# SPDX-License-Identifier: Apache-2.0
# Copyright 2019-2022 The meson development team
# Copyright © 2023-2025 Intel Corporation

from __future__ import annotations

"""Provides mixins for GNU compilers and GNU-like compilers."""

import abc
import functools
import os
import pathlib
import re
import subprocess
import typing as T

from ... import mesonlib
from ... import mlog
from ...options import OptionKey, UserStdOption
from mesonbuild.compilers.compilers import CompileCheckMode

if T.TYPE_CHECKING:
    from ..._typing import ImmutableListProtocol
    from ...build import BuildTarget
    from ...options import MutableKeyedOptionDictType
    from ..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

# XXX: prevent circular references.
# FIXME: this really is a posix interface not a c-like interface
clike_debug_args: T.Dict[bool, T.List[str]] = {
    False: [],
    True: ['-g'],
}

gnu_optimization_args: T.Dict[str, T.List[str]] = {
    'plain': [],
    '0': ['-O0'],
    'g': ['-Og'],
    '1': ['-O1'],
    '2': ['-O2'],
    '3': ['-O3'],
    's': ['-Os'],
}

gnulike_instruction_set_args: T.Dict[str, T.List[str]] = {
    'mmx': ['-mmmx'],
    'sse': ['-msse'],
    'sse2': ['-msse2'],
    'sse3': ['-msse3'],
    'ssse3': ['-mssse3'],
    'sse41': ['-msse4.1'],
    'sse42': ['-msse4.2'],
    'avx': ['-mavx'],
    'avx2': ['-mavx2'],
    'neon': ['-mfpu=neon'],
}

gnu_symbol_visibility_args: T.Dict[str, T.List[str]] = {
    '': [],
    'default': ['-fvisibility=default'],
    'internal': ['-fvisibility=internal'],
    'hidden': ['-fvisibility=hidden'],
    'protected': ['-fvisibility=protected'],
    'inlineshidden': ['-fvisibility=hidden', '-fvisibility-inlines-hidden'],
}

gnu_color_args: T.Dict[str, T.List[str]] = {
    'auto': ['-fdiagnostics-color=auto'],
    'always': ['-fdiagnostics-color=always'],
    'never': ['-fdiagnostics-color=never'],
}

# Warnings collected from the GCC source and documentation.  This is an
# objective set of all the warnings flags that apply to general projects: the
# only ones omitted are those that require a project-specific value, or are
# related to non-standard or legacy language support.  This behaves roughly
# like -Weverything in clang.  Warnings implied by -Wall, -Wextra, or
# higher-level warnings already enabled here are not included in these lists to
# keep them as short as possible.  History goes back to GCC 3.0.0, everything
# earlier is considered historical and listed under version 0.0.0.

# GCC warnings for all C-family languages
# Omitted non-general warnings:
#   -Wabi=
#   -Waggregate-return
#   -Walloc-size-larger-than=BYTES
#   -Walloca-larger-than=BYTES
#   -Wframe-larger-than=BYTES
#   -Wlarger-than=BYTES
#   -Wstack-usage=BYTES
#   -Wsystem-headers
#   -Wtrampolines
#   -Wvla-larger-than=BYTES
#
# Omitted warnings enabled elsewhere in meson:
#   -Winvalid-pch (GCC 3.4.0)
gnu_common_warning_args: T.Dict[str, T.List[str]] = {
    "0.0.0": [
        "-Wcast-qual",
        "-Wconversion",
        "-Wfloat-equal",
        "-Wformat=2",
        "-Winline",
        "-Wmissing-declarations",
        "-Wredundant-decls",
        "-Wshadow",
        "-Wundef",
        "-Wuninitialized",
        "-Wwrite-strings",
    ],
    "3.0.0": [
        "-Wdisabled-optimization",
        "-Wpacked",
        "-Wpadded",
    ],
    "3.3.0": [
        "-Wmultichar",
        "-Wswitch-default",
        "-Wswitch-enum",
        "-Wunused-macros",
    ],
    "4.0.0": [
        "-Wmissing-include-dirs",
    ],
    "4.1.0": [
        "-Wunsafe-loop-optimizations",
        "-Wstack-protector",
    ],
    "4.2.0": [
        "-Wstrict-overflow=5",
    ],
    "4.3.0": [
        "-Warray-bounds=2",
        "-Wlogical-op",
        "-Wstrict-aliasing=3",
        "-Wvla",
    ],
    "4.6.0": [
        "-Wdouble-promotion",
        "-Wsuggest-attribute=const",
        "-Wsuggest-attribute=noreturn",
        "-Wsuggest-attribute=pure",
        "-Wtrampolines",
    ],
    "4.7.0": [
        "-Wvector-operation-performance",
    ],
    "4.8.0": [
        "-Wsuggest-attribute=format",
    ],
    "4.9.0": [
        "-Wdate-time",
    ],
    "5.1.0": [
        "-Wformat-signedness",
        "-Wnormalized=nfc",
    ],
    "6.1.0": [
        "-Wduplicated-cond",
        "-Wnull-dereference",
        "-Wshift-negative-value",
        "-Wshift-overflow=2",
        "-Wunused-const-variable=2",
    ],
    "7.1.0": [
        "-Walloca",
        "-Walloc-zero",
        "-Wformat-overflow=2",
        "-Wformat-truncation=2",
        "-Wstringop-overflow=3",
    ],
    "7.2.0": [
        "-Wduplicated-branches",
    ],
    "8.1.0": [
        "-Wcast-align=strict",
        "-Wsuggest-attribute=cold",
        "-Wsuggest-attribute=malloc",
    ],
    "9.1.0": [
        "-Wattribute-alias=2",
    ],
    "10.1.0": [
        "-Wanalyzer-too-complex",
        "-Warith-conversion",
    ],
    "12.1.0": [
        "-Wbidi-chars=ucn",
        "-Wopenacc-parallelism",
        "-Wtrivial-auto-var-init",
    ],
}

# GCC warnings for C
# Omitted non-general or legacy warnings:
#   -Wc11-c2x-compat
#   -Wc90-c99-compat
#   -Wc99-c11-compat
#   -Wdeclaration-after-statement
#   -Wtraditional
#   -Wtraditional-conversion
#   -Wunsuffixed-float-constants
gnu_c_warning_args: T.Dict[str, T.List[str]] = {
    "0.0.0": [
        "-Wbad-function-cast",
        "-Wmissing-prototypes",
        "-Wnested-externs",
        "-Wstrict-prototypes",
    ],
    "3.4.0": [
        "-Wold-style-definition",
        "-Winit-self",
    ],
    "4.1.0": [
        "-Wc++-compat",
    ],
}

# GCC warnings for C++
# Omitted non-general or legacy warnings:
#   -Wc++0x-compat
#   -Wc++1z-compat
#   -Wc++2a-compat
#   -Wctad-maybe-unsupported
#   -Wnamespaces
#   -Wtemplates
gnu_cpp_warning_args: T.Dict[str, T.List[str]] = {
    "0.0.0": [
        "-Wctor-dtor-privacy",
        "-Weffc++",
        "-Wnon-virtual-dtor",
        "-Wold-style-cast",
        "-Woverloaded-virtual",
        "-Wsign-promo",
    ],
    "4.0.1": [
        "-Wstrict-null-sentinel",
    ],
    "4.6.0": [
        "-Wnoexcept",
    ],
    "4.7.0": [
        "-Wzero-as-null-pointer-constant",
    ],
    "4.8.0": [
        "-Wabi-tag",
        "-Wuseless-cast",
    ],
    "4.9.0": [
        "-Wconditionally-supported",
    ],
    "5.1.0": [
        "-Wsuggest-final-methods",
        "-Wsuggest-final-types",
        "-Wsuggest-override",
    ],
    "6.1.0": [
        "-Wmultiple-inheritance",
        "-Wplacement-new=2",
        "-Wvirtual-inheritance",
    ],
    "7.1.0": [
        "-Waligned-new=all",
        "-Wnoexcept-type",
        "-Wregister",
    ],
    "8.1.0": [
        "-Wcatch-value=3",
        "-Wextra-semi",
    ],
    "9.1.0": [
        "-Wdeprecated-copy-dtor",
        "-Wredundant-move",
    ],
    "10.1.0": [
        "-Wcomma-subscript",
        "-Wmismatched-tags",
        "-Wredundant-tags",
        "-Wvolatile",
    ],
    "11.1.0": [
        "-Wdeprecated-enum-enum-conversion",
        "-Wdeprecated-enum-float-conversion",
        "-Winvalid-imported-macros",
    ],
}

# GCC warnings for Objective C and Objective C++
# Omitted non-general or legacy warnings:
#   -Wtraditional
#   -Wtraditional-conversion
gnu_objc_warning_args: T.Dict[str, T.List[str]] = {
    "0.0.0": [
        "-Wselector",
    ],
    "3.3": [
        "-Wundeclared-selector",
    ],
    "4.1.0": [
        "-Wassign-intercept",
        "-Wstrict-selector-match",
    ],
}

gnu_lang_map = {
    'c': 'c',
    'cpp': 'c++',
    'objc': 'objective-c',
    'objcpp': 'objective-c++'
}

@functools.lru_cache(maxsize=None)
def gnulike_default_include_dirs(compiler: T.Tuple[str, ...], lang: str) -> 'ImmutableListProtocol[str]':
    if lang not in gnu_lang_map:
        return []
    lang = gnu_lang_map[lang]
    env = os.environ.copy()
    env["LC_ALL"] = 'C'
    cmd = list(compiler) + [f'-x{lang}', '-E', '-v', '-']
    _, stdout, _ = mesonlib.Popen_safe(cmd, stderr=subprocess.STDOUT, env=env)
    parse_state = 0
    paths: T.List[str] = []
    for line in stdout.split('\n'):
        line = line.strip(' \n\r\t')
        if parse_state == 0:
            if line == '#include "..." search starts here:':
                parse_state = 1
        elif parse_state == 1:
            if line == '#include <...> search starts here:':
                parse_state = 2
            else:
                paths.append(line)
        elif parse_state == 2:
            if line == 'End of search list.':
                break
            else:
                paths.append(line)
    if not paths:
        mlog.warning('No include directory found parsing "{cmd}" output'.format(cmd=" ".join(cmd)))
    # Append a normalized copy of paths to make path lookup easier
    paths += [os.path.normpath(x) for x in paths]
    return paths


class GnuLikeCompiler(Compiler, metaclass=abc.ABCMeta):
    """
    GnuLikeCompiler is a common interface to all compilers implementing
    the GNU-style commandline interface. This includes GCC, Clang
    and ICC. Certain functionality between them is different and requires
    that the actual concrete subclass define their own implementation.
    """

    LINKER_PREFIX = '-Wl,'

    def __init__(self) -> None:
        self.base_options = {
            OptionKey(o) for o in ['b_pch', 'b_lto', 'b_pgo', 'b_coverage',
                                   'b_ndebug', 'b_staticpic', 'b_pie']}
        if not (self.info.is_windows() or self.info.is_cygwin() or self.info.is_openbsd()):
            self.base_options.add(OptionKey('b_lundef'))
        if not self.info.is_windows() or self.info.is_cygwin():
            self.base_options.add(OptionKey('b_asneeded'))
        if not self.info.is_hurd():
            self.base_options.add(OptionKey('b_sanitize'))
        # All GCC-like backends can do assembly
        self.can_compile_suffixes.add('s')
        self.can_compile_suffixes.add('sx')

    def get_pic_args(self) -> T.List[str]:
        if self.info.is_windows() or self.info.is_cygwin() or self.info.is_darwin() or self.info.is_os2():
            return [] # On Window, OS X and OS/2, pic is always on.
        return ['-fPIC']

    def get_pie_args(self) -> T.List[str]:
        return ['-fPIE']

    @abc.abstractmethod
    def get_optimization_args(self, optimization_level: str) -> T.List[str]:
        pass

    def get_debug_args(self, is_debug: bool) -> T.List[str]:
        return clike_debug_args[is_debug]

    @abc.abstractmethod
    def get_pch_suffix(self) -> str:
        pass

    def split_shlib_to_parts(self, fname: str) -> T.Tuple[str, str]:
        return os.path.dirname(fname), fname

    def get_instruction_set_args(self, instruction_set: str) -> T.Optional[T.List[str]]:
        return gnulike_instruction_set_args.get(instruction_set, None)

    def get_default_include_dirs(self) -> T.List[str]:
        return gnulike_default_include_dirs(tuple(self.get_exelist(ccache=False)), self.language).copy()

    @abc.abstractmethod
    def openmp_flags(self) -> T.List[str]:
        pass

    def gnu_symbol_visibility_args(self, vistype: str) -> T.List[str]:
        if vistype == 'inlineshidden' and self.language not in {'cpp', 'objcpp'}:
            vistype = 'hidden'
        return gnu_symbol_visibility_args[vistype]

    @staticmethod
    def get_argument_syntax() -> str:
        return 'gcc'

    def get_profile_generate_args(self) -> T.List[str]:
        return ['-fprofile-generate']

    def get_profile_use_args(self) -> T.List[str]:
        return ['-fprofile-use']

    def compute_parameters_with_absolute_paths(self, parameter_list: T.List[str], build_dir: str) -> T.List[str]:
        for idx, i in enumerate(parameter_list):
            if i[:2] == '-I' or i[:2] == '-L':
                parameter_list[idx] = i[:2] + os.path.normpath(os.path.join(build_dir, i[2:]))

        return parameter_list

    @functools.lru_cache()
    def _get_search_dirs(self) -> str:
        extra_args = ['--print-search-dirs']
        with self._build_wrapper('', extra_args=extra_args,
                                 dependencies=None, mode=CompileCheckMode.COMPILE,
                                 want_output=True) as p:
            return p.stdout

    def _split_fetch_real_dirs(self, pathstr: str) -> T.List[str]:
        # We need to use the path separator used by the compiler for printing
        # lists of paths ("gcc --print-search-dirs"). By default
        # we assume it uses the platform native separator.
        pathsep = os.pathsep

        # clang uses ':' instead of ';' on Windows https://reviews.llvm.org/D61121
        # so we need to repair things like 'C:\foo:C:\bar'
        if pathsep == ';':
            pathstr = re.sub(r':([^/\\])', r';\1', pathstr)

        # pathlib treats empty paths as '.', so filter those out
        paths = [p for p in pathstr.split(pathsep) if p]

        result: T.List[str] = []
        for p in paths:
            # GCC returns paths like this:
            # /usr/lib/gcc/x86_64-linux-gnu/8/../../../../x86_64-linux-gnu/lib
            # It would make sense to normalize them to get rid of the .. parts
            # Sadly when you are on a merged /usr fs it also kills these:
            # /lib/x86_64-linux-gnu
            # since /lib is a symlink to /usr/lib. This would mean
            # paths under /lib would be considered not a "system path",
            # which is wrong and breaks things. Store everything, just to be sure.
            pobj = pathlib.Path(p)
            if pobj.exists():
                try:
                    resolved = pobj.resolve(True).as_posix()
                    if resolved not in result:
                        result.append(resolved)
                except FileNotFoundError:
                    pass
                unresolved = pobj.as_posix()
                if unresolved not in result:
                    result.append(unresolved)
        return result

    def get_compiler_dirs(self, name: str) -> T.List[str]:
        '''
        Get dirs from the compiler, either `libraries:` or `programs:`
        '''
        stdo = self._get_search_dirs()
        for line in stdo.split('\n'):
            if line.startswith(name + ':'):
                return self._split_fetch_real_dirs(line.split('=', 1)[1])
        return []

    def get_lto_compile_args(self, *, target: T.Optional[BuildTarget] = None, threads: int = 0,
                             mode: str = 'default') -> T.List[str]:
        # This provides a base for many compilers, GCC and Clang override this
        # for their specific arguments
        return ['-flto']

    def sanitizer_compile_args(self, target: T.Optional[BuildTarget], value: T.List[str]) -> T.List[str]:
        if not value:
            return value
        args = ['-fsanitize=' + ','.join(value)]
        if 'address' in value:
            args.append('-fno-omit-frame-pointer')
        return args

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

    def get_dependency_gen_args(self, outtarget: str, outfile: str) -> T.List[str]:
        return ['-MD', '-MQ', outtarget, '-MF', outfile]

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

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

    @classmethod
    def use_linker_args(cls, linker: str, version: str) -> T.List[str]:
        if linker not in {'bfd', 'eld', 'gold', 'lld'}:
            raise mesonlib.MesonException(
                f'Unsupported linker, only bfd, eld, gold, and lld are supported, not {linker}.')
        return [f'-fuse-ld={linker}']

    def get_coverage_args(self) -> T.List[str]:
        return ['--coverage']

    def get_preprocess_to_file_args(self) -> T.List[str]:
        # We want to allow preprocessing files with any extension, such as
        # foo.c.in. In that case we need to tell GCC/CLANG to treat them as
        # assembly file.
        if self.language == 'fortran':
            return self.get_preprocess_only_args()
        lang = gnu_lang_map.get(self.language, 'assembler-with-cpp')
        return self.get_preprocess_only_args() + [f'-x{lang}']


class GnuCompiler(GnuLikeCompiler):
    """
    GnuCompiler represents an actual GCC in its many incarnations.
    Compilers imitating GCC (Clang/Intel) should use the GnuLikeCompiler ABC.
    """
    id = 'gcc'

    _COLOR_VERSION = '>=4.9.0'
    _WPEDANTIC_VERSION = '>=4.8.0'
    _LTO_AUTO_VERSION = '>=10.0'
    _LTO_CACHE_VERSION = '>=15.1'
    _USE_MOLD_VERSION = '>=12.0.1'

    def __init__(self, defines: T.Optional[T.Dict[str, str]]):
        super().__init__()
        self.defines = defines or {}
        self.base_options.update({OptionKey('b_colorout'), OptionKey('b_lto_threads'),
                                  OptionKey('b_thinlto_cache'), OptionKey('b_thinlto_cache_dir')})
        self._has_color_support = mesonlib.version_compare(self.version, self._COLOR_VERSION)
        self._has_wpedantic_support = mesonlib.version_compare(self.version, self._WPEDANTIC_VERSION)
        self._has_lto_auto_support = mesonlib.version_compare(self.version, self._LTO_AUTO_VERSION)
        self._has_lto_cache_support = mesonlib.version_compare(self.version, self._LTO_CACHE_VERSION)

    def get_colorout_args(self, colortype: str) -> T.List[str]:
        if self._has_color_support:
            return gnu_color_args[colortype][:]
        return []

    def get_warn_args(self, level: str) -> T.List[str]:
        # Mypy doesn't understand cooperative inheritance
        args = super().get_warn_args(level)
        if not self._has_wpedantic_support and '-Wpedantic' in args:
            # -Wpedantic was added in 4.8.0
            # https://gcc.gnu.org/gcc-4.8/changes.html
            args[args.index('-Wpedantic')] = '-pedantic'
        return args

    def supported_warn_args(self, warn_args_by_version: T.Dict[str, T.List[str]]) -> T.List[str]:
        result: T.List[str] = []
        for version, warn_args in warn_args_by_version.items():
            if mesonlib.version_compare(self.version, '>=' + version):
                result += warn_args
        return result

    def has_builtin_define(self, define: str) -> bool:
        return define in self.defines

    def get_builtin_define(self, define: str) -> T.Optional[str]:
        if define in self.defines:
            return self.defines[define]
        return None

    def get_optimization_args(self, optimization_level: str) -> T.List[str]:
        return gnu_optimization_args[optimization_level]

    def get_pch_suffix(self) -> str:
        return 'gch'

    def openmp_flags(self) -> T.List[str]:
        return ['-fopenmp']

    def has_arguments(self, args: T.List[str], code: str,
                      mode: CompileCheckMode) -> T.Tuple[bool, bool]:
        # For some compiler command line arguments, the GNU compilers will
        # emit a warning on stderr indicating that an option is valid for a
        # another language, but still complete with exit_success
        with self._build_wrapper(code, args, None, mode) as p:
            result = p.returncode == 0
            if self.language in {'cpp', 'objcpp'} and 'is valid for C/ObjC' in p.stderr:
                result = False
            if self.language in {'c', 'objc'} and 'is valid for C++/ObjC++' in p.stderr:
                result = False
        return result, p.cached

    def get_has_func_attribute_extra_args(self, name: str) -> T.List[str]:
        # GCC only warns about unknown or ignored attributes, so force an
        # error.
        return ['-Werror=attributes']

    def get_prelink_args(self, prelink_name: str, obj_list: T.List[str]) -> T.Tuple[T.List[str], T.List[str]]:
        return [prelink_name], ['-r', '-o', prelink_name] + obj_list

    def get_lto_compile_args(self, *, target: T.Optional[BuildTarget] = None, threads: int = 0,
                             mode: str = 'default', thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
        args: T.List[str] = []

        if threads == 0:
            if self._has_lto_auto_support:
                args.append('-flto=auto')
            else:
                # This matches gcc's behavior of using the number of cpus, but
                # obeying meson's MESON_NUM_PROCESSES convention.
                args.append(f'-flto={mesonlib.determine_worker_count()}')
        elif threads > 0:
            args.append(f'-flto={threads}')
        else:
            args.extend(super().get_lto_compile_args(target=target, threads=threads))

        if thinlto_cache_dir is not None:
            # We check for ThinLTO linker support above in get_lto_compile_args, and all of them support
            # get_thinlto_cache_args as well
            args.extend(self.get_thinlto_cache_args(thinlto_cache_dir))

        return args

    def get_thinlto_cache_args(self, path: str) -> T.List[str]:
        # Unlike the ThinLTO support for Clang, everything is handled in GCC
        # and the linker has no direct involvement other than the usual w/ LTO.
        return [f'-flto-incremental={path}']

    @classmethod
    def use_linker_args(cls, linker: str, version: str) -> T.List[str]:
        if linker == 'mold' and mesonlib.version_compare(version, cls._USE_MOLD_VERSION):
            return ['-fuse-ld=mold']
        return super().use_linker_args(linker, version)

    def get_lto_link_args(self, *, target: T.Optional[BuildTarget] = None, threads: int = 0,
                          mode: str = 'default', thinlto_cache_dir: T.Optional[str] = None) -> T.List[str]:
        args: T.List[str] = []
        args.extend(self.get_lto_compile_args(target=target, threads=threads, thinlto_cache_dir=thinlto_cache_dir))
        return args

    def get_profile_use_args(self) -> T.List[str]:
        return super().get_profile_use_args() + ['-fprofile-correction']

    def get_always_args(self) -> T.List[str]:
        args: T.List[str] = []
        if self.info.is_os2() and self.environment.coredata.optstore.get_value_for(OptionKey('os2_emxomf')):
            args += ['-Zomf']
        return super().get_always_args() + args


class GnuCStds(Compiler):

    """Mixin class for gcc based compilers for setting C standards."""

    _C18_VERSION = '>=8.0.0'
    _C2X_VERSION = '>=9.0.0'
    _C23_VERSION = '>=14.0.0'
    _C2Y_VERSION = '>=15.0.0'

    def get_options(self) -> MutableKeyedOptionDictType:
        opts = super().get_options()
        stds = ['c89', 'c99', 'c11']
        if mesonlib.version_compare(self.version, self._C18_VERSION):
            stds += ['c17', 'c18']
        if mesonlib.version_compare(self.version, self._C2X_VERSION):
            stds += ['c2x']
        if mesonlib.version_compare(self.version, self._C23_VERSION):
            stds += ['c23']
        if mesonlib.version_compare(self.version, self._C2Y_VERSION):
            stds += ['c2y']
        key = self.form_compileropt_key('std')
        std_opt = opts[key]
        assert isinstance(std_opt, UserStdOption), 'for mypy'
        std_opt.set_versions(stds, gnu=True)
        return opts


class GnuCPPStds(Compiler):

    """Mixin class for GNU based compilers for setting CPP standards."""

    _CPP23_VERSION = '>=11.0.0'
    _CPP26_VERSION = '>=14.0.0'

    def get_options(self) -> MutableKeyedOptionDictType:
        opts = super().get_options()

        stds = [
            'c++98', 'c++03', 'c++11', 'c++14', 'c++17', 'c++1z',
            'c++2a', 'c++20',
        ]
        if mesonlib.version_compare(self.version, self._CPP23_VERSION):
            stds.append('c++23')
        if mesonlib.version_compare(self.version, self._CPP26_VERSION):
            stds.append('c++26')
        key = self.form_compileropt_key('std')
        std_opt = opts[key]
        assert isinstance(std_opt, UserStdOption), 'for mypy'
        std_opt.set_versions(stds, gnu=True)
        return opts
