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1 bazel
baszel 用于构建项目，作用类似于 CMake，但是比 CMake 更快。
示例项目的目录结构：
example
├── lib
│ ├── BUILD
│ ├── print-time.cc
│ └── print-time.h
├── main
│ ├── BUILD
│ ├── hello-greet.cc
│ ├── hello-greet.h
│ └── hello-world.cc
└── WORKSPACE- WORKSPACE 文件标识其所在目录为 bazel 工作空间，它位于项目根目录下，包含第三方依赖，可以为空。
- BUILD 文件告诉 bazel 如何构建 lib、bin 等，它位于每个 package 下。
lib/print-time.h:
#ifndef LIB_PRINT_TIME_H_
#define LIB_PRINT_TIME_H_
void print_localtime();
#endif
lib/print-time.cc:
#include "lib/print-time.h"
#include <ctime>
#include <iostream>
void print_localtime() {
std::time_t result = std::time(nullptr);
std::cout << std::asctime(std::localtime(&result));
}
lib/BUILD 生成 //lib:print-time 库：
load("@rules_cc//cc:defs.bzl", "cc_library")
cc_library(
name = "print-time",
srcs = ["print-time.cc"],
hdrs = ["print-time.h"],
visibility = ["//main:__pkg__"],
)
main/hello-greet.h:
#ifndef MAIN_HELLO_GREET_H_
#define MAIN_HELLO_GREET_H_
#include <string>
std::string get_greet(const std::string &thing);
#endif
main/hello-greet.cc:
#include "main/hello-greet.h"
#include <string>
std::string get_greet(const std::string& who) {
return "Hello " + who;
}
main/hello-world.cc:
#include <iostream>
#include <string>
#include "lib/print-time.h"
#include "main/hello-greet.h"
int main(int argc, char** argv) {
std::string who = "world";
if (argc > 1) {
who = argv[1];
}
std::cout << get_greet(who) << std::endl;
print_localtime();
return 0;
}
main/BUILD;
load("@rules_cc//cc:defs.bzl", "cc_binary", "cc_library")
cc_library(
name = "hello-greet",
srcs = ["hello-greet.cc"],
hdrs = ["hello-greet.h"],
)
cc_binary(
name = "hello-world",
srcs = ["hello-world.cc"],
deps = [
":hello-greet",
"//lib:print-time",
],
)在生成最终的 hello-world 二进制文件时，依赖了 hello-greet 和 //lib:print-time 库。
构建 hello-world:
$ bazel build //main:hello-world会自动构建其依赖的所有库，构建结果位于 bazel-bin 下。
运行生成的 hello-world:
$ ./bazel-bin/main/hello-world
Hello world
Wed May 5 19:31:18 20212 gflags
gflags 用于从命令行解析参数。
修改 WORKSPACE，获取 gflags 包：
workspace(name = "example")
load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
http_archive(
name = "com_github_gflags_gflags",
sha256 = "34af2f15cf7367513b352bdcd2493ab14ce43692d2dcd9dfc499492966c64dcf",
strip_prefix = "gflags-2.2.2",
urls = ["https://github.com/gflags/gflags/archive/v2.2.2.tar.gz"],
)
修改 mian/BUILD，生成 hello-world 时添加 gflags 依赖：
...
cc_binary(
name = "hello-world",
srcs = ["hello-world.cc"],
deps = [
":hello-greet",
"//lib:print-time",
"@com_github_gflags_gflags//:gflags",
],
)修改 main/hello-world.cc，添加 gflags 头文件，并从命令行中解析参数：
#include <iostream>
#include <string>
#include "gflags/gflags.h"
#include "lib/print-time.h"
#include "main/hello-greet.h"
DEFINE_string(name, "nobody", "user's name");
int main(int argc, char** argv) {
google::ParseCommandLineFlags(&argc, &argv, true);
std::cout << get_greet(FLAGS_name) << std::endl;
print_localtime();
return 0;
}
构建并运行：
$ bazel build //main:hello-world
$ ./bazel-bin/main/hello-world --name=Tom
Hello Tom
Wed May 5 20:05:49 20213 glog
glog 用于打印日志。
修改 WORKSPACE，获取 glog 包：
...
http_archive(
name = "com_github_google_glog",
sha256 = "62efeb57ff70db9ea2129a16d0f908941e355d09d6d83c9f7b18557c0a7ab59e",
strip_prefix = "glog-d516278b1cd33cd148e8989aec488b6049a4ca0b",
urls = ["https://github.com/google/glog/archive/d516278b1cd33cd148e8989aec488b6049a4ca0b.zip"],
)
修改 mian/BUILD，生成 hello-world 时添加 glog 依赖：
...
cc_binary(
name = "hello-world",
srcs = ["hello-world.cc"],
deps = [
":hello-greet",
"//lib:print-time",
"@com_github_gflags_gflags//:gflags",
"@com_github_google_glog//:glog",
],
)修改 main/hello-world.cc，添加 glog 头文件，并打印日志：
#include <iostream>
#include <string>
#include "gflags/gflags.h"
#include "glog/logging.h"
#include "lib/print-time.h"
#include "main/hello-greet.h"
DEFINE_string(name, "nobody", "user's name");
int main(int argc, char** argv) {
google::InitGoogleLogging(argv[0]);
google::ParseCommandLineFlags(&argc, &argv, true);
std::cout << get_greet(FLAGS_name) << std::endl;
LOG(ERROR) << FLAGS_name;
print_localtime();
return 0;
}
构建并运行：
$ bazel build //main:hello-world
$ ./bazel-bin/main/hello-world --name=Tom
Hello Tom
E20210506 19:04:58.778676 9023 hello-world.cc:18] Tom
Thu May 6 19:04:58 20214 gtest
gtest 用于单元测试。
修改 WORKSPACE，获取 gtest 包：
...
http_archive(
name = "com_google_googletest",
urls = ["https://github.com/google/googletest/archive/609281088cfefc76f9d0ce82e1ff6c30cc3591e5.zip"],
strip_prefix = "googletest-609281088cfefc76f9d0ce82e1ff6c30cc3591e5",
)编写测试文件 hello-test.cc：
#include "gtest/gtest.h"
// Demonstrate some basic assertions.
TEST(HelloTest, BasicAssertions) {
// Expect two strings not to be equal.
EXPECT_STRNE("hello", "world");
// Expect equality.
EXPECT_EQ(7 * 6, 42);
}
测试：
$ bazel test //main:hello_test
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