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Last active April 13, 2020 11:37
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Basics of generating a compile_commands.json file with Bazel
py_binary(
name = 'generate_compile_command',
srcs = [
'generate_compile_command.py',
],
deps = [
'//third_party/bazel:extra_actions_proto_py',
],
)
action_listener(
name = 'generate_compile_commands_listener',
visibility = ['//visibility:public'],
mnemonics = [
'CppCompile',
],
extra_actions = [':generate_compile_commands_action'],
)
extra_action(
name = 'generate_compile_commands_action',
tools = [
':generate_compile_command',
],
out_templates = [
'$(ACTION_ID)_compile_command',
],
cmd = '$(location :generate_compile_command) $(EXTRA_ACTION_FILE)' +
' $(output $(ACTION_ID)_compile_command)',
)
// Copyright 2014 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.
//
// proto definitions for the blaze extra_action feature.
syntax = "proto2";
package blaze;
option java_multiple_files = true;
option java_package = "com.google.devtools.build.lib.actions.extra";
// option cc_api_version = 2;
// option java_api_version = 2;
// A list of extra actions and metadata for the print_action command.
message ExtraActionSummary {
repeated DetailedExtraActionInfo action = 1;
}
// An individual action printed by the print_action command.
message DetailedExtraActionInfo {
// If the given action was included in the output due to a request for a
// specific file, then this field contains the name of that file so that the
// caller can correctly associate the extra action with that file.
//
// The data in this message is currently not sufficient to run the action on a
// production machine, because not all necessary input files are identified,
// especially for C++.
//
// There is no easy way to fix this; we could require that all header files
// are declared and then add all of them here (which would be a huge superset
// of the files that are actually required), or we could run the include
// scanner and add those files here.
optional string triggering_file = 1;
// The actual action.
required ExtraActionInfo action = 2;
}
// Provides information to an extra_action on the original action it is
// shadowing.
message ExtraActionInfo {
extensions 1000 to max;
// The label of the ActionOwner of the shadowed action.
optional string owner = 1;
// Only set if the owner is an Aspect.
// Corresponds to AspectValue.AspectKey.getAspectClass.getName()
// This field is deprecated as there might now be
// multiple aspects applied to the same target.
// This is the aspect name of the last aspect
// in 'aspects' (8) field.
optional string aspect_name = 6 [deprecated = true];
// Only set if the owner is an Aspect.
// Corresponds to AspectValue.AspectKey.getParameters()
// This field is deprecated as there might now be
// multiple aspects applied to the same target.
// These are the aspect parameters of the last aspect
// in 'aspects' (8) field.
map<string, StringList> aspect_parameters = 7 [deprecated = true];
message StringList {
option deprecated = true;
repeated string value = 1;
}
message AspectDescriptor {
// Corresponds to AspectDescriptor.getName()
optional string aspect_name = 1;
// Corresponds to AspectDescriptor.getParameters()
map<string, StringList> aspect_parameters = 2;
message StringList {
repeated string value = 1;
}
}
// If the owner is an aspect, all aspects applied to the target
repeated AspectDescriptor aspects = 8;
// An id uniquely describing the shadowed action at the ActionOwner level.
optional string id = 2;
// The mnemonic of the shadowed action. Used to distinguish actions with the
// same ActionType.
optional string mnemonic = 5;
}
message EnvironmentVariable {
// It is possible that this name is not a valid variable identifier.
required string name = 1;
// The value is unescaped and unquoted.
required string value = 2;
}
// Provides access to data that is specific to spawn actions.
// Usually provided by actions using the "Spawn" & "Genrule" Mnemonics.
message SpawnInfo {
extend ExtraActionInfo {
optional SpawnInfo spawn_info = 1003;
}
repeated string argument = 1;
// A list of environment variables and their values. No order is enforced.
repeated EnvironmentVariable variable = 2;
repeated string input_file = 4;
repeated string output_file = 5;
}
// Provides access to data that is specific to C++ compile actions.
// Usually provided by actions using the "CppCompile" Mnemonic.
message CppCompileInfo {
extend ExtraActionInfo {
optional CppCompileInfo cpp_compile_info = 1001;
}
optional string tool = 1;
repeated string compiler_option = 2;
optional string source_file = 3;
optional string output_file = 4;
// Due to header discovery, this won't include headers unless the build is
// actually performed. If set, this field will include the value of
// "source_file" in addition to the headers.
repeated string sources_and_headers = 5;
// A list of environment variables and their values. No order is enforced.
repeated EnvironmentVariable variable = 6;
}
// Provides access to data that is specific to C++ link actions.
// Usually provided by actions using the "CppLink" Mnemonic.
message CppLinkInfo {
extend ExtraActionInfo {
optional CppLinkInfo cpp_link_info = 1002;
}
repeated string input_file = 1;
optional string output_file = 2;
optional string interface_output_file = 3;
optional string link_target_type = 4;
optional string link_staticness = 5;
repeated string link_stamp = 6;
repeated string build_info_header_artifact = 7;
// The list of command line options used for running the linking tool.
repeated string link_opt = 8;
}
// Provides access to data that is specific to java compile actions.
// Usually provided by actions using the "Javac" Mnemonic.
message JavaCompileInfo {
extend ExtraActionInfo {
optional JavaCompileInfo java_compile_info = 1000;
}
optional string outputjar = 1;
repeated string classpath = 2;
repeated string sourcepath = 3;
repeated string source_file = 4;
repeated string javac_opt = 5;
repeated string processor = 6;
repeated string processorpath = 7;
repeated string bootclasspath = 8;
repeated string argument = 9;
}
// Provides access to data that is specific to python rules.
// Usually provided by actions using the "Python" Mnemonic.
message PythonInfo {
extend ExtraActionInfo {
optional PythonInfo python_info = 1005;
}
repeated string source_file = 1;
repeated string dep_file = 2;
}
# This is the implementation of a Bazel extra_action which genenerates
# _compile_command files for generate_compile_commands.py to consume.
import sys
import third_party.bazel.protos.extra_actions_base_pb2 as extra_actions_base_pb2
def _get_cpp_command(cpp_compile_info):
compiler = cpp_compile_info.tool
options = ' '.join(cpp_compile_info.compiler_option)
source = cpp_compile_info.source_file
output = cpp_compile_info.output_file
return '%s %s -c %s -o %s' % (compiler, options, source, output), source
def main(argv):
action = extra_actions_base_pb2.ExtraActionInfo()
with open(argv[1], 'rb') as f:
action.MergeFromString(f.read())
command, source_file = _get_cpp_command(
action.Extensions[extra_actions_base_pb2.CppCompileInfo.cpp_compile_info])
with open(argv[2], 'w') as f:
f.write(command)
f.write('\0')
f.write(source_file)
if __name__ == '__main__':
sys.exit(main(sys.argv))
#!/usr/bin/python3
# This reads the _compile_command files :generate_compile_commands_action
# generates a outputs a compile_commands.json file at the top of the source
# tree for things like clang-tidy to read.
# Overall usage directions: run bazel with
# --experimental_action_listener=//tools/actions:generate_compile_commands_listener
# for all the files you want to use clang-tidy with and then run this script.
# Afer that, `clang-tidy build_tests/gflags.cc` should work.
import sys
import pathlib
import os.path
import subprocess
'''
Args:
path: The pathlib.Path to _compile_command file.
command_directory: The directory commands are run from.
Returns a string to stick in compile_commands.json.
'''
def _get_command(path, command_directory):
with path.open('r') as f:
contents = f.read().split('\0')
if len(contents) != 2:
# Old/incomplete file or something; silently ignore it.
return None
return '''{
"directory": "%s",
"command": "%s",
"file": "%s",
},''' % (command_directory, contents[0].replace('"', '\\"'), contents[1])
'''
Args:
path: A directory pathlib.Path to look for _compile_command files under.
command_directory: The directory commands are run from.
Yields strings to stick in compile_commands.json.
'''
def _get_compile_commands(path, command_directory):
for f in path.iterdir():
if f.is_dir():
yield from _get_compile_commands(f, command_directory)
elif f.name.endswith('_compile_command'):
command = _get_command(f, command_directory)
if command:
yield command
def main(argv):
source_path = os.path.join(os.path.dirname(__file__), '../..')
action_outs = os.path.join(source_path,
'bazel-bin/../extra_actions',
'tools/actions/generate_compile_commands_action')
command_directory = subprocess.check_output(
('bazel', 'info', 'execution_root'),
cwd=source_path).decode('utf-8').rstrip()
commands = _get_compile_commands(pathlib.Path(action_outs), command_directory)
with open(os.path.join(source_path, 'compile_commands.json'), 'w') as f:
f.write('[')
for command in commands:
f.write(command)
f.write(']')
if __name__ == '__main__':
sys.exit(main(sys.argv))
@deyuhua
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deyuhua commented Apr 13, 2020

I had quite some trouble to understand where which file goes and what to do with them, so here is how I got it to work: (under Linux / Arch)
(and see the file-tree at the bottom to make it clearer where which file goes)

in your WORKSPACE root, create /tools/actions folder(s)
create all files from above in there.

download / create the file from (github bazel source) bazel/src/main/protobuf/extra_actions_base.proto (anywhere really, we don't need the proto file afterwards)
and run protoc extra_actions_base.proto --python_out=.
(you need to have protocol buffers installed on your system)

create a new folder (relative to thoe WORKSPACE root) /third_party/bazel/protos and move the Python file we just generated (extra_actions_base_pb2.py) there.
in /third_party/bazel (not /protos) we now create a BUILD file with the following content:

licenses(["notice"])

py_library(
name = "extra_actions_proto_py",
srcs = ["protos/extra_actions_base_pb2.py"],
visibility = ["//visibility:public"],
)

now make sure your python has google.protobuf installed ( [sudo] pip install protobuf )

now if you run the bazel build command, i.e.
bazel build --experimental_action_listener=//tools/actions:generate_compile_commands_listener main:hello-world
it should work, i.e. not throw any errors.

Then do (from WORKSPACE root) cd tools/actions and from this folder you run the _json script:
python generate_compile_commands_json.py

Now there should be a compile_commands.json in your WORKSPACE root folder. Congratulations, it worked! :)

Below a file tree to make it easier to see where all the files are. The project is just the bazel C++ tutorial.

.
├── compile_commands.json
├── extra_actions_base.proto <- This can be anywhere and can be deleted as soon as we have the .py file
├── gtest.BUILD
├── lib
│ ├── BUILD
│ ├── hello-greet.cc
│ └── hello-greet.h
├── main
│ ├── BUILD
│ ├── hello-time.cc
│ ├── hello-time.h
│ ├── hello-world.cc
├── test
│ ├── BUILD
│ └── hello-test.cc
├── third_party
│ └── bazel
│ ├── BUILD
│ └── protos
│ └── extra_actions_base_pb2.py
├── tools
│ └── actions
│ ├── BUILD
│ ├── generate_compile_command.py
│ └── generate_compile_commands_json.py
└── WORKSPACE

Hope it helps someone ¯(ツ)/¯

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