, self.ninja_version) = ninja
        outfilename = os.path.join(self.environment.get_build_dir(), self.ninja_filename)
        tempfilename = outfilename + '~'
        with open(tempfilename, 'w', encoding='utf-8') as outfile:
            outfile.write('# This is the build file for project "{}"\n'.format(self.build.get_project()))
            outfile.write('# It is autogenerated by the Meson build system.\n')
            outfile.write('# Do not edit by hand.\n\n')
            outfile.write('ninja_required_version = 1.8.2\n\n')

            num_pools = self.environment.coredata.options[OptionKey('backend_max_links')].value
            if num_pools > 0:
                outfile.write('''pool link_pool
  depth = {}

'''.format(num_pools))

        with self.detect_vs_dep_prefix(tempfilename) as outfile:
            self.generate_rules()

            self.build_elements = []
            self.generate_phony()
            self.add_build_comment(NinjaComment('Build rules for targets'))
            for t in ProgressBar(self.build.get_targets().values(), desc='Generating targets'):
                self.generate_target(t)
            self.add_build_comment(NinjaComment('Test rules'))
            self.generate_tests()
            self.add_build_comment(NinjaComment('Install rules'))
            self.generate_install()
            self.generate_dist()
            key = OptionKey('b_coverage')
            if (key in self.environment.coredata.options and
                    self.environment.coredata.options[key].value):
                self.add_build_comment(NinjaComment('Coverage rules'))
                self.generate_coverage_rules()
            self.add_build_comment(NinjaComment('Suffix'))
            self.generate_utils()
            self.generate_ending()

            self.write_rules(outfile)
            self.write_builds(outfile)

            default = 'default all\n\n'
            outfile.write(default)
        # Only overwrite the old build file after the new one has been
        # fully created.
        os.replace(tempfilename, outfilename)
        mlog.cmd_ci_include(outfilename)  # For CI debugging
        self.generate_compdb()

    # http://clang.llvm.org/docs/JSONCompilationDatabase.html
    def generate_compdb(self):
        rules = []
        # TODO: Rather than an explicit list here, rules could be marked in the
        # rule store as being wanted in compdb
        for for_machine in MachineChoice:
            for lang in self.environment.coredata.compilers[for_machine]:
                rules += ["%s%s" % (rule, ext) for rule in [self.get_compiler_rule_name(lang, for_machine)]
                          for ext in ['', '_RSP']]
                rules += ["%s%s" % (rule, ext) for rule in [self.get_pch_rule_name(lang, for_machine)]
                          for ext in ['', '_RSP']]
        compdb_options = ['-x'] if mesonlib.version_compare(self.ninja_version, '>=1.9') else []
        ninja_compdb = self.ninja_command + ['-t', 'compdb'] + compdb_options + rules
        builddir = self.environment.get_build_dir()
        try:
            jsondb = subprocess.check_output(ninja_compdb, cwd=builddir)
            with open(os.path.join(builddir, 'compile_commands.json'), 'wb') as f:
                f.write(jsondb)
        except Exception:
            mlog.warning('Could not create compilation database.')

    # Get all generated headers. Any source file might need them so
    # we need to add an order dependency to them.
    def get_generated_headers(self, target):
        if hasattr(target, 'cached_generated_headers'):
            return target.cached_generated_headers
        header_deps = []
        # XXX: Why don't we add deps to CustomTarget headers here?
        for genlist in target.get_generated_sources():
            if isinstance(genlist, (build.CustomTarget, build.CustomTargetIndex)):
                continue
            for src in genlist.get_outputs():
                if self.environment.is_header(src):
                    header_deps.append(self.get_target_generated_dir(target, genlist, src))
        if 'vala' in target.compilers and not isinstance(target, build.Executable):
            vala_header = File.from_built_file(self.get_target_dir(target), target.vala_header)
            header_deps.append(vala_header)
        # Recurse and find generated headers
        for dep in itertools.chain(target.link_targets, target.link_whole_targets):
            if isinstance(dep, (build.StaticLibrary, build.SharedLibrary)):
                header_deps += self.get_generated_headers(dep)
        target.cached_generated_headers = header_deps
        return header_deps

    def get_target_generated_sources(self, target):
        """
        Returns a dictionary with the keys being the path to the file
        (relative to the build directory) of that type and the value
        being the GeneratorList or CustomTarget that generated it.
        """
        srcs = OrderedDict()
        for gensrc in target.get_generated_sources():
            for s in gensrc.get_outputs():
                f = self.get_target_generated_dir(target, gensrc, s)
                srcs[f] = s
        return srcs

    def get_target_sources(self, target):
        srcs = OrderedDict()
        for s in target.get_sources():
            # BuildTarget sources are always mesonlib.File files which are
            # either in the source root, or generated with configure_file and
            # in the build root
            if not isinstance(s, File):
                raise InvalidArguments('All sources in target {!r} must be of type mesonlib.File'.format(s))
            f = s.rel_to_builddir(self.build_to_src)
            srcs[f] = s
        return srcs

    # Languages that can mix with C or C++ but don't support unity builds yet
    # because the syntax we use for unity builds is specific to C/++/ObjC/++.
    # Assembly files cannot be unitified and neither can LLVM IR files
    langs_cant_unity = ('d', 'fortran')

    def get_target_source_can_unity(self, target, source):
        if isinstance(source, File):
            source = source.fname
        if self.environment.is_llvm_ir(source) or \
           self.environment.is_assembly(source):
            return False
        suffix = os.path.splitext(source)[1][1:]
        for lang in self.langs_cant_unity:
            if lang not in target.compilers:
                continue
            if suffix in target.compilers[lang].file_suffixes:
                return False
        return True

    def create_target_source_introspection(self, target: build.Target, comp: compilers.Compiler, parameters, sources, generated_sources):
        '''
        Adds the source file introspection information for a language of a target

        Internal introspection storage formart:
        self.introspection_data = {
            '<target ID>': {
                <id tuple>: {
                    'language: 'lang',
                    'compiler': ['comp', 'exe', 'list'],
                    'parameters': ['UNIQUE', 'parameter', 'list'],
                    'sources': [],
                    'generated_sources': [],
                }
            }
        }
        '''
        tid = target.get_id()
        lang = comp.get_language()
        tgt = self.introspection_data[tid]
        # Find an existing entry or create a new one
        id_hash = (lang, tuple(parameters))
        src_block = tgt.get(id_hash, None)
        if src_block is None:
            # Convert parameters
            if isinstance(parameters, CompilerArgs):
                parameters = parameters.to_native(copy=True)
            parameters = comp.compute_parameters_with_absolute_paths(parameters, self.build_dir)
            # The new entry
            src_block = {
                'language': lang,
                'compiler': comp.get_exelist(),
                'parameters': parameters,
                'sources': [],
                'generated_sources': [],
            }
            tgt[id_hash] = src_block
        # Make source files absolute
        sources = [x.absolute_path(self.source_dir, self.build_dir) if isinstance(x, File) else os.path.normpath(os.path.join(self.build_dir, x))
                   for x in sources]
        generated_sources = [x.absolute_path(self.source_dir, self.build_dir) if isinstance(x, File) else os.path.normpath(os.path.join(self.build_dir, x))
                             for x in generated_sources]
        # Add the source files
        src_block['sources'] += sources
        src_block['generated_sources'] += generated_sources

    def generate_target(self, target):
        try:
            if isinstance(target, build.BuildTarget):
                os.makedirs(self.get_target_private_dir_abs(target))
        except FileExistsError:
            pass
        if isinstance(target, build.CustomTarget):
            self.generate_custom_target(target)
        if isinstance(target, build.RunTarget):
            self.generate_run_target(target)
        compiled_sources = []
        source2object = {}
        name = target.get_id()
        if name in self.processed_targets:
            return
        self.processed_targets[name] = True
        # Initialize an empty introspection source list
        self.introspection_data[name] = {}
        # Generate rules for all dependency targets
        self.process_target_dependencies(target)
        # If target uses a language that cannot link to C objects,
        # just generate for that language and return.
        if isinstance(target, build.Jar):
            self.generate_jar_target(target)
            return
        if target.uses_rust():
            self.generate_rust_target(target)
            return
        if 'cs' in target.compilers:
            self.generate_cs_target(target)
            return
        if 'swift' in target.compilers:
            self.generate_swift_target(target)
            return

        # Now we handle the following languages:
        # ObjC++, ObjC, C++, C, D, Fortran, Vala

        # target_sources:
        #   Pre-existing target C/C++ sources to be built; dict of full path to
        #   source relative to build root and the original File object.
        # generated_sources:
        #   GeneratedList and CustomTarget sources to be built; dict of the full
        #   path to source relative to build root and the generating target/list
        # vala_generated_sources:
        #   Array of sources generated by valac that have to be compiled
        if 'vala' in target.compilers:
            # Sources consumed by valac are filtered out. These only contain
            # C/C++ sources, objects, generated libs, and unknown sources now.
            target_sources, generated_sources, \
                vala_generated_sources = self.generate_vala_compile(target)
        else:
            target_sources = self.get_target_sources(target)
            generated_sources = self.get_target_generated_sources(target)
            vala_generated_sources = []
        self.scan_fortran_module_outputs(target)
        # Generate rules for GeneratedLists
        self.generate_generator_list_rules(target)

        # Generate rules for building the remaining source files in this target
        outname = self.get_target_filename(target)
        obj_list = []
        is_unity = self.is_unity(target)
        header_deps = []
        unity_src = []
        unity_deps = [] # Generated sources that must be built before compiling a Unity target.
        header_deps += self.get_generated_headers(target)

        if is_unity:
            # Warn about incompatible sources if a unity build is enabled
            langs = set(target.compilers.keys())
            langs_cant = langs.intersection(self.langs_cant_unity)
            if langs_cant:
                langs_are = langs = ', '.join(langs_cant).upper()
                langs_are += ' are' if len(langs_cant) > 1 else ' is'
                msg = '{} not supported in Unity builds yet, so {} ' \
                      'sources in the {!r} target will be compiled normally' \
                      ''.format(langs_are, langs, target.name)
                mlog.log(mlog.red('FIXME'), msg)

        # Get a list of all generated headers that will be needed while building
        # this target's sources (generated sources and pre-existing sources).
        # This will be set as dependencies of all the target's sources. At the
        # same time, also deal with generated sources that need to be compiled.
        generated_source_files = []
        for rel_src in generated_sources.keys():
            dirpart, fnamepart = os.path.split(rel_src)
            raw_src = File(True, dirpart, fnamepart)
            if self.environment.is_source(rel_src) and not self.environment.is_header(rel_src):
                if is_unity and self.get_target_source_can_unity(target, rel_src):
                    unity_deps.append(raw_src)
                    abs_src = os.path.join(self.environment.get_build_dir(), rel_src)
                    unity_src.append(abs_src)
                else:
                    generated_source_files.append(raw_src)
            elif self.environment.is_object(rel_src):
                obj_list.append(rel_src)
            elif self.environment.is_library(rel_src) or modules.is_module_library(rel_src):
                pass
            else:
                # Assume anything not specifically a source file is a header. This is because
                # people generate files with weird suffixes (.inc, .fh) that they then include
                # in their source files.
                header_deps.append(raw_src)
        # These are the generated source files that need to be built for use by
        # this target. We create the Ninja build file elements for this here
        # because we need `header_deps` to be fully generated in the above loop.
        for src in generated_source_files:
            if self.environment.is_llvm_ir(src):
                o, s = self.generate_llvm_ir_compile(target, src)
            else:
                o, s = self.generate_single_compile(target, src, True,
                                                 order_deps=header_deps)
            compiled_sources.append(s)
            source2object[s] = o
            obj_list.append(o)

        use_pch = self.environment.coredata.options.get(OptionKey('b_pch'))
        if use_pch and target.has_pch():
            pch_objects = self.generate_pch(target, header_deps=header_deps)
        else:
            pch_objects = []

        # Generate compilation targets for C sources generated from Vala
        # sources. This can be extended to other $LANG->C compilers later if
        # necessary. This needs to be separate for at least Vala
        vala_generated_source_files = []
        for src in vala_generated_sources:
            dirpart, fnamepart = os.path.split(src)
            raw_src = File(True, dirpart, fnamepart)
            if is_unity:
                unity_src.append(os.path.join(self.environment.get_build_dir(), src))
                header_deps.append(raw_src)
            else:
                # Generated targets are ordered deps because the must exist
                # before the sources compiling them are used. After the first
                # compile we get precise dependency info from dep files.
                # This should work in all cases. If it does not, then just
                # move them from orderdeps to proper deps.
                if self.environment.is_header(src):
                    header_deps.append(raw_src)
                else:
                    # We gather all these and generate compile rules below
                    # after `header_deps` (above) is fully generated
                    vala_generated_source_files.append(raw_src)
        for src in vala_generated_source_files:
            # Passing 'vala' here signifies that we want the compile
            # arguments to be specialized for C code generated by
            # valac. For instance, no warnings should be emitted.
            o, s = self.generate_single_compile(target, src, 'vala', [], header_deps)
            obj_list.append(o)

        # Generate compile targets for all the pre-existing sources for this target
        for src in target_sources.values():
            if not self.environment.is_header(src):
                if self.environment.is_llvm_ir(src):
                    o, s = self.generate_llvm_ir_compile(target, src)
                    obj_list.append(o)
                elif is_unity and self.get_target_source_can_unity(target, src):
                    abs_src = os.path.join(self.environment.get_build_dir(),
                                           src.rel_to_builddir(self.build_to_src))
                    unity_src.append(abs_src)
                else:
                    o, s = self.generate_single_compile(target, src, False, [], header_deps)
                    obj_list.append(o)
                    compiled_sources.append(s)
                    source2object[s] = o

        obj_list += self.flatten_object_list(target)
        if is_unity:
            for src in self.generate_unity_files(target, unity_src):
                o, s = self.generate_single_compile(target, src, True, unity_deps + header_deps)
                obj_list.append(o)
                compiled_sources.append(s)
                source2object[s] = o
        linker, stdlib_args = self.determine_linker_and_stdlib_args(target)
        if isinstance(target, build.StaticLibrary) and target.prelink:
            final_obj_list = self.generate_prelink(target, obj_list)
        else:
            final_obj_list = obj_list
        elem = self.generate_link(target, outname, final_obj_list, linker, pch_objects, stdlib_args=stdlib_args)
        self.generate_dependency_scan_target(target, compiled_sources, source2object)
        self.generate_shlib_aliases(target, self.get_target_dir(target))
        self.add_build(elem)

    def should_use_dyndeps_for_target(self, target: 'build.BuildTarget') -> bool:
        if mesonlib.version_compare(self.ninja_version, '<1.10.0'):
            return False
        if 'fortran' in target.compilers:
            return True
        if 'cpp' not in target.compilers:
            return False
        # Currently only the preview version of Visual Studio is supported.
        cpp = target.compilers['cpp']
        if cpp.get_id() != 'msvc':
            return False
        if self.environment.coredata.options[OptionKey('std', machine=target.for_machine, lang='cpp')] != 'latest':
            return False
        if not mesonlib.current_vs_supports_modules():
            return False
        if mesonlib.version_compare(cpp.version, '<19.28.28617'):
            return False
        return True

    def generate_dependency_scan_target(self, target, compiled_sources, source2object):
        if not self.should_use_dyndeps_for_target(target):
            return
        depscan_file = self.get_dep_scan_file_for(target)
        pickle_base = target.name + '.dat'
        pickle_file = os.path.join(self.get_target_private_dir(target), pickle_base).replace('\\', '/')
        pickle_abs = os.path.join(self.get_target_private_dir_abs(target), pickle_base).replace('\\', '/')
        rule_name = 'depscan'
        scan_sources = self.select_sources_to_scan(compiled_sources)
        elem = NinjaBuildElement(self.all_outputs, depscan_file, rule_name, scan_sources)
        elem.add_item('picklefile', pickle_file)
        scaninfo = TargetDependencyScannerInfo(self.get_target_private_dir(target), source2object)
        with open(pickle_abs, 'wb') as p:
            pickle.dump(scaninfo, p)
        self.add_build(elem)

    def select_sources_to_scan(self, compiled_sources):
        # in practice pick up C++ and Fortran files. If some other language
        # requires scanning (possibly Java to deal with inner class files)
        # then add them here.
        all_suffixes = set(compilers.lang_suffixes['cpp']) | set(compilers.lang_suffixes['fortran'])
        selected_sources = []
        for source in compiled_sources:
            ext = os.path.splitext(source)[1][1:]
            if ext in all_suffixes:
                selected_sources.append(source)
        return selected_sources

    def process_target_dependencies(self, target):
        for t in target.get_dependencies():
            if t.get_id() not in self.processed_targets:
                self.generate_target(t)

    def custom_target_generator_inputs(self, target):
        for s in unholder(target.sources):
            if isinstance(s, build.GeneratedList):
                self.generate_genlist_for_target(s, target)

    def unwrap_dep_list(self, target):
        deps = []
        for i in target.get_dependencies():
            # FIXME, should not grab element at zero but rather expand all.
            if isinstance(i, list):
                i = i[0]
            # Add a dependency on all the outputs of this target
            for output in i.get_outputs():
                deps.append(os.path.join(self.get_target_dir(i), output))
        return deps

    def generate_custom_target(self, target):
        self.custom_target_generator_inputs(target)
        (srcs, ofilenames, cmd) = self.eval_custom_target_command(target)
        deps = self.unwrap_dep_list(target)
        deps += self.get_custom_target_depend_files(target)
        desc = 'Generating {0} with a custom command{1}'
        if target.build_always_stale:
            deps.append('PHONY')
        if target.depfile is None:
            rulename = 'CUSTOM_COMMAND'
        else:
            rulename = 'CUSTOM_COMMAND_DEP'
        elem = NinjaBuildElement(self.all_outputs, ofilenames, rulename, srcs)
        elem.add_dep(deps)
        for d in target.extra_depends:
            # Add a dependency on all the outputs of this target
            for output in d.get_outputs():
                elem.add_dep(os.path.join(self.get_target_dir(d), output))

        meson_exe_cmd, reason = self.as_meson_exe_cmdline(target.name, target.command[0], cmd[1:],
                                                          extra_bdeps=target.get_transitive_build_target_deps(),
                                                          capture=ofilenames[0] if target.capture else None)
        if meson_exe_cmd:
            cmd = meson_exe_cmd
            cmd_type = ' (wrapped by meson {})'.format(reason)
        else:
            cmd_type = ''
        if target.depfile is not None:
            depfile = target.get_dep_outname(elem.infilenames)
            rel_dfile = os.path.join(self.get_target_dir(target), depfile)
            abs_pdir = os.path.join(self.environment.get_build_dir(), self.get_target_dir(target))
            os.makedirs(abs_pdir, exist_ok=True)
            elem.add_item('DEPFILE', rel_dfile)
        if target.console:
            elem.add_item('pool', 'console')
        cmd = self.replace_paths(target, cmd)
        elem.add_item('COMMAND', cmd)
        elem.add_item('description', desc.format(target.name, cmd_type))
        self.add_build(elem)
        self.processed_targets[target.get_id()] = True

    def build_run_target_name(self, target):
        if target.subproject != '':
            subproject_prefix = '{}@@'.format(target.subproject)
        else:
            subproject_prefix = ''
        return '{}{}'.format(subproject_prefix, target.name)

    def generate_run_target(self, target):
        cmd = self.environment.get_build_command() + ['--internal', 'commandrunner']
        deps = self.unwrap_dep_list(target)
        arg_strings = []
        for i in target.args:
            if isinstance(i, str):
                arg_strings.append(i)
            elif isinstance(i, (build.BuildTarget, build.CustomTarget)):
                relfname = self.get_target_filename(i)
                arg_strings.append(os.path.join(self.environment.get_build_dir(), relfname))
                deps.append(relfname)
            elif isinstance(i, mesonlib.File):
                relfname = i.rel_to_builddir(self.build_to_src)
                arg_strings.append(os.path.join(self.environment.get_build_dir(), relfname))
            else:
                raise AssertionError('Unreachable code in generate_run_target: ' + str(i))
        cmd += [self.environment.get_source_dir(),
                self.environment.get_build_dir(),
                target.subdir] + self.environment.get_build_command()
        texe = target.command
        try:
            texe = texe.held_object
        except AttributeError:
            pass
        if isinstance(texe, build.Executable):
            abs_exe = os.path.join(self.environment.get_build_dir(), self.get_target_filename(texe))
            deps.append(self.get_target_filename(texe))
            if self.environment.is_cross_build():
                exe_wrap = self.environment.get_exe_wrapper()
                if exe_wrap:
                    if not exe_wrap.found():
                        msg = 'The exe_wrapper {!r} defined in the cross file is ' \
                              'needed by run target {!r}, but was not found. ' \
                              'Please check the command and/or add it to PATH.'
                        raise MesonException(msg.format(exe_wrap.name, target.name))
                    cmd += exe_wrap.get_command()
            cmd.append(abs_exe)
        elif isinstance(texe, dependencies.ExternalProgram):
            cmd += texe.get_command()
        elif isinstance(texe, build.CustomTarget):
            deps.append(self.get_target_filename(texe))
            cmd += [os.path.join(self.environment.get_build_dir(), self.get_target_filename(texe))]
        elif isinstance(texe, mesonlib.File):
            cmd.append(texe.absolute_path(self.environment.get_source_dir(), self.environment.get_build_dir()))
        else:
            cmd.append(target.command)
        cmd += arg_strings

        if texe:
            target_name = 'meson-{}'.format(self.build_run_target_name(target))
            elem = NinjaBuildElement(self.all_outputs, target_name, 'CUSTOM_COMMAND', [])
            elem.add_item('COMMAND', cmd)
            elem.add_item('description', 'Running external command {}'.format(target.name))
            elem.add_item('pool', 'console')
            # Alias that runs the target defined above with the name the user specified
            self.create_target_alias(target_name)
        else:
            target_name = self.build_run_target_name(target)
            elem = NinjaBuildElement(self.all_outputs, target_name, 'phony', [])

        elem.add_dep(deps)
        self.add_build(elem)
        self.processed_targets[target.get_id()] = True

    def generate_coverage_command(self, elem, outputs):
        targets = self.build.get_targets().values()
        use_llvm_cov = False
        for target in targets:
            if not hasattr(target, 'compilers'):
                continue
            for compiler in target.compilers.values():
                if compiler.get_id() == 'clang' and not compiler.info.is_darwin():
                    use_llvm_cov = True
                    break
        elem.add_item('COMMAND', self.environment.get_build_command() +
                      ['--internal', 'coverage'] +
                      outputs +
                      [self.environment.get_source_dir(),
                       os.path.join(self.environment.get_source_dir(),
                                    self.build.get_subproject_dir()),
                       self.environment.get_build_dir(),
                       self.environment.get_log_dir()] +
                      (['--use_llvm_cov'] if use_llvm_cov else []))

    def generate_coverage_rules(self):
        e = NinjaBuildElement(self.all_outputs, 'meson-coverage', 'CUSTOM_COMMAND', 'PHONY')
        self.generate_coverage_command(e, [])
        e.add_item('description', 'Generates coverage reports')
        self.add_build(e)
        # Alias that runs the target defined above
        self.create_target_alias('meson-coverage')
        self.generate_coverage_legacy_rules()

    def generate_coverage_legacy_rules(self):
        e = NinjaBuildElement(self.all_outputs, 'meson-coverage-xml', 'CUSTOM_COMMAND', 'PHONY')
        self.generate_coverage_command(e, ['--xml'])
        e.add_item('description', 'Generates XML coverage report')
        self.add_build(e)
        # Alias that runs the target defined above
        self.create_target_alias('meson-coverage-xml')

        e = NinjaBuildElement(self.all_outputs, 'meson-coverage-text', 'CUSTOM_COMMAND', 'PHONY')
        self.generate_coverage_command(e, ['--text'])
        e.add_item('description', 'Generates text coverage report')
        self.add_build(e)
        # Alias that runs the target defined above
        self.create_target_alias('meson-coverage-text')

        e = NinjaBuildElement(self.all_outputs, 'meson-coverage-html', 'CUSTOM_COMMAND', 'PHONY')
        self.generate_coverage_command(e, ['--html'])
        e.add_item('description', 'Generates HTML coverage report')
        self.add_build(e)
        # Alias that runs the target defined above
        self.create_target_alias('meson-coverage-html')

    def generate_install(self):
        self.create_install_data_files()
        elem = NinjaBuildElement(self.all_outputs, 'meson-install', 'CUSTOM_COMMAND', 'PHONY')
        elem.add_dep('all')
        elem.add_item('DESC', 'Installing files.')
        elem.add_item('COMMAND', self.environment.get_build_command() + ['install', '--no-rebuild'])
        elem.add_item('pool', 'console')
        self.add_build(elem)
        # Alias that runs the target defined above
        self.create_target_alias('meson-install')

    def generate_tests(self):
        self.serialize_tests()
        cmd = self.environment.get_build_command(True) + ['test', '--no-rebuild']
        if not self.environment.coredata.get_option(OptionKey('stdsplit')):
            cmd += ['--no-stdsplit']
        if self.environment.coredata.get_option(OptionKey('errorlogs')):
            cmd += ['--print-errorlogs']
        elem = NinjaBuildElement(self.all_outputs, 'meson-test', 'CUSTOM_COMMAND', ['all', 'PHONY'])
        elem.add_item('COMMAND', cmd)
        elem.add_item('DESC', 'Running all tests.')
        elem.add_item('pool', 'console')
        self.add_build(elem)
        # Alias that runs the above-defined meson-test target
        self.create_target_alias('meson-test')

        # And then benchmarks.
        cmd = self.environment.get_build_command(True) + [
            'test', '--benchmark', '--logbase',
            'benchmarklog', '--num-processes=1', '--no-rebuild']
        elem = NinjaBuildElement(self.all_outputs, 'meson-benchmark', 'CUSTOM_COMMAND', ['all', 'PHONY'])
        elem.add_item('COMMAND', cmd)
        elem.add_item('DESC', 'Running benchmark suite.')
        elem.add_item('pool', 'console')
        self.add_build(elem)
        # Alias that runs the above-defined meson-benchmark target
        self.create_target_alias('meson-benchmark')

    def generate_rules(self):
        self.rules = []
        self.ruledict = {}

        self.add_rule_comment(NinjaComment('Rules for module scanning.'))
        self.generate_scanner_rules()
        self.add_rule_comment(NinjaComment('Rules for compiling.'))
        self.generate_compile_rules()
        self.add_rule_comment(NinjaComment('Rules for linking.'))
        self.generate_static_link_rules()
        self.generate_dynamic_link_rules()
        self.add_rule_comment(NinjaComment('Other rules'))
        # Ninja errors out if you have deps = gcc but no depfile, so we must
        # have two rules for custom commands.
        self.add_rule(NinjaRule('CUSTOM_COMMAND', ['$COMMAND'], [], '$DESC',
                                extra='restat = 1'))
        self.add_rule(NinjaRule('CUSTOM_COMMAND_DEP', ['$COMMAND'], [], '$DESC',
                                deps='gcc', depfile='$DEPFILE',
                                extra='restat = 1'))

        c = self.environment.get_build_command() + \
            ['--internal',
             'regenerate',
             self.environment.get_source_dir(),
             self.environment.get_build_dir(),
             '--backend',
             'ninja']
        self.add_rule(NinjaRule('REGENERATE_BUILD',
                                c, [],
                                'Regenerating build files.',
                                extra='generator = 1'))

    def add_rule_comment(self, comment):
        self.rules.append(comment)

    def add_build_comment(self, comment):
        self.build_elements.append(comment)

    def add_rule(self, rule):
        if rule.name in self.ruledict:
            raise MesonException('Tried to add rule {} twice.'.format(rule.name))
        self.rules.append(rule)
        self.ruledict[rule.name] = rule

    def add_build(self, build):
        self.build_elements.append(build)

        if build.rulename != 'phony':
            # reference rule
            if build.rulename in self.ruledict:
                build.rule = self.ruledict[build.rulename]
            else:
                mlog.warning("build statement for {} references non-existent rule {}".format(build.outfilenames, build.rulename))

    def write_rules(self, outfile):
        for b in self.build_elements:
            if isinstance(b, NinjaBuildElement):
                b.count_rule_references()

        for r in self.rules:
            r.write(outfile)

    def write_builds(self, outfile):
        for b in ProgressBar(self.build_elements, desc='Writing build.ninja'):
            b.write(outfile)

    def generate_phony(self):
        self.add_build_comment(NinjaComment('Phony build target, always out of date'))
        elem = NinjaBuildElement(self.all_outputs, 'PHONY', 'phony', '')
        self.add_build(elem)

    def generate_jar_target(self, target):
        fname = target.get_filename()
        outname_rel = os.path.join(self.get_target_dir(target), fname)
        src_list = target.get_sources()
        class_list = []
        compiler = target.compilers['java']
        c = 'c'
        m = 'm'
        e = ''
        f = 'f'
        main_class = target.get_main_class()
        if main_class != '':
            e = 'e'

        # Add possible java generated files to src list
        generated_sources = self.get_target_generated_sources(target)
        gen_src_list = []
        for rel_src in generated_sources.keys():
            dirpart, fnamepart = os.path.split(rel_src)
            raw_src = File(True, dirpart, fnamepart)
            if rel_src.endswith('.java'):
                gen_src_list.append(raw_src)

        compile_args = self.determine_single_java_compile_args(target, compiler)
        for src in src_list + gen_src_list:
            plain_class_path = self.generate_single_java_compile(src, target, compiler, compile_args)
            class_list.append(plain_class_path)
        class_dep_list = [os.path.join(self.get_target_private_dir(target), i) for i in class_list]
        manifest_path = os.path.join(self.get_target_private_dir(target), 'META-INF', 'MANIFEST.MF')
        manifest_fullpath = os.path.join(self.environment.get_build_dir(), manifest_path)
        os.makedirs(os.path.dirname(manifest_fullpath), exist_ok=True)
        with open(manifest_fullpath, 'w') as manifest:
            if any(target.link_targets):
                manifest.write('Class-Path: ')
                cp_paths = [os.path.join(self.get_target_dir(l), l.get_filename()) for l in target.link_targets]
                manifest.write(' '.join(cp_paths))
            manifest.write('\n')
        jar_rule = 'java_LINKER'
        commands = [c + m + e + f]
        commands.append(manifest_path)
        if e != '':
            commands.append(main_class)
        commands.append(self.get_target_filename(target))
        # Java compilation can produce an arbitrary number of output
        # class files for a single source file. Thus tell jar to just
        # grab everything in the final package.
        commands += ['-C', self.get_target_private_dir(target), '.']
        elem = NinjaBuildElement(self.all_outputs, outname_rel, jar_rule, [])
        elem.add_dep(class_dep_list)
        elem.add_item('ARGS', commands)
        self.add_build(elem)
        # Create introspection information
        self.create_target_source_introspection(target, compiler, compile_args, src_list, gen_src_list)

    def generate_cs_resource_tasks(self, target):
        args = []
        deps = []
        for r in target.resources:
            rel_sourcefile = os.path.join(self.build_to_src, target.subdir, r)
            if r.endswith('.resources'):
                a = '-resource:' + rel_sourcefile
            elif r.endswith('.txt') or r.endswith('.resx'):
                ofilebase = os.path.splitext(os.path.basename(r))[0] + '.resources'
                ofilename = os.path.join(self.get_target_private_dir(target), ofilebase)
                elem = NinjaBuildElement(self.all_outputs, ofilename, "CUSTOM_COMMAND", rel_sourcefile)
                elem.add_item('COMMAND', ['resgen', rel_sourcefile, ofilename])
                elem.add_item('DESC', 'Compiling resource {}'.format(rel_sourcefile))
                self.add_build(elem)
                deps.append(ofilename)
                a = '-resource:' + ofilename
            else:
                raise InvalidArguments('Unknown resource file {}.'.format(r))
            args.append(a)
        return args, deps

    def generate_cs_target(self, target: build.BuildTarget):
        buildtype = self.get_option_for_target(OptionKey('buildtype'), target)
        fname = target.get_filename()
        outname_rel = os.path.join(self.get_target_dir(target), fname)
        src_list = target.get_sources()
        compiler = target.compilers['cs']
        rel_srcs = [os.path.normpath(s.rel_to_builddir(self.build_to_src)) for s in src_list]
        deps = []
        commands = compiler.compiler_args(target.extra_args.get('cs', []))
        commands += compiler.get_buildtype_args(buildtype)
        commands += compiler.get_optimization_args(self.get_option_for_target(OptionKey('optimization'), target))
        commands += compiler.get_debug_args(self.get_option_for_target(OptionKey('debug'), target))
        if isinstance(target, build.Executable):
            commands.append('-target:exe')
        elif isinstance(target, build.SharedLibrary):
            commands.append('-target:library')
        else:
            raise MesonException('Unknown C# target type.')
        (resource_args, resource_deps) = self.generate_cs_resource_tasks(target)
        commands += resource_args
        deps += resource_deps
        commands += compiler.get_output_args(outname_rel)
        for l in target.link_targets:
            lname = os.path.join(self.get_target_dir(l), l.get_filename())
            commands += compiler.get_link_args(lname)
            deps.append(lname)
        if '-g' in commands:
            outputs = [outname_rel, outname_rel + '.mdb']
        else:
            outputs = [outname_rel]
        generated_sources = self.get_target_generated_sources(target)
        generated_rel_srcs = []
        for rel_src in generated_sources.keys():
            if rel_src.lower().endswith('.cs'):
                generated_rel_srcs.append(os.path.normpath(rel_src))
            deps.append(os.path.normpath(rel_src))

        for dep in target.get_external_deps():
            commands.extend_direct(dep.get_link_args())
        commands += self.build.get_project_args(compiler, target.subproject, target.for_machine)
        commands += self.build.get_global_args(compiler, target.for_machine)

        elem = NinjaBuildElement(self.all_outputs, outputs, self.get_compiler_rule_name('cs', target.for_machine), rel_srcs + generated_rel_srcs)
        elem.add_dep(deps)
        elem.add_item('ARGS', commands)
        self.add_build(elem)

        self.generate_generator_list_rules(target)
        self.create_target_source_introspection(target, compiler, commands, rel_srcs, generated_rel_srcs)

    def determine_single_java_compile_args(self, target, compiler):
        args = []
        args += compiler.get_buildtype_args(self.get_option_for_target(OptionKey('buildtype'), target))
        args += self.build.get_global_args(compiler, target.for_machine)
        args += self.build.get_project_args(compiler, target.subproject, target.for_machine)
        args += target.get_java_args()
        args += compiler.get_output_args(self.get_target_private_dir(target))
        args += target.get_classpath_args()
        curdir = target.get_subdir()
        sourcepath = os.path.join(self.build_to_src, curdir) + os.pathsep
        sourcepath += os.path.normpath(curdir) + os.pathsep
        for i in target.include_dirs:
            for idir in i.get_incdirs():
                sourcepath += os.path.join(self.build_to_src, i.curdir, idir) + os.pathsep
        args += ['-sourcepath', sourcepath]
        return args

    def generate_single_java_compile(self, src, target, compiler, args):
        deps = [os.path.join(self.get_target_dir(l), l.get_filename()) for l in target.link_targets]
        generated_sources = self.get_target_generated_sources(target)
        for rel_src in generated_sources.keys():
            if rel_src.endswith('.java'):
                deps.append(rel_src)
        rel_src = src.rel_to_builddir(self.build_to_src)
        plain_class_path = src.fname[:-4] + 'class'
        rel_obj = os.path.join(self.get_target_private_dir(target), plain_class_path)
        element = NinjaBuildElement(self.all_outputs, rel_obj, self.compiler_to_rule_name(compiler), rel_src)
        element.add_dep(deps)
        element.add_item('ARGS', args)
        self.add_build(element)
        return plain_class_path

    def generate_java_link(self):
        rule = 'java_LINKER'
        command = ['jar', '$ARGS']
        description = 'Creating JAR $out'
        self.add_rule(NinjaRule(rule, command, [], description))

    def determine_dep_vapis(self, target):
        """
        Peek into the sources of BuildTargets we're linking with, and if any of
        them was built with Vala, assume that it also generated a .vapi file of
        the same name as the BuildTarget and return the path to it relative to
        the build directory.
        """
        result = OrderedSet()
        for dep in itertools.chain(target.link_targets, target.link_whole_targets):
            if not dep.is_linkable_target():
                continue
            for i in dep.sources:
                if hasattr(i, 'fname'):
                    i = i.fname
                if i.endswith('vala'):
                    vapiname = dep.vala_vapi
                    fullname = os.path.join(self.get_target_dir(dep), vapiname)
                    result.add(fullname)
                    break
        return list(result)

    def split_vala_sources(self, t):
        """
        Splits the target's sources into .vala, .gs, .vapi, and other sources.
        Handles both pre-existing and generated sources.

        Returns a tuple (vala, vapi, others) each of which is a dictionary with
        the keys being the path to the file (relative to the build directory)
        and the value being the object that generated or represents the file.
        """
        vala = OrderedDict()
        vapi = OrderedDict()
        others = OrderedDict()
        othersgen = OrderedDict()
        # Split pre-existing sources
        for s in t.get_sources():
            # BuildTarget sources are always mesonlib.File files which are
            # either in the source root, or generated with configure_file and
            # in the build root
            if not isinstance(s, File):
                msg = 'All sources in target {!r} must be of type ' \
                      'mesonlib.File, not {!r}'.format(t, s)
                raise InvalidArguments(msg)
            f = s.rel_to_builddir(self.build_to_src)
            if s.endswith(('.vala', '.gs')):
                srctype = vala
            elif s.endswith('.vapi'):
                srctype = vapi
            else:
                srctype = others
            srctype[f] = s
        # Split generated sources
        for gensrc in t.get_generated_sources():
            for s in gensrc.get_outputs():
                f = self.get_target_generated_dir(t, gensrc, s)
                if s.endswith(('.vala', '.gs')):
                    srctype = vala
                elif s.endswith('.vapi'):
                    srctype = vapi
                # Generated non-Vala (C/C++) sources. Won't be used for
                # generating the Vala compile rule below.
                else:
                    srctype = othersgen
                # Duplicate outputs are disastrous
                if f in srctype and srctype[f] is not gensrc:
                    msg = 'Duplicate output {0!r} from {1!r} {2!r}; ' \
                          'conflicts with {0!r} from {4!r} {3!r}' \
                          ''.format(f, type(gensrc).__name__, gensrc.name,
                                    srctype[f].name, type(srctype[f]).__name__)
                    raise InvalidArguments(msg)
                # Store 'somefile.vala': GeneratedList (or CustomTarget)
                srctype[f] = gensrc
        return vala, vapi, (others, othersgen)

    def generate_vala_compile(self, target):
        """Vala is compiled into C. Set up all necessary build steps here."""
        (vala_src, vapi_src, other_src) = self.split_vala_sources(target)
        extra_dep_files = []
        if not vala_src:
            msg = 'Vala library {!r} has no Vala or Genie source files.'
            raise InvalidArguments(msg.format(target.name))

        valac = target.compilers['vala']
        c_out_dir = self.get_target_private_dir(target)
        # C files generated by valac
        vala_c_src = []
        # Files generated by valac
        valac_outputs = []
        # All sources that are passed to valac on the commandline
        all_files = list(vapi_src.keys())
        # Passed as --basedir
        srcbasedir = os.path.join(self.build_to_src, target.get_subdir())
        for (vala_file, gensrc) in vala_src.items():
            all_files.append(vala_file)
            # Figure out where the Vala compiler will write the compiled C file
            #
            # If the Vala file is in a subdir of the build dir (in our case
            # because it was generated/built by something else), and is also
            # a subdir of --basedir (because the builddir is in the source
            # tree, and the target subdir is the source root), the subdir
            # components from the source root till the private builddir will be
            # duplicated inside the private builddir. Otherwise, just the
            # basename will be used.
            #
            # If the Vala file is outside the build directory, the paths from
            # the --basedir till the subdir will be duplicated inside the
            # private builddir.
            if isinstance(gensrc, (build.CustomTarget, build.GeneratedList)) or gensrc.is_built:
                vala_c_file = os.path.splitext(os.path.basename(vala_file))[0] + '.c'
                # Check if the vala file is in a subdir of --basedir
                abs_srcbasedir = os.path.join(self.environment.get_source_dir(), target.get_subdir())
                abs_vala_file = os.path.join(self.environment.get_build_dir(), vala_file)
                if PurePath(os.path.commonpath((abs_srcbasedir, abs_vala_file))) == PurePath(abs_srcbasedir):
                    vala_c_subdir = PurePath(abs_vala_file).parent.relative_to(abs_srcbasedir)
                    vala_c_file = os.path.join(str(vala_c_subdir), vala_c_file)
            else:
                path_to_target = os.path.join(self.build_to_src, target.get_subdir())
                if vala_file.startswith(path_to_target):
                    vala_c_file = os.path.splitext(os.path.relpath(vala_file, path_to_target))[0] + '.c'
                else:
                    vala_c_file = os.path.splitext(os.path.basename(vala_file))[0] + '.c'
            # All this will be placed inside the c_out_dir
            vala_c_file = os.path.join(c_out_dir, vala_c_file)
            vala_c_src.append(vala_c_file)
            valac_outputs.append(vala_c_file)

        args = self.generate_basic_compiler_args(target, valac)
        args += valac.get_colorout_args(self.environment.coredata.options.get(OptionKey('b_colorout')).value)
        # Tell Valac to output everything in our private directory. Sadly this
        # means it will also preserve the directory components of Vala sources
        # found inside the build tree (generated sources).