【软件工具】Bazel

1.Introduce

1.1. Features

High-level build language
fast and reliable
multi-platform
large scales and extensible

1.2. workflow

Set up Bazel. Download and install Bazel.
Set up a project workspace, which is a directory where Bazel looks for build inputs and BUILD files, and where it stores build outputs.
Write a BUILD file, which tells Bazel what to build and how to build it.

You write your BUILD file by declaring build targets using Starlark, a domain-specific language. (See example here.)

A build target specifies a set of input artifacts that Bazel will build plus their dependencies, the build rule Bazel will use to build it, and options that configure the build rule.

A build rule specifies the build tools Bazel will use, such as compilers and linkers, and their configurations. Bazel ships with a number of build rules covering the most common artifact types in the supported languages on supported platforms.
Run Bazel from the command line. Bazel places your outputs within the workspace.

1.3. backend workflow

Loads the BUILD files relevant to the target.
Analyzes the inputs and their dependencies, applies the specified build rules, and produces an action graph.
Executes the build actions on the inputs until the final build outputs are produced.

Since all previous build work is cached, Bazel can identify and reuse cached artifacts and only rebuild or retest what’s changed. To further enforce correctness, you can set up Bazel to run builds and tests hermetically through sandboxing, minimizing skew and maximizing reproducibility.

1.4. Download

sudo apt install g++ unzip zip
# Ubuntu 16.04 (LTS) uses OpenJDK 8 by default:
sudo apt-get install openjdk-8-jdk

# Ubuntu 18.04 (LTS) uses OpenJDK 11 by default:
sudo apt-get install openjdk-11-jdk
chmod +x bazel-<version>-installer-linux-x86_64.sh
./bazel-<version>-installer-linux-x86_64.sh --user

export PATH="$PATH:$HOME/bin"

2. Example

2.1. Structure&SingleBuild

the CPP examples structure

examples
└── cpp-tutorial
    ├──stage1
    │  ├── main
    │  │   ├── BUILD
    │  │   └── hello-world.cc
    │  └── WORKSPACE
    ├──stage2
    │  ├── main
    │  │   ├── BUILD
    │  │   ├── hello-world.cc
    │  │   ├── hello-greet.cc
    │  │   └── hello-greet.h
    │  └── WORKSPACE
    └──stage3
       ├── main
       │   ├── BUILD
       │   ├── hello-world.cc
       │   ├── hello-greet.cc
       │   └── hello-greet.h
       ├── lib
       │   ├── BUILD
       │   ├── hello-time.cc
       │   └── hello-time.h
       └── WORKSPACE

workspace: a directory that holds your project’s source files and Bazel’s build outputs. It also contains files that Bazel recognizes as special:
- The WORKSPACE file, which identifies the directory and its contents as a Bazel workspace and lives at the root of the project’s directory structure,
- One or more BUILD files, which tell Bazel how to build different parts of the project. (A directory within the workspace that contains a BUILD file is a package. You will learn about packages later in this tutorial.)
Build File:

cc_binary(
    name = "hello-world",
    srcs = ["hello-world.cc"],
)

**Build Project: **

bazel build //main:hello-world # in the stage1//

Review dependency graph:

bazel query --notool_deps --noimplicit_deps "deps(//main:hello-world)" \
  --output graph

# view the graph locally by installing GraphViz and the xdot Dot Viewer:
sudo apt update && sudo apt install graphviz xdot
# generate and view the graph by piping the text output above straight to xdot:
xdot <(bazel query --notool_deps --noimplicit_deps "deps(//main:hello-world)" \
  --output graph)

【软件工具】Bazel-LMLPHP

2.2. Multi-build

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",
    ],
)

2.3. Multi-Package

Take a look at the lib/BUILD file:

cc_library(
    name = "hello-time",
    srcs = ["hello-time.cc"],
    hdrs = ["hello-time.h"],
    visibility = ["//main:__pkg__"],
)

And at the main/BUILD file:

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:hello-time",
    ],
)

【软件工具】Bazel-LMLPHP

3. Common rules

3.1. including multiple files in a target

cc_library(
    name = "build-all-the-files",
    srcs = glob(["*.cc"]),
    hdrs = glob(["*.h"]),
)

3.2. Using transitive includes

cc_library(
    name = "sandwich",
    srcs = ["sandwich.cc"],
    hdrs = ["sandwich.h"],
    deps = [":bread"],
)
cc_library(
    name = "bread",
    srcs = ["bread.cc"],
    hdrs = ["bread.h"],
    deps = [":flour"],
)
cc_library(
    name = "flour",
    srcs = ["flour.cc"],
    hdrs = ["flour.h"],
)

3.3. Adding including paths

└── my-project
    ├── legacy
    │   └── some_lib
    │       ├── BUILD
    │       ├── include
    │       │   └── some_lib.h
    │       └── some_lib.cc
    └── WORKSPACE

cc_library(
    name = "some_lib",
    srcs = ["some_lib.cc"],
    hdrs = ["include/some_lib.h"],
    copts = ["-Ilegacy/some_lib/include"],
)

3.4. Adding dependencies on precompiled libraries

cc_library(
    name = "mylib",
    srcs = ["mylib.so"],
    hdrs = ["mylib.h"],
)

3.5. including external libraries

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

http_archive(
    name = "gtest",
    url = "https://github.com/google/googletest/archive/release-1.7.0.zip",
    sha256 = "b58cb7547a28b2c718d1e38aee18a3659c9e3ff52440297e965f5edffe34b6d0",
    build_file = "@//:gtest.BUILD",
)

cc_library(
    name = "main",
    srcs = glob(
        ["googletest-release-1.7.0/src/*.cc"],
        exclude = ["googletest-release-1.7.0/src/gtest-all.cc"]
    ),
    hdrs = glob([
        "googletest-release-1.7.0/include/**/*.h",
        "googletest-release-1.7.0/src/*.h"
    ]),
    copts = [
        "-Iexternal/gtest/googletest-release-1.7.0/include",
        "-Iexternal/gtest/googletest-release-1.7.0"
    ],
    linkopts = ["-pthread"],
    visibility = ["//visibility:public"],
)

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

http_archive(
    name = "gtest",
    url = "https://github.com/google/googletest/archive/release-1.7.0.zip",
    sha256 = "b58cb7547a28b2c718d1e38aee18a3659c9e3ff52440297e965f5edffe34b6d0",
    build_file = "@//:gtest.BUILD",
    strip_prefix = "googletest-release-1.7.0",
)

cc_library(
    name = "main",
    srcs = glob(
        ["src/*.cc"],
        exclude = ["src/gtest-all.cc"]
    ),
    hdrs = glob([
        "include/**/*.h",
        "src/*.h"
    ]),
    copts = ["-Iexternal/gtest/include"],
    linkopts = ["-pthread"],
    visibility = ["//visibility:public"],

3.5.1 depending on other bazel projects

local_repository(
    name = "coworkers_project",
    path = "/path/to/coworkers-project",
)

3.5.2.depending on non-bazel projects

new_local_repository(
    name = "coworkers_project",
    path = "/path/to/coworkers-project",
    build_file = "coworker.BUILD",
)

3.6. Shadowing dependencies

workspace(name = "myproject")
local_repository(
    name = "A",
    path = "../A",
)
local_repository(
    name = "B",
    path = "../B",
)

A/WORKSPACE

workspace(name = "A")

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
http_archive(
    name = "testrunner",
    urls = ["https://github.com/testrunner/v1.zip"],
    sha256 = "...",
)

B/WORKSPACE

workspace(name = "B")

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
http_archive(
    name = "testrunner",
    urls = ["https://github.com/testrunner/v2.zip"],
    sha256 = "..."
)

the above confront verson differ problem which can be solved by follows:

workspace(name = "myproject")

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
http_archive(
    name = "testrunner-v1",
    urls = ["https://github.com/testrunner/v1.zip"],
    sha256 = "..."
)
http_archive(
    name = "testrunner-v2",
    urls = ["https://github.com/testrunner/v2.zip"],
    sha256 = "..."
)
local_repository(
    name = "A",
    path = "../A",
    repo_mapping = {"@testrunner" : "@testrunner-v1"}
)
local_repository(
    name = "B",
    path = "../B",
    repo_mapping = {"@testrunner" : "@testrunner-v2"}
)

3.7. Visibility

"//visibility:public": Anyone can use this target. (May not be combined with any other specification.)
"//visibility:private": Only targets in this package can use this target. (May not be combined with any other specification.)
"//foo/bar:__pkg__": Grants access to targets defined in //foo/bar (but not its subpackages). Here, __pkg__ is a special piece of syntax representing all of the targets in a package.
"//foo/bar:__subpackages__": Grants access to targets defined in //foo/bar, or any of its direct or indirect subpackages. Again, __subpackages__ is special syntax.
"//foo/bar:my_package_group": Grants access to all of the packages named by the given package group.
- Package groups do not support the special __pkg__ and __subpackages__ syntax. Within a package group, "//foo/bar" is equivalent to "//foo/bar:__pkg__" and "//foo/bar/..." is equivalent to "//foo/bar:__subpackages__".

learn from: https://docs.bazel.build/versions/master/build-ref.html

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