some bootstrap stuff

dzbarsky · dzbarsky · commit dba01b96b9f2 · 2026-02-18T10:55:14.000-05:00
diff --git a/examples/cross_compile_nix/bazel/toolchains/rust/aarch64-apple-darwin/BUILD.bazel b/examples/cross_compile_nix/bazel/toolchains/rust/aarch64-apple-darwin/BUILD.bazel
@@ -18,6 +18,7 @@ rust_toolchain(
     extra_rustc_flags = [
         "-Clinker-flavor=ld64.lld",
     ],
+    process_wrapper = "@rules_rust//util/process_wrapper",
     rust_doc = "@nix_rust//:rustdoc",
     rust_std = "@nix_rust//:rust_std-aarch64-apple-darwin",
     rustc = "@nix_rust//:rustc",
diff --git a/examples/cross_compile_nix/bazel/toolchains/rust/aarch64-apple-ios/BUILD.bazel b/examples/cross_compile_nix/bazel/toolchains/rust/aarch64-apple-ios/BUILD.bazel
@@ -18,6 +18,7 @@ rust_toolchain(
     extra_rustc_flags = [
         "-Clinker-flavor=ld64.lld",
     ],
+    process_wrapper = "@rules_rust//util/process_wrapper",
     rust_doc = "@nix_rust//:rustdoc",
     rust_std = "@nix_rust//:rust_std-aarch64-apple-ios",
     rustc = "@nix_rust//:rustc",
diff --git a/examples/cross_compile_nix/bazel/toolchains/rust/aarch64-linux-android/BUILD.bazel b/examples/cross_compile_nix/bazel/toolchains/rust/aarch64-linux-android/BUILD.bazel
@@ -11,6 +11,7 @@ rust_toolchain(
     exec_triple = "x86_64-unknown-nixos-gnu",
     extra_exec_rustc_flags = [],
     extra_rustc_flags = [],
+    process_wrapper = "@rules_rust//util/process_wrapper",
     rust_doc = "@nix_rust//:rustdoc",
     rust_std = "@nix_rust//:rust_std-aarch64-linux-android",
     rustc = "@nix_rust//:rustc",
diff --git a/examples/cross_compile_nix/bazel/toolchains/rust/aarch64-unknown-linux-gnu/BUILD.bazel b/examples/cross_compile_nix/bazel/toolchains/rust/aarch64-unknown-linux-gnu/BUILD.bazel
@@ -11,6 +11,7 @@ rust_toolchain(
     exec_triple = "x86_64-unknown-nixos-gnu",
     extra_exec_rustc_flags = [],
     extra_rustc_flags = [],
+    process_wrapper = "@rules_rust//util/process_wrapper",
     rust_doc = "@nix_rust//:rustdoc",
     rust_std = "@nix_rust//:rust_std-aarch64-unknown-linux-gnu",
     rustc = "@nix_rust//:rustc",
diff --git a/examples/cross_compile_nix/bazel/toolchains/rust/wasm32-unknown-unknown/BUILD.bazel b/examples/cross_compile_nix/bazel/toolchains/rust/wasm32-unknown-unknown/BUILD.bazel
@@ -11,6 +11,7 @@ rust_toolchain(
     exec_triple = "x86_64-unknown-nixos-gnu",
     extra_exec_rustc_flags = [],
     extra_rustc_flags = [],
+    process_wrapper = "@rules_rust//util/process_wrapper",
     rust_doc = "@nix_rust//:rustdoc",
     rust_std = "@nix_rust//:rust_std-wasm32-unknown-unknown",
     rustc = "@nix_rust//:rustc",
diff --git a/examples/cross_compile_nix/bazel/toolchains/rust/wasm32-wasip1/BUILD.bazel b/examples/cross_compile_nix/bazel/toolchains/rust/wasm32-wasip1/BUILD.bazel
@@ -11,6 +11,7 @@ rust_toolchain(
     exec_triple = "x86_64-unknown-nixos-gnu",
     extra_exec_rustc_flags = [],
     extra_rustc_flags = [],
+    process_wrapper = "@rules_rust//util/process_wrapper",
     rust_doc = "@nix_rust//:rustdoc",
     rust_std = "@nix_rust//:rust_std-wasm32-wasip1",
     rustc = "@nix_rust//:rustc",
diff --git a/examples/cross_compile_nix/bazel/toolchains/rust/x86_64-apple-darwin/BUILD.bazel b/examples/cross_compile_nix/bazel/toolchains/rust/x86_64-apple-darwin/BUILD.bazel
@@ -18,6 +18,7 @@ rust_toolchain(
     extra_rustc_flags = [
         "-Clinker-flavor=ld64.lld",
     ],
+    process_wrapper = "@rules_rust//util/process_wrapper",
     rust_doc = "@nix_rust//:rustdoc",
     rust_std = "@nix_rust//:rust_std-x86_64-apple-darwin",
     rustc = "@nix_rust//:rustc",
diff --git a/examples/cross_compile_nix/bazel/toolchains/rust/x86_64-pc-windows-msvc/BUILD.bazel b/examples/cross_compile_nix/bazel/toolchains/rust/x86_64-pc-windows-msvc/BUILD.bazel
@@ -11,6 +11,7 @@ rust_toolchain(
     exec_triple = "x86_64-unknown-nixos-gnu",
     extra_exec_rustc_flags = [],
     extra_rustc_flags = [],
+    process_wrapper = "@rules_rust//util/process_wrapper",
     rust_doc = "@nix_rust//:rustdoc",
     rust_std = "@nix_rust//:rust_std-x86_64-pc-windows-msvc",
     rustc = "@nix_rust//:rustc",
diff --git a/examples/cross_compile_nix/bazel/toolchains/rust/x86_64-unknown-linux-gnu/BUILD.bazel b/examples/cross_compile_nix/bazel/toolchains/rust/x86_64-unknown-linux-gnu/BUILD.bazel
@@ -11,6 +11,7 @@ rust_toolchain(
     exec_triple = "x86_64-unknown-nixos-gnu",
     extra_exec_rustc_flags = [],
     extra_rustc_flags = [],
+    process_wrapper = "@rules_rust//util/process_wrapper",
     rust_doc = "@nix_rust//:rustdoc",
     rust_std = "@nix_rust//:rust_std-x86_64-unknown-linux-gnu",
     rustc = "@nix_rust//:rustc",
diff --git a/examples/cross_compile_nix/bazel/toolchains/rust/x86_64-unknown-nixos-gnu/BUILD.bazel b/examples/cross_compile_nix/bazel/toolchains/rust/x86_64-unknown-nixos-gnu/BUILD.bazel
@@ -11,6 +11,7 @@ rust_toolchain(
     exec_triple = "x86_64-unknown-nixos-gnu",
     extra_exec_rustc_flags = [],
     extra_rustc_flags = [],
+    process_wrapper = "@rules_rust//util/process_wrapper",
     rust_doc = "@nix_rust//:rustdoc",
     rust_std = "@nix_rust//:rust_std-x86_64-unknown-linux-gnu",
     rustc = "@nix_rust//:rustc",
diff --git a/extensions/prost/private/prost.bzl b/extensions/prost/private/prost.bzl
@@ -196,7 +196,7 @@ def _compile_rust(
             extension = ".rmeta",
         )
         rmeta = ctx.actions.declare_file(rmeta_name)
-        rustc_rmeta_output = generate_output_diagnostics(ctx, rmeta)
+        rustc_rmeta_output = generate_output_diagnostics(ctx, toolchain, rmeta)
         metadata_supports_pipelining = can_use_metadata_for_pipelining(toolchain, "rlib")
 
     providers = rustc_compile_action(
diff --git a/extensions/protobuf/proto.bzl b/extensions/protobuf/proto.bzl
@@ -211,7 +211,7 @@ def _rust_proto_compile(protos, descriptor_sets, imports, crate_name, ctx, is_gr
             crate_name,
             output_hash,
         ))
-        rustc_rmeta_output = generate_output_diagnostics(ctx, rust_metadata)
+        rustc_rmeta_output = generate_output_diagnostics(ctx, toolchain, rust_metadata)
         metadata_supports_pipelining = can_use_metadata_for_pipelining(toolchain, "rlib")
 
     # Gather all dependencies for compilation
diff --git a/extensions/wasm_bindgen/private/wasm_bindgen_test.bzl b/extensions/wasm_bindgen/private/wasm_bindgen_test.bzl
@@ -123,7 +123,7 @@ def _rust_wasm_bindgen_test_impl(ctx):
         proc_macro_deps = depset(proc_macro_deps, transitive = [crate.proc_macro_deps]).to_list(),
         aliases = {},
         output = output,
-        rustc_output = generate_output_diagnostics(ctx, output),
+        rustc_output = generate_output_diagnostics(ctx, toolchain, output),
         edition = crate.edition,
         rustc_env = rustc_env,
         rustc_env_files = rustc_env_files,
diff --git a/rust/private/BUILD.bazel b/rust/private/BUILD.bazel
@@ -1,4 +1,5 @@
 load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
+load("@bazel_skylib//rules:common_settings.bzl", "bool_setting")
 load("//rust/private:rust_analyzer.bzl", "rust_analyzer_detect_sysroot")
 load("//rust/private:rustc.bzl", "is_proc_macro_dep", "is_proc_macro_dep_enabled")
 
@@ -54,3 +55,26 @@ rust_analyzer_detect_sysroot(
     name = "rust_analyzer_detect_sysroot",
     visibility = ["//visibility:public"],
 )
+
+# This setting lets us configure a bootstrap toolchain to build the process_wrapper
+# and a "full" toolchain (that uses process_wrapper) to build user code.
+bool_setting(
+    name = "bootstrap_setting",
+    build_setting_default = False,
+)
+
+config_setting(
+    name = "bootstrapped",
+    flag_values = {
+        ":bootstrap_setting": "0",
+    },
+    visibility = ["//visibility:public"],
+)
+
+config_setting(
+    name = "bootstrapping",
+    flag_values = {
+        ":bootstrap_setting": "1",
+    },
+    visibility = ["//visibility:public"],
+)
diff --git a/rust/private/repository_utils.bzl b/rust/private/repository_utils.bzl
@@ -322,6 +322,41 @@ rust_toolchain(
     rust_doc = "//:rustdoc",
     rust_std = "//:rust_std-{target_triple}",
     rustc = "//:rustc",
+    process_wrapper = "@rules_rust//util/process_wrapper",
+    linker = {linker_label},
+    linker_type = {linker_type},
+    rustfmt = {rustfmt_label},
+    cargo = "//:cargo",
+    clippy_driver = "//:clippy_driver_bin",
+    cargo_clippy = "//:cargo_clippy_bin",
+    llvm_cov = {llvm_cov_label},
+    llvm_profdata = {llvm_profdata_label},
+    llvm_lib = {llvm_lib_label},
+    rustc_lib = "//:rustc_lib",
+    allocator_library = {allocator_library},
+    global_allocator_library = {global_allocator_library},
+    binary_ext = "{binary_ext}",
+    staticlib_ext = "{staticlib_ext}",
+    dylib_ext = "{dylib_ext}",
+    stdlib_linkflags = [{stdlib_linkflags}],
+    default_edition = "{default_edition}",
+    exec_triple = "{exec_triple}",
+    target_triple = "{target_triple}",
+    visibility = ["//visibility:public"],
+    extra_rustc_flags = {extra_rustc_flags},
+    extra_exec_rustc_flags = {extra_exec_rustc_flags},
+    opt_level = {opt_level},
+    strip_level = {strip_level},
+    tags = ["rust_version={version}"],
+)
+
+rust_toolchain(
+    name = "{toolchain_name}_bootstrap",
+    bootstrapping = True,
+    rust_doc = "//:rustdoc",
+    rust_std = "//:rust_std-{target_triple}",
+    rustc = "//:rustc",
+    process_wrapper = "@rules_rust//util/process_wrapper:bootstrap_process_wrapper",
     linker = {linker_label},
     linker_type = {linker_type},
     rustfmt = {rustfmt_label},
@@ -449,7 +484,20 @@ toolchain(
     target_compatible_with = {target_constraint_sets_serialized},
     toolchain = "{toolchain}",
     toolchain_type = "{toolchain_type}",
-    {target_settings}
+    target_settings = [
+        "@rules_rust//rust/private:bootstrapped",{target_settings}
+    ],
+)
+
+toolchain(
+    name = "{name}_bootstrap",
+    exec_compatible_with = {exec_constraint_sets_serialized},
+    target_compatible_with = {target_constraint_sets_serialized},
+    toolchain = "{toolchain}_bootstrap",
+    toolchain_type = "{toolchain_type}",
+    target_settings = [
+        "@rules_rust//rust/private:bootstrapping",{target_settings}
+    ],
 )
 """
 
@@ -460,7 +508,7 @@ def BUILD_for_toolchain(
         target_settings,
         target_compatible_with,
         exec_compatible_with):
-    target_settings_value = "target_settings = {},".format(json.encode(target_settings)) if target_settings else "# target_settings = []"
+    target_settings_value = ",\n        ".join([repr(setting) for setting in target_settings])
 
     return _build_file_for_toolchain_template.format(
         name = name,
diff --git a/rust/private/rust.bzl b/rust/private/rust.bzl
@@ -209,7 +209,7 @@ def _rust_library_common(ctx, crate_type):
             paths.replace_extension(rust_lib_name, ".rmeta"),
             sibling = rust_lib,
         )
-        rustc_rmeta_output = generate_output_diagnostics(ctx, rust_metadata)
+        rustc_rmeta_output = generate_output_diagnostics(ctx, toolchain, rust_metadata)
         metadata_supports_pipelining = (
             can_use_metadata_for_pipelining(toolchain, crate_type) and
             not ctx.attr.disable_pipelining
@@ -232,7 +232,7 @@ def _rust_library_common(ctx, crate_type):
             proc_macro_deps = proc_macro_deps,
             aliases = ctx.attr.aliases,
             output = rust_lib,
-            rustc_output = generate_output_diagnostics(ctx, rust_lib),
+            rustc_output = generate_output_diagnostics(ctx, toolchain, rust_lib),
             metadata = rust_metadata,
             metadata_supports_pipelining = metadata_supports_pipelining,
             rustc_rmeta_output = rustc_rmeta_output,
@@ -282,7 +282,7 @@ def _rust_binary_impl(ctx):
             paths.replace_extension("lib" + crate_name, ".rmeta"),
             sibling = output,
         )
-        rustc_rmeta_output = generate_output_diagnostics(ctx, rust_metadata)
+        rustc_rmeta_output = generate_output_diagnostics(ctx, toolchain, rust_metadata)
 
     providers = rustc_compile_action(
         ctx = ctx,
@@ -297,7 +297,7 @@ def _rust_binary_impl(ctx):
             proc_macro_deps = proc_macro_deps,
             aliases = ctx.attr.aliases,
             output = output,
-            rustc_output = generate_output_diagnostics(ctx, output),
+            rustc_output = generate_output_diagnostics(ctx, toolchain, output),
             metadata = rust_metadata,
             rustc_rmeta_output = rustc_rmeta_output,
             edition = get_edition(ctx.attr, toolchain, ctx.label),
@@ -394,7 +394,7 @@ def _rust_test_impl(ctx):
                 paths.replace_extension("lib" + crate_name, ".rmeta"),
                 sibling = output,
             )
-            rustc_rmeta_output = generate_output_diagnostics(ctx, rust_metadata)
+            rustc_rmeta_output = generate_output_diagnostics(ctx, toolchain, rust_metadata)
 
         # Need to consider all src files together when transforming
         srcs = depset(ctx.files.srcs, transitive = [crate.srcs]).to_list()
@@ -429,7 +429,7 @@ def _rust_test_impl(ctx):
             proc_macro_deps = depset(proc_macro_deps, transitive = [crate.proc_macro_deps]).to_list(),
             aliases = aliases,
             output = output,
-            rustc_output = generate_output_diagnostics(ctx, output),
+            rustc_output = generate_output_diagnostics(ctx, toolchain, output),
             metadata = rust_metadata,
             rustc_rmeta_output = rustc_rmeta_output,
             edition = crate.edition,
@@ -473,7 +473,7 @@ def _rust_test_impl(ctx):
                 paths.replace_extension("lib" + crate_name, ".rmeta"),
                 sibling = output,
             )
-            rustc_rmeta_output = generate_output_diagnostics(ctx, rust_metadata)
+            rustc_rmeta_output = generate_output_diagnostics(ctx, toolchain, rust_metadata)
 
         if ctx.attr.rustc_env:
             rustc_env = expand_dict_value_locations(
@@ -495,7 +495,7 @@ def _rust_test_impl(ctx):
             proc_macro_deps = proc_macro_deps,
             aliases = ctx.attr.aliases,
             output = output,
-            rustc_output = generate_output_diagnostics(ctx, output),
+            rustc_output = generate_output_diagnostics(ctx, toolchain, output),
             metadata = rust_metadata,
             rustc_rmeta_output = rustc_rmeta_output,
             edition = get_edition(ctx.attr, toolchain, ctx.label),
@@ -645,13 +645,6 @@ RUSTC_ATTRS = {
     "_per_crate_rustc_flag": attr.label(
         default = Label("//rust/settings:experimental_per_crate_rustc_flag"),
     ),
-    "_process_wrapper": attr.label(
-        doc = "A process wrapper for running rustc on all platforms.",
-        default = Label("//util/process_wrapper"),
-        executable = True,
-        allow_single_file = True,
-        cfg = "exec",
-    ),
     "_rustc_output_diagnostics": attr.label(
         default = Label("//rust/settings:rustc_output_diagnostics"),
     ),
@@ -1314,21 +1307,6 @@ rust_binary = rule(
 def _common_attrs_for_binary_without_process_wrapper(attrs):
     new_attr = dict(attrs)
 
-    # use a fake process wrapper
-    new_attr["_process_wrapper"] = attr.label(
-        default = None,
-        executable = True,
-        allow_single_file = True,
-        cfg = "exec",
-    )
-
-    new_attr["_bootstrap_process_wrapper"] = attr.label(
-        default = Label("//util/process_wrapper:bootstrap_process_wrapper"),
-        executable = True,
-        allow_single_file = True,
-        cfg = "exec",
-    )
-
     # fix stamp = 0
     new_attr["stamp"] = attr.int(
         doc = dedent("""\
@@ -1346,20 +1324,31 @@ _RustBuiltWithoutProcessWrapperInfo = provider(
     fields = {},
 )
 
+def _bootstrap_process_wrapper_transition_impl(_settings, _attr):
+    return {str(Label("//rust/private:bootstrap_setting")): True}
+
+_bootstrap_process_wrapper_transition = transition(
+    implementation = _bootstrap_process_wrapper_transition_impl,
+    inputs = [],
+    outputs = [str(Label("//rust/private:bootstrap_setting"))],
+)
+
 def _rust_binary_without_process_wrapper_impl(ctx):
     providers = _rust_binary_impl(ctx)
     return providers + [_RustBuiltWithoutProcessWrapperInfo()]
 
-# Provides an internal rust_{binary,library} to use that we can use to build the process
-# wrapper, this breaks the dependency of rust_* on the process wrapper by
-# setting it to None, which the functions in rustc detect and build accordingly.
 rust_binary_without_process_wrapper = rule(
     implementation = _rust_binary_without_process_wrapper_impl,
     doc = "A variant of `rust_binary` that uses a minimal process wrapper for `Rustc` actions.",
     provides = COMMON_PROVIDERS + [_RustBuiltWithoutProcessWrapperInfo],
-    attrs = _common_attrs_for_binary_without_process_wrapper(_common_attrs | _rust_binary_attrs),
+    attrs = _common_attrs_for_binary_without_process_wrapper(_common_attrs | _rust_binary_attrs) | {
+        "_allowlist_function_transition": attr.label(
+            default = Label("//tools/allowlists/function_transition_allowlist"),
+        ),
+    },
     executable = True,
     fragments = ["cpp"],
+    cfg = _bootstrap_process_wrapper_transition,
     toolchains = [
         str(Label("//rust:toolchain_type")),
         config_common.toolchain_type("@bazel_tools//tools/cpp:toolchain_type", mandatory = False),
diff --git a/rust/private/rustc.bzl b/rust/private/rustc.bzl
diff --git a/rust/private/unpretty.bzl b/rust/private/unpretty.bzl
diff --git a/rust/private/utils.bzl b/rust/private/utils.bzl
diff --git a/rust/toolchain.bzl b/rust/toolchain.bzl
diff --git a/test/integration/cc_common_link/unit/cc_common_link_test.bzl b/test/integration/cc_common_link/unit/cc_common_link_test.bzl
diff --git a/test/toolchain/toolchain_test.bzl b/test/toolchain/toolchain_test.bzl
diff --git a/test/unit/toolchain/toolchain_test.bzl b/test/unit/toolchain/toolchain_test.bzl
diff --git a/util/process_wrapper/BUILD.bazel b/util/process_wrapper/BUILD.bazel
