Bazel example

Include multiple targets and deps

In this stage we step it up and showcase how to integrate multiple cc_library targets from different packages.

Below, we see a similar configuration from Stage 2, except that this BUILD file is in a subdirectory called lib. In Bazel, subdirectories containing BUILD files are known as packages. The new property visibility will tell Bazel which package(s) can reference this target, in this case the //main package can use hello-time library.

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

To use our hello-time libary, an extra dependency is added in the form of //path/to/package:target_name, in this case, it's //lib:hello-time

cc_binary(
    name = "hello-world",
    srcs = ["hello-world.cc"],
    deps = [
        ":hello-greet",
        "//lib:hello-time",
    ],
)

To build this example you use (notice that 3 slashes are required in windows)

bazel build //main:hello-world

# In Windows, note the three slashes

bazel build ///main:hello-world

This example is referred from bazel document

External dependency and gtest example

In this step we will see how to include external dependency, for example gtest.

Let's write a test test/hello-test.cc for testing get_greet() function.

#include "gtest/gtest.h"
#include "main/hello-greet.h"

TEST(HelloTest, GetGreet) {
    EXPECT_EQ(get_greet("Bazel"), "Hello Bazel");
}

Now lets create test/BUILD

cc_test(
    name = "hello-test",
    srcs = ["hello-test.cc"],
    copts = ["-Iexternal/gtest/include"],
    deps = [
        "@gtest//:gtest-main",
        "//main:hello-greet",
    ]
)

Observe how copts is used to include gtest/include. Bravo but where is gtest-main dependnecy ha? i.e "@gtest//:gtest-main" ?

In WORKSPACE specify external repositiry to use in this project usiing new repository.

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

In external-deps/gtest.BUILD we will define BUILD target for gtest as follow

cc_library(
    name = "gtest-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"],
)

now run

bazel test //test:hello-test

Yaay!!