[llvm-branch-commits] [libc] [llvm] [libc][bazel] Add targets for startup objects on linux (PR #218995)

[Alexey Samsonov via llvm-branch-commits]

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@@ -0,0 +1,176 @@
+# This file is licensed under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+"""LLVM libc starlark rules for building startup objects."""
+
+load("@bazel_skylib//lib:paths.bzl", "paths")
+load("@rules_cc//cc:action_names.bzl", "ACTION_NAMES")
+load("@rules_cc//cc:find_cc_toolchain.bzl", "find_cc_toolchain", "use_cc_toolchain")
+load("@rules_cc//cc/common:cc_common.bzl", "cc_common")
+load("@rules_cc//cc/common:cc_info.bzl", "CcInfo")
+load("//libc:libc_build_rules.bzl", "libc_startup_library")
+
+def _get_compilation_outputs(deps):
+    outputs = []
+    for dep in deps:
+        if OutputGroupInfo in dep and "compilation_outputs" in dep[OutputGroupInfo]:
+            outputs.extend(dep[OutputGroupInfo].compilation_outputs.to_list())
+    return outputs
+
+def _extract_object_file_impl(ctx):
+    output = ctx.actions.declare_file(ctx.label.name + ".o")
+    input_objs = _get_compilation_outputs([ctx.attr.dep])
+    if len(input_objs) != 1:
+        fail("Expected exactly one input object, got: {}".format(input_objs))
+
+    input_obj = input_objs[0]
+
+    ctx.actions.symlink(
+        output = output,
+        target_file = input_obj,
+    )
+
+    return [DefaultInfo(files = depset([output]))]
+
+_extract_object_file = rule(
+    implementation = _extract_object_file_impl,
+    attrs = {
+        "dep": attr.label(
+            mandatory = True,
+            providers = [CcInfo],
+        ),
+    },
+)
+
+def libc_startup_object(name, src, visibility = None, **kwargs):
+    """Compiles a C++ source file into a startup object file.
+
+    Args:
+        name: The name of the target.
+        src: The C++ source file to compile.
+        visibility: Visibility of targets created by this macro.
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vonosmas wrote:

Why do we care about visibility here?

https://github.com/llvm/llvm-project/pull/218995