Revert "process_wrapper: replace C++ implementation with rust. (bazelbuild#1159)"

This reverts commit d9ba374.

Author: korDen

rust/private/rustc.bzl

@@ -922,41 +922,20 @@ def rustc_compile_action(
             dsym_folder = ctx.actions.declare_directory(crate_info.output.basename + ".dSYM")
             action_outputs.append(dsym_folder)
 
-    # This uses startswith as on windows the basename will be process_wrapper_fake.exe.
-    if not ctx.executable._process_wrapper.basename.startswith("process_wrapper_fake"):
-        # Run as normal
-        ctx.actions.run(
-            executable = ctx.executable._process_wrapper,
-            inputs = compile_inputs,
-            outputs = action_outputs,
-            env = env,
-            arguments = args.all,
-            mnemonic = "Rustc",
-            progress_message = "Compiling Rust {} {}{} ({} files)".format(
-                crate_info.type,
-                ctx.label.name,
-                formatted_version,
-                len(crate_info.srcs.to_list()),
-            ),
-        )
-    else:
-        # Run without process_wrapper
-        if build_env_files or build_flags_files or stamp:
-            fail("build_env_files, build_flags_files, stamp are not supported if use_process_wrapper is False")
-        ctx.actions.run(
-            executable = toolchain.rustc,
-            inputs = compile_inputs,
-            outputs = action_outputs,
-            env = env,
-            arguments = [args.rustc_flags],
-            mnemonic = "Rustc",
-            progress_message = "Compiling Rust (without process_wrapper) {} {}{} ({} files)".format(
-                crate_info.type,
-                ctx.label.name,
-                formatted_version,
-                len(crate_info.srcs.to_list()),
-            ),
-        )
+    ctx.actions.run(
+        executable = ctx.executable._process_wrapper,
+        inputs = compile_inputs,
+        outputs = action_outputs,
+        env = env,
+        arguments = args.all,
+        mnemonic = "Rustc",
+        progress_message = "Compiling Rust {} {}{} ({} files)".format(
+            crate_info.type,
+            ctx.label.name,
+            formatted_version,
+            len(crate_info.srcs.to_list()),
+        ),
+    )
 
     runfiles = ctx.runfiles(
         files = getattr(ctx.files, "data", []),

rust/private/transitions.bzl

@@ -64,48 +64,3 @@ with_import_macro_bootstrapping_mode = rule(
         ),
     },
 )
-
-def _without_process_wrapper_transition_impl(_settings, _attr):
-    """This transition allows rust_* rules to invoke rustc without process_wrapper."""
-    return {
-        "//rust/settings:use_process_wrapper": False,
-    }
-
-without_process_wrapper_transition = transition(
-    implementation = _without_process_wrapper_transition_impl,
-    inputs = [],
-    outputs = ["//rust/settings:use_process_wrapper"],
-)
-
-def _without_process_wrapper_impl(ctx):
-    executable = ctx.executable.target
-    link_name = ctx.label.name
-
-    # Append .exe if on windows
-    if executable.extension:
-        link_name = link_name + "." + executable.extension
-    link = ctx.actions.declare_file(link_name)
-    ctx.actions.symlink(
-        output = link,
-        target_file = executable,
-    )
-    return [
-        DefaultInfo(
-            executable = link,
-        ),
-    ]
-
-without_process_wrapper = rule(
-    implementation = _without_process_wrapper_impl,
-    attrs = {
-        "target": attr.label(
-            cfg = without_process_wrapper_transition,
-            allow_single_file = True,
-            mandatory = True,
-            executable = True,
-        ),
-        "_allowlist_function_transition": attr.label(
-            default = Label("@bazel_tools//tools/allowlists/function_transition_allowlist"),
-        ),
-    },
-)

rust/settings/BUILD.bazel

@@ -29,13 +29,6 @@ bool_flag(
     build_setting_default = False,
 )
 
-# A flag that enables/disables the use of process_wrapper when invoking rustc.
-# This is useful for building process_wrapper itself without causing dependency cycles.
-bool_flag(
-    name = "use_process_wrapper",
-    build_setting_default = True,
-)
-
 bzl_library(
     name = "bzl_lib",
     srcs = glob(["**/*.bzl"]),

util/process_wrapper/BUILD.bazel

@@ -1,45 +1,26 @@
 load("@rules_cc//cc:defs.bzl", "cc_binary")
-load("//rust:defs.bzl", "rust_binary", "rust_test")
 
-# buildifier: disable=bzl-visibility
-load("//rust/private:transitions.bzl", "without_process_wrapper")
-
-alias(
+cc_binary(
     name = "process_wrapper",
-    actual = select({
-        # This will never get used, it's only here to break the circular dependency to allow building process_wrapper
-        ":use_fake_process_wrapper": ":process_wrapper_fake",
-        "//conditions:default": ":process_wrapper_impl",
+    srcs = [
+        "process_wrapper.cc",
+        "system.h",
+        "utils.h",
+        "utils.cc",
+    ] + select({
+        "@bazel_tools//src/conditions:host_windows": [
+            "system_windows.cc",
+        ],
+        "//conditions:default": [
+            "system_posix.cc",
+        ],
+    }),
+    defines = [] + select({
+        "@bazel_tools//src/conditions:host_windows": [
+            "UNICODE",
+            "_UNICODE",
+        ],
+        "//conditions:default": [],
     }),
     visibility = ["//visibility:public"],
 )
-
-cc_binary(
-    name = "process_wrapper_fake",
-    srcs = ["fake.cc"],
-)
-
-config_setting(
-    name = "use_fake_process_wrapper",
-    flag_values = {
-        "//rust/settings:use_process_wrapper": "False",
-    },
-)
-
-# Changing the name of this rule requires a corresponding
-# change in //rust/private/rustc.bzl:925
-without_process_wrapper(
-    name = "process_wrapper_impl",
-    target = ":process_wrapper_bin",
-    visibility = ["//visibility:public"],
-)
-
-rust_binary(
-    name = "process_wrapper_bin",
-    srcs = glob(["*.rs"]),
-)
-
-rust_test(
-    name = "process_wrapper_test",
-    crate = ":process_wrapper_bin",
-)