bazel 测试过程

google的bazel如日中天，尽管我觉得make已经很好用，但是还是尝试一下，记录之。

首先，从 https://github.com/bazelbuild/bazel/releases 下载对应的bazel 文件，
我下载的版本是：0.5.2
三个文件：
200 MBbazel-0.5.2-installer-linux-x86_64.sh
104 Bytesbazel-0.5.2-installer-linux-x86_64.sh.sha256
543 Bytesbazel-0.5.2-installer-linux-x86_64.sh.sig

安装：
[root@centos7 tensorflow_test]# chmod +x bazel-0.5.2-installer-linux-x86_64.sh
[root@centos7 tensorflow_test]# ./bazel-0.5.2-installer-linux-x86_64.sh

看到如下打印，安装相当快。
Bazel is now installed!

Make sure you have "/usr/local/bin" in your path. You can also activate bash
completion by adding the following line to your ~/.bashrc:
source /usr/local/lib/bazel/bin/bazel-complete.bash

See http://bazel.build/docs/getting-started.html to start a new project!

下一步，参考help文件：
https://docs.bazel.build/versions/master/tutorial/cpp.html

下载examples文件：
[root@centos7 examples-master]# ls
AUTHORS CONTRIBUTING.md CONTRIBUTORS cpp-tutorial java-maven java-tutorial LICENSE.txt README.md rules tutorial

进入路径：
[root@centos7 stage1]# pwd
/home/caq/code/bazelbuild/examples-master/cpp-tutorial/stage1

编译，看起来也不快，与期望值不相符合啊：
[root@centos7 stage1]# bazel build //main:hello-world
WARNING: ignoring http_proxy in environment.
..................................................................................................................
INFO: Found 1 target...
Target //main:hello-world up-to-date:
bazel-bin/main/hello-world
INFO: Elapsed time: 14.059s, Critical Path: 0.84s

执行：
[root@centos7 stage1]# ./bazel-bin/main/hello-world
Hello world

分析依赖图：
bazel query --nohost_deps --noimplicit_deps 'deps(//main:hello-world)' \
--output graph

WARNING: ignoring http_proxy in environment.
digraph mygraph {
node [shape=box];
"//main:hello-world"
"//main:hello-world" -> "//main:hello-world.cc" 这个说明只依赖于.cc文件
"//main:hello-world.cc"
}

好，进一步的，增加依赖，进入starge2
[root@centos7 main]# pwd
/home/caq/code/bazelbuild/examples-master/cpp-tutorial/stage2/main

[root@centos7 main]# bazel build //main:hello-world
WARNING: ignoring http_proxy in environment.
..................................................................................................................
INFO: Found 1 target...
Target //main:hello-world up-to-date:
bazel-bin/main/hello-world
INFO: Elapsed time: 13.470s, Critical Path: 0.35s

执行bin文件测试：
[root@centos7 stage2]# ./bazel-bin/main/hello-world
Thu Jul 27 19:49:41 2017

发现源文件少了一行代码，补上之后结果：
[root@centos7 stage2]# bazel-bin/main/hello-world
Hello world
Thu Jul 27 19:56:21 2017
[root@centos7 stage2]# bazel-bin/main/hello-world hahaha
Hello hahaha
Thu Jul 27 19:56:25 2017
[root@centos7 stage2]# bazel-bin/main/hello-world caq
Hello caq
Thu Jul 27 19:56:29 2017

那么，多个依赖怎么写？

[root@centos7 stage3]# pwd
/home/caq/code/bazelbuild/examples-master/cpp-tutorial/stage3
[root@centos7 stage3]# bazel build //main:hello-world
WARNING: ignoring http_proxy in environment.
..................................................................................................................
INFO: Found 1 target...
Target //main:hello-world up-to-date:
bazel-bin/main/hello-world
INFO: Elapsed time: 13.557s, Critical Path: 0.35s

[root@centos7 stage3]# bazel-bin/main/hello-world
Hello world
Thu Jul 27 19:59:20 2017
[root@centos7 stage3]# bazel-bin/main/hello-world caq
Hello caq
Thu Jul 27 19:59:23 2017

如果有疑问，可以直接从https://docs.bazel.build/versions/master/tutorial/cpp.html找到答案。
完毕。