--- title: C++ 项目构建工具 Bazel 学习笔记 date: 2024-06-30T03:12:15+08:00 draft: false weight: 1 enableToc: true enableBlogBreadcrumb: false tocLevels: ["h2", "h3", "h4"] description: C++ 项目构建工具 Bazel 学习笔记 tags: - C++ - build --- # Bazel 概述 ## Bazel 概念与对象 ![bazel-overview.drawio.svg](bazel-overview.drawio.svg) *[用 Draw.io 打开 bazel-overview.drawio.svg](https://app.diagrams.net/?ui=sketch#Uhttps%3A%2F%2Fblog.mygraphql.com%2Fzh%2Fnotes%2Fcc%2Fbazel%2Fbazel-overview.drawio.svg)* ![bazel-concept.drawio.svg](bazel-concept.drawio.svg) *[用 Draw.io 打开 bazel-concept.drawio.svg](https://app.diagrams.net/?ui=sketch#Uhttps%3A%2F%2Fblog.mygraphql.com%2Fzh%2Fnotes%2Fcc%2Fbazel%2Fbazel-concept.drawio.svg)* ![bazel-external-dep.drawio.svg](bazel-external-dep.drawio.svg) *[用 Draw.io 打开 bazel-external-dep.drawio.svg](https://app.diagrams.net/?ui=sketch#Uhttps%3A%2F%2Fblog.mygraphql.com%2Fzh%2Fnotes%2Fcc%2Fbazel%2Fbazel-external-dep.drawio.svg)* ## CPP use cases ### Adding include paths > https://bazel.build/tutorials/cpp-use-cases#add-include-paths Sometimes you cannot (or do not want to) root include paths at the workspace root. Existing libraries might already have an include directory that doesn't match its path in your workspace. For example, suppose you have the following directory structure: ``` └── my-project ├── legacy │ └── some_lib │ ├── BUILD │ ├── include │ │ └── some_lib.h │ └── some_lib.cc └── WORKSPACE ``` Bazel will expect `some_lib.h` to be included as `legacy/some_lib/include/some_lib.h`, but suppose `some_lib.cc` includes `"some_lib.h"`. To make that include path valid, `legacy/some_lib/BUILD` will need to specify that the `some_lib/include` directory is an include directory: ```python cc_library( name = "some_lib", srcs = ["some_lib.cc"], hdrs = ["include/some_lib.h"], copts = ["-Ilegacy/some_lib/include"], ) ``` This is especially useful for external dependencies, as their header files must otherwise be included with a `/` prefix. ### Include external libraries > https://bazel.build/tutorials/cpp-use-cases#include-external-libraries Suppose you are using [Google Test](https://github.com/google/googletest) {: .external}. You can use one of the repository functions in the `WORKSPACE` file to download Google Test and make it available in your repository: ```python load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive") http_archive( name = "gtest", url = "https://github.com/google/googletest/archive/release-1.10.0.zip", sha256 = "94c634d499558a76fa649edb13721dce6e98fb1e7018dfaeba3cd7a083945e91", build_file = "@//:gtest.BUILD", ) ``` **Note:** If the destination already contains a `BUILD` file, you can leave out the `build_file` attribute. Then create `gtest.BUILD`, a `BUILD` file used to compile Google Test. ```python cc_library( name = "main", srcs = glob( ["googletest-release-1.10.0/googletest/src/*.cc"], exclude = ["googletest-release-1.10.0/googletest/src/gtest-all.cc"] ), hdrs = glob([ "googletest-release-1.10.0/googletest/include/**/*.h", "googletest-release-1.10.0/googletest/src/*.h" ]), copts = [ "-Iexternal/gtest/googletest-release-1.10.0/googletest/include", "-Iexternal/gtest/googletest-release-1.10.0/googletest" ], linkopts = ["-pthread"], visibility = ["//visibility:public"], ) ``` ### Writing and running C++ tests > https://bazel.build/tutorials/cpp-use-cases#run-c-tests For example, you could create a test `./test/hello-test.cc`, such as: ```cpp #include "gtest/gtest.h" #include "main/hello-greet.h" TEST(HelloTest, GetGreet) { EXPECT_EQ(get_greet("Bazel"), "Hello Bazel"); } ``` Then create `./test/BUILD` file for your tests: ```python cc_test( name = "hello-test", srcs = ["hello-test.cc"], copts = [ "-Iexternal/gtest/googletest/include", "-Iexternal/gtest/googletest", ], deps = [ "@gtest//:main", "//main:hello-greet", ], ) ``` To make `hello-greet` visible to `hello-test`, you must add `"//test:__pkg__",` to the `visibility` attribute in `./main/BUILD`. Now you can use `bazel test` to run the test. ``` bazel test test:hello-test ``` This produces the following output: ``` INFO: Found 1 test target... Target //test:hello-test up-to-date: bazel-bin/test/hello-test INFO: Elapsed time: 4.497s, Critical Path: 2.53s //test:hello-test PASSED in 0.3s Executed 1 out of 1 tests: 1 test passes. ``` ## External Dependency ### Directory layout > https://bazel.build/external/overview#directory-layout After being fetched, the repo can be found in the subdirectory `external` in the [output base](https://bazel.build/remote/output-directories), under its canonical name. You can run the following command to see the contents of the repo with the canonical name `canonical_name`: ```sh ls $(bazel info output_base)/external/ canonical_name ``` e.g: ```bash /workspaces/envoy$ bazel info output_base /build/.cache/bazel/_bazel_vscode/2d35de14639eaad1ac7060a4dd7e3351 ``` ## Inspect ### Query > https://bazel.build/query/guide > > https://bazel.build/query/language #### dependency graph > https://bazel.build/tutorials/cpp-dependency ```bash bazel query --notool_deps --noimplicit_deps "deps(//main:hello-world)" \ --output graph ``` Envoy repo as example: ```bash bazel query "deps(//source/exe:envoy)" bazel query --notool_deps "deps(//source/exe:envoy)" --output graph | dot -Tsvg > /tmp/deps.svg ``` #### What packages exist beneath(下面) `//source/` ``` $ bazel query '//source/...' --output package | head Loading: 0 packages loaded source/common/access_log source/common/api source/common/buffer source/common/common source/common/config source/common/conn_pool source/common/crypto source/common/event source/common/filesystem source/common/filter ``` #### What rules are defined in the `//source/exe` package? ``` $ bazel query 'kind(rule, //source/exe:*)' --output label_kind | head Loading: 0 packages loaded alias rule //source/exe:envoy cc_binary rule //source/exe:envoy-static cc_library rule //source/exe:envoy_common_lib cc_library rule //source/exe:envoy_common_lib_with_external_headers cc_library rule //source/exe:envoy_common_with_core_extensions_lib cc_library rule //source/exe:envoy_common_with_core_extensions_lib_with_external_headers cc_library rule //source/exe:envoy_main_common_lib cc_library rule //source/exe:envoy_main_common_lib_with_external_headers cc_library rule //source/exe:envoy_main_common_with_core_extensions_lib cc_library rule //source/exe:envoy_main_common_with_core_extensions_lib_with_external_headers ``` #### What files are generated by rules in the `foo` package? ``` $ bazel query 'kind("generated file", //source/exe:*)' //source/exe:envoy-static.dwp //source/exe:envoy-static.stripped Loading: 0 packages loaded ```