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Make cc_library(alwayslink=True) apply to .a in srcs #574

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Make cc_library(alwayslink=True) apply to .a in srcs #574

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8 changes: 5 additions & 3 deletions cc/private/rules_impl/cc_library.bzl
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Original file line number Diff line number Diff line change
Expand Up @@ -194,6 +194,7 @@ def _cc_library_impl(ctx):
feature_configuration,
ctx.fragments.cpp.force_pic(),
precompiled_files,
ctx.attr.alwayslink,
)

if not cc_helper.is_compilation_outputs_empty(compilation_outputs):
Expand Down Expand Up @@ -373,7 +374,8 @@ def _convert_precompiled_libraries_to_library_to_link(
cc_toolchain,
feature_configuration,
force_pic,
precompiled_files):
precompiled_files,
alwayslink):
static_libraries = _build_map_identifier_to_artifact(precompiled_files[2])
pic_static_libraries = _build_map_identifier_to_artifact(precompiled_files[3])
alwayslink_static_libraries = _build_map_identifier_to_artifact(precompiled_files[4])
Expand Down Expand Up @@ -413,7 +415,7 @@ def _convert_precompiled_libraries_to_library_to_link(
static_library = static_library,
pic_static_library = pic_static_library,
dynamic_library = dynamic_library,
alwayslink = identifier in alwayslink_static_libraries,
alwayslink = alwayslink or identifier in alwayslink_static_libraries,
)
libraries.append(library)

Expand All @@ -435,7 +437,7 @@ def _convert_precompiled_libraries_to_library_to_link(
feature_configuration = feature_configuration,
cc_toolchain = cc_toolchain,
pic_static_library = pic_static_library,
alwayslink = identifier in alwayslink_static_libraries,
alwayslink = alwayslink or identifier in alwayslink_static_libraries,
)
libraries.append(library)

Expand Down
62 changes: 62 additions & 0 deletions tests/alwayslink_srcs/BUILD
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Original file line number Diff line number Diff line change
@@ -0,0 +1,62 @@
# Copyright 2026 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.

load("//cc:cc_library.bzl", "cc_library")
load("//cc:cc_test.bzl", "cc_test")

licenses(["notice"])

# Library that provides the registration state (was_registered/set_registered).
cc_library(
name = "registered",
srcs = ["registered.c"],
hdrs = ["registered.h"],
)

# Library that registers itself via a static constructor.
cc_library(
name = "registerer_lib",
srcs = ["registerer.c"],
deps = [":registered"],
)

# Copy the .a file produced by registerer_lib, simulates having a prebuilt .a file.
genrule(
name = "copy_registerer_archive",
srcs = [":registerer_lib"],
outs = ["libregisterer_copied.a"],
cmd = "for f in $(locations :registerer_lib); do if [[ $$f == *.a ]]; then cp $$f $@; fi; done",
)

# Library that uses the copied .a file in srcs with alwayslink=True.
# Without alwayslink, the registerer would be dropped since nothing
# directly references its symbols.
cc_library(
name = "registerer_alwayslink",
srcs = [":copy_registerer_archive"],
deps = [":registered"],
alwayslink = True,
)

# Test that verifies the symbol was loaded at runtime.
# The test does not directly reference any symbol from registerer,
# so without alwayslink the static constructor would not run.
cc_test(
name = "alwayslink_test",
srcs = ["alwayslink_test.c"],
deps = [
":registered",
":registerer_alwayslink",
],
)
29 changes: 29 additions & 0 deletions tests/alwayslink_srcs/alwayslink_test.c
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@@ -0,0 +1,29 @@
// Copyright 2026 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.

#include <stdio.h>

#include "tests/alwayslink_srcs/registered.h"

int main(void) {
// If alwayslink worked correctly, the registerer library should have been
// linked even though nothing directly references its symbols. The static
// constructor should have called set_registered().
if (!was_registered()) {
fprintf(stderr, "FAILED: alwayslink did not work - static constructor was not executed\n");
return 1;
}
printf("PASSED: alwayslink worked - static constructor was executed\n");
return 0;
}
21 changes: 21 additions & 0 deletions tests/alwayslink_srcs/registered.c
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@@ -0,0 +1,21 @@
// Copyright 2026 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.

#include "tests/alwayslink_srcs/registered.h"

static int g_registered = 0;

int was_registered(void) { return g_registered; }

void set_registered(void) { g_registered = 1; }
24 changes: 24 additions & 0 deletions tests/alwayslink_srcs/registered.h
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// Copyright 2026 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.

#ifndef TESTS_ALWAYSLINK_SRCS_REGISTERED_H_
#define TESTS_ALWAYSLINK_SRCS_REGISTERED_H_

// Returns 1 if the registerer constructor was executed.
int was_registered(void);

// Called by the registerer's constructor.
void set_registered(void);

#endif // TESTS_ALWAYSLINK_SRCS_REGISTERED_H_
20 changes: 20 additions & 0 deletions tests/alwayslink_srcs/registerer.c
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// Copyright 2026 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.

#include "tests/alwayslink_srcs/registered.h"

// Static constructor that registers on load.
__attribute__((constructor)) static void registerer_init(void) {
set_registered();
}