Replace sysroot with a cc_sysroot macro.

BEGIN_PUBLIC
Replace sysroot with a cc_sysroot macro.

This is part of what amontanez@ and I discussed about making C++ toolchains less "magic".
I'd like to do the same for cxx_builtin_include_directories, but that will require significantly more effort.

END_PUBLIC

PiperOrigin-RevId: 666607531
Change-Id: Ic9cfb157e892c05a9c875f240c0ed9a1048dea19

cc/toolchains/args/sysroot.bzl

@@ -0,0 +1,39 @@
+# Copyright 2024 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Implementation of the cc_sysroot macro."""
+
+load("//cc/toolchains:args.bzl", "cc_args")
+
+visibility("public")
+
+def cc_sysroot(name, sysroot, **kwargs):
+    """Creates args for a sysroot.
+
+    Args:
+      name: (str) The name of the target
+      sysroot: (bazel_skylib's directory rule) The directory that should be the
+        sysroot.
+      **kwargs: kwargs to pass to cc_args.
+    """
+    cc_args(
+        name = name,
+        actions = [
+            "//cc/toolchains/actions:cpp_compile_actions",
+            "//cc/toolchains/actions:c_compile",
+            "//cc/toolchains/actions:link_actions",
+        ],
+        args = ["--sysroot={sysroot}"],
+        format = {"sysroot": sysroot},
+        **kwargs
+    )

cc/toolchains/features/legacy/BUILD

@@ -203,11 +203,8 @@ cc_external_feature(
     overridable = True,
 )
 
-cc_external_feature(
+# Instead of the "sysroot" legacy flag, use the cc_sysroot macro in
-    name = "sysroot",
+# //cc/toolchains/args:sysroot.bzl
-    feature_name = "sysroot",
-    overridable = True,
-)
 
 cc_external_feature(
     name = "unfiltered_compile_flags",
@@ -269,7 +266,6 @@ cc_feature_set(
         ":gcc_coverage_map_format",
         ":fully_static_link",
         ":user_compile_flags",
-        ":sysroot",
         ":unfiltered_compile_flags",
         ":linker_param_file",
         ":compiler_input_flags",

cc/toolchains/impl/toolchain_config.bzl

@@ -66,10 +66,6 @@ def _cc_toolchain_config_impl(ctx):
 
     legacy = convert_toolchain(toolchain_config)
 
-    sysroot = None
-    if ctx.attr.sysroot:
-        sysroot = ctx.attr.sysroot[DirectoryInfo].path
-
     cxx_builtin_include_directories = [
         d[DirectoryInfo].path
         for d in ctx.attr.cxx_builtin_include_directories
@@ -93,7 +89,6 @@ def _cc_toolchain_config_impl(ctx):
             compiler = "",
             abi_version = "",
             abi_libc_version = "",
-            builtin_sysroot = sysroot,
         ),
         # This allows us to support all_files.
         # If all_files was simply an alias to
@@ -117,7 +112,6 @@ cc_toolchain_config = rule(
         "_enabled": attr.label(default = "//cc/toolchains:experimental_enable_rule_based_toolchains"),
 
         # Attributes translated from legacy cc toolchains.
-        "sysroot": attr.label(providers = [DirectoryInfo]),
         "cxx_builtin_include_directories": attr.label_list(providers = [DirectoryInfo]),
     },
     provides = [ToolchainConfigInfo],

cc/toolchains/variables/BUILD

@@ -400,10 +400,8 @@ cc_variable(
     type = types.list(types.string),
 )
 
-cc_variable(
+# Instead of the "sysroot" variable, use the cc_sysroot macro in
-    name = "sysroot",
+# //cc/toolchains/args:sysroot.bzl
-    type = types.directory,
-)
 
 cc_variable(
     name = "system_include_paths",
@@ -526,7 +524,6 @@ cc_builtin_variables(
         ":source_file",
         ":strip_debug_symbols",
         ":stripopts",
-        ":sysroot",
         ":system_include_paths",
         ":thinlto_index",
         ":thinlto_indexing_param_file",

tests/rule_based_toolchain/toolchain_config/BUILD

@@ -3,6 +3,7 @@ load("//cc/toolchains:args.bzl", "cc_args")
 load("//cc/toolchains:feature.bzl", "cc_feature")
 load("//cc/toolchains:feature_set.bzl", "cc_feature_set")
 load("//cc/toolchains:tool_map.bzl", "cc_tool_map")
+load("//cc/toolchains/args:sysroot.bzl", "cc_sysroot")
 load("//cc/toolchains/impl:external_feature.bzl", "cc_external_feature")
 load("//cc/toolchains/impl:toolchain_config.bzl", "cc_legacy_file_group", "cc_toolchain_config")
 load("//tests/rule_based_toolchain:analysis_test_suite.bzl", "analysis_test_suite")
@@ -40,17 +41,24 @@ util.helper_target(
     env = {"CPP_COMPILE": "1"},
 )
 
+cc_sysroot(
+    name = "sysroot",
+    sysroot = "//tests/rule_based_toolchain/testdata:directory",
+)
+
 util.helper_target(
     cc_toolchain_config,
     name = "collects_files_toolchain_config",
-    args = [":c_compile_args"],
+    args = [
+        ":sysroot",
+        ":c_compile_args",
+    ],
     cxx_builtin_include_directories = [
         "//tests/rule_based_toolchain/testdata:directory",
     ],
     enabled_features = [":simple_feature"],
     known_features = [":compile_feature"],
     skip_experimental_flag_validation_for_test = True,
-    sysroot = "//tests/rule_based_toolchain/testdata:directory",
     tool_map = ":compile_tool_map",
 )
 

tests/rule_based_toolchain/toolchain_config/toolchain_config_test.bzl

@@ -204,12 +204,37 @@ def _toolchain_collects_files_test(env, targets):
         legacy_feature(
             name = "implied_by_always_enabled",
             enabled = True,
-            flag_sets = [legacy_flag_set(
+            flag_sets = [
+                legacy_flag_set(
+                    actions = [
+                        "c++-compile",
+                        "c++-header-parsing",
+                        "c++-link-dynamic-library",
+                        "c++-link-executable",
+                        "c++-link-nodeps-dynamic-library",
+                        "c++-module-codegen",
+                        "c++-module-compile",
+                        "c-compile",
+                        "clif-match",
+                        "linkstamp-compile",
+                        "lto-backend",
+                        "lto-index-for-dynamic-library",
+                        "lto-index-for-executable",
+                        "lto-index-for-nodeps-dynamic-library",
+                    ],
+                    flag_groups = [
+                        legacy_flag_group(flags = [
+                            "--sysroot=tests/rule_based_toolchain/testdata",
+                        ]),
+                    ],
+                ),
+                legacy_flag_set(
                     actions = ["c_compile"],
                     flag_groups = [
                         legacy_flag_group(flags = ["c_compile_args"]),
                     ],
-            )],
+                ),
+            ],
         ),
     ]).in_order()