Adding upstream version 115.8.0esr.upstream/115.8.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3194 insertions, 0 deletions

diff --git a/build/moz.configure/toolchain.configure b/build/moz.configure/toolchain.configure
new file mode 100644
index 0000000000..3f91d71537
--- /dev/null
+++ b/build/moz.configure/toolchain.configure
@@ -0,0 +1,3194 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# Code optimization
+# ==============================================================
+
+option("--disable-optimize", nargs="?", help="Disable optimizations via compiler flags")
+
+
+@depends("--enable-optimize")
+def moz_optimize(option):
+    flags = None
+
+    if len(option):
+        val = "2"
+        flags = option[0]
+    elif option:
+        val = "1"
+    else:
+        val = None
+
+    return namespace(
+        optimize=val,
+        flags=flags,
+    )
+
+
+set_config("MOZ_OPTIMIZE", moz_optimize.optimize)
+add_old_configure_assignment("MOZ_OPTIMIZE", moz_optimize.optimize)
+add_old_configure_assignment("MOZ_CONFIGURE_OPTIMIZE_FLAGS", moz_optimize.flags)
+
+# Android NDK
+# ==============================================================
+
+
+@depends("--disable-compile-environment", target)
+def compiling_android(compile_env, target):
+    return compile_env and target.os == "Android"
+
+
+include("android-ndk.configure", when=compiling_android)
+
+with only_when(target_is_osx):
+    # MacOS deployment target version
+    # ==============================================================
+    # This needs to happen before any compilation test is done.
+
+    option(
+        "--enable-macos-target",
+        env="MACOSX_DEPLOYMENT_TARGET",
+        nargs=1,
+        default=depends(target, developer_options)
+        # We continue to target 10.12 on Intel, but can target 11.0 for
+        # aarch64 since the earliest hardware was released alongside 11.0.
+        # For local builds, we want to target 10.12 regardless of the
+        # underlying platform to catch any errors or warnings that wouldn't
+        # show up when targeting 11.0, since these would later show up on
+        # CI for Intel builds.
+        (lambda t, d: "11.0" if (t.cpu == "aarch64" and not d) else "10.12"),
+        help="Set the minimum MacOS version needed at runtime{|}",
+    )
+
+    @depends_if("--enable-macos-target", developer_options)
+    def macos_target(value, _):
+        return value[0]
+
+
+with only_when(host_is_osx | target_is_osx):
+    # MacOS SDK
+    # =========
+    option(
+        "--with-macos-sdk",
+        env="MACOS_SDK_DIR",
+        nargs=1,
+        help="Location of platform SDK to use",
+    )
+
+    @imports("plistlib")
+    @imports(_from="__builtin__", _import="open")
+    @imports(_from="__builtin__", _import="Exception")
+    def get_sdk_version(sdk):
+        with open(os.path.join(sdk, "SDKSettings.plist"), "rb") as plist:
+            obj = plistlib.load(plist)
+        if not obj:
+            raise Exception(
+                "Error parsing SDKSettings.plist in the SDK directory: %s" % sdk
+            )
+        if "Version" not in obj:
+            raise Exception(
+                "Error finding Version information in SDKSettings.plist from the SDK: %s"
+                % sdk
+            )
+        return Version(obj["Version"])
+
+    def sdk_min_version():
+        return "13.3"
+
+    @depends(
+        "--with-macos-sdk",
+        host,
+        bootstrap_path(
+            "MacOSX{}.sdk".format(sdk_min_version()),
+            when=depends("--with-macos-sdk")(lambda x: not x),
+        ),
+    )
+    @imports(_from="__builtin__", _import="Exception")
+    @imports(_from="os.path", _import="isdir")
+    @imports(_from="os", _import="listdir")
+    def macos_sdk(sdk, host, bootstrapped):
+        if bootstrapped:
+            sdk = [bootstrapped]
+        if sdk:
+            sdk = sdk[0]
+            try:
+                version = get_sdk_version(sdk)
+            except Exception as e:
+                die(e)
+        elif host.os == "OSX":
+            sdk = check_cmd_output(
+                "xcrun", "--show-sdk-path", onerror=lambda: ""
+            ).rstrip()
+            if not sdk:
+                die(
+                    "Could not find the macOS SDK. Please use --with-macos-sdk to give "
+                    "the path to a macOS SDK."
+                )
+            # Scan the parent directory xcrun returns for the most recent SDK.
+            sdk_dir = os.path.dirname(sdk)
+            versions = []
+            for d in listdir(sdk_dir):
+                if d.lower().startswith("macos"):
+                    try:
+                        sdk = os.path.join(sdk_dir, d)
+                        versions.append((get_sdk_version(sdk), sdk))
+                    except Exception:
+                        pass
+            version, sdk = max(versions)
+        else:
+            die(
+                "Need a macOS SDK when targeting macOS. Please use --with-macos-sdk "
+                "to give the path to a macOS SDK."
+            )
+
+        if not isdir(sdk):
+            die(
+                "SDK not found in %s. When using --with-macos-sdk, you must specify a "
+                "valid SDK. SDKs are installed when the optional cross-development "
+                "tools are selected during the Xcode/Developer Tools installation."
+                % sdk
+            )
+        if version < Version(sdk_min_version()):
+            die(
+                'SDK version "%s" is too old. Please upgrade to at least %s. Try '
+                "updating your system Xcode." % (version, sdk_min_version())
+            )
+        return sdk
+
+    set_config("MACOS_SDK_DIR", macos_sdk)
+
+
+with only_when(target_is_osx):
+    with only_when(cross_compiling):
+        option(
+            "--with-macos-private-frameworks",
+            env="MACOS_PRIVATE_FRAMEWORKS_DIR",
+            nargs=1,
+            help="Location of private frameworks to use",
+        )
+
+        @depends_if("--with-macos-private-frameworks")
+        @imports(_from="os.path", _import="isdir")
+        def macos_private_frameworks(value):
+            if value and not isdir(value[0]):
+                die(
+                    "PrivateFrameworks not found not found in %s. When using "
+                    "--with-macos-private-frameworks, you must specify a valid "
+                    "directory",
+                    value[0],
+                )
+            return value[0]
+
+    @depends(macos_private_frameworks, macos_sdk)
+    def macos_private_frameworks(value, sdk):
+        if value:
+            return value
+        return os.path.join(sdk or "/", "System/Library/PrivateFrameworks")
+
+    set_config("MACOS_PRIVATE_FRAMEWORKS_DIR", macos_private_frameworks)
+
+
+# GC rooting and hazard analysis.
+# ==============================================================
+option(env="MOZ_HAZARD", help="Build for the GC rooting hazard analysis")
+
+
+@depends("MOZ_HAZARD")
+def hazard_analysis(value):
+    if value:
+        return True
+
+
+set_config("MOZ_HAZARD", hazard_analysis)
+
+
+# Cross-compilation related things.
+# ==============================================================
+option(
+    "--with-toolchain-prefix",
+    env="TOOLCHAIN_PREFIX",
+    nargs=1,
+    help="Prefix for the target toolchain",
+)
+
+
+@depends("--with-toolchain-prefix", host, target, cross_compiling)
+def toolchain_prefix(value, host, target, cross_compiling):
+    if value:
+        return tuple(value)
+    # We don't want a toolchain prefix by default when building on mac for mac.
+    if cross_compiling and not (target.os == "OSX" and host.os == "OSX"):
+        return ("%s-" % target.toolchain, "%s-" % target.alias)
+
+
+@depends(toolchain_prefix, target)
+def first_toolchain_prefix(toolchain_prefix, target):
+    # Pass TOOLCHAIN_PREFIX down to the build system if it was given from the
+    # command line/environment (in which case there's only one value in the tuple),
+    # or when cross-compiling for Android or OSX.
+    if toolchain_prefix and (
+        target.os in ("Android", "OSX") or len(toolchain_prefix) == 1
+    ):
+        return toolchain_prefix[0]
+
+
+set_config("TOOLCHAIN_PREFIX", first_toolchain_prefix)
+add_old_configure_assignment("TOOLCHAIN_PREFIX", first_toolchain_prefix)
+
+
+# Compilers
+# ==============================================================
+include("compilers-util.configure")
+
+
+def try_preprocess(
+    configure_cache, compiler, language, source, onerror=None, wrapper=[]
+):
+    return try_invoke_compiler(
+        configure_cache, compiler, language, source, ["-E"], onerror, wrapper
+    )
+
+
+@imports(_from="mozbuild.configure.constants", _import="CompilerType")
+@imports(_from="mozbuild.configure.constants", _import="CPU_preprocessor_checks")
+@imports(_from="mozbuild.configure.constants", _import="kernel_preprocessor_checks")
+@imports(_from="mozbuild.configure.constants", _import="OS_preprocessor_checks")
+@imports(_from="textwrap", _import="dedent")
+@imports(_from="__builtin__", _import="Exception")
+def get_compiler_info(configure_cache, compiler, language):
+    """Returns information about the given `compiler` (command line in the
+    form of a list or tuple), in the given `language`.
+
+    The returned information includes:
+    - the compiler type (clang-cl, clang or gcc)
+    - the compiler version
+    - the compiler supported language
+    - the compiler supported language version
+    """
+    # Xcode clang versions are different from the underlying llvm version (they
+    # instead are aligned with the Xcode version). Fortunately, we can tell
+    # apart plain clang from Xcode clang, and convert the Xcode clang version
+    # into the more or less corresponding plain clang version.
+    check = dedent(
+        """\
+        #if defined(_MSC_VER) && defined(__clang__) && defined(_MT)
+        %COMPILER "clang-cl"
+        %VERSION __clang_major__.__clang_minor__.__clang_patchlevel__
+        #elif defined(__clang__)
+        %COMPILER "clang"
+        %VERSION __clang_major__.__clang_minor__.__clang_patchlevel__
+        #  ifdef __apple_build_version__
+        %XCODE 1
+        #  endif
+        #elif defined(__GNUC__) && !defined(__MINGW32__)
+        %COMPILER "gcc"
+        %VERSION __GNUC__.__GNUC_MINOR__.__GNUC_PATCHLEVEL__
+        #endif
+
+        #if __cplusplus
+        %cplusplus __cplusplus
+        #elif __STDC_VERSION__
+        %STDC_VERSION __STDC_VERSION__
+        #endif
+    """
+    )
+
+    # While we're doing some preprocessing, we might as well do some more
+    # preprocessor-based tests at the same time, to check the toolchain
+    # matches what we want.
+    for name, preprocessor_checks in (
+        ("CPU", CPU_preprocessor_checks),
+        ("KERNEL", kernel_preprocessor_checks),
+        ("OS", OS_preprocessor_checks),
+    ):
+        for n, (value, condition) in enumerate(preprocessor_checks.items()):
+            check += dedent(
+                """\
+                #%(if)s %(condition)s
+                %%%(name)s "%(value)s"
+            """
+                % {
+                    "if": "elif" if n else "if",
+                    "condition": condition,
+                    "name": name,
+                    "value": value,
+                }
+            )
+        check += "#endif\n"
+
+    # Also check for endianness. The advantage of living in modern times is
+    # that all the modern compilers we support now have __BYTE_ORDER__ defined
+    # by the preprocessor.
+    check += dedent(
+        """\
+        #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+        %ENDIANNESS "little"
+        #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+        %ENDIANNESS "big"
+        #endif
+    """
+    )
+
+    result = try_preprocess(configure_cache, compiler, language, check)
+
+    if not result:
+        raise FatalCheckError("Unknown compiler or compiler not supported.")
+
+    # Metadata emitted by preprocessors such as GCC with LANG=ja_JP.utf-8 may
+    # have non-ASCII characters. Treat the output as bytearray.
+    data = {}
+    for line in result.splitlines():
+        if line.startswith("%"):
+            k, _, v = line.partition(" ")
+            k = k.lstrip("%")
+            data[k] = v.replace(" ", "").lstrip('"').rstrip('"')
+            log.debug("%s = %s", k, data[k])
+
+    try:
+        type = CompilerType(data["COMPILER"])
+    except Exception:
+        raise FatalCheckError("Unknown compiler or compiler not supported.")
+
+    cplusplus = int(data.get("cplusplus", "0L").rstrip("L"))
+    stdc_version = int(data.get("STDC_VERSION", "0L").rstrip("L"))
+
+    version = data.get("VERSION")
+    if version:
+        version = Version(version)
+        if data.get("XCODE"):
+            # Derived from https://en.wikipedia.org/wiki/Xcode#Toolchain_versions
+            # with enough granularity for major.minor version checks further
+            # down the line
+            if version < "9.1":
+                version = Version("4.0.0.or.less")
+            elif version < "10.0":
+                version = Version("5.0.2")
+            elif version < "10.0.1":
+                version = Version("6.0.1")
+            elif version < "11.0":
+                version = Version("7.0.0")
+            elif version < "11.0.3":
+                version = Version("8.0.0")
+            elif version < "12.0":
+                version = Version("9.0.0")
+            elif version < "12.0.5":
+                version = Version("10.0.0")
+            elif version < "13.0":
+                version = Version("11.1.0")
+            elif version < "13.0.1":
+                version = Version("12.0.0")
+            elif version < "14.0":
+                version = Version("13.0.0")
+            elif version < "15.0":
+                version = Version("14.0.0")
+            else:
+                version = Version("14.0.0.or.more")
+
+    return namespace(
+        type=type,
+        version=version,
+        cpu=data.get("CPU"),
+        kernel=data.get("KERNEL"),
+        endianness=data.get("ENDIANNESS"),
+        os=data.get("OS"),
+        language="C++" if cplusplus else "C",
+        language_version=cplusplus if cplusplus else stdc_version,
+        xcode=bool(data.get("XCODE")),
+    )
+
+
+def same_arch_different_bits():
+    return (
+        ("x86", "x86_64"),
+        ("ppc", "ppc64"),
+        ("sparc", "sparc64"),
+    )
+
+
+@imports(_from="mozbuild.shellutil", _import="quote")
+@imports(_from="mozbuild.configure.constants", _import="OS_preprocessor_checks")
+def check_compiler(configure_cache, compiler, language, target, android_version):
+    info = get_compiler_info(configure_cache, compiler, language)
+
+    flags = []
+
+    # Check language standards
+    # --------------------------------------------------------------------
+    if language != info.language:
+        raise FatalCheckError(
+            "`%s` is not a %s compiler." % (quote(*compiler), language)
+        )
+
+    # Note: We do a strict version check because there sometimes are backwards
+    # incompatible changes in the standard, and not all code that compiles as
+    # C99 compiles as e.g. C11 (as of writing, this is true of libnestegg, for
+    # example)
+    if info.language == "C" and info.language_version != 199901:
+        if info.type == "clang-cl":
+            flags.append("-Xclang")
+        flags.append("-std=gnu99")
+
+    cxx17_version = 201703
+    if info.language == "C++":
+        if info.language_version != cxx17_version:
+            # MSVC headers include C++17 features, but don't guard them
+            # with appropriate checks.
+            if info.type == "clang-cl":
+                flags.append("-Xclang")
+                flags.append("-std=c++17")
+            else:
+                flags.append("-std=gnu++17")
+
+    # Check compiler target
+    # --------------------------------------------------------------------
+    has_target = False
+    if target.os == "Android" and android_version:
+        # This makes clang define __ANDROID_API__ and use versioned library
+        # directories from the NDK.
+        toolchain = "%s%d" % (target.toolchain, android_version)
+    else:
+        toolchain = target.toolchain
+
+    if info.type == "clang":
+        # Add the target explicitly when the target is aarch64 macosx, because
+        # the Xcode clang target is named differently, and we need to work around
+        # https://github.com/rust-lang/rust-bindgen/issues/1871 and
+        # https://github.com/alexcrichton/cc-rs/issues/542 so we always want
+        # the target on the command line, even if the compiler would default to
+        # that.
+        if info.xcode and target.os == "OSX" and target.cpu == "aarch64":
+            if "--target=arm64-apple-darwin" not in compiler:
+                flags.append("--target=arm64-apple-darwin")
+            has_target = True
+
+        elif (
+            not info.kernel
+            or info.kernel != target.kernel
+            or not info.endianness
+            or info.endianness != target.endianness
+        ):
+            flags.append("--target=%s" % toolchain)
+            has_target = True
+
+        # Add target flag when there is an OS mismatch (e.g. building for Android on
+        # Linux). However, only do this if the target OS is in our whitelist, to
+        # keep things the same on other platforms.
+        elif target.os in OS_preprocessor_checks and (
+            not info.os or info.os != target.os
+        ):
+            flags.append("--target=%s" % toolchain)
+            has_target = True
+
+    if not has_target and (not info.cpu or info.cpu != target.cpu):
+        same_arch = same_arch_different_bits()
+        if (target.cpu, info.cpu) in same_arch:
+            flags.append("-m32")
+        elif (info.cpu, target.cpu) in same_arch:
+            flags.append("-m64")
+        elif info.type == "clang-cl" and target.cpu == "aarch64":
+            flags.append("--target=%s" % toolchain)
+        elif info.type == "clang":
+            flags.append("--target=%s" % toolchain)
+
+    return namespace(
+        type=info.type,
+        version=info.version,
+        target_cpu=info.cpu,
+        target_kernel=info.kernel,
+        target_endianness=info.endianness,
+        target_os=info.os,
+        flags=flags,
+    )
+
+
+@imports(_from="__builtin__", _import="open")
+@imports("json")
+@imports("os")
+def get_vc_paths(topsrcdir):
+    def vswhere(args):
+        program_files = os.environ.get("PROGRAMFILES(X86)") or os.environ.get(
+            "PROGRAMFILES"
+        )
+        if not program_files:
+            return []
+        vswhere = os.path.join(
+            program_files, "Microsoft Visual Studio", "Installer", "vswhere.exe"
+        )
+        if not os.path.exists(vswhere):
+            return []
+        return json.loads(check_cmd_output(vswhere, "-format", "json", *args))
+
+    for install in vswhere(
+        [
+            "-products",
+            "*",
+            "-requires",
+            "Microsoft.VisualStudio.Component.VC.Tools.x86.x64",
+        ]
+    ):
+        path = install["installationPath"]
+        tools_version = (
+            open(
+                os.path.join(
+                    path, r"VC\Auxiliary\Build\Microsoft.VCToolsVersion.default.txt"
+                ),
+                "r",
+            )
+            .read()
+            .strip()
+        )
+        tools_path = os.path.join(path, r"VC\Tools\MSVC", tools_version)
+        yield (Version(install["installationVersion"]), tools_path)
+
+
+@depends(target, host)
+def is_windows(target, host):
+    return host.kernel == "WINNT" or target.kernel == "WINNT"
+
+
+# Calling this a sysroot is a little weird, but it's the terminology clang went
+# with with its -winsysroot flag.
+option(
+    env="WINSYSROOT",
+    nargs=1,
+    when=is_windows,
+    help='Path to a Windows "sysroot" (directory containing MSVC, SDKs)',
+)
+
+
+@depends(
+    "WINSYSROOT",
+    bootstrap_path(
+        "vs",
+        when=depends("WINSYSROOT", when=is_windows)(lambda x: not x),
+    ),
+    when=is_windows,
+)
+def winsysroot(winsysroot, bootstrapped):
+    if bootstrapped:
+        return bootstrapped
+    if winsysroot:
+        return winsysroot[0]
+
+
+option(
+    env="VC_PATH",
+    nargs=1,
+    when=is_windows,
+    help="Path to the Microsoft Visual C/C++ compiler",
+)
+
+
+@depends(
+    host,
+    build_environment,
+    "VC_PATH",
+    winsysroot,
+    when=is_windows,
+)
+@imports("os")
+@imports(_from="operator", _import="itemgetter")
+def vc_compiler_paths_for_version(host, env, vc_path, winsysroot):
+    if winsysroot:
+        if vc_path:
+            die("WINSYSROOT and VC_PATH cannot be set together.")
+        base_vc_path = os.path.join(winsysroot, "VC", "Tools", "MSVC")
+        versions = os.listdir(base_vc_path)
+        vc_path = [os.path.join(base_vc_path, str(max(Version(v) for v in versions)))]
+    if vc_path:
+        # Use an arbitrary version, it doesn't matter.
+        all_versions = [(Version("15"), vc_path[0])]
+    elif host.kernel != "WINNT":
+        # Don't try to do anything when VC_PATH is not set on cross-compiles.
+        return
+    else:
+        all_versions = sorted(get_vc_paths(env.topsrcdir), key=itemgetter(0))
+    if not all_versions:
+        return
+    # Choose the newest version.
+    path = all_versions[-1][1]
+    host_dir = {
+        "x86_64": "Hostx64",
+        "x86": "Hostx86",
+    }.get(host.cpu)
+    if host_dir:
+        path = os.path.join(path, "bin", host_dir)
+        return {
+            "x64": [os.path.join(path, "x64")],
+            # The cross toolchains require DLLs from the native x64 toolchain.
+            "x86": [os.path.join(path, "x86"), os.path.join(path, "x64")],
+            "arm64": [os.path.join(path, "arm64"), os.path.join(path, "x64")],
+        }
+
+
+@depends(target, vc_compiler_paths_for_version, when=is_windows)
+def vc_compiler_path(target, paths):
+    vc_target = {
+        "x86": "x86",
+        "x86_64": "x64",
+        "arm": "arm",
+        "aarch64": "arm64",
+    }.get(target.cpu)
+    if not paths:
+        return
+    return paths.get(vc_target)
+
+
+@depends(vc_compiler_path, original_path)
+@imports("os")
+@imports(_from="os", _import="environ")
+def vc_toolchain_search_path(vc_compiler_path, original_path):
+    result = list(original_path)
+
+    if vc_compiler_path:
+        # The second item, if there is one, is necessary to have in $PATH for
+        # Windows to load the required DLLs from there.
+        if len(vc_compiler_path) > 1:
+            environ["PATH"] = os.pathsep.join(result + vc_compiler_path[1:])
+
+        # The first item is where the programs are going to be
+        result.append(vc_compiler_path[0])
+
+    return result
+
+
+@depends_if(vc_compiler_path, when=is_windows)
+def vc_compiler_version(vc_compiler_path):
+    version = Version(
+        os.path.basename(
+            os.path.dirname(os.path.dirname(os.path.dirname(vc_compiler_path[0])))
+        )
+    )
+    # MSVC path with version 14.x is actually version 19.x
+    if version.major == 14:
+        return Version(f"19.{version.minor}")
+
+
+@depends_if(vc_compiler_version)
+def is_vs2019_or_more(vc_compiler_version):
+    return vc_compiler_version >= Version("19.20")
+
+
+add_old_configure_assignment("IS_VS2019_OR_MORE", is_vs2019_or_more)
+
+
+@depends_if(vc_compiler_version)
+def msvs_version(vc_compiler_version):
+    # clang-cl emulates the same version scheme as cl. And MSVS_VERSION needs to
+    # be set for GYP on Windows.
+    if vc_compiler_version >= Version("19.30"):
+        return "2022"
+    if vc_compiler_version >= Version("19.20"):
+        return "2019"
+    if vc_compiler_version >= Version("19.10"):
+        return "2017"
+
+    return ""
+
+
+set_config("MSVS_VERSION", msvs_version)
+
+
+clang_search_path = bootstrap_search_path("clang/bin")
+
+
+@depends(
+    bootstrap_search_path("rustc/bin", when="MOZ_AUTOMATION"),
+    bootstrap_search_path_order,
+    original_path,
+)
+@imports("os")
+@imports(_from="os", _import="environ")
+def rust_search_path(rust_path, search_order, original_path):
+    result = list(rust_path or original_path)
+    # Also add the rustup install directory for cargo/rustc.
+    cargo_home = environ.get("CARGO_HOME", "")
+    if cargo_home:
+        cargo_home = os.path.abspath(cargo_home)
+    else:
+        cargo_home = os.path.expanduser(os.path.join("~", ".cargo"))
+    rustup_path = os.path.join(cargo_home, "bin")
+    if search_order == "prepend":
+        result.insert(0, rustup_path)
+    else:
+        result.append(rustup_path)
+    return result
+
+
+# Prepend the mozilla-build msys2 path, since otherwise we can get mismatched
+# cygwin dll errors during configure if we get called from another msys2
+# environment, see bug 1801826.
+@depends(mozillabuild_bin_paths, clang_search_path, target, original_path)
+@imports("os")
+def altered_path(mozillabuild_bin_paths, clang_search_path, target, original_path):
+    altered_path = mozillabuild_bin_paths
+    if target.kernel == "Darwin":
+        # The rust compiler wants to execute dsymutil, but it does so in a
+        # non-configurable way (https://github.com/rust-lang/rust/issues/52728)
+        # so we add the clang path.
+        path = clang_search_path
+    else:
+        path = original_path
+    for p in path:
+        if p not in altered_path:
+            altered_path.append(p)
+    return os.pathsep.join(altered_path)
+
+
+set_config("PATH", altered_path)
+
+
+# Compiler wrappers
+# ==============================================================
+option(
+    "--with-compiler-wrapper",
+    env="COMPILER_WRAPPER",
+    nargs=1,
+    help="Enable compiling with wrappers such as distcc and ccache",
+)
+
+option("--with-ccache", env="CCACHE", nargs="?", help="Enable compiling with ccache")
+
+
+@depends_if("--with-ccache")
+def ccache(value):
+    if len(value):
+        return value
+    # If --with-ccache was given without an explicit value, we default to
+    # 'ccache'.
+    return "ccache"
+
+
+ccache = check_prog(
+    "CCACHE",
+    progs=(),
+    input=ccache,
+    paths=bootstrap_search_path(
+        "sccache", when=depends("CCACHE")(lambda c: len(c) and c[0] == "sccache")
+    ),
+    allow_missing=True,
+)
+
+option(env="CCACHE_PREFIX", nargs=1, help="Compiler prefix to use when using ccache")
+
+ccache_prefix = depends_if("CCACHE_PREFIX")(lambda prefix: prefix[0])
+set_config("CCACHE_PREFIX", ccache_prefix)
+
+# Distinguish ccache from sccache.
+
+
+@depends_if(ccache)
+def ccache_is_sccache(ccache):
+    return check_cmd_output(ccache, "--version").startswith("sccache")
+
+
+@depends(ccache, ccache_is_sccache)
+def using_ccache(ccache, ccache_is_sccache):
+    return ccache and not ccache_is_sccache
+
+
+@depends_if(ccache, ccache_is_sccache)
+def using_sccache(ccache, ccache_is_sccache):
+    return ccache and ccache_is_sccache
+
+
+option(env="RUSTC_WRAPPER", nargs=1, help="Wrap rust compilation with given tool")
+
+
+@depends(ccache, ccache_is_sccache, "RUSTC_WRAPPER")
+@imports(_from="textwrap", _import="dedent")
+@imports("os")
+def check_sccache_version(ccache, ccache_is_sccache, rustc_wrapper):
+    sccache_min_version = Version("0.2.13")
+
+    def check_version(path):
+        out = check_cmd_output(path, "--version")
+        version = Version(out.rstrip().split()[-1])
+        if version < sccache_min_version:
+            die(
+                dedent(
+                    """\
+            sccache %s or later is required. sccache in use at %s has
+            version %s.
+
+            Please upgrade or acquire a new version with |./mach bootstrap|.
+            """
+                ),
+                sccache_min_version,
+                path,
+                version,
+            )
+
+    if ccache and ccache_is_sccache:
+        check_version(ccache)
+
+    if rustc_wrapper and (
+        os.path.splitext(os.path.basename(rustc_wrapper[0]))[0].lower() == "sccache"
+    ):
+        check_version(rustc_wrapper[0])
+
+
+set_config("MOZ_USING_CCACHE", using_ccache)
+set_config("MOZ_USING_SCCACHE", using_sccache)
+
+option(env="SCCACHE_VERBOSE_STATS", help="Print verbose sccache stats after build")
+
+
+@depends(using_sccache, "SCCACHE_VERBOSE_STATS")
+def sccache_verbose_stats(using_sccache, verbose_stats):
+    return using_sccache and bool(verbose_stats)
+
+
+set_config("SCCACHE_VERBOSE_STATS", sccache_verbose_stats)
+
+
+@depends("--with-compiler-wrapper", ccache)
+@imports(_from="mozbuild.shellutil", _import="split", _as="shell_split")
+def compiler_wrapper(wrapper, ccache):
+    if wrapper:
+        raw_wrapper = wrapper[0]
+        wrapper = shell_split(raw_wrapper)
+        wrapper_program = find_program(wrapper[0])
+        if not wrapper_program:
+            die(
+                "Cannot find `%s` from the given compiler wrapper `%s`",
+                wrapper[0],
+                raw_wrapper,
+            )
+        wrapper[0] = wrapper_program
+
+    if ccache:
+        if wrapper:
+            return tuple([ccache] + wrapper)
+        else:
+            return (ccache,)
+    elif wrapper:
+        return tuple(wrapper)
+
+
+@depends_if(compiler_wrapper)
+def using_compiler_wrapper(compiler_wrapper):
+    return True
+
+
+set_config("MOZ_USING_COMPILER_WRAPPER", using_compiler_wrapper)
+
+
+@dependable
+def wasm():
+    return split_triplet("wasm32-wasi", allow_wasi=True)
+
+
+@template
+def default_c_compilers(host_or_target, other_c_compiler=None):
+    """Template defining the set of default C compilers for the host and
+    target platforms.
+    `host_or_target` is either `host` or `target` (the @depends functions
+    from init.configure.
+    `other_c_compiler` is the `target` C compiler when `host_or_target` is `host`.
+    """
+    assert host_or_target in {host, target, wasm}
+
+    other_c_compiler = () if other_c_compiler is None else (other_c_compiler,)
+
+    @depends(host_or_target, target, toolchain_prefix, *other_c_compiler)
+    def default_c_compilers(
+        host_or_target, target, toolchain_prefix, *other_c_compiler
+    ):
+        if host_or_target.kernel == "WINNT":
+            if host_or_target.abi:
+                if host_or_target.abi == "msvc":
+                    supported = types = ("clang-cl",)
+                elif host_or_target.abi == "mingw":
+                    supported = types = ("clang",)
+            else:
+                supported = types = ("clang-cl", "clang")
+        elif host_or_target.kernel == "Darwin":
+            types = ("clang",)
+            supported = ("clang", "gcc")
+        elif host_or_target.kernel == "WASI":
+            supported = types = ("clang",)
+        else:
+            supported = types = ("clang", "gcc")
+
+        info = other_c_compiler[0] if other_c_compiler else None
+        if info and info.type in supported:
+            # When getting default C compilers for the host, we prioritize the
+            # same compiler as the target C compiler.
+            prioritized = info.compiler
+            if info.type == "gcc":
+                same_arch = same_arch_different_bits()
+                if (
+                    target.cpu != host_or_target.cpu
+                    and (target.cpu, host_or_target.cpu) not in same_arch
+                    and (host_or_target.cpu, target.cpu) not in same_arch
+                ):
+                    # If the target C compiler is GCC, and it can't be used with
+                    # -m32/-m64 for the host, it's probably toolchain-prefixed,
+                    # so we prioritize a raw 'gcc' instead.
+                    prioritized = info.type
+            if target.os != "WINNT" and host_or_target.os == "WINNT":
+                # When cross-compiling on Windows, don't prioritize. We'll fallback
+                # to checking for clang-cl first.
+                pass
+            else:
+                types = [prioritized] + [t for t in types if t != info.type]
+
+        gcc = ("gcc",)
+        if toolchain_prefix and host_or_target is target:
+            gcc = tuple("%sgcc" % p for p in toolchain_prefix) + gcc
+
+        result = []
+        for type in types:
+            if type == "gcc":
+                result.extend(gcc)
+            else:
+                result.append(type)
+
+        return tuple(result)
+
+    return default_c_compilers
+
+
+@template
+def default_cxx_compilers(c_compiler, other_c_compiler=None, other_cxx_compiler=None):
+    """Template defining the set of default C++ compilers for the host and
+    target platforms.
+    `c_compiler` is the @depends function returning a Compiler instance for
+    the desired platform.
+
+    Because the build system expects the C and C++ compilers to be from the
+    same compiler suite, we derive the default C++ compilers from the C
+    compiler that was found if none was provided.
+
+    We also factor in the target C++ compiler when getting the default host
+    C++ compiler, using the target C++ compiler if the host and target C
+    compilers are the same.
+    """
+
+    assert (other_c_compiler is None) == (other_cxx_compiler is None)
+    if other_c_compiler is not None:
+        other_compilers = (other_c_compiler, other_cxx_compiler)
+    else:
+        other_compilers = ()
+
+    @depends(c_compiler, *other_compilers)
+    def default_cxx_compilers(c_compiler, *other_compilers):
+        if other_compilers:
+            other_c_compiler, other_cxx_compiler = other_compilers
+            if other_c_compiler.compiler == c_compiler.compiler:
+                return (other_cxx_compiler.compiler,)
+
+        dir = os.path.dirname(c_compiler.compiler)
+        file = os.path.basename(c_compiler.compiler)
+
+        if c_compiler.type == "gcc":
+            return (os.path.join(dir, file.replace("gcc", "g++")),)
+
+        if c_compiler.type == "clang":
+            return (os.path.join(dir, file.replace("clang", "clang++")),)
+
+        return (c_compiler.compiler,)
+
+    return default_cxx_compilers
+
+
+@template
+def provided_program(env_var, when=None):
+    """Template handling cases where a program can be specified either as a
+    path or as a path with applicable arguments.
+    """
+
+    @depends_if(env_var, when=when)
+    @imports(_from="itertools", _import="takewhile")
+    @imports(_from="mozbuild.shellutil", _import="split", _as="shell_split")
+    def provided(cmd):
+        # Assume the first dash-prefixed item (and any subsequent items) are
+        # command-line options, the item before the dash-prefixed item is
+        # the program we're looking for, and anything before that is a wrapper
+        # of some kind (e.g. sccache).
+        cmd = shell_split(cmd[0])
+
+        without_flags = list(takewhile(lambda x: not x.startswith("-"), cmd))
+
+        return namespace(
+            wrapper=without_flags[:-1],
+            program=without_flags[-1],
+            flags=cmd[len(without_flags) :],
+        )
+
+    return provided
+
+
+@template
+def sysroot(host_or_target, target_sysroot=None):
+    assert target_sysroot or host_or_target is target
+    bootstrap_target_when = target_is_linux_or_wasi
+    if host_or_target is host:
+        host_or_target_str = "host"
+        opt = "--with-host-sysroot"
+        env = "HOST_SYSROOT"
+        when = depends(host)(lambda h: h.kernel == "Linux")
+        # Only bootstrap a host sysroot when using a bootstrapped target sysroot
+        # or when the target doesn't use a bootstrapped sysroot in the first place.
+        @depends(when, bootstrap_target_when, target_sysroot.bootstrapped)
+        def bootstrap_when(when, bootstrap_target_when, bootstrapped):
+            return when and (bootstrapped or not bootstrap_target_when)
+
+    else:
+        assert host_or_target is target
+        host_or_target_str = "target"
+        opt = "--with-sysroot"
+        env = "SYSROOT"
+        when = target_is_linux_or_wasi
+        bootstrap_when = bootstrap_target_when
+
+    option(
+        opt,
+        env=env,
+        nargs=1,
+        when=when,
+        help="Use the given sysroot directory for %s build" % host_or_target_str,
+    )
+
+    sysroot_input = depends(opt, when=when)(lambda x: x)
+    bootstrap_sysroot = depends(bootstrap_when, sysroot_input)(
+        # Only bootstrap when no flag was explicitly given (either --with or --without)
+        lambda bootstrap, input: bootstrap
+        and not input
+        and input.origin == "default"
+    )
+
+    @depends(
+        sysroot_input,
+        host_or_target,
+        macos_sdk,
+        bootstrap_path(
+            depends(host_or_target)(lambda t: "sysroot-{}".format(t.toolchain)),
+            when=bootstrap_sysroot,
+        ),
+    )
+    @imports("os")
+    def sysroot(sysroot_input, host_or_target, macos_sdk, path):
+        version = None
+        if sysroot_input:
+            path = sysroot_input[0]
+        elif host_or_target.kernel == "Darwin" and macos_sdk:
+            path = macos_sdk
+        if path:
+            # Find the version of libstdc++ headears in the sysroot
+            include = os.path.join(path, "usr/include/c++")
+            if os.path.isdir(include):
+                with os.scandir(include) as d:
+                    version = max(Version(e.name) for e in d if e.is_dir())
+            log.info("Using %s sysroot in %s", host_or_target_str, path)
+        return namespace(
+            path=path,
+            bootstrapped=bool(path and not sysroot_input),
+            stdcxx_version=version,
+        )
+
+    return sysroot
+
+
+target_sysroot = sysroot(target)
+
+
+# Use `system_lib_option` instead of `option` for options that enable building
+# with a system library for which the development headers are not available in
+# the bootstrapped sysroots.
+@template
+def system_lib_option(name, *args, **kwargs):
+    option(name, *args, **kwargs)
+
+    @depends(name, target_sysroot.bootstrapped)
+    def no_system_lib_in_sysroot(value, bootstrapped):
+        if bootstrapped and value:
+            die(
+                "%s is not supported with bootstrapped sysroot. "
+                "Drop the option, or use --without-sysroot or --disable-bootstrap",
+                value.format(name),
+            )
+
+
+host_sysroot = sysroot(host, target_sysroot)
+
+
+@template
+def multiarch_dir(host_or_target):
+    sysroot = {
+        host: host_sysroot,
+        target: target_sysroot,
+    }[host_or_target]
+
+    @depends(host_or_target, when=sysroot.path)
+    def multiarch_dir(target):
+        if target.cpu == "x86":
+            # Turn e.g. i686-linux-gnu into i386-linux-gnu
+            return target.toolchain.replace(target.raw_cpu, "i386")
+        return target.toolchain
+
+    return multiarch_dir
+
+
+target_multiarch_dir = multiarch_dir(target)
+host_multiarch_dir = multiarch_dir(host)
+
+
+def minimum_gcc_version():
+    return Version("8.1.0")
+
+
+@template
+def compiler(
+    language,
+    host_or_target,
+    c_compiler=None,
+    other_compiler=None,
+    other_c_compiler=None,
+):
+    """Template handling the generic base checks for the compiler for the
+    given `language` on the given platform (`host_or_target`).
+    `host_or_target` is either `host` or `target` (the @depends functions
+    from init.configure.
+    When the language is 'C++', `c_compiler` is the result of the `compiler`
+    template for the language 'C' for the same `host_or_target`.
+    When `host_or_target` is `host`, `other_compiler` is the result of the
+    `compiler` template for the same `language` for `target`.
+    When `host_or_target` is `host` and the language is 'C++',
+    `other_c_compiler` is the result of the `compiler` template for the
+    language 'C' for `target`.
+    """
+    assert host_or_target in {host, target, wasm}
+    assert language in ("C", "C++")
+    assert language == "C" or c_compiler is not None
+    assert host_or_target is target or other_compiler is not None
+    assert language == "C" or host_or_target is target or other_c_compiler is not None
+
+    host_or_target_str = {
+        host: "host",
+        target: "target",
+        wasm: "wasm",
+    }[host_or_target]
+
+    sysroot = {
+        host: host_sysroot,
+        target: target_sysroot,
+        wasm: dependable(lambda: namespace(path=None)),
+    }[host_or_target]
+
+    multiarch_dir = {
+        host: host_multiarch_dir,
+        target: target_multiarch_dir,
+        wasm: never,
+    }[host_or_target]
+
+    var = {
+        ("C", target): "CC",
+        ("C++", target): "CXX",
+        ("C", host): "HOST_CC",
+        ("C++", host): "HOST_CXX",
+        ("C", wasm): "WASM_CC",
+        ("C++", wasm): "WASM_CXX",
+    }[language, host_or_target]
+
+    default_compilers = {
+        "C": lambda: default_c_compilers(host_or_target, other_compiler),
+        "C++": lambda: default_cxx_compilers(
+            c_compiler, other_c_compiler, other_compiler
+        ),
+    }[language]()
+
+    what = "the %s %s compiler" % (host_or_target_str, language)
+
+    option(env=var, nargs=1, help="Path to %s" % what)
+
+    # Handle the compiler given by the user through one of the CC/CXX/HOST_CC/
+    # HOST_CXX variables.
+    provided_compiler = provided_program(var)
+
+    # Normally, we'd use `var` instead of `_var`, but the interaction with
+    # old-configure complicates things, and for now, we a) can't take the plain
+    # result from check_prog as CC/CXX/HOST_CC/HOST_CXX and b) have to let
+    # old-configure AC_SUBST it (because it's autoconf doing it, not us)
+    compiler = check_prog(
+        "_%s" % var,
+        what=what,
+        progs=default_compilers,
+        input=provided_compiler.program,
+        paths=clang_search_path,
+    )
+
+    @depends(
+        configure_cache,
+        compiler,
+        provided_compiler,
+        compiler_wrapper,
+        host_or_target,
+        sysroot,
+        macos_target,
+        android_version,
+        vc_compiler_version,
+        multiarch_dir,
+        winsysroot,
+        host,
+    )
+    @checking("whether %s can be used" % what, lambda x: bool(x))
+    @imports(_from="mozbuild.shellutil", _import="quote")
+    @imports("os")
+    def valid_compiler(
+        configure_cache,
+        compiler,
+        provided_compiler,
+        compiler_wrapper,
+        host_or_target,
+        sysroot,
+        macos_target,
+        android_version,
+        vc_compiler_version,
+        multiarch_dir,
+        winsysroot,
+        host,
+    ):
+        wrapper = list(compiler_wrapper or ())
+        flags = []
+        if sysroot.path:
+            if host_or_target.kernel == "Darwin":
+                # While --sysroot and -isysroot are roughly equivalent, when not using
+                # -isysroot on mac, clang takes the SDKROOT environment variable into
+                # consideration, which may be set by python and break things.
+                flags.extend(("-isysroot", sysroot.path))
+            else:
+                flags.extend(("--sysroot", sysroot.path))
+        if host_or_target.os == "OSX" and macos_target:
+            flags.append("-mmacosx-version-min=%s" % macos_target)
+        if provided_compiler:
+            wrapper.extend(provided_compiler.wrapper)
+            flags.extend(provided_compiler.flags)
+
+        info = check_compiler(
+            configure_cache,
+            wrapper + [compiler] + flags,
+            language,
+            host_or_target,
+            android_version,
+        )
+
+        # When not given an explicit compatibility version, clang-cl tries
+        # to get one from MSVC, which might not even be the one used by the
+        # build. And when it can't find one, its default might also not match
+        # what the build is using. So if we were able to figure out the version
+        # we're building with, explicitly use that.
+        # This also means that, as a side effect, clang-cl will not try to find
+        # MSVC, which saves a little overhead.
+        if info.type == "clang-cl" and vc_compiler_version:
+            flags.append(f"-fms-compatibility-version={vc_compiler_version}")
+
+        if info.type == "clang" and language == "C++" and host_or_target.os == "OSX":
+            flags.append("-stdlib=libc++")
+
+        # Check that the additional flags we got are enough to not require any
+        # more flags. If we get an exception, just ignore it; it's liable to be
+        # invalid command-line flags, which means the compiler we're checking
+        # doesn't support those command-line flags and will fail one or more of
+        # the checks below.
+        try:
+            if info.flags:
+                flags += info.flags
+                info = check_compiler(
+                    configure_cache,
+                    wrapper + [compiler] + flags,
+                    language,
+                    host_or_target,
+                    android_version,
+                )
+        except FatalCheckError:
+            pass
+
+        if not info.target_cpu or info.target_cpu != host_or_target.cpu:
+            raise FatalCheckError(
+                "%s %s compiler target CPU (%s) does not match --%s CPU (%s)"
+                % (
+                    host_or_target_str.capitalize(),
+                    language,
+                    info.target_cpu or "unknown",
+                    host_or_target_str,
+                    host_or_target.raw_cpu,
+                )
+            )
+
+        if not info.target_kernel or (info.target_kernel != host_or_target.kernel):
+            raise FatalCheckError(
+                "%s %s compiler target kernel (%s) does not match --%s kernel (%s)"
+                % (
+                    host_or_target_str.capitalize(),
+                    language,
+                    info.target_kernel or "unknown",
+                    host_or_target_str,
+                    host_or_target.kernel,
+                )
+            )
+
+        if not info.target_endianness or (
+            info.target_endianness != host_or_target.endianness
+        ):
+            raise FatalCheckError(
+                "%s %s compiler target endianness (%s) does not match --%s "
+                "endianness (%s)"
+                % (
+                    host_or_target_str.capitalize(),
+                    language,
+                    info.target_endianness or "unknown",
+                    host_or_target_str,
+                    host_or_target.endianness,
+                )
+            )
+
+        # Compiler version checks
+        # ===================================================
+        # Check the compiler version here instead of in `compiler_version` so
+        # that the `checking` message doesn't pretend the compiler can be used
+        # to then bail out one line later.
+        if info.type == "gcc":
+            if host_or_target.os == "Android":
+                raise FatalCheckError(
+                    "GCC is not supported on Android.\n"
+                    "Please use clang from the Android NDK instead."
+                )
+            gcc_version = minimum_gcc_version()
+            if info.version < gcc_version:
+                raise FatalCheckError(
+                    "Only GCC %d.%d or newer is supported (found version %s)."
+                    % (gcc_version.major, gcc_version.minor, info.version)
+                )
+
+            # Force GCC to use the C++ headers from the sysroot, and to prefer the
+            # sysroot system headers to /usr/include.
+            # Non-Debian GCC also doesn't look at headers in multiarch directory.
+            if sysroot.bootstrapped and sysroot.stdcxx_version:
+                version = sysroot.stdcxx_version
+                for path in (
+                    "usr/include/c++/{}".format(version),
+                    "usr/include/{}/c++/{}".format(multiarch_dir, version),
+                    "usr/include/{}".format(multiarch_dir),
+                    "usr/include",
+                ):
+                    flags.extend(("-isystem", os.path.join(sysroot.path, path)))
+
+        if info.type == "clang-cl":
+            if info.version < "9.0.0":
+                raise FatalCheckError(
+                    "Only clang-cl 9.0 or newer is supported (found version %s)"
+                    % info.version
+                )
+            if winsysroot and host.os != "WINNT":
+                overlay = os.path.join(winsysroot, "overlay.yaml")
+                if os.path.exists(overlay):
+                    overlay_flags = ["-Xclang", "-ivfsoverlay", "-Xclang", overlay]
+                    if info.version >= "16.0" or (
+                        # clang-cl 15 normally doesn't support the root-relative
+                        # overlay we use, but the bootstrapped clang-cl 15 is patched
+                        # to support it, so check we're using a patched version.
+                        info.version >= "15.0"
+                        and try_preprocess(
+                            configure_cache,
+                            [compiler] + flags + overlay_flags,
+                            language,
+                            "",
+                            onerror=lambda: False,
+                            wrapper=wrapper,
+                        )
+                    ):
+                        flags.extend(overlay_flags)
+
+        if (info.type, host_or_target.abi) in (
+            ("clang", "msvc"),
+            ("clang-cl", "mingw"),
+        ):
+            raise FatalCheckError("Unknown compiler or compiler not supported.")
+
+        # If you want to bump the version check here ensure the version
+        # is known for Xcode in get_compiler_info.
+        if info.type == "clang" and info.version < "7.0":
+            raise FatalCheckError(
+                "Only clang/llvm 7.0 or newer is supported (found version %s)."
+                % info.version
+            )
+
+        if host_or_target.kernel == "WASI":
+            if info.type != "clang":
+                raise FatalCheckError(
+                    "Only clang is supported for %s" % host_or_target.alias
+                )
+            if info.version < "8.0":
+                raise FatalCheckError(
+                    "Only clang/llvm 8.0 or newer is supported for %s (found version %s)."
+                    % (host_or_target.alias, info.version)
+                )
+
+        if host_or_target.os == "Android":
+            # Need at least clang 13 for compiler-rt/libunwind being the default.
+            if info.type == "clang" and info.version < "13.0":
+                raise FatalCheckError(
+                    "Only clang/llvm 13.0 or newer is supported for %s (found version %s)."
+                    % (host_or_target.alias, info.version)
+                )
+
+        if info.flags:
+            raise FatalCheckError("Unknown compiler or compiler not supported.")
+
+        return namespace(
+            wrapper=wrapper,
+            compiler=compiler,
+            flags=flags,
+            type=info.type,
+            version=info.version,
+            language=language,
+        )
+
+    @depends(valid_compiler)
+    @checking("%s version" % what)
+    def compiler_version(compiler):
+        return compiler.version
+
+    if language == "C++":
+
+        @depends(valid_compiler, c_compiler)
+        def valid_compiler(compiler, c_compiler):
+            if compiler.type != c_compiler.type:
+                die(
+                    "The %s C compiler is %s, while the %s C++ compiler is "
+                    "%s. Need to use the same compiler suite.",
+                    host_or_target_str,
+                    c_compiler.type,
+                    host_or_target_str,
+                    compiler.type,
+                )
+
+            if compiler.version != c_compiler.version:
+                die(
+                    "The %s C compiler is version %s, while the %s C++ "
+                    "compiler is version %s. Need to use the same compiler "
+                    "version.",
+                    host_or_target_str,
+                    c_compiler.version,
+                    host_or_target_str,
+                    compiler.version,
+                )
+            return compiler
+
+    # Set CC/CXX/HOST_CC/HOST_CXX for old-configure, which needs the wrapper
+    # and the flags that were part of the user input for those variables to
+    # be provided.
+    add_old_configure_assignment(
+        var,
+        depends_if(valid_compiler)(
+            lambda x: list(x.wrapper) + [x.compiler] + list(x.flags)
+        ),
+    )
+
+    if host_or_target is target:
+        add_old_configure_assignment(
+            "ac_cv_prog_%s" % var,
+            depends_if(valid_compiler)(
+                lambda x: list(x.wrapper) + [x.compiler] + list(x.flags)
+            ),
+        )
+        # We check that it works in python configure already.
+        add_old_configure_assignment("ac_cv_prog_%s_works" % var.lower(), "yes")
+        add_old_configure_assignment(
+            "ac_cv_prog_%s_cross" % var.lower(),
+            depends(cross_compiling)(lambda x: "yes" if x else "no"),
+        )
+        gcc_like = depends(valid_compiler.type)(
+            lambda x: "yes" if x in ("gcc", "clang") else "no"
+        )
+        add_old_configure_assignment("ac_cv_prog_%s_g" % var.lower(), gcc_like)
+        if language == "C":
+            add_old_configure_assignment("ac_cv_prog_gcc", gcc_like)
+        if language == "C++":
+            add_old_configure_assignment("ac_cv_prog_gxx", gcc_like)
+
+    # Set CC_TYPE/CC_VERSION/HOST_CC_TYPE/HOST_CC_VERSION to allow
+    # old-configure to do some of its still existing checks.
+    if language == "C":
+        set_config("%s_TYPE" % var, valid_compiler.type)
+        add_old_configure_assignment("%s_TYPE" % var, valid_compiler.type)
+        set_config(
+            "%s_VERSION" % var, depends(valid_compiler.version)(lambda v: str(v))
+        )
+
+    valid_compiler = compiler_class(valid_compiler, host_or_target)
+
+    def compiler_error():
+        raise FatalCheckError(
+            "Failed compiling a simple %s source with %s" % (language, what)
+        )
+
+    valid_compiler.try_compile(check_msg="%s works" % what, onerror=compiler_error)
+
+    set_config("%s_BASE_FLAGS" % var, valid_compiler.flags)
+
+    # Set CPP/CXXCPP for both the build system and old-configure. We don't
+    # need to check this works for preprocessing, because we already relied
+    # on $CC -E/$CXX -E doing preprocessing work to validate the compiler
+    # in the first place.
+    if host_or_target is target:
+        pp_var = {
+            "C": "CPP",
+            "C++": "CXXCPP",
+        }[language]
+
+        preprocessor = depends_if(valid_compiler)(
+            lambda x: list(x.wrapper) + [x.compiler, "-E"] + list(x.flags)
+        )
+
+        set_config(pp_var, preprocessor)
+        add_old_configure_assignment(pp_var, preprocessor)
+
+    if language == "C":
+        linker_var = {
+            target: "LD",
+            host: "HOST_LD",
+        }.get(host_or_target)
+
+        if linker_var:
+
+            @deprecated_option(env=linker_var, nargs=1)
+            def linker(value):
+                if value:
+                    return value[0]
+
+            @depends(linker)
+            def unused_linker(linker):
+                if linker:
+                    log.warning(
+                        "The value of %s is not used by this build system." % linker_var
+                    )
+
+    return valid_compiler
+
+
+c_compiler = compiler("C", target)
+cxx_compiler = compiler("C++", target, c_compiler=c_compiler)
+host_c_compiler = compiler("C", host, other_compiler=c_compiler)
+host_cxx_compiler = compiler(
+    "C++",
+    host,
+    c_compiler=host_c_compiler,
+    other_compiler=cxx_compiler,
+    other_c_compiler=c_compiler,
+)
+
+
+@template
+def windows_abi(host_or_target, c_compiler):
+    @depends(host_or_target)
+    def windows_abi(host_or_target):
+        if host_or_target.os == "WINNT":
+            return host_or_target.abi
+
+    @depends(host_or_target, windows_abi)
+    def need_windows_abi_from_compiler(host_or_target, windows_abi):
+        return host_or_target.os == "WINNT" and windows_abi is None
+
+    @depends(host_or_target, c_compiler, when=need_windows_abi_from_compiler)
+    def windows_abi_from_compiler(host_or_target, c_compiler):
+        if host_or_target.os == "WINNT":
+            if c_compiler.type == "clang-cl":
+                return "msvc"
+            return "mingw"
+
+    return windows_abi | windows_abi_from_compiler
+
+
+target_windows_abi = windows_abi(target, c_compiler)
+host_windows_abi = windows_abi(host, host_c_compiler)
+
+
+# Generic compiler-based conditions.
+building_with_gcc = depends(c_compiler)(lambda info: info.type == "gcc")
+
+
+@depends(cxx_compiler, ccache_prefix)
+@imports("os")
+def cxx_is_icecream(info, ccache_prefix):
+    if (
+        os.path.islink(info.compiler)
+        and os.path.basename(os.readlink(info.compiler)) == "icecc"
+    ):
+        return True
+    if ccache_prefix and os.path.basename(ccache_prefix) == "icecc":
+        return True
+
+
+set_config("CXX_IS_ICECREAM", cxx_is_icecream)
+
+
+# Linker detection
+# ==============================================================
+# The policy is as follows:
+# For Windows:
+# - the linker is picked via the LINKER environment variable per windows.configure,
+#   but ought to be llvm-lld in any case.
+# For macOS:
+# - the linker is lld if the clang used is >= 15 (per LLVM version, not Xcode version).
+# - the linker is also lld on local developer builds if the clang used is >= 13 (per LLVM
+#   version, not Xcode version)
+# - otherwise the linker is ld64, either from XCode on macOS, or from cctools-ports when
+#   cross-compiling.
+# For other OSes:
+# - on local developer builds: lld is used if present. Otherwise gold is used if present
+#   otherwise, BFD ld is used.
+# - on release/official builds: whatever the compiler uses by default, except on Android
+#   (see enable_linker_default below). Usually what the compiler uses by default is BFD
+#   ld, except with the Android NDK compiler, where the default varies depending on the
+#   NDK version. The default also varies by platform and clang version.
+#   lld is not used by default on Linux and Android because it introduces layout changes
+#   that prevent elfhack from working. See e.g.
+#   https://bugzilla.mozilla.org/show_bug.cgi?id=1563654#c2.
+@template
+def is_not_winnt_or_sunos(host_or_target):
+    @depends(host_or_target)
+    def is_not_winnt_or_sunos(host_or_target):
+        if host_or_target.kernel not in ("WINNT", "SunOS"):
+            return True
+
+    return is_not_winnt_or_sunos
+
+
+is_linker_option_enabled = is_not_winnt_or_sunos(target)
+
+
+@deprecated_option("--enable-gold", env="MOZ_FORCE_GOLD", when=is_linker_option_enabled)
+def enable_gold(value):
+    if value:
+        die("--enable-gold is deprecated, use --enable-linker=gold instead")
+    else:
+        die("--disable-gold is deprecated, use --enable-linker=something_else instead")
+
+
+@depends(target, developer_options)
+def enable_linker_default(target, developer_options):
+    # Recent versions of clang default to lld when targetting Android, but we don't
+    # want that as the default for non developer builds (see above).
+    # So we want to force the default to whatever it was with older versions of clang,
+    # but with caveats/workarounds:
+    # - x86-64 gold has bugs in how it lays out .note.* sections. See bug 1573820.
+    # - x86-32 gold has a bug when assembly files are built. See bug 1651699.
+    # That leaves us with aarch64 and armv7, which respectively defaulted to
+    # bfd and gold.
+    # On developer builds, select_linker will pick lld if it's not the default.
+    if target.os == "Android" and not developer_options:
+        return "bfd" if target.cpu in ("x86", "x86_64", "aarch64") else "gold"
+
+
+option(
+    "--enable-linker",
+    nargs=1,
+    help="Select the linker {bfd, gold, ld64, lld, lld-*, mold}{|}",
+    default=enable_linker_default,
+    when=is_linker_option_enabled,
+)
+
+
+# No-op to enable depending on --enable-linker from default_elfhack in
+# toolkit/moz.configure.
+@depends("--enable-linker", when=is_linker_option_enabled)
+def enable_linker(linker):
+    return linker
+
+
+@template
+def select_linker_tmpl(host_or_target):
+    if host_or_target is target:
+        deps = depends(
+            "--enable-linker",
+            c_compiler,
+            developer_options,
+            extra_toolchain_flags,
+            target,
+            when=is_linker_option_enabled,
+        )
+        host_or_target_str = "target"
+    else:
+        deps = depends(
+            dependable(None),
+            host_c_compiler,
+            developer_options,
+            dependable(None),
+            host,
+            when=is_not_winnt_or_sunos(host_or_target),
+        )
+        host_or_target_str = "host"
+
+    @deps
+    @checking(f"for {host_or_target_str} linker", lambda x: x.KIND)
+    @imports("os")
+    @imports("shutil")
+    def select_linker(linker, c_compiler, developer_options, toolchain_flags, target):
+
+        if linker:
+            linker = linker[0]
+        else:
+            linker = None
+
+        def is_valid_linker(linker):
+            if target.kernel == "Darwin":
+                valid_linkers = ("ld64", "lld")
+            else:
+                valid_linkers = ("bfd", "gold", "lld", "mold")
+            if linker in valid_linkers:
+                return True
+            if "lld" in valid_linkers and linker.startswith("lld-"):
+                return True
+            return False
+
+        if linker and not is_valid_linker(linker):
+            # Check that we are trying to use a supported linker
+            die("Unsupported linker " + linker)
+
+        # Check the kind of linker
+        version_check = ["-Wl,--version"]
+        cmd_base = c_compiler.wrapper + [c_compiler.compiler] + c_compiler.flags
+
+        def try_linker(linker):
+            # Generate the compiler flag
+            if linker == "ld64":
+                linker_flag = ["-fuse-ld=ld"]
+            elif linker:
+                linker_flag = ["-fuse-ld=" + linker]
+            else:
+                linker_flag = []
+            cmd = cmd_base + linker_flag + version_check
+            if toolchain_flags:
+                cmd += toolchain_flags
+
+            # ld64 doesn't have anything to print out a version. It does print out
+            # "ld64: For information on command line options please use 'man ld'."
+            # but that would require doing two attempts, one with --version, that
+            # would fail, and another with --help.
+            # Instead, abuse its LD_PRINT_OPTIONS feature to detect a message
+            # specific to it on stderr when it fails to process --version.
+            env = dict(os.environ)
+            env["LD_PRINT_OPTIONS"] = "1"
+            # Some locales might not print out the strings we are looking for, so
+            # ensure consistent output.
+            env["LC_ALL"] = "C"
+            retcode, stdout, stderr = get_cmd_output(*cmd, env=env)
+            if retcode == 1 and "Logging ld64 options" in stderr:
+                kind = "ld64"
+
+            elif retcode != 0:
+                return None
+
+            elif "mold" in stdout:
+                kind = "mold"
+
+            elif "GNU ld" in stdout:
+                # We are using the normal linker
+                kind = "bfd"
+
+            elif "GNU gold" in stdout:
+                kind = "gold"
+
+            elif "LLD" in stdout:
+                kind = "lld"
+
+            else:
+                kind = "unknown"
+
+            if kind == "unknown" or is_valid_linker(kind):
+                return namespace(
+                    KIND=kind,
+                    LINKER_FLAG=linker_flag,
+                )
+
+        result = try_linker(linker)
+        if result is None and linker:
+            die("Could not use {} as linker".format(linker))
+
+        if (
+            linker is None
+            and target.kernel == "Darwin"
+            and c_compiler.type == "clang"
+            and (
+                (developer_options and c_compiler.version >= "13.0")
+                or c_compiler.version >= "15.0"
+            )
+        ):
+            result = try_linker("lld")
+        elif (
+            linker is None
+            and (
+                developer_options
+                or (host_or_target_str == "host" and c_compiler.type == "clang")
+            )
+            and (result is None or result.KIND in ("bfd", "gold"))
+        ):
+            # try and use lld if available.
+            tried = try_linker("lld")
+            if (result is None or result.KIND != "gold") and (
+                tried is None or tried.KIND != "lld"
+            ):
+                tried = try_linker("gold")
+                if tried is None or tried.KIND != "gold":
+                    tried = None
+            if tried:
+                result = tried
+
+        if result is None:
+            die("Failed to find an adequate linker")
+
+        # If an explicit linker was given, error out if what we found is different.
+        if linker and not linker.startswith(result.KIND):
+            die("Could not use {} as linker".format(linker))
+
+        return result
+
+    return select_linker
+
+
+select_linker = select_linker_tmpl(target)
+set_config("LINKER_KIND", select_linker.KIND)
+
+
+@template
+def linker_ldflags_tmpl(host_or_target):
+    if host_or_target is target:
+        deps = depends_if(
+            select_linker,
+            target,
+            target_sysroot,
+            target_multiarch_dir,
+            android_sysroot,
+            android_version,
+            c_compiler,
+            developer_options,
+        )
+    else:
+        deps = depends_if(
+            select_linker_tmpl(host),
+            host,
+            host_sysroot,
+            host_multiarch_dir,
+            dependable(None),
+            dependable(None),
+            host_c_compiler,
+            developer_options,
+        )
+
+    @deps
+    @imports("os")
+    def linker_ldflags(
+        linker,
+        target,
+        sysroot,
+        multiarch_dir,
+        android_sysroot,
+        android_version,
+        c_compiler,
+        developer_options,
+    ):
+        flags = list((linker and linker.LINKER_FLAG) or [])
+        # rpath-link is irrelevant to wasm, see for more info https://github.com/emscripten-core/emscripten/issues/11076.
+        if sysroot.path and multiarch_dir and target.os != "WASI":
+            for d in ("lib", "usr/lib"):
+                multiarch_lib_dir = os.path.join(sysroot.path, d, multiarch_dir)
+                if os.path.exists(multiarch_lib_dir):
+                    # Non-Debian-patched binutils linkers (both BFD and gold) don't lookup
+                    # in multi-arch directories.
+                    flags.append("-Wl,-rpath-link,%s" % multiarch_lib_dir)
+                    # GCC also needs -L.
+                    if c_compiler.type == "gcc":
+                        flags.append("-L%s" % multiarch_lib_dir)
+            if (
+                c_compiler.type == "gcc"
+                and sysroot.bootstrapped
+                and sysroot.stdcxx_version
+            ):
+                flags.append(
+                    "-L{}/usr/lib/gcc/{}/{}".format(
+                        sysroot.path, multiarch_dir, sysroot.stdcxx_version
+                    )
+                )
+        if android_sysroot:
+            # BFD/gold linkers need a manual --rpath-link for indirect
+            # dependencies.
+            flags += [
+                "-Wl,--rpath-link={}/usr/lib/{}".format(
+                    android_sysroot, target.toolchain
+                ),
+                "-Wl,--rpath-link={}/usr/lib/{}/{}".format(
+                    android_sysroot, target.toolchain, android_version
+                ),
+            ]
+        if (
+            developer_options
+            and linker
+            and linker.KIND == "lld"
+            and target.kernel != "WINNT"
+        ):
+            flags.append("-Wl,-O0")
+        return flags
+
+    return linker_ldflags
+
+
+linker_ldflags = linker_ldflags_tmpl(target)
+add_old_configure_assignment("LINKER_LDFLAGS", linker_ldflags)
+
+add_old_configure_assignment("HOST_LINKER_LDFLAGS", linker_ldflags_tmpl(host))
+
+
+# There's a wrinkle with MinGW: linker configuration is not enabled, so
+# `select_linker` is never invoked.  Hard-code around it.
+@depends(select_linker, target, c_compiler)
+def gcc_use_gnu_ld(select_linker, target, c_compiler):
+    if select_linker is not None and target.kernel != "Darwin":
+        return select_linker.KIND in ("bfd", "gold", "lld", "mold")
+    if target.kernel == "WINNT" and c_compiler.type == "clang":
+        return True
+    return None
+
+
+# GCC_USE_GNU_LD=1 means the linker is command line compatible with GNU ld.
+set_config("GCC_USE_GNU_LD", gcc_use_gnu_ld)
+add_old_configure_assignment("GCC_USE_GNU_LD", gcc_use_gnu_ld)
+
+
+include("compile-checks.configure")
+include("arm.configure", when=depends(target.cpu)(lambda cpu: cpu == "arm"))
+
+
+@depends(
+    have_64_bit,
+    try_compile(
+        body='static_assert(sizeof(void *) == 8, "")', check_msg="for 64-bit OS"
+    ),
+)
+def check_have_64_bit(have_64_bit, compiler_have_64_bit):
+    if have_64_bit != compiler_have_64_bit:
+        configure_error(
+            "The target compiler does not agree with configure "
+            "about the target bitness."
+        )
+
+
+@depends(cxx_compiler, target)
+def needs_libstdcxx_newness_check(cxx_compiler, target):
+    # We only have to care about this on Linux and MinGW.
+    if cxx_compiler.type == "clang-cl":
+        return
+
+    if target.kernel not in ("Linux", "WINNT"):
+        return
+
+    if target.os == "Android":
+        return
+
+    return True
+
+
+def die_on_old_libstdcxx():
+    die(
+        "The libstdc++ in use is not new enough.  Please run "
+        "./mach bootstrap to update your compiler, or update your system "
+        "libstdc++ installation."
+    )
+
+
+try_compile(
+    includes=["cstddef"],
+    body="\n".join(
+        [
+            # _GLIBCXX_RELEASE showed up in libstdc++ 7.
+            "#if defined(__GLIBCXX__) && !defined(_GLIBCXX_RELEASE)",
+            "#  error libstdc++ not new enough",
+            "#endif",
+            "#if defined(_GLIBCXX_RELEASE)",
+            "#  if _GLIBCXX_RELEASE < %d" % minimum_gcc_version().major,
+            "#    error libstdc++ not new enough",
+            "#  else",
+            "     (void) 0",
+            "#  endif",
+            "#endif",
+        ]
+    ),
+    check_msg="for new enough STL headers from libstdc++",
+    when=needs_libstdcxx_newness_check,
+    onerror=die_on_old_libstdcxx,
+)
+
+
+@depends(c_compiler, target)
+def default_debug_flags(compiler_info, target):
+    # Debug info is ON by default.
+    if compiler_info.type == "clang-cl":
+        return "-Z7"
+    elif target.kernel == "WINNT" and compiler_info.type == "clang":
+        return "-g -gcodeview"
+    # The oldest versions of supported compilers default to DWARF-4, but
+    # newer versions may default to DWARF-5 or newer (e.g. clang 14), which
+    # Valgrind doesn't support. Force-use DWARF-4.
+    return "-gdwarf-4"
+
+
+option(env="MOZ_DEBUG_FLAGS", nargs=1, help="Debug compiler flags")
+
+imply_option("--enable-debug-symbols", depends_if("--enable-debug")(lambda v: v))
+
+option(
+    "--disable-debug-symbols",
+    nargs="?",
+    help="Disable debug symbols using the given compiler flags",
+)
+
+set_config("MOZ_DEBUG_SYMBOLS", depends_if("--enable-debug-symbols")(lambda _: True))
+
+
+@depends("MOZ_DEBUG_FLAGS", "--enable-debug-symbols", default_debug_flags)
+def debug_flags(env_debug_flags, enable_debug_flags, default_debug_flags):
+    # If MOZ_DEBUG_FLAGS is set, and --enable-debug-symbols is set to a value,
+    # --enable-debug-symbols takes precedence. Note, the value of
+    # --enable-debug-symbols may be implied by --enable-debug.
+    if len(enable_debug_flags):
+        return enable_debug_flags[0]
+    if env_debug_flags:
+        return env_debug_flags[0]
+    return default_debug_flags
+
+
+set_config("MOZ_DEBUG_FLAGS", debug_flags)
+add_old_configure_assignment("MOZ_DEBUG_FLAGS", debug_flags)
+
+
+@depends(c_compiler, host)
+@imports(
+    _from="mach.logging", _import="enable_blessed", _as="_enable_ansi_escape_codes"
+)
+def color_cflags(info, host):
+    # We could test compiling with flags. By why incur the overhead when
+    # color support should always be present in a specific toolchain
+    # version?
+
+    # Code for auto-adding this flag to compiler invocations needs to
+    # determine if an existing flag isn't already present. That is likely
+    # using exact string matching on the returned value. So if the return
+    # value changes to e.g. "<x>=always", exact string match may fail and
+    # multiple color flags could be added. So examine downstream consumers
+    # before adding flags to return values.
+    if info.type == "gcc":
+        return "-fdiagnostics-color"
+    elif info.type in ["clang", "clang-cl"]:
+        if host.os == "WINNT" and _enable_ansi_escape_codes():
+            return "-fcolor-diagnostics -fansi-escape-codes"
+        else:
+            return "-fcolor-diagnostics"
+    else:
+        return ""
+
+
+set_config("COLOR_CFLAGS", color_cflags)
+
+# Some standard library headers (notably bionic on Android) declare standard
+# functions (e.g. getchar()) and also #define macros for those standard
+# functions.  libc++ deals with this by doing something like the following
+# (explanatory comments added):
+#
+#   #ifdef FUNC
+#   // Capture the definition of FUNC.
+#   inline _LIBCPP_INLINE_VISIBILITY int __libcpp_FUNC(...) { return FUNC(...); }
+#   #undef FUNC
+#   // Use a real inline definition.
+#   inline _LIBCPP_INLINE_VISIBILITY int FUNC(...) { return _libcpp_FUNC(...); }
+#   #endif
+#
+# _LIBCPP_INLINE_VISIBILITY is typically defined as:
+#
+#   __attribute__((__visibility__("hidden"), __always_inline__))
+#
+# Unfortunately, this interacts badly with our system header wrappers, as the:
+#
+#   #pragma GCC visibility push(default)
+#
+# that they do prior to including the actual system header is treated by the
+# compiler as an explicit declaration of visibility on every function declared
+# in the header.  Therefore, when the libc++ code above is encountered, it is
+# as though the compiler has effectively seen:
+#
+#   int FUNC(...) __attribute__((__visibility__("default")));
+#   int FUNC(...) __attribute__((__visibility__("hidden")));
+#
+# and the compiler complains about the mismatched visibility declarations.
+#
+# However, libc++ will only define _LIBCPP_INLINE_VISIBILITY if there is no
+# existing definition.  We can therefore define it to the empty string (since
+# we are properly managing visibility ourselves) and avoid this whole mess.
+# Note that we don't need to do this with gcc, as libc++ detects gcc and
+# effectively does the same thing we are doing here.
+#
+# _LIBCPP_ALWAYS_INLINE needs a similar workarounds, since it too declares
+# hidden visibility.
+#
+# _LIBCPP_HIDE_FROM_ABI is a macro in libc++ versions in NDKs >=r19.  It too
+# declares hidden visibility, but it also declares functions as excluded from
+# explicit instantiation (roughly: the function can be unused in the current
+# compilation, but does not then trigger an actual definition of the function;
+# it is assumed the real definition comes from elsewhere).  We need to replicate
+# this setup.
+
+
+@depends(c_compiler, target)
+def libcxx_override_visibility(c_compiler, target):
+    if c_compiler.type == "clang" and target.os == "Android":
+        return namespace(
+            empty="",
+            hide_from_abi="__attribute__((__exclude_from_explicit_instantiation__))",
+        )
+
+
+set_define("_LIBCPP_INLINE_VISIBILITY", libcxx_override_visibility.empty)
+set_define("_LIBCPP_ALWAYS_INLINE", libcxx_override_visibility.empty)
+
+set_define("_LIBCPP_HIDE_FROM_ABI", libcxx_override_visibility.hide_from_abi)
+
+
+@depends(target, build_environment)
+def visibility_flags(target, env):
+    if target.os != "WINNT":
+        if target.kernel == "Darwin":
+            return ("-fvisibility=hidden", "-fvisibility-inlines-hidden")
+        return (
+            "-I%s/system_wrappers" % os.path.join(env.dist),
+            "-include",
+            "%s/config/gcc_hidden.h" % env.topsrcdir,
+        )
+
+
+@depends(target, visibility_flags)
+def wrap_system_includes(target, visibility_flags):
+    if visibility_flags and target.kernel != "Darwin":
+        return True
+
+
+set_define(
+    "HAVE_VISIBILITY_HIDDEN_ATTRIBUTE",
+    depends(visibility_flags)(lambda v: bool(v) or None),
+)
+set_define(
+    "HAVE_VISIBILITY_ATTRIBUTE", depends(visibility_flags)(lambda v: bool(v) or None)
+)
+set_config("WRAP_SYSTEM_INCLUDES", wrap_system_includes)
+set_config("VISIBILITY_FLAGS", visibility_flags)
+
+
+@template
+def depend_cflags(host_or_target_c_compiler):
+    @depends(host_or_target_c_compiler)
+    def depend_cflags(host_or_target_c_compiler):
+        if host_or_target_c_compiler.type != "clang-cl":
+            return ["-MD", "-MP", "-MF $(MDDEPDIR)/$(@F).pp"]
+        else:
+            # clang-cl doesn't accept the normal -MD -MP -MF options that clang
+            # does, but the underlying cc1 binary understands how to generate
+            # dependency files.  These options are based on analyzing what the
+            # normal clang driver sends to cc1 when given the "correct"
+            # dependency options.
+            return [
+                "-Xclang",
+                "-MP",
+                "-Xclang",
+                "-dependency-file",
+                "-Xclang",
+                "$(MDDEPDIR)/$(@F).pp",
+                "-Xclang",
+                "-MT",
+                "-Xclang",
+                "$@",
+            ]
+
+    return depend_cflags
+
+
+set_config("_DEPEND_CFLAGS", depend_cflags(c_compiler))
+set_config("_HOST_DEPEND_CFLAGS", depend_cflags(host_c_compiler))
+
+
+@depends(c_compiler)
+def preprocess_option(compiler):
+    # The uses of PREPROCESS_OPTION depend on the spacing for -o/-Fi.
+    if compiler.type in ("gcc", "clang"):
+        return "-E -o "
+    else:
+        return "-P -Fi"
+
+
+set_config("PREPROCESS_OPTION", preprocess_option)
+
+
+# We only want to include windows.configure when we are compiling on
+# Windows, or for Windows.
+include("windows.configure", when=is_windows)
+
+
+# On Power ISA, determine compiler flags for VMX, VSX and VSX-3.
+
+set_config(
+    "PPC_VMX_FLAGS",
+    ["-maltivec"],
+    when=depends(target.cpu)(lambda cpu: cpu.startswith("ppc")),
+)
+
+set_config(
+    "PPC_VSX_FLAGS",
+    ["-mvsx"],
+    when=depends(target.cpu)(lambda cpu: cpu.startswith("ppc")),
+)
+
+set_config(
+    "PPC_VSX3_FLAGS",
+    ["-mvsx", "-mcpu=power9"],
+    when=depends(target.cpu)(lambda cpu: cpu.startswith("ppc")),
+)
+
+# ASAN
+# ==============================================================
+
+option("--enable-address-sanitizer", help="Enable Address Sanitizer")
+
+
+@depends(when="--enable-address-sanitizer")
+def asan():
+    return True
+
+
+add_old_configure_assignment("MOZ_ASAN", asan)
+
+# MSAN
+# ==============================================================
+
+option("--enable-memory-sanitizer", help="Enable Memory Sanitizer")
+
+
+@depends(when="--enable-memory-sanitizer")
+def msan():
+    return True
+
+
+add_old_configure_assignment("MOZ_MSAN", msan)
+
+# TSAN
+# ==============================================================
+
+option("--enable-thread-sanitizer", help="Enable Thread Sanitizer")
+
+
+@depends(when="--enable-thread-sanitizer")
+def tsan():
+    return True
+
+
+add_old_configure_assignment("MOZ_TSAN", tsan)
+
+# UBSAN
+# ==============================================================
+
+option(
+    "--enable-undefined-sanitizer", nargs="*", help="Enable UndefinedBehavior Sanitizer"
+)
+
+
+@depends_if("--enable-undefined-sanitizer")
+def ubsan(options):
+    default_checks = [
+        "bool",
+        "bounds",
+        "enum",
+        "function",
+        "integer-divide-by-zero",
+        "object-size",
+        "pointer-overflow",
+        "return",
+        "vla-bound",
+    ]
+
+    checks = options if len(options) else default_checks
+
+    return ",".join(checks)
+
+
+add_old_configure_assignment("MOZ_UBSAN_CHECKS", ubsan)
+
+
+option(
+    "--enable-signed-overflow-sanitizer",
+    help="Enable UndefinedBehavior Sanitizer (Signed Integer Overflow Parts)",
+)
+
+
+@depends(when="--enable-signed-overflow-sanitizer")
+def ub_signed_overflow_san():
+    return True
+
+
+add_old_configure_assignment("MOZ_SIGNED_OVERFLOW_SANITIZE", ub_signed_overflow_san)
+
+
+option(
+    "--enable-unsigned-overflow-sanitizer",
+    help="Enable UndefinedBehavior Sanitizer (Unsigned Integer Overflow Parts)",
+)
+
+
+@depends(when="--enable-unsigned-overflow-sanitizer")
+def ub_unsigned_overflow_san():
+    return True
+
+
+add_old_configure_assignment("MOZ_UNSIGNED_OVERFLOW_SANITIZE", ub_unsigned_overflow_san)
+
+# Security Hardening
+# ==============================================================
+
+option(
+    "--enable-hardening",
+    env="MOZ_SECURITY_HARDENING",
+    help="Enables security hardening compiler options",
+)
+
+
+# This function is a bit confusing. It adds or removes hardening flags in
+# three stuations: if --enable-hardening is passed; if --disable-hardening
+# is passed, and if no flag is passed.
+#
+# At time of this comment writing, all flags are actually added in the
+# default no-flag case; making --enable-hardening the same as omitting the
+# flag. --disable-hardening will omit the security flags. (However, not all
+# possible security flags will be omitted by --disable-hardening, as many are
+# compiler-default options we do not explicitly enable.)
+@depends(
+    "--enable-hardening",
+    "--enable-address-sanitizer",
+    "--enable-debug",
+    "--enable-optimize",
+    c_compiler,
+    target,
+)
+def security_hardening_cflags(
+    hardening_flag, asan, debug, optimize, c_compiler, target
+):
+    compiler_is_gccish = c_compiler.type in ("gcc", "clang")
+    mingw_clang = c_compiler.type == "clang" and target.os == "WINNT"
+
+    flags = []
+    ldflags = []
+    trivial_auto_var_init = []
+
+    # WASI compiler doesn't support security hardening cflags
+    if target.os == "WASI":
+        return
+
+    # ----------------------------------------------------------
+    # If hardening is explicitly enabled, or not explicitly disabled
+    if hardening_flag.origin == "default" or hardening_flag:
+        # FORTIFY_SOURCE ------------------------------------
+        # Require optimization for FORTIFY_SOURCE. See Bug 1417452
+        # Also, undefine it before defining it just in case a distro adds it, see Bug 1418398
+        if compiler_is_gccish and optimize and not asan:
+            flags.append("-U_FORTIFY_SOURCE")
+            flags.append("-D_FORTIFY_SOURCE=2")
+            if mingw_clang:
+                # mingw-clang needs to link in ssp which is not done by default
+                ldflags.append("-lssp")
+
+        # fstack-protector ------------------------------------
+        # Enable only if hardening is not disabled and ASAN is
+        # not on as ASAN will catch the crashes for us
+        if compiler_is_gccish and not asan:
+            flags.append("-fstack-protector-strong")
+            ldflags.append("-fstack-protector-strong")
+
+            if (
+                c_compiler.type == "clang"
+                and c_compiler.version >= "11.0.1"
+                and target.os not in ("WINNT", "OSX")
+                and target.cpu in ("x86", "x86_64", "ppc64", "s390x")
+            ):
+                flags.append("-fstack-clash-protection")
+                ldflags.append("-fstack-clash-protection")
+
+        # ftrivial-auto-var-init ------------------------------
+        # Initialize local variables with a 0xAA pattern in clang builds.
+        # Linux32 fails some xpcshell tests with -ftrivial-auto-var-init
+        linux32 = target.kernel == "Linux" and target.cpu == "x86"
+        if (
+            (c_compiler.type == "clang" or c_compiler.type == "clang-cl")
+            and c_compiler.version >= "8"
+            and not linux32
+        ):
+            if c_compiler.type == "clang-cl":
+                trivial_auto_var_init.append("-Xclang")
+            trivial_auto_var_init.append("-ftrivial-auto-var-init=pattern")
+            # Always enable on debug builds.
+            if debug:
+                flags.extend(trivial_auto_var_init)
+
+        # ASLR ------------------------------------------------
+        # ASLR (dynamicbase) is enabled by default in clang-cl; but the
+        # mingw-clang build requires it to be explicitly enabled
+        if mingw_clang:
+            ldflags.append("-Wl,--dynamicbase")
+
+        # Control Flow Guard (CFG) ----------------------------
+        if (
+            c_compiler.type == "clang-cl"
+            and c_compiler.version >= "8"
+            and (target.cpu != "aarch64" or c_compiler.version >= "8.0.1")
+        ):
+            if target.cpu == "aarch64" and c_compiler.version >= "10.0.0":
+                # The added checks in clang 10 make arm64 builds crash. (Bug 1639318)
+                flags.append("-guard:cf,nochecks")
+            else:
+                flags.append("-guard:cf")
+            # nolongjmp is needed because clang doesn't emit the CFG tables of
+            # setjmp return addresses https://bugs.llvm.org/show_bug.cgi?id=40057
+            ldflags.append("-guard:cf,nolongjmp")
+
+    # ----------------------------------------------------------
+    # If ASAN _is_ on, disable FORTIFY_SOURCE just to be safe
+    if asan:
+        flags.append("-D_FORTIFY_SOURCE=0")
+
+    # fno-common -----------------------------------------
+    # Do not merge variables for ASAN; can detect some subtle bugs
+    if asan:
+        # clang-cl does not recognize the flag, it must be passed down to clang
+        if c_compiler.type == "clang-cl":
+            flags.append("-Xclang")
+        flags.append("-fno-common")
+
+    return namespace(
+        flags=flags,
+        ldflags=ldflags,
+        trivial_auto_var_init=trivial_auto_var_init,
+    )
+
+
+set_config("MOZ_HARDENING_CFLAGS", security_hardening_cflags.flags)
+set_config("MOZ_HARDENING_LDFLAGS", security_hardening_cflags.ldflags)
+set_config(
+    "MOZ_TRIVIAL_AUTO_VAR_INIT",
+    security_hardening_cflags.trivial_auto_var_init,
+)
+
+
+# Intel Control-flow Enforcement Technology
+# ==============================================================
+# We keep this separate from the hardening flags above, because we want to be
+# able to easily remove the flags in the build files for certain executables.
+@depends(c_compiler, target)
+def cet_ldflags(c_compiler, target):
+    ldflags = []
+    if (
+        c_compiler.type == "clang-cl"
+        and c_compiler.version >= "11"
+        and target.cpu == "x86_64"
+    ):
+        ldflags.append("-CETCOMPAT")
+    return ldflags
+
+
+set_config("MOZ_CETCOMPAT_LDFLAGS", cet_ldflags)
+
+# Frame pointers
+# ==============================================================
+@depends(c_compiler)
+def frame_pointer_flags(compiler):
+    if compiler.type == "clang-cl":
+        return namespace(
+            enable=["-Oy-"],
+            disable=["-Oy"],
+        )
+    return namespace(
+        enable=["-fno-omit-frame-pointer", "-funwind-tables"],
+        disable=["-fomit-frame-pointer", "-funwind-tables"],
+    )
+
+
+@depends(
+    moz_optimize.optimize,
+    moz_debug,
+    target,
+    "--enable-memory-sanitizer",
+    "--enable-address-sanitizer",
+    "--enable-undefined-sanitizer",
+)
+def frame_pointer_default(optimize, debug, target, msan, asan, ubsan):
+    return bool(
+        not optimize
+        or debug
+        or msan
+        or asan
+        or ubsan
+        or (target.os == "WINNT" and target.cpu in ("x86", "aarch64"))
+        or target.os == "OSX"
+    )
+
+
+option(
+    "--enable-frame-pointers",
+    default=frame_pointer_default,
+    help="{Enable|Disable} frame pointers",
+)
+
+
+@depends("--enable-frame-pointers", frame_pointer_flags)
+def frame_pointer_flags(enable, flags):
+    if enable:
+        return flags.enable
+    return flags.disable
+
+
+set_config("MOZ_FRAMEPTR_FLAGS", frame_pointer_flags)
+
+
+# Code Coverage
+# ==============================================================
+
+option("--enable-coverage", env="MOZ_CODE_COVERAGE", help="Enable code coverage")
+
+
+@depends("--enable-coverage")
+def code_coverage(value):
+    if value:
+        return True
+
+
+set_config("MOZ_CODE_COVERAGE", code_coverage)
+set_define("MOZ_CODE_COVERAGE", code_coverage)
+
+
+@depends(target, c_compiler, build_environment, when=code_coverage)
+@imports("os")
+@imports("re")
+@imports(_from="__builtin__", _import="open")
+def coverage_cflags(target, c_compiler, build_env):
+    cflags = ["--coverage"]
+
+    # clang 11 no longer accepts this flag (its behavior became the default)
+    if c_compiler.type in ("clang", "clang-cl") and c_compiler.version < "11.0.0":
+        cflags += [
+            "-Xclang",
+            "-coverage-no-function-names-in-data",
+        ]
+
+    exclude = []
+    if target.os == "WINNT" and c_compiler.type == "clang-cl":
+        # VS files
+        exclude.append("^.*[vV][sS]20[0-9]{2}.*$")
+        # Files in fetches directory.
+        exclude.append("^.*[\\\\/]fetches[\\\\/].*$")
+    elif target.os == "OSX":
+        # Files in fetches directory.
+        exclude.append("^.*/fetches/.*$")
+    elif target.os == "GNU":
+        # Files in fetches directory.
+        exclude.append("^.*/fetches/.*$")
+        # Files in /usr/
+        exclude.append("^/usr/.*$")
+
+    if exclude:
+        exclude = ";".join(exclude)
+        cflags += [
+            f"-fprofile-exclude-files={exclude}",
+        ]
+
+    response_file_path = os.path.join(build_env.topobjdir, "code_coverage_cflags")
+
+    with open(response_file_path, "w") as f:
+        f.write(" ".join(cflags))
+
+    return ["@{}".format(response_file_path)]
+
+
+set_config("COVERAGE_CFLAGS", coverage_cflags)
+
+# Assembler detection
+# ==============================================================
+
+option(env="AS", nargs=1, help="Path to the assembler")
+
+
+@depends(target, c_compiler)
+def as_info(target, c_compiler):
+    if c_compiler.type == "clang-cl":
+        ml = {
+            "x86": "ml.exe",
+            "x86_64": "ml64.exe",
+            "aarch64": "armasm64.exe",
+        }.get(target.cpu)
+        return namespace(type="masm", names=(ml,))
+    # When building with anything but clang-cl, we just use the C compiler as the assembler.
+    return namespace(type="gcc", names=(c_compiler.compiler,))
+
+
+# One would expect the assembler to be specified merely as a program.  But in
+# cases where the assembler is passed down into js/, it can be specified in
+# the same way as CC: a program + a list of argument flags.  We might as well
+# permit the same behavior in general, even though it seems somewhat unusual.
+# So we have to do the same sort of dance as we did above with
+# `provided_compiler`.
+provided_assembler = provided_program("AS")
+assembler = check_prog(
+    "_AS",
+    input=provided_assembler.program,
+    what="the assembler",
+    progs=as_info.names,
+    paths=vc_toolchain_search_path,
+)
+
+
+@depends(as_info, assembler, provided_assembler, c_compiler)
+def as_with_flags(as_info, assembler, provided_assembler, c_compiler):
+    if provided_assembler:
+        return provided_assembler.wrapper + [assembler] + provided_assembler.flags
+
+    if as_info.type == "masm":
+        return assembler
+
+    assert as_info.type == "gcc"
+
+    # Need to add compiler wrappers and flags as appropriate.
+    return c_compiler.wrapper + [assembler] + c_compiler.flags
+
+
+set_config("AS", as_with_flags)
+
+
+@depends(assembler, c_compiler, extra_toolchain_flags)
+@imports("subprocess")
+@imports(_from="os", _import="devnull")
+def gnu_as(assembler, c_compiler, toolchain_flags):
+    # clang uses a compatible GNU assembler.
+    if c_compiler.type == "clang":
+        return True
+
+    if c_compiler.type == "gcc":
+        cmd = [assembler] + c_compiler.flags
+        if toolchain_flags:
+            cmd += toolchain_flags
+        cmd += ["-Wa,--version", "-c", "-o", devnull, "-x", "assembler", "-"]
+        # We don't actually have to provide any input on stdin, `Popen.communicate` will
+        # close the stdin pipe.
+        # clang will error if it uses its integrated assembler for this target,
+        # so handle failures gracefully.
+        if "GNU" in check_cmd_output(*cmd, stdin=subprocess.PIPE, onerror=lambda: ""):
+            return True
+
+
+set_config("GNU_AS", gnu_as)
+
+
+@depends(as_info, target)
+def as_dash_c_flag(as_info, target):
+    # armasm64 doesn't understand -c.
+    if as_info.type == "masm" and target.cpu == "aarch64":
+        return ""
+    else:
+        return "-c"
+
+
+set_config("AS_DASH_C_FLAG", as_dash_c_flag)
+
+
+@depends(as_info, target)
+def as_outoption(as_info, target):
+    # The uses of ASOUTOPTION depend on the spacing for -o/-Fo.
+    if as_info.type == "masm" and target.cpu != "aarch64":
+        return "-Fo"
+
+    return "-o "
+
+
+set_config("ASOUTOPTION", as_outoption)
+
+# clang plugin handling
+# ==============================================================
+
+option(
+    "--enable-clang-plugin",
+    env="ENABLE_CLANG_PLUGIN",
+    help="Enable building with the Clang plugin (gecko specific static analyzers)",
+)
+
+add_old_configure_assignment(
+    "ENABLE_CLANG_PLUGIN", depends_if("--enable-clang-plugin")(lambda _: True)
+)
+
+
+@depends(host_c_compiler, c_compiler, when="--enable-clang-plugin")
+def llvm_config(host_c_compiler, c_compiler):
+    clang = None
+    for compiler in (host_c_compiler, c_compiler):
+        if compiler and compiler.type == "clang":
+            clang = compiler.compiler
+            break
+        elif compiler and compiler.type == "clang-cl":
+            clang = os.path.join(os.path.dirname(compiler.compiler), "clang")
+            break
+
+    if not clang:
+        die("Cannot --enable-clang-plugin when not building with clang")
+    llvm_config = "llvm-config"
+    out = check_cmd_output(clang, "--print-prog-name=llvm-config", onerror=lambda: None)
+    if out:
+        llvm_config = out.rstrip()
+    return (llvm_config,)
+
+
+llvm_config = check_prog(
+    "LLVM_CONFIG",
+    llvm_config,
+    what="llvm-config",
+    when="--enable-clang-plugin",
+    paths=clang_search_path,
+)
+
+add_old_configure_assignment("LLVM_CONFIG", llvm_config)
+
+
+option(
+    "--enable-clang-plugin-alpha",
+    env="ENABLE_CLANG_PLUGIN_ALPHA",
+    help="Enable static analysis with clang-plugin alpha checks.",
+)
+
+
+@depends("--enable-clang-plugin", "--enable-clang-plugin-alpha")
+def check_clang_plugin_alpha(enable_clang_plugin, enable_clang_plugin_alpha):
+    if enable_clang_plugin_alpha:
+        if enable_clang_plugin:
+            return True
+        die("Cannot enable clang-plugin alpha checkers without --enable-clang-plugin.")
+
+
+add_old_configure_assignment("ENABLE_CLANG_PLUGIN_ALPHA", check_clang_plugin_alpha)
+set_define("MOZ_CLANG_PLUGIN_ALPHA", check_clang_plugin_alpha)
+
+option(
+    "--enable-mozsearch-plugin",
+    env="ENABLE_MOZSEARCH_PLUGIN",
+    help="Enable building with the mozsearch indexer plugin",
+)
+
+add_old_configure_assignment(
+    "ENABLE_MOZSEARCH_PLUGIN", depends_if("--enable-mozsearch-plugin")(lambda _: True)
+)
+
+# Libstdc++ compatibility hacks
+# ==============================================================
+#
+@depends(target, host)
+def target_or_host_is_linux(target, host):
+    return any(t.os == "GNU" and t.kernel == "Linux" for t in (target, host))
+
+
+option(
+    "--enable-stdcxx-compat",
+    env="MOZ_STDCXX_COMPAT",
+    help="Enable compatibility with older libstdc++",
+    when=target_or_host_is_linux,
+)
+
+
+@depends("--enable-stdcxx-compat", when=target_or_host_is_linux)
+def stdcxx_compat(value):
+    if value:
+        return True
+
+
+set_config("MOZ_STDCXX_COMPAT", True, when=stdcxx_compat)
+add_flag(
+    "-D_GLIBCXX_USE_CXX11_ABI=0",
+    cxx_compiler,
+    when=stdcxx_compat,
+)
+add_flag(
+    "-D_GLIBCXX_USE_CXX11_ABI=0",
+    host_cxx_compiler,
+    when=stdcxx_compat,
+)
+
+
+# Support various fuzzing options
+# ==============================================================
+option("--enable-fuzzing", help="Enable fuzzing support")
+
+
+@depends(build_project)
+def js_build(build_project):
+    return build_project == "js"
+
+
+option(
+    "--enable-js-fuzzilli",
+    when=js_build,
+    help="Enable fuzzilli support for the JS engine",
+)
+
+
+option(
+    "--enable-snapshot-fuzzing",
+    help="Enable experimental snapshot fuzzing support",
+)
+
+
+imply_option("--enable-fuzzing", True, when="--enable-snapshot-fuzzing")
+
+
+@depends("--enable-snapshot-fuzzing")
+def enable_snapshot_fuzzing(value):
+    if value:
+        return True
+
+
+@depends("--enable-fuzzing")
+def enable_fuzzing(value):
+    if value:
+        return True
+
+
+@depends("--enable-js-fuzzilli", when=js_build)
+def enable_js_fuzzilli(value):
+    if value:
+        return True
+
+
+@depends(enable_fuzzing, enable_snapshot_fuzzing)
+def check_aflfuzzer(fuzzing, snapshot_fuzzing):
+    if fuzzing and not snapshot_fuzzing:
+        return True
+
+
+@depends(
+    try_compile(
+        body="__AFL_COMPILER;", check_msg="for AFL compiler", when=check_aflfuzzer
+    )
+)
+def enable_aflfuzzer(afl):
+    if afl:
+        return True
+
+
+@depends(enable_fuzzing, enable_aflfuzzer, enable_snapshot_fuzzing, c_compiler, target)
+def enable_libfuzzer(fuzzing, afl, snapshot_fuzzing, c_compiler, target):
+    if (
+        fuzzing
+        and not afl
+        and not snapshot_fuzzing
+        and c_compiler.type == "clang"
+        and target.os != "Android"
+    ):
+        return True
+
+
+@depends(enable_fuzzing, enable_aflfuzzer, enable_libfuzzer, enable_js_fuzzilli)
+def enable_fuzzing_interfaces(fuzzing, afl, libfuzzer, enable_js_fuzzilli):
+    if fuzzing and (afl or libfuzzer) and not enable_js_fuzzilli:
+        return True
+
+
+set_config("FUZZING", enable_fuzzing)
+set_define("FUZZING", enable_fuzzing)
+
+set_config("LIBFUZZER", enable_libfuzzer)
+set_define("LIBFUZZER", enable_libfuzzer)
+add_old_configure_assignment("LIBFUZZER", enable_libfuzzer)
+
+set_config("AFLFUZZ", enable_aflfuzzer)
+set_define("AFLFUZZ", enable_aflfuzzer)
+
+set_config("FUZZING_INTERFACES", enable_fuzzing_interfaces)
+set_define("FUZZING_INTERFACES", enable_fuzzing_interfaces)
+add_old_configure_assignment("FUZZING_INTERFACES", enable_fuzzing_interfaces)
+
+set_config("FUZZING_JS_FUZZILLI", enable_js_fuzzilli)
+set_define("FUZZING_JS_FUZZILLI", enable_js_fuzzilli)
+
+set_config("FUZZING_SNAPSHOT", enable_snapshot_fuzzing)
+set_define("FUZZING_SNAPSHOT", enable_snapshot_fuzzing)
+
+
+@depends(
+    c_compiler.try_compile(
+        flags=["-fsanitize=fuzzer-no-link"],
+        when=enable_fuzzing,
+        check_msg="whether the C compiler supports -fsanitize=fuzzer-no-link",
+    ),
+    tsan,
+    enable_js_fuzzilli,
+)
+def libfuzzer_flags(value, tsan, enable_js_fuzzilli):
+    if tsan:
+        # With ThreadSanitizer, we should not use any libFuzzer instrumentation because
+        # it is incompatible (e.g. there are races on global sanitizer coverage counters).
+        # Instead we use an empty set of flags here but still build the fuzzing targets.
+        # With this setup, we can still run files through these targets in TSan builds,
+        # e.g. those obtained from regular fuzzing.
+        # This code can be removed once libFuzzer has been made compatible with TSan.
+        #
+        # Also, this code needs to be kept in sync with certain gyp files, currently:
+        #   - dom/media/webrtc/transport/third_party/nICEr/nicer.gyp
+        return namespace(no_link_flag_supported=False, use_flags=[])
+
+    if enable_js_fuzzilli:
+        # Fuzzilli comes with its own trace-pc interceptors and flag requirements.
+        no_link_flag_supported = False
+        use_flags = ["-fsanitize-coverage=trace-pc-guard", "-g"]
+    elif value:
+        no_link_flag_supported = True
+        # recommended for (and only supported by) clang >= 6
+        use_flags = ["-fsanitize=fuzzer-no-link"]
+    else:
+        no_link_flag_supported = False
+        use_flags = ["-fsanitize-coverage=trace-pc-guard,trace-cmp"]
+
+    return namespace(
+        no_link_flag_supported=no_link_flag_supported,
+        use_flags=use_flags,
+    )
+
+
+set_config("HAVE_LIBFUZZER_FLAG_FUZZER_NO_LINK", libfuzzer_flags.no_link_flag_supported)
+set_config("LIBFUZZER_FLAGS", libfuzzer_flags.use_flags)
+add_old_configure_assignment("LIBFUZZER_FLAGS", libfuzzer_flags.use_flags)
+
+# Shared library building
+# ==============================================================
+
+# XXX: The use of makefile constructs in these variables is awful.
+@depends(target, c_compiler)
+def make_shared_library(target, compiler):
+    if target.os == "WINNT":
+        if compiler.type == "gcc":
+            return namespace(
+                mkshlib=["$(CXX)", "$(DSO_LDOPTS)", "-o", "$@"],
+                mkcshlib=["$(CC)", "$(DSO_LDOPTS)", "-o", "$@"],
+            )
+        elif compiler.type == "clang":
+            return namespace(
+                mkshlib=[
+                    "$(CXX)",
+                    "$(DSO_LDOPTS)",
+                    "-Wl,-pdb,$(LINK_PDBFILE)",
+                    "-o",
+                    "$@",
+                ],
+                mkcshlib=[
+                    "$(CC)",
+                    "$(DSO_LDOPTS)",
+                    "-Wl,-pdb,$(LINK_PDBFILE)",
+                    "-o",
+                    "$@",
+                ],
+            )
+        else:
+            linker = [
+                "$(LINKER)",
+                "-NOLOGO",
+                "-DLL",
+                "-OUT:$@",
+                "-PDB:$(LINK_PDBFILE)",
+                "$(DSO_LDOPTS)",
+            ]
+            return namespace(
+                mkshlib=linker,
+                mkcshlib=linker,
+            )
+
+    cc = ["$(CC)", "$(COMPUTED_C_LDFLAGS)"]
+    cxx = ["$(CXX)", "$(COMPUTED_CXX_LDFLAGS)"]
+    flags = ["$(PGO_CFLAGS)", "$(DSO_LDOPTS)"]
+    output = ["-o", "$@"]
+
+    if target.kernel == "Darwin":
+        soname = []
+    elif target.os == "NetBSD":
+        soname = ["-Wl,-soname,$(DSO_SONAME)"]
+    else:
+        assert compiler.type in ("gcc", "clang")
+
+        soname = ["-Wl,-h,$(DSO_SONAME)"]
+
+    return namespace(
+        mkshlib=cxx + flags + soname + output,
+        mkcshlib=cc + flags + soname + output,
+    )
+
+
+set_config("MKSHLIB", make_shared_library.mkshlib)
+set_config("MKCSHLIB", make_shared_library.mkcshlib)
+
+
+@depends(c_compiler, toolchain_prefix, when=target_is_windows)
+def rc_names(c_compiler, toolchain_prefix):
+    if c_compiler.type in ("gcc", "clang"):
+        return tuple("%s%s" % (p, "windres") for p in ("",) + (toolchain_prefix or ()))
+    return ("llvm-rc",)
+
+
+check_prog("RC", rc_names, paths=clang_search_path, when=target_is_windows)
+
+
+@template
+def ar_config(c_compiler, toolchain_prefix=None):
+    if not toolchain_prefix:
+        toolchain_prefix = dependable(None)
+
+    @depends(toolchain_prefix, c_compiler)
+    def ar_config(toolchain_prefix, c_compiler):
+        if c_compiler.type == "clang-cl":
+            return namespace(
+                names=("llvm-lib",),
+                flags=("-llvmlibthin", "-out:$@"),
+            )
+
+        names = tuple("%s%s" % (p, "ar") for p in (toolchain_prefix or ()) + ("",))
+        if c_compiler.type == "clang":
+            # Get the llvm-ar path as per the output from clang --print-prog-name=llvm-ar
+            # so that we directly get the one under the clang directory, rather than one
+            # that might be in /usr/bin and that might point to one from a different version
+            # of clang.
+            out = check_cmd_output(
+                c_compiler.compiler, "--print-prog-name=llvm-ar", onerror=lambda: None
+            )
+            llvm_ar = out.rstrip() if out else "llvm-ar"
+            names = (llvm_ar,) + names
+
+        return namespace(
+            names=names,
+            flags=("crs", "$@"),
+        )
+
+    return ar_config
+
+
+target_ar_config = ar_config(c_compiler, toolchain_prefix)
+
+check_prog("AR", target_ar_config.names, paths=clang_search_path)
+
+set_config("AR_FLAGS", target_ar_config.flags)
+
+host_ar_config = ar_config(host_c_compiler)
+
+check_prog("HOST_AR", host_ar_config.names, paths=clang_search_path)
+
+
+@depends(toolchain_prefix, c_compiler)
+def nm_names(toolchain_prefix, c_compiler):
+    names = tuple("%s%s" % (p, "nm") for p in (toolchain_prefix or ()) + ("",))
+    if c_compiler.type == "clang":
+        # Get the llvm-nm path as per the output from clang --print-prog-name=llvm-nm
+        # so that we directly get the one under the clang directory, rather than one
+        # that might be in /usr/bin and that might point to one from a different version
+        # of clang.
+        out = check_cmd_output(
+            c_compiler.compiler, "--print-prog-name=llvm-nm", onerror=lambda: None
+        )
+        llvm_nm = out.rstrip() if out else "llvm-nm"
+        names = (llvm_nm,) + names
+
+    return names
+
+
+check_prog("NM", nm_names, paths=clang_search_path, when=target_has_linux_kernel)
+
+
+option("--enable-cpp-rtti", help="Enable C++ RTTI")
+
+add_old_configure_assignment("_MOZ_USE_RTTI", "1", when="--enable-cpp-rtti")
+
+
+option(
+    "--enable-path-remapping",
+    nargs="*",
+    choices=("c", "rust"),
+    help="Enable remapping source and object paths in compiled outputs.",
+)
+
+
+@depends("--enable-path-remapping")
+def path_remapping(value):
+    if len(value):
+        return value
+    if bool(value):
+        return ["c", "rust"]
+    return []
+
+
+@depends(
+    target,
+    build_environment,
+    target_sysroot.path,
+    valid_windows_sdk_dir,
+    vc_path,
+    when="--enable-path-remapping",
+)
+def path_remappings(target, build_env, sysroot_path, windows_sdk_dir, vc_path):
+    win = target.kernel == "WINNT"
+
+    # The prefix maps are processed in the order they're specified on the
+    # command line.  Therefore, to accommodate object directories in the source
+    # directory, it's important that we map the topobjdir before the topsrcdir,
+    # 'cuz we might have /src/obj/=/o/ and /src/=/s/.  The various other
+    # directories might be subdirectories of topsrcdir as well, so they come
+    # earlier still.
+
+    path_remappings = []
+
+    # We will have only one sysroot or SDK, so all can have the same mnemonic: K
+    # for "kit" (since S is taken for "source").  See
+    # https://blog.llvm.org/2019/11/deterministic-builds-with-clang-and-lld.html
+    # for how to use the Windows `subst` command to map these in debuggers and
+    # IDEs.
+    if sysroot_path:
+        path_remappings.append((sysroot_path, "k:/" if win else "/sysroot/"))
+    if windows_sdk_dir:
+        path_remappings.append(
+            (windows_sdk_dir.path, "k:/" if win else "/windows_sdk/")
+        )
+    if vc_path:
+        path_remappings.append((vc_path, "v:/" if win else "/vc/"))
+
+    path_remappings += [
+        (build_env.topobjdir, "o:/" if win else "/topobjdir/"),
+        (build_env.topsrcdir, "s:/" if win else "/topsrcdir/"),
+    ]
+
+    path_remappings = [
+        (normsep(old).rstrip("/") + "/", new) for old, new in path_remappings
+    ]
+
+    # It is tempting to sort these, but we want the order to be the same across
+    # machines so that we can share cache hits.  Therefore we reject bad
+    # configurations rather than trying to make the configuration good.
+    for i in range(len(path_remappings) - 1):
+        p = path_remappings[i][0]
+        for q, _ in path_remappings[i + 1 :]:
+            if q.startswith(p):
+                die(f"Cannot remap paths because {p} is an ancestor of {q}")
+
+    return path_remappings
+
+
+set_config("MMX_FLAGS", ["-mmmx"])
+set_config("SSE_FLAGS", ["-msse"])
+set_config("SSE2_FLAGS", ["-msse2"])
+set_config("SSSE3_FLAGS", ["-mssse3"])
+set_config("SSE4_2_FLAGS", ["-msse4.2"])
+set_config("FMA_FLAGS", ["-mfma"])
+set_config("AVX2_FLAGS", ["-mavx2"])