# SPDX-License-Identifier: Apache-2.0
# Copyright 2012-2023 The Meson development team

from __future__ import annotations


"""Mixin classes to be shared between C and C++ compilers.

Without this we'll end up with awful diamond inheritance problems. The goal
of this is to have mixin's, which are classes that are designed *not* to be
standalone, they only work through inheritance.
"""

import collections
import functools
import glob
import itertools
import os
import re
import subprocess
import copy
import typing as T
from pathlib import Path

from ... import arglist
from ... import mesonlib
from ... import mlog
from ...linkers.linkers import GnuLikeDynamicLinkerMixin, SolarisDynamicLinker, CompCertDynamicLinker
from ...mesonlib import LibType
from .. import compilers
from ..compilers import CompileCheckMode
from .visualstudio import VisualStudioLikeCompiler

if T.TYPE_CHECKING:
    from ...dependencies import Dependency
    from ..._typing import ImmutableListProtocol
    from ...environment import Environment
    from ...compilers.compilers import Compiler
else:
    # This is a bit clever, for mypy we pretend that these mixins descend from
    # Compiler, so we get all of the methods and attributes defined for us, but
    # for runtime we make them descend from object (which all classes normally
    # do). This gives up DRYer type checking, with no runtime impact
    Compiler = object

GROUP_FLAGS = re.compile(r'''^(?!-Wl,) .*\.so (?:\.[0-9]+)? (?:\.[0-9]+)? (?:\.[0-9]+)?$ |
                             ^(?:-Wl,)?-l |
                             \.a$''', re.X)

class CLikeCompilerArgs(arglist.CompilerArgs):
    # Note: ``-isystem`` is deliberately absent from prepend_prefixes.
    # Because ``-isystem`` is appended by __iadd__ rather than
    # prepended, the reversed iteration in the ninja backend causes
    # directories listed *last* in include_directories() to appear
    # *first* on the command line (and thus be searched first).  This
    # is the opposite convention from ``-I``, where first-listed means
    # first-searched.  Existing projects (e.g. systemd) rely on this
    # ``-isystem`` ordering, so adding ``-isystem`` to prepend_prefixes
    # would silently break them by reversing their include priority.
    # See NinjaBackend._generate_single_compile_target_args().
    prepend_prefixes = ('-I', '-L')
    dedup2_prefixes = ('-I', '-isystem', '-L', '-D', '-U')

    # NOTE: not thorough. A list of potential corner cases can be found in
    # https://github.com/mesonbuild/meson/pull/4593#pullrequestreview-182016038
    dedup1_prefixes = ('-l', '-Wl,-l', '-Wl,-rpath,', '-Wl,-rpath-link,')
    dedup1_suffixes = ('.lib', '.dll', '.so', '.dylib', '.a')
    dedup1_args = ('-c', '-S', '-E', '-pipe', '-pthread', '-Wl,--export-dynamic', '-fopenmp', '-qopenmp')

    def to_native(self, copy: bool = False) -> T.List[str]:
        # This seems to be allowed, but could never work?
        assert isinstance(self.compiler, compilers.Compiler), 'How did you get here'

        # Check if we need to add --start/end-group for circular dependencies
        # between static libraries, and for recursively searching for symbols
        # needed by static libraries that are provided by object files or
        # shared libraries.
        self.flush_pre_post()
        if copy:
            new = self.copy()
        else:
            new = self
        # This covers all ld.bfd, ld.gold, ld.gold, and xild on Linux, which
        # all act like (or are) gnu ld
        # TODO: this could probably be added to the DynamicLinker instead
        if isinstance(self.compiler.linker, (GnuLikeDynamicLinkerMixin, SolarisDynamicLinker, CompCertDynamicLinker)):
            group_start = -1
            group_end = -1
            for i, each in enumerate(new):
                if not GROUP_FLAGS.search(each):
                    continue
                group_end = i
                if group_start < 0:
                    # First occurrence of a library
                    group_start = i
            # Only add groups if there are multiple libraries.
            if group_end > group_start >= 0:
                # Last occurrence of a library
                new.insert(group_end + 1, '-Wl,--end-group')
                new.insert(group_start, '-Wl,--start-group')
        # Remove system/default include paths added with -isystem
        default_dirs = self.compiler.get_default_include_dirs()
        if default_dirs:
            real_default_dirs = [self._cached_realpath(i) for i in default_dirs]
            bad_idx_list: T.List[int] = []
            for i, each in enumerate(new):
                if not each.startswith('-isystem'):
                    continue

                # Remove the -isystem and the path if the path is a default path
                if each == '-isystem':
                    if i < (len(new) - 1) and self._cached_realpath(new[i + 1]) in real_default_dirs:
                        bad_idx_list += [i, i + 1]
                elif each.startswith('-isystem='):
                    if self._cached_realpath(each[9:]) in real_default_dirs:
                        bad_idx_list += [i]
                elif self._cached_realpath(each[8:]) in real_default_dirs:
                    bad_idx_list += [i]
            for i in reversed(bad_idx_list):
                new.pop(i)
        return self.compiler.unix_args_to_native(new._container)

    @staticmethod
    @functools.lru_cache(maxsize=None)
    def _cached_realpath(arg: str) -> str:
        return os.path.realpath(arg)

    def __repr__(self) -> str:
        self.flush_pre_post()
        return f'CLikeCompilerArgs({self.compiler!r}, {self._container!r})'


class CLikeCompiler(Compiler):

    """Shared bits for the C and CPP Compilers."""

    if T.TYPE_CHECKING:
        warn_args: T.Dict[str, T.List[str]] = {}

    # TODO: Replace this manual cache with functools.lru_cache
    find_library_cache: T.Dict[T.Tuple[T.Tuple[str, ...], str, T.Tuple[str, ...], str, LibType, bool, bool], T.Optional[T.List[str]]] = {}
    find_framework_cache: T.Dict[T.Tuple[T.Tuple[str, ...], str, T.Tuple[str, ...], bool], T.Optional[T.List[str]]] = {}
    internal_libs = arglist.UNIXY_COMPILER_INTERNAL_LIBS

    def __init__(self) -> None:
        # If a child ObjC or CPP class has already set it, don't set it ourselves
        self.can_compile_suffixes.add('h')
        # Lazy initialized in get_preprocessor()
        self.preprocessor: T.Optional[Compiler] = None

    def compiler_args(self, args: T.Optional[T.Iterable[str]] = None) -> CLikeCompilerArgs:
        # This is correct, mypy just doesn't understand co-operative inheritance
        return CLikeCompilerArgs(self, args)

    def needs_static_linker(self) -> bool:
        return True # When compiling static libraries, so yes.

    def get_always_args(self) -> T.List[str]:
        '''
        Args that are always-on for all C compilers other than MSVC
        '''
        return self.get_largefile_args()

    def get_no_stdinc_args(self) -> T.List[str]:
        return ['-nostdinc']

    def get_no_stdlib_link_args(self) -> T.List[str]:
        return ['-nostdlib']

    def get_warn_args(self, level: str) -> T.List[str]:
        # TODO: this should be an enum
        return self.warn_args[level]

    def get_depfile_suffix(self) -> str:
        return 'd'

    def get_preprocess_only_args(self) -> T.List[str]:
        return ['-E', '-P']

    def get_compile_only_args(self) -> T.List[str]:
        return ['-c']

    def get_no_optimization_args(self) -> T.List[str]:
        return ['-O0', '-U_FORTIFY_SOURCE']

    def get_output_args(self, outputname: str) -> T.List[str]:
        return ['-o', outputname]

    def get_werror_args(self) -> T.List[str]:
        return ['-Werror']

    def get_include_args(self, path: str, is_system: bool) -> T.List[str]:
        if path == '':
            path = '.'
        if is_system:
            return ['-isystem', path]
        return ['-I' + path]

    def get_compiler_dirs(self, name: str) -> T.List[str]:
        '''
        Get dirs from the compiler, either `libraries:` or `programs:`
        '''
        return []

    @functools.lru_cache()
    def _get_library_dirs(self, elf_class: T.Optional[int] = None) -> 'ImmutableListProtocol[str]':
        # TODO: replace elf_class with enum
        dirs = self.get_compiler_dirs('libraries')
        if elf_class is None or elf_class == 0:
            return dirs

        # if we do have an elf class for 32-bit or 64-bit, we want to check that
        # the directory in question contains libraries of the appropriate class. Since
        # system directories aren't mixed, we only need to check one file for each
        # directory and go by that. If we can't check the file for some reason, assume
        # the compiler knows what it's doing, and accept the directory anyway.
        retval: T.List[str] = []
        for d in dirs:
            files = [f for f in os.listdir(d) if f.endswith('.so') and os.path.isfile(os.path.join(d, f))]
            # if no files, accept directory and move on
            if not files:
                retval.append(d)
                continue

            for f in files:
                file_to_check = os.path.join(d, f)
                try:
                    with open(file_to_check, 'rb') as fd:
                        header = fd.read(5)
                        # if file is not an ELF file, it's weird, but accept dir
                        # if it is elf, and the class matches, accept dir
                        if header[1:4] != b'ELF' or int(header[4]) == elf_class:
                            retval.append(d)
                        # at this point, it's an ELF file which doesn't match the
                        # appropriate elf_class, so skip this one
                    # stop scanning after the first successful read
                    break
                except OSError:
                    # Skip the file if we can't read it
                    pass

        return retval

    def get_library_dirs(self, elf_class: T.Optional[int] = None) -> T.List[str]:
        """Wrap the lru_cache so that we return a new copy and don't allow
        mutation of the cached value.
        """
        return self._get_library_dirs(elf_class).copy()

    @functools.lru_cache()
    def _get_program_dirs(self) -> 'ImmutableListProtocol[str]':
        '''
        Programs used by the compiler. Also where toolchain DLLs such as
        libstdc++-6.dll are found with MinGW.
        '''
        return self.get_compiler_dirs('programs')

    def get_program_dirs(self) -> T.List[str]:
        return self._get_program_dirs().copy()

    def get_pic_args(self) -> T.List[str]:
        return ['-fPIC']

    def get_pch_use_args(self, pch_dir: str, header: str) -> T.List[str]:
        return ['-include', os.path.basename(header)]

    def get_pch_name(self, name: str) -> str:
        return os.path.basename(name) + '.' + self.get_pch_suffix()

    def get_default_include_dirs(self) -> T.List[str]:
        return []

    def gen_export_dynamic_link_args(self) -> T.List[str]:
        return self.linker.export_dynamic_args()

    def gen_import_library_args(self, implibname: str) -> T.List[str]:
        return self.linker.import_library_args(implibname)

    def _sanity_check_compile_args(self, sourcename: str, binname: str
                                   ) -> T.Tuple[T.List[str], T.List[str]]:
        # Cross-compiling is hard. For example, you might need -nostdlib, or to pass --target, etc.
        mode = CompileCheckMode.COMPILE if self.is_cross and not self.environment.has_exe_wrapper() else CompileCheckMode.LINK
        cargs, b_largs = self._get_basic_compiler_args(mode)
        largs = self.linker_to_compiler_args(b_largs)
        s_args, s_largs = super()._sanity_check_compile_args(sourcename, binname)
        return s_args + cargs, s_largs + largs

    def check_header(self, hname: str, prefix: str, *,
                     extra_args: T.Union[None, T.List[str], T.Callable[['CompileCheckMode'], T.List[str]]] = None,
                     dependencies: T.Optional[T.List['Dependency']] = None) -> T.Tuple[bool, bool]:
        code = f'''{prefix}
        #include <{hname}>'''
        return self.compiles(code, extra_args=extra_args, dependencies=dependencies)

    def has_header(self, hname: str, prefix: str, *,
                   extra_args: T.Union[None, T.List[str], T.Callable[['CompileCheckMode'], T.List[str]]] = None,
                   dependencies: T.Optional[T.List['Dependency']] = None,
                   disable_cache: bool = False) -> T.Tuple[bool, bool]:
        code = f'''{prefix}
        #ifdef __has_include
         #if !__has_include("{hname}")
          #error "Header '{hname}' could not be found"
         #endif
        #else
         #include <{hname}>
        #endif'''
        return self.compiles(code, extra_args=extra_args,
                             dependencies=dependencies, mode=CompileCheckMode.PREPROCESS, disable_cache=disable_cache)

    def has_header_symbol(self, hname: str, symbol: str, prefix: str, *,
                          extra_args: T.Union[None, T.List[str], T.Callable[[CompileCheckMode], T.List[str]]] = None,
                          dependencies: T.Optional[T.List['Dependency']] = None) -> T.Tuple[bool, bool]:
        t = f'''{prefix}
        #include <{hname}>
        int main(void) {{
            /* If it's not defined as a macro, try to use as a symbol */
            #ifndef {symbol}
                {symbol};
            #endif
            return 0;
        }}'''
        return self.compiles(t, extra_args=extra_args,
                             dependencies=dependencies)

    def _get_basic_compiler_args(self, mode: CompileCheckMode) -> T.Tuple[T.List[str], T.List[str]]:
        cargs: T.List[str] = []
        largs: T.List[str] = []
        if mode is CompileCheckMode.LINK:
            # Sometimes we need to manually select the CRT to use with MSVC.
            # One example is when trying to do a compiler check that involves
            # linking with static libraries since MSVC won't select a CRT for
            # us in that case and will error out asking us to pick one.
            try:
                crt_val = self.environment.coredata.optstore.get_value_for('b_vscrt')
                assert isinstance(crt_val, str), 'for mypy'
                cargs += self.get_crt_compile_args(crt_val, self.environment)
                largs += self.get_crt_link_args(crt_val, self.environment)
            except (KeyError, AttributeError):
                pass

        # Add CFLAGS/CXXFLAGS/OBJCFLAGS/OBJCXXFLAGS and CPPFLAGS from the env
        sys_args = self.environment.coredata.get_external_args(self.for_machine, self.language)
        if isinstance(sys_args, str):
            sys_args = [sys_args]
        # Apparently it is a thing to inject linker flags both
        # via CFLAGS _and_ LDFLAGS, even though the former are
        # also used during linking. These flags can break
        # argument checks. Thanks, Autotools.
        cleaned_sys_args = self.remove_linkerlike_args(sys_args)
        cargs += cleaned_sys_args

        if mode is CompileCheckMode.LINK:
            ld_value = self.environment.lookup_binary_entry(self.for_machine, self.language + '_ld')
            if ld_value is not None:
                largs += self.use_linker_args(ld_value[0], self.version)

            # Add LDFLAGS from the env
            sys_ld_args = self.environment.coredata.get_external_link_args(self.for_machine, self.language)
            # CFLAGS and CXXFLAGS go to both linking and compiling, but we want them
            # to only appear on the command line once. Remove dupes.
            largs += [x for x in sys_ld_args if x not in cleaned_sys_args]

        cargs += self.get_compiler_args_for_mode(mode)
        return cargs, largs

    def build_wrapper_args(self,
                           extra_args: T.Union[None, arglist.CompilerArgs, T.List[str], T.Callable[[CompileCheckMode], T.List[str]]],
                           dependencies: T.Optional[T.List['Dependency']],
                           mode: CompileCheckMode = CompileCheckMode.COMPILE) -> arglist.CompilerArgs:
        # TODO: the caller should handle the listing of these arguments
        if extra_args is None:
            extra_args = []
        else:
            # TODO: we want to do this in the caller
            extra_args = mesonlib.listify(extra_args)
        extra_args = mesonlib.listify([e(mode) if callable(e) else e for e in extra_args])

        if dependencies is None:
            dependencies = []
        elif not isinstance(dependencies, collections.abc.Iterable):
            # TODO: we want to ensure the front end does the listifing here
            dependencies = [dependencies]
        # Collect compiler arguments
        cargs: arglist.CompilerArgs = self.compiler_args()
        largs: T.List[str] = []
        for d in dependencies:
            # Add compile flags needed by dependencies
            cargs += d.get_compile_args()
            system_incdir = d.get_include_type() == 'system'
            for i in d.get_include_dirs():
                for idir in i.abs_string_list(self.environment.get_source_dir(), self.environment.get_build_dir()):
                    cargs.extend(self.get_include_args(idir, system_incdir))
            if mode is CompileCheckMode.LINK:
                # Add link flags needed to find dependencies
                largs += d.get_link_args()

        ca, la = self._get_basic_compiler_args(mode)
        cargs += ca

        cargs += self.get_compiler_check_args(mode)

        # on MSVC compiler and linker flags must be separated by the "/link" argument
        # at this point, the '/link' argument may already be part of extra_args, otherwise, it is added here
        largs += [l for l in self.linker_to_compiler_args(la) if l != '/link']

        if self.linker_to_compiler_args([]) == ['/link']:
            if largs != [] and '/link' not in extra_args:
                extra_args += ['/link']
            # all linker flags must be converted now, otherwise the reordering
            # of arglist will apply and -L flags will be reordered into
            # breaking form. See arglist._should_prepend
            largs = self.unix_args_to_native(largs)

        args = cargs + extra_args + largs
        return args

    def _compile_int(self, expression: str, prefix: str,
                     extra_args: T.Union[None, T.List[str], T.Callable[[CompileCheckMode], T.List[str]]],
                     dependencies: T.Optional[T.List['Dependency']]) -> bool:
        t = f'''{prefix}
        #include <stddef.h>
        int main(void) {{ static int a[1-2*!({expression})]; a[0]=0; return 0; }}'''
        return self.compiles(t, extra_args=extra_args, dependencies=dependencies)[0]

    def _cross_compute_int(self, expression: str, low: T.Optional[int], high: T.Optional[int],
                           guess: T.Optional[int], prefix: str,
                           extra_args: T.Union[None, T.List[str], T.Callable[[CompileCheckMode], T.List[str]]] = None,
                           dependencies: T.Optional[T.List['Dependency']] = None) -> int:
        # Try user's guess first
        if isinstance(guess, int):
            if self._compile_int(f'{expression} == {guess}', prefix, extra_args, dependencies):
                return guess

        # Try to expand the expression and evaluate it on the build machines compiler
        if self.language in self.environment.coredata.compilers.build:
            try:
                expanded, _ = self.get_define(expression, prefix, extra_args, dependencies, False)
                evaluate_expanded = f'''
                #include <stdio.h>
                #include <stdint.h>
                int main(void) {{ int expression = {expanded}; printf("%d", expression); return 0; }}'''
                run = self.environment.coredata.compilers.build[self.language].run(evaluate_expanded)
                if run and run.compiled and run.returncode == 0:
                    if self._compile_int(f'{expression} == {run.stdout}', prefix, extra_args, dependencies):
                        return int(run.stdout)
            except mesonlib.EnvironmentException:
                pass

        # If no bounds are given, compute them in the limit of int32
        maxint = 0x7fffffff
        minint = -0x80000000
        if not isinstance(low, int) or not isinstance(high, int):
            if self._compile_int(f'{expression} >= 0', prefix, extra_args, dependencies):
                low = cur = 0
                while self._compile_int(f'{expression} > {cur}', prefix, extra_args, dependencies):
                    low = cur + 1
                    if low > maxint:
                        raise mesonlib.EnvironmentException('Cross-compile check overflowed')
                    cur = min(cur * 2 + 1, maxint)
                high = cur
            else:
                high = cur = -1
                while self._compile_int(f'{expression} < {cur}', prefix, extra_args, dependencies):
                    high = cur - 1
                    if high < minint:
                        raise mesonlib.EnvironmentException('Cross-compile check overflowed')
                    cur = max(cur * 2, minint)
                low = cur
        else:
            # Sanity check limits given by user
            if high < low:
                raise mesonlib.EnvironmentException('high limit smaller than low limit')
            condition = f'{expression} <= {high} && {expression} >= {low}'
            if not self._compile_int(condition, prefix, extra_args, dependencies):
                raise mesonlib.EnvironmentException('Value out of given range')

        # Binary search
        while low != high:
            cur = low + int((high - low) / 2)
            if self._compile_int(f'{expression} <= {cur}', prefix, extra_args, dependencies):
                high = cur
            else:
                low = cur + 1

        return low

    def compute_int(self, expression: str, low: T.Optional[int], high: T.Optional[int],
                    guess: T.Optional[int], prefix: str, *,
                    extra_args: T.Union[None, T.List[str], T.Callable[[CompileCheckMode], T.List[str]]],
                    dependencies: T.Optional[T.List['Dependency']] = None) -> int:
        if extra_args is None:
            extra_args = []
        if self.is_cross:
            return self._cross_compute_int(expression, low, high, guess, prefix, extra_args, dependencies)
        t = f'''{prefix}
        #include<stddef.h>
        #include<stdio.h>
        int main(void) {{
            printf("%ld\\n", (long)({expression}));
            return 0;
        }}'''
        res = self.run(t, extra_args=extra_args,
                       dependencies=dependencies)
        if not res.compiled:
            return -1
        if res.returncode != 0:
            raise mesonlib.EnvironmentException('Could not run compute_int test binary.')
        return int(res.stdout)

    def _cross_sizeof(self, typename: str, prefix: str, *,
                      extra_args: T.Union[None, T.List[str], T.Callable[[CompileCheckMode], T.List[str]]] = None,
                      dependencies: T.Optional[T.List['Dependency']] = None) -> int:
        if extra_args is None:
            extra_args = []
        t = f'''{prefix}
        #include <stddef.h>
        int main(void) {{
            {typename} something;
            return 0;
        }}'''
        if not self.compiles(t, extra_args=extra_args,
                             dependencies=dependencies)[0]:
            return -1
        return self._cross_compute_int(f'sizeof({typename})', None, None, None, prefix, extra_args, dependencies)

    def sizeof(self, typename: str, prefix: str, *,
               extra_args: T.Union[None, T.List[str], T.Callable[[CompileCheckMode], T.List[str]]] = None,
               dependencies: T.Optional[T.List['Dependency']] = None) -> T.Tuple[int, bool]:
        if extra_args is None:
            extra_args = []
        if self.is_cross:
            r = self._cross_sizeof(typename, prefix, extra_args=extra_args,
                                   dependencies=dependencies)
            return r, False
        t = f'''{prefix}
        #include<stddef.h>
        #include<stdio.h>
        int main(void) {{
            printf("%ld\\n", (long)(sizeof({typename})));
            return 0;
        }}'''
        res = self.cached_run(t, extra_args=extra_args,
                              dependencies=dependencies)
        if not res.compiled:
            return -1, False
        if res.returncode != 0:
            raise mesonlib.EnvironmentException('Could not run sizeof test binary.')
        return int(res.stdout), res.cached

    def _cross_alignment(self, typename: str, prefix: str, *,
                         extra_args: T.Optional[T.List[str]] = None,
                         dependencies: T.Optional[T.List['Dependency']] = None) -> int:
        if extra_args is None:
            extra_args = []
        t = f'''{prefix}
        #include <stddef.h>
        int main(void) {{
            {typename} something;
            return 0;
        }}'''
        if not self.compiles(t, extra_args=extra_args,
                             dependencies=dependencies)[0]:
            return -1
        t = f'''{prefix}
        #include <stddef.h>
        struct tmp {{
            char c;
            {typename} target;
        }};'''
        return self._cross_compute_int('offsetof(struct tmp, target)', None, None, None, t, extra_args, dependencies)

    def alignment(self, typename: str, prefix: str, *,
                  extra_args: T.Optional[T.List[str]] = None,
                  dependencies: T.Optional[T.List['Dependency']] = None) -> T.Tuple[int, bool]:
        if extra_args is None:
            extra_args = []
        if self.is_cross:
            r = self._cross_alignment(typename, prefix, extra_args=extra_args,
                                      dependencies=dependencies)
            return r, False
        t = f'''{prefix}
        #include <stdio.h>
        #include <stddef.h>
        struct tmp {{
            char c;
            {typename} target;
        }};
        int main(void) {{
            printf("%d", (int)offsetof(struct tmp, target));
            return 0;
        }}'''
        res = self.cached_run(t, extra_args=extra_args,
                              dependencies=dependencies)
        if not res.compiled:
            raise mesonlib.EnvironmentException('Could not compile alignment test.')
        if res.returncode != 0:
            raise mesonlib.EnvironmentException('Could not run alignment test binary.')

        align: int
        try:
            align = int(res.stdout)
        except ValueError:
            # If we get here, the user is most likely using a script that is
            # pretending to be a compiler.
            raise mesonlib.EnvironmentException('Could not run alignment test binary.')
        if align == 0:
            raise mesonlib.EnvironmentException(f'Could not determine alignment of {typename}. Sorry. You might want to file a bug.')

        return align, res.cached

    def get_define(self, dname: str, prefix: str,
                   extra_args: T.Union[T.List[str], T.Callable[[CompileCheckMode], T.List[str]]],
                   dependencies: T.Optional[T.List['Dependency']],
                   disable_cache: bool = False) -> T.Tuple[str, bool]:
        delim_start = '"MESON_GET_DEFINE_DELIMITER_START"\n'
        delim_end = '\n"MESON_GET_DEFINE_DELIMITER_END"'
        sentinel_undef = '"MESON_GET_DEFINE_UNDEFINED_SENTINEL"'
        code = f'''
        {prefix}
        #ifndef {dname}
        # define {dname} {sentinel_undef}
        #endif
        {delim_start}{dname}{delim_end}'''
        args = self.build_wrapper_args(extra_args, dependencies,
                                       mode=CompileCheckMode.PREPROCESS).to_native()
        func = functools.partial(self.cached_compile, code, extra_args=args, mode=CompileCheckMode.PREPROCESS)
        if disable_cache:
            func = functools.partial(self.compile, code, extra_args=args, mode=CompileCheckMode.PREPROCESS)
        with func() as p:
            cached = p.cached
            if p.returncode != 0:
                raise mesonlib.EnvironmentException(f'Could not get define {dname!r}')

        # Get the preprocessed value between the delimiters
        star_idx = p.stdout.find(delim_start)
        end_idx = p.stdout.rfind(delim_end)
        if (star_idx == -1) or (end_idx == -1) or (star_idx == end_idx):
            raise mesonlib.MesonBugException('Delimiters not found in preprocessor output.')
        define_value = p.stdout[star_idx + len(delim_start):end_idx]

        if define_value == sentinel_undef:
            define_value = None
        else:
            # Merge string literals
            define_value = self._concatenate_string_literals(define_value).strip()

        return define_value, cached

    def get_return_value(self, fname: str, rtype: str, prefix: str,
                         extra_args: T.Optional[T.List[str]],
                         dependencies: T.Optional[T.List['Dependency']]) -> T.Union[str, int]:
        # TODO: rtype should be an enum.
        # TODO: maybe we can use overload to tell mypy when this will return int vs str?
        if rtype == 'string':
            fmt = '%s'
            cast = '(char*)'
        elif rtype == 'int':
            fmt = '%lli'
            cast = '(long long int)'
        else:
            raise AssertionError(f'BUG: Unknown return type {rtype!r}')
        code = f'''{prefix}
        #include <stdio.h>
        int main(void) {{
            printf ("{fmt}", {cast} {fname}());
            return 0;
        }}'''
        res = self.run(code, extra_args=extra_args, dependencies=dependencies)
        if not res.compiled:
            raise mesonlib.EnvironmentException(f'Could not get return value of {fname}()')
        if rtype == 'string':
            return res.stdout
        elif rtype == 'int':
            try:
                return int(res.stdout.strip())
            except ValueError:
                raise mesonlib.EnvironmentException(f'Return value of {fname}() is not an int')
        assert False, 'Unreachable'

    @staticmethod
    def _no_prototype_templ() -> T.Tuple[str, str]:
        """
        Try to find the function without a prototype from a header by defining
        our own dummy prototype and trying to link with the C library (and
        whatever else the compiler links in by default). This is very similar
        to the check performed by Autoconf for AC_CHECK_FUNCS.
        """
        # Define the symbol to something else since it is defined by the
        # includes or defines listed by the user or by the compiler. This may
        # include, for instance _GNU_SOURCE which must be defined before
        # limits.h, which includes features.h
        # Then, undef the symbol to get rid of it completely.
        head = '''
        #define {func} meson_disable_define_of_{func}
        {prefix}
        #include <limits.h>
        #undef {func}
        '''
        # Override any GCC internal prototype and declare our own definition for
        # the symbol. Use char because that's unlikely to be an actual return
        # value for a function which ensures that we override the definition.
        head += '''
        #ifdef __cplusplus
        extern "C"
        #endif
        char {func} (void);
        '''
        # The actual function call
        main = '''
        int main(void) {{
          return {func} ();
        }}'''
        return head, main

    @staticmethod
    def _have_prototype_templ() -> T.Tuple[str, str]:
        """
        Returns a head-er and main() call that uses the headers listed by the
        user for the function prototype while checking if a function exists.
        """
        # Add the 'prefix', aka defines, includes, etc that the user provides
        # This may include, for instance _GNU_SOURCE which must be defined
        # before limits.h, which includes features.h
        head = '{prefix}\n#include <limits.h>\n'
        # We don't know what the function takes or returns, so return it as an int.
        # Just taking the address or comparing it to void is not enough because
        # compilers are smart enough to optimize it away. The resulting binary
        # is not run so we don't care what the return value is.
        main = '''\nint main(void) {{
            void *a = (void*) &{func};
            long long b = (long long) a;
            return (int) b;
        }}'''
        return head, main

    def has_function(self, funcname: str, prefix: str, *,
                     extra_args: T.Optional[T.List[str]] = None,
                     dependencies: T.Optional[T.List['Dependency']] = None) -> T.Tuple[bool, bool]:
        """Determine if a function exists.

        First, this function looks for the symbol in the default libraries
        provided by the compiler (stdlib + a few others usually). If that
        fails, it checks if any of the headers specified in the prefix provide
        an implementation of the function, and if that fails, it checks if it's
        implemented as a compiler-builtin.
        """
        if extra_args is None:
            extra_args = []

        # Short-circuit if the check is already provided by the cross-info file
        varname = 'has function ' + funcname
        varname = varname.replace(' ', '_')
        if self.is_cross:
            val = self.environment.properties.host.get(varname, None)
            if val is not None:
                if isinstance(val, bool):
                    return val, False
                raise mesonlib.EnvironmentException(f'Cross variable {varname} is not a boolean.')

        # TODO: we really need a protocol for this,
        #
        # class StrProto(typing.Protocol):
        #    def __str__(self) -> str: ...
        fargs: T.Dict[str, T.Union[str, bool, int]] = {'prefix': prefix, 'func': funcname}

        # glibc defines functions that are not available on Linux as stubs that
        # fail with ENOSYS (such as e.g. lchmod). In this case we want to fail
        # instead of detecting the stub as a valid symbol.
        # We already included limits.h earlier to ensure that these are defined
        # for stub functions.
        stubs_fail = '''
        #if defined __stub_{func} || defined __stub___{func}
        fail fail fail this function is not going to work
        #endif
        '''

        # If we have any includes in the prefix supplied by the user, assume
        # that the user wants us to use the symbol prototype defined in those
        # includes. If not, then try to do the Autoconf-style check with
        # a dummy prototype definition of our own.
        # This is needed when the linker determines symbol availability from an
        # SDK based on the prototype in the header provided by the SDK.
        # Ignoring this prototype would result in the symbol always being
        # marked as available.
        if '#include' in prefix:
            head, main = self._have_prototype_templ()
        else:
            head, main = self._no_prototype_templ()
        templ = head + stubs_fail + main

        res, cached = self.links(templ.format(**fargs), extra_args=extra_args,
                                 dependencies=dependencies)
        if res:
            return True, cached

        # MSVC does not have compiler __builtin_-s.
        if self.get_id() in {'msvc', 'intel-cl'}:
            return False, False

        # Detect function as a built-in
        #
        # Some functions like alloca() are defined as compiler built-ins which
        # are inlined by the compiler and you can't take their address, so we
        # need to look for them differently. On nice compilers like clang, we
        # can just directly use the __has_builtin() macro.
        fargs['no_includes'] = '#include' not in prefix
        is_builtin = funcname.startswith('__builtin_')
        fargs['is_builtin'] = is_builtin
        fargs['__builtin_'] = '' if is_builtin else '__builtin_'
        t = '''{prefix}
        int main(void) {{

        /* With some toolchains (MSYS2/mingw for example) the compiler
         * provides various builtins which are not really implemented and
         * fall back to the stdlib where they aren't provided and fail at
         * build/link time. In case the user provides a header, including
         * the header didn't lead to the function being defined, and the
         * function we are checking isn't a builtin itself we assume the
         * builtin is not functional and we just error out. */
        #if !{no_includes:d} && !defined({func}) && !{is_builtin:d}
            #error "No definition for {__builtin_}{func} found in the prefix"
        #endif

        #ifdef __has_builtin
            #if !__has_builtin({__builtin_}{func})
                #error "{__builtin_}{func} not found"
            #endif
        #elif ! defined({func})
            {__builtin_}{func};
        #endif
        return 0;
        }}'''
        return self.links(t.format(**fargs), extra_args=extra_args,
                          dependencies=dependencies)

    def has_members(self, typename: str, membernames: T.List[str], prefix: str, *,
                    extra_args: T.Union[None, T.List[str], T.Callable[[CompileCheckMode], T.List[str]]] = None,
                    dependencies: T.Optional[T.List['Dependency']] = None) -> T.Tuple[bool, bool]:
        if extra_args is None:
            extra_args = []
        # Create code that accesses all members
        members = ''.join(f'(void) ( foo.{member} );\n' for member in membernames)
        t = f'''{prefix}
        void bar(void) {{
            {typename} foo;
            {members}
            (void) foo;
        }}'''
        return self.compiles(t, extra_args=extra_args, dependencies=dependencies)

    def has_type(self, typename: str, prefix: str,
                 extra_args: T.Union[T.List[str], T.Callable[[CompileCheckMode], T.List[str]]], *,
                 dependencies: T.Optional[T.List['Dependency']] = None) -> T.Tuple[bool, bool]:
        t = f'''{prefix}
        void bar(void) {{
            (void) sizeof({typename});
        }}'''
        return self.compiles(t, extra_args=extra_args, dependencies=dependencies)

    def _symbols_have_underscore_prefix_searchbin(self) -> bool:
        '''
        Check if symbols have underscore prefix by compiling a small test binary
        and then searching the binary for the string,
        '''
        symbol_name = b'meson_uscore_prefix'
        code = '''#ifdef __cplusplus
        extern "C" {
        #endif
        void ''' + symbol_name.decode() + ''' (void) {}
        #ifdef __cplusplus
        }
        #endif
        '''
        args = self.get_compiler_check_args(CompileCheckMode.COMPILE)
        n = '_symbols_have_underscore_prefix_searchbin'
        with self._build_wrapper(code, extra_args=args, mode=CompileCheckMode.COMPILE, want_output=True) as p:
            if p.returncode != 0:
                raise RuntimeError(f'BUG: Unable to compile {n!r} check: {p.stderr}')
            if not os.path.isfile(p.output_name):
                raise RuntimeError(f'BUG: Can\'t find compiled test code for {n!r} check')
            with open(p.output_name, 'rb') as o:
                for line in o:
                    # Check if the underscore form of the symbol is somewhere
                    # in the output file.
                    if b'_' + symbol_name in line:
                        mlog.debug("Underscore prefix check found prefixed function in binary")
                        return True
                    # Else, check if the non-underscored form is present
                    elif symbol_name in line:
                        mlog.debug("Underscore prefix check found non-prefixed function in binary")
                        return False
        raise RuntimeError(f'BUG: {n!r} check did not find symbol string in binary')

    def _symbols_have_underscore_prefix_define(self) -> T.Optional[bool]:
        '''
        Check if symbols have underscore prefix by querying the
        __USER_LABEL_PREFIX__ define that most compilers provide
        for this. Return if functions have underscore prefix or None
        if it was not possible to determine, like when the compiler
        does not set the define or the define has an unexpected value.
        '''
        delim = '"MESON_HAVE_UNDERSCORE_DELIMITER" '
        code = f'''
        #ifndef __USER_LABEL_PREFIX__
        #define MESON_UNDERSCORE_PREFIX unsupported
        #else
        #define MESON_UNDERSCORE_PREFIX __USER_LABEL_PREFIX__
        #endif
        {delim}MESON_UNDERSCORE_PREFIX
        '''
        with self._build_wrapper(code, mode=CompileCheckMode.PREPROCESS, want_output=False) as p:
            if p.returncode != 0:
                raise RuntimeError(f'BUG: Unable to preprocess _symbols_have_underscore_prefix_define check: {p.stdout}')
            symbol_prefix = p.stdout.partition(delim)[-1].rstrip()

            mlog.debug(f'Queried compiler for function prefix: __USER_LABEL_PREFIX__ is "{symbol_prefix!s}"')
            if symbol_prefix == '_':
                return True
            elif symbol_prefix == '':
                return False
            else:
                return None

    def _symbols_have_underscore_prefix_list(self) -> T.Optional[bool]:
        '''
        Check if symbols have underscore prefix by consulting a hardcoded
        list of cases where we know the results.
        Return if functions have underscore prefix or None if unknown.
        '''
        # Darwin always uses the underscore prefix, not matter what
        if self.info.is_darwin():
            return True
        # Windows uses the underscore prefix on x86 (32bit) only
        if self.info.is_windows() or self.info.is_cygwin():
            return self.info.cpu_family == 'x86'
        return None

    def symbols_have_underscore_prefix(self) -> bool:
        '''
        Check if the compiler prefixes an underscore to global C symbols
        '''
        # First, try to query the compiler directly
        result = self._symbols_have_underscore_prefix_define()
        if result is not None:
            return result

        # Else, try to consult a hardcoded list of cases we know
        # absolutely have an underscore prefix
        result = self._symbols_have_underscore_prefix_list()
        if result is not None:
            return result

        # As a last resort, try search in a compiled binary, which is the
        # most unreliable way of checking this, see #5482
        return self._symbols_have_underscore_prefix_searchbin()

    def _get_patterns(self, prefixes: T.List[str], suffixes: T.List[str], shared: bool = False) -> T.List[str]:
        patterns: T.List[str] = []
        if self.info.is_os2():
            # On OS/2, search order for shared libs is
            #   1. libfoo_dll.a
            #   2. foo_dll.a
            #   3. libfoo.a
            #   4. foo.a
            #   5. foo.dll
            # For static libs, `_s' is used instead of `_dll'.
            for s in suffixes:
                dot = '' if s.startswith(('_dll.', '_s.')) else '.'
                for p in prefixes:
                    patterns.append(p + '{}' + dot + s)
            return patterns
        for p in prefixes:
            for s in suffixes:
                patterns.append(p + '{}.' + s)
        if shared and self.info.is_openbsd():
            # Shared libraries on OpenBSD can be named libfoo.so.X.Y:
            # https://www.openbsd.org/faq/ports/specialtopics.html#SharedLibs
            #
            # This globbing is probably the best matching we can do since regex
            # is expensive. It's wrong in many edge cases, but it will match
            # correctly-named libraries and hopefully no one on OpenBSD names
            # their files libfoo.so.9a.7b.1.0
            for p in prefixes:
                patterns.append(p + '{}.so.[0-9]*.[0-9]*')
        return patterns

    def get_library_naming(self, libtype: LibType, strict: bool = False) -> T.Tuple[str, ...]:
        '''
        Get library prefixes and suffixes for the target platform ordered by
        priority
        '''
        stlibext = ['a']
        # We've always allowed libname to be both `foo` and `libfoo`, and now
        # people depend on it. Also, some people use prebuilt `foo.so` instead
        # of `libfoo.so` for unknown reasons, and may also want to create
        # `foo.so` by setting name_prefix to ''
        # lib prefix is not usually used with msvc and OS/2
        if strict and not isinstance(self, VisualStudioLikeCompiler) and not self.info.is_os2():
            prefixes = ['lib']
        else:
            prefixes = ['lib', '']
        # Library suffixes and prefixes
        if self.info.is_darwin():
            shlibext = ['dylib', 'so']
        elif self.info.is_windows():
            # FIXME: .lib files can be import or static so we should read the
            # file, figure out which one it is, and reject the wrong kind.
            if isinstance(self, VisualStudioLikeCompiler):
                shlibext = ['lib']
            else:
                shlibext = ['dll.a', 'lib', 'dll']
            # Yep, static libraries can also be foo.lib
            stlibext += ['lib']
        elif self.info.is_cygwin():
            shlibext = ['dll', 'dll.a']
            prefixes = ['cyg'] + prefixes
        elif self.id.lower() in {'c6000', 'c2000', 'ti'}:
            # TI C28x compilers can use both extensions for static or dynamic libs.
            stlibext = ['a', 'lib']
            shlibext = ['dll', 'so']
        elif self.info.is_os2():
            stlibext = ['_s.lib', '_s.a', 'lib', 'a']
            shlibext = ['_dll.lib', '_dll.a', 'lib', 'a', 'dll']
        else:
            # Linux/BSDs
            shlibext = ['so']
        # Search priority
        if libtype is LibType.PREFER_SHARED:
            patterns = self._get_patterns(prefixes, shlibext, True)
            patterns.extend([x for x in self._get_patterns(prefixes, stlibext, False) if x not in patterns])
        elif libtype is LibType.PREFER_STATIC:
            patterns = self._get_patterns(prefixes, stlibext, False)
            patterns.extend([x for x in self._get_patterns(prefixes, shlibext, True) if x not in patterns])
        elif libtype is LibType.SHARED:
            patterns = self._get_patterns(prefixes, shlibext, True)
        else:
            assert libtype is LibType.STATIC
            patterns = self._get_patterns(prefixes, stlibext, False)
        return tuple(patterns)

    @staticmethod
    def _sort_shlibs_openbsd(libs: T.List[str]) -> T.List[str]:
        def tuple_key(x: str) -> T.Tuple[int, ...]:
            ver = x.rsplit('.so.', maxsplit=1)[1]
            return tuple(int(i) for i in ver.split('.'))

        filtered: T.List[str] = []
        for lib in libs:
            # Validate file as a shared library of type libfoo.so.X.Y
            ret = lib.rsplit('.so.', maxsplit=1)
            if len(ret) != 2:
                continue
            try:
                tuple(int(i) for i in ret[1].split('.'))
            except ValueError:
                continue
            filtered.append(lib)
        return sorted(filtered, key=tuple_key, reverse=True)

    @classmethod
    def _get_trials_from_pattern(cls, pattern: str, directory: str, libname: str) -> T.List[str]:
        f = os.path.join(directory, pattern.format(libname))
        # Globbing for OpenBSD
        if '*' in pattern:
            # NOTE: globbing matches directories and broken symlinks
            # so we have to do an isfile test on it later
            return cls._sort_shlibs_openbsd(glob.glob(f))
        return [f]

    @staticmethod
    def _get_file_from_list(env: Environment, paths: T.List[str]) -> T.Optional[Path]:
        '''
        Check whether the library exists by filename. On macOS, we also
        check if the library matches our target architecture.
        '''
        for p in paths:
            if os.path.isfile(p):

                if env.machines.host.is_darwin() and env.machines.build.is_darwin():
                    # Run `lipo` and check if the library supports the arch we want
                    archs = mesonlib.darwin_get_object_archs(p)
                    if not archs or env.machines.host.cpu_family not in archs:
                        mlog.debug(f'Rejected {p}, supports {archs} but need {env.machines.host.cpu_family}')
                        continue

                return Path(p)

        return None

    @functools.lru_cache()
    def output_is_64bit(self) -> bool:
        '''
        returns true if the output produced is 64-bit, false if 32-bit
        '''
        return self.sizeof('void *', '')[0] == 8

    def _find_library_real(self, libname: str, extra_dirs: T.List[str], code: str, libtype: LibType,
                           lib_prefix_warning: bool, ignore_system_dirs: bool,
                           skip_link_check: bool = False) -> T.Optional[T.List[str]]:
        # First try if we can just add the library as -l.
        # Gcc + co seem to prefer builtin lib dirs to -L dirs.
        # Only try to find std libs if no extra dirs specified.
        # The built-in search procedure will always favour .so and then always
        # search for .a. This is only allowed if libtype is LibType.PREFER_SHARED
        if ((not extra_dirs and libtype is LibType.PREFER_SHARED) or
                libname in self.internal_libs):
            cargs = ['-l' + libname]
            largs = self.get_linker_always_args() + self.get_allow_undefined_link_args()
            extra_args = cargs + self.linker_to_compiler_args(largs)

            if self.links(code, extra_args=extra_args, disable_cache=True)[0]:
                return cargs
            # Don't do a manual search for internal libs
            if libname in self.internal_libs:
                return None
        # Not found or we want to use a specific libtype? Try to find the
        # library file itself.
        patterns = self.get_library_naming(libtype)
        # try to detect if we are 64-bit or 32-bit. If we can't
        # detect, we will just skip path validity checks done in
        # get_library_dirs() call
        try:
            if self.output_is_64bit():
                elf_class = 2
            else:
                elf_class = 1
        except (mesonlib.MesonException, KeyError): # TODO evaluate if catching KeyError is wanted here
            elf_class = 0
        # Search in the specified dirs, and then in the system libraries
        largs = self.get_linker_always_args() + self.get_allow_undefined_link_args()
        lcargs = self.linker_to_compiler_args(largs)
        for d in itertools.chain(extra_dirs, [] if ignore_system_dirs else self.get_library_dirs(elf_class)):
            for p in patterns:
                trials = self._get_trials_from_pattern(p, d, libname)
                if not trials:
                    continue

                trial_result = ""
                for trial in trials:
                    if not os.path.isfile(trial):
                        continue
                    # When skip_link_check is True (e.g. for pkg-config
                    # libraries which are trusted to be linkable), skip the
                    # potentially expensive link check and just verify that the
                    # file exists.
                    extra_args = [trial] + lcargs
                    if skip_link_check or self.links(code, extra_args=extra_args, disable_cache=True)[0]:
                        trial_result = trial
                        break

                if not trial_result:
                    continue
                if libname.startswith('lib') and trial_result.startswith(libname) and lib_prefix_warning:
                    mlog.warning(f'find_library({libname!r}) starting in "lib" only works by accident and is not portable')
                return [Path(trial_result).as_posix()]
        return None

    def _find_library_impl(self, libname: str, extra_dirs: T.List[str], code: str, libtype: LibType,
                           lib_prefix_warning: bool, ignore_system_dirs: bool,
                           skip_link_check: bool = False) -> T.Optional[T.List[str]]:
        # These libraries are either built-in or invalid
        if libname in self.ignore_libs:
            return []
        if isinstance(extra_dirs, str):
            extra_dirs = [extra_dirs]
        key = (tuple(self.exelist), libname, tuple(extra_dirs), code, libtype, ignore_system_dirs, skip_link_check)
        if key not in self.find_library_cache:
            value = self._find_library_real(libname, extra_dirs, code, libtype, lib_prefix_warning, ignore_system_dirs, skip_link_check)
            self.find_library_cache[key] = value
        else:
            value = self.find_library_cache[key]
        if value is None:
            return None
        return value.copy()

    def find_library(self, libname: str, extra_dirs: T.List[str], libtype: LibType = LibType.PREFER_SHARED,
                     lib_prefix_warning: bool = True, ignore_system_dirs: bool = False,
                     skip_link_check: bool = False) -> T.Optional[T.List[str]]:
        code = 'int main(void) { return 0; }\n'
        return self._find_library_impl(libname, extra_dirs, code, libtype, lib_prefix_warning, ignore_system_dirs, skip_link_check)

    def find_framework_paths(self) -> T.List[str]:
        '''
        These are usually /Library/Frameworks and /System/Library/Frameworks,
        unless you select a particular macOS SDK with the -isysroot flag.
        You can also add to this by setting -F in CFLAGS.
        '''
        # TODO: this really needs to be *AppleClang*, not just any clang.
        if self.id != 'clang':
            raise mesonlib.MesonException('Cannot find framework path with non-clang compiler')
        # Construct the compiler command-line
        commands = self.get_exelist(ccache=False) + ['-v', '-E', '-']
        commands += self.get_always_args()
        # Add CFLAGS/CXXFLAGS/OBJCFLAGS/OBJCXXFLAGS from the env
        commands += self.environment.coredata.get_external_args(self.for_machine, self.language)
        mlog.debug('Finding framework path by running: ', ' '.join(commands), '\n')
        os_env = os.environ.copy()
        os_env['LC_ALL'] = 'C'
        _, _, stde = mesonlib.Popen_safe(commands, env=os_env, stdin=subprocess.PIPE)
        paths: T.List[str] = []
        for line in stde.split('\n'):
            if '(framework directory)' not in line:
                continue
            # line is of the form:
            # ` /path/to/framework (framework directory)`
            paths.append(line[:-21].strip())
        return paths

    def _find_framework_real(self, name: str, extra_dirs: T.List[str], allow_system: bool) -> T.Optional[T.List[str]]:
        code = 'int main(void) { return 0; }'
        link_args: T.List[str] = []
        for d in extra_dirs:
            link_args += ['-F' + d]
        # We can pass -Z to disable searching in the system frameworks, but
        # then we must also pass -L/usr/lib to pick up libSystem.dylib
        extra_args = [] if allow_system else ['-Z', '-L/usr/lib']
        link_args += ['-framework', name]
        if self.links(code, extra_args=(extra_args + link_args), disable_cache=True)[0]:
            return link_args
        return None

    def _find_framework_impl(self, name: str, extra_dirs: T.List[str],
                             allow_system: bool) -> T.Optional[T.List[str]]:
        if isinstance(extra_dirs, str):
            extra_dirs = [extra_dirs]
        key = (tuple(self.exelist), name, tuple(extra_dirs), allow_system)
        if key in self.find_framework_cache:
            value = self.find_framework_cache[key]
        else:
            value = self._find_framework_real(name, extra_dirs, allow_system)
            self.find_framework_cache[key] = value
        if value is None:
            return None
        return value.copy()

    def find_framework(self, name: str, extra_dirs: T.List[str],
                       allow_system: bool = True) -> T.Optional[T.List[str]]:
        '''
        Finds the framework with the specified name, and returns link args for
        the same or returns None when the framework is not found.
        '''
        # TODO: should probably check for macOS?
        return self._find_framework_impl(name, extra_dirs, allow_system)

    def get_crt_compile_args(self, crt_val: str, env: Environment) -> T.List[str]:
        # TODO: does this belong here or in GnuLike or maybe PosixLike?
        return []

    def get_crt_link_args(self, crt_val: str, env: Environment) -> T.List[str]:
        # TODO: does this belong here or in GnuLike or maybe PosixLike?
        return []

    def thread_flags(self) -> T.List[str]:
        # TODO: does this belong here or in GnuLike or maybe PosixLike?
        if self.info.is_haiku() or self.info.is_darwin():
            return []
        if self.info.is_os2():
            return ['-lpthread']
        return ['-pthread']

    def linker_to_compiler_args(self, args: T.List[str]) -> T.List[str]:
        return args.copy()

    def has_arguments(self, args: T.List[str], code: str,
                      mode: CompileCheckMode) -> T.Tuple[bool, bool]:
        return self.compiles(code, extra_args=args, mode=mode)

    def _has_multi_arguments(self, args: T.List[str], code: str) -> T.Tuple[bool, bool]:
        new_args: T.List[str] = []
        for arg in args:
            # some compilers, e.g. GCC, don't warn for unsupported warning-disable
            # flags, so when we are testing a flag like "-Wno-forgotten-towel", also
            # check the equivalent enable flag too "-Wforgotten-towel".
            if arg.startswith('-Wno-'):
                # Make an exception for -Wno-attributes=x as -Wattributes=x is invalid
                # for GCC at least.  Also, the positive form of some flags require a
                # value to be specified, i.e. we need to pass -Wfoo=N rather than just
                # -Wfoo.
                if arg.startswith('-Wno-attributes='):
                    pass
                elif arg in {'-Wno-alloc-size-larger-than',
                             '-Wno-alloca-larger-than',
                             '-Wno-frame-larger-than',
                             '-Wno-stack-usage',
                             '-Wno-vla-larger-than'}:
                    # Pass an arbitrary value to the enabling flag; since the test program
                    # is trivial, it is unlikely to provoke any of these warnings.
                    new_args.append('-W' + arg[5:] + '=1000')
                else:
                    new_args.append('-W' + arg[5:])
            if arg.startswith('-Wl,'):
                mlog.warning(f'{arg} looks like a linker argument, '
                             'but has_argument and other similar methods only '
                             'support checking compiler arguments. Using them '
                             'to check linker arguments are never supported, '
                             'and results are likely to be wrong regardless of '
                             'the compiler you are using. has_link_argument or '
                             'other similar method can be used instead.')
            new_args.append(arg)
        return self.has_arguments(new_args, code, mode=CompileCheckMode.COMPILE)

    def has_multi_arguments(self, args: T.List[str]) -> T.Tuple[bool, bool]:
        return self._has_multi_arguments(args, 'extern int i;\nint i;\n')

    def _has_multi_link_arguments(self, args: T.List[str], code: str) -> T.Tuple[bool, bool]:
        args = self.linker.fatal_warnings() + args
        args = self.linker_to_compiler_args(args)
        return self.has_arguments(args, code, mode=CompileCheckMode.LINK)

    def has_multi_link_arguments(self, args: T.List[str], to_host_args: bool = True) -> T.Tuple[bool, bool]:
        return self._has_multi_link_arguments(args, 'int main(void) { return 0; }\n')

    @staticmethod
    def _concatenate_string_literals(s: str) -> str:
        pattern = re.compile(r'(?P<pre>.*([^\\]")|^")(?P<str1>([^\\"]|\\.)*)"\s+"(?P<str2>([^\\"]|\\.)*)(?P<post>".*)')
        ret = s
        m = pattern.match(ret)
        while m:
            ret = ''.join(m.group('pre', 'str1', 'str2', 'post'))
            m = pattern.match(ret)
        return ret

    def get_has_func_attribute_extra_args(self, name: str) -> T.List[str]:
        # Most compilers (such as GCC and Clang) only warn about unknown or
        # ignored attributes, so force an error. Overridden in GCC and Clang
        # mixins.
        return ['-Werror']

    def has_func_attribute(self, name: str) -> T.Tuple[bool, bool]:
        # Just assume that if we're not on windows that dllimport and dllexport
        # don't work
        if not (self.info.is_windows() or self.info.is_cygwin()):
            if name in {'dllimport', 'dllexport'}:
                return False, False

        return self.compiles(self.attribute_check_func(name),
                             extra_args=self.get_has_func_attribute_extra_args(name))

    def get_assert_args(self, disable: bool) -> T.List[str]:
        if disable:
            return ['-DNDEBUG']
        return []

    @functools.lru_cache(maxsize=None)
    def can_compile(self, src: 'mesonlib.FileOrString') -> bool:
        # Files we preprocess can be anything, e.g. .in
        if self.mode == 'PREPROCESSOR':
            return True
        return super().can_compile(src)

    def get_preprocessor(self) -> Compiler:
        if not self.preprocessor:
            self.preprocessor = copy.copy(self)
            self.preprocessor.exelist = self.exelist + self.get_preprocess_to_file_args()
            self.preprocessor.mode = 'PREPROCESSOR'
            self.modes.append(self.preprocessor)
        return self.preprocessor
