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Add env var to disable macOS toolchain #744

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keith wants to merge 8 commits into from
+12 −10
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Add env var to disable macOS toolchain #744

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25152f7
Disable macOS toolchain by default
keith Jun 10, 2026
cdba71f
flip
keith Jun 10, 2026
ef4db82
try this for testing
keith Jun 11, 2026
c0f1e71
disable nodeps in test
keith Jun 11, 2026
4f90f6c
fix more
keith Jun 11, 2026
3036bbb
flip default to enabled
keith Jun 16, 2026
f8eeea6
drop for now
keith Jun 16, 2026
d1df3e0
revert for now
keith Jun 16, 2026
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22 changes: 12 additions & 10 deletions cc/private/toolchain/cc_configure.bzl
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Original file line number Diff line number Diff line change
Expand Up @@ -21,18 +21,20 @@ load(
load(":unix_cc_configure.bzl", "configure_unix_toolchain")
load(":windows_cc_configure.bzl", "configure_windows_toolchain")

def _should_disable_toolchain(repository_ctx):
"""Returns true if the toolchain should be disabled based on environment variables."""
env = repository_ctx.os.environ
disabled_via_env = "BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN" in env and env["BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN"] == "1"

@armandomontanez armandomontanez Jun 17, 2026

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Nit: this is easier to read if you do early returns

    if "BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN" in env and env["BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN"] == "1":
        return True
    macos_legacy_support = env.get("BAZEL_USE_LEGACY_MACOS_TOOLCHAIN", "1") == "1"
    if repository_ctx.os.name.startswith("mac os") and not macos_legacy_support:
        return True
    return False

@keith keith Jun 18, 2026

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changed in #755

macos_legacy_support = env.get("BAZEL_USE_LEGACY_MACOS_TOOLCHAIN", "1") == "1"
return disabled_via_env or (repository_ctx.os.name.startswith("mac os") and not macos_legacy_support)

def cc_autoconf_toolchains_impl(repository_ctx):
"""Generate BUILD file with 'toolchain' targets for the local host C++ toolchain.

Args:
repository_ctx: repository context
"""
env = repository_ctx.os.environ

# Should we try to find C++ toolchain at all? If not, we don't have to generate toolchains for C++ at all.
should_detect_cpp_toolchain = "BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN" not in env or env["BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN"] != "1"

if should_detect_cpp_toolchain:
if not _should_disable_toolchain(repository_ctx):
if repository_ctx.os.name.lower().find("windows") != -1:
build_path = "@rules_cc//cc/private/toolchain:BUILD.windows_toolchains.tpl"
else:
Expand All @@ -47,11 +49,12 @@ def cc_autoconf_toolchains_impl(repository_ctx):
{"%{name}": get_cpu_value(repository_ctx)},
)
else:
repository_ctx.file("BUILD", "# C++ toolchain autoconfiguration was disabled by BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN env variable.")
repository_ctx.file("BUILD", "# C++ toolchain autoconfiguration was disabled by BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN=1 or BAZEL_USE_LEGACY_MACOS_TOOLCHAIN=0.")

cc_autoconf_toolchains = repository_rule(
environ = [
"BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN",
"BAZEL_USE_LEGACY_MACOS_TOOLCHAIN",
],
implementation = cc_autoconf_toolchains_impl,
configure = True,
Expand All @@ -64,10 +67,8 @@ def cc_autoconf_impl(repository_ctx, overriden_tools = dict()):
repository_ctx: repository context
overriden_tools: dict of tool paths to use instead of autoconfigured tools
"""

env = repository_ctx.os.environ
cpu_value = get_cpu_value(repository_ctx)
if "BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN" in env and env["BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN"] == "1":
if _should_disable_toolchain(repository_ctx):
paths = resolve_labels(repository_ctx, [
"@rules_cc//cc/private/toolchain:BUILD.empty.tpl",
"@rules_cc//cc/private/toolchain:empty_cc_toolchain_config.bzl",
Expand Down Expand Up @@ -130,6 +131,7 @@ cc_autoconf = repository_rule(
"BAZEL_TARGET_LIBC",
"BAZEL_TARGET_SYSTEM",
"BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN",
"BAZEL_USE_LEGACY_MACOS_TOOLCHAIN",
"BAZEL_USE_LLVM_NATIVE_COVERAGE",
"BAZEL_WIN32_WINNT",
"BAZEL_LLVM",
Expand Down