platform dependent linker flags in bazel (for glut)

Question

I am trying to build the c++ app with glut using bazel. It should work on both macos and linux. Now the problem is that on macos it requires passing "-framework OpenGL", "-framework GLUT" to linker flags, while on linux I should probably do soemthing like cc_library( name = "glut", srcs = glob(["local/lib/libglut*.dylib", "lib/libglut*.so"]), ... in glut.BUILD. So the question is 1. How to provide platform-dependent linker options to cc_library rules in general? 2. And in particular how to link to glut in platform-independent way using bazel?

Answer 1

You can do this using the Bazel select() function. Something like this might work:

config_setting(
    name = "linux_x86_64",
    values = {"cpu": "k8"},
    visibility = ["//visibility:public"],
)

config_setting(
    name = "darwin_x86_64",
    values = {"cpu": "darwin_x86_64"},
    visibility = ["//visibility:public"],
)

cc_library(
    name = "glut",
    srcs = select({
        ":darwin_x86_64": [],
        ":linux_x86_64": glob(["local/lib/libglut*.dylib", "lib/libglut*.so"]),
    }),
    linkopts = select({
        ":darwin_x86_64": [
            "-framework OpenGL",
             "-framework GLUT"
        ],
        ":linux_x86_64": [],
    })
    ...
)

Dig around in the Bazel github repository, it's got some good real world examples of using select().