support fully static binaries

[mikedanese]

Users should be able to produce fully static binaries from go source, especially exclusively go source.

[pmbethe09]

The current binaries presumably have a shared dependency on libpthread and libc?

I get the same result on linux if I say 'go install github.com/bazelbuild/rules_go/go/tools/gazelle/gazelle as when I
bazel build //go/tools/gazelle/gazelle:gazelle

What is the magic flag to 'go build' to make it fully static?

[mikedanese]

CGO_ENABLED=0 go install github.com/bazelbuild/rules_go/go/tools/gazelle/gazelle

Should produce a static binary.

[powelljo]

I was just looking for how to set this particular variable, and see it's been discussed here already. Has there been any progress made on passing along values of environment variables that Go builds can depend on? I see there is limited support, specifically for GOOS and GOARCH, already in def.bzl.

[GinFungYJF]

Any update about this? If no, are there any workarounds?

[pmbethe09]

@jayconrod may look into this

[jayconrod]

I'm definitely planning to improve this. Cross compilation is a slightly higher priority in the short term though.

[mikedanese]

Also related: #217

Specifically, this would partially solve (although I believe this uses libc rather than the go libc implementation):

go_binary(
    name = "foo",
    srcs = ["foo.go"],
    gc_linkopts = [
        "-linkmode external",
        "-extldflags -static",
    ],
)

[GinFungYJF]

@mikedanese The gc_linkopts attribute seems to has not been implemented.

[mikedanese]

@GinFungYJF It is not implemented in the opensource rules but it does exist in the google internal rules (which are completely different). #217 proposes we implement similar feature in opensource.

[jayconrod]

gc_linkopts has been merged for a little while now. So static builds should work even with cgo present.

go_binary(
    name = "main",
    srcs = ["main.go"],
    go_linkopts = [
      "-extldflags",
      "-static",
    ],
    library = ":cgo_lib",
)

cgo_library(
    name = "cgo_lib",
    srcs = ["cgo_lib.go"],
    cdeps = [":foo"],
)

cc_library(
    name = "foo",
    srcs = ["foo.c"],
)

Couple things to note:

• Linking without cgo is static by default. -linkmode external is not necessary.
• -extldflags must be a separate string from the actual flags, which must all be one string.
• Static linking with cgo does not work on macOS.

@mikedanese, is anything missing? Should anything work differently?

[jayconrod]

I'm closing this because go_linkopts gc_linkopts gives control over static linking, but please re-open if anything more needs to be done.

[mikedanese]

@jayconrod I can't think of anything (other than mac support :) ). Thanks!

[gsf]

The correct attribute is gc_linkopts, not go_linkopts, correct?

[jayconrod]

Yes, gc_linkopts is the correct option.

[achew22]

Are there more flags that need to be passed in to statically link pthread?

My rule looks like this

  go_binary(
      name = "bin",
      library = ":go_default_library",
      gc_linkopts = [
        "-extldflags",
        "-static",
      ],
  )

when I compile it

$ ldd bazel-bin/my/path/bin
        linux-vdso.so.1 =>  (0x00007ffc97130000)
        libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f021b5e6000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f021b21d000)
        /lib64/ld-linux-x86-64.so.2 (0x0000556425e6d000)

Following the dependencies, pthread is coming in from a dependency on sqlite

[mikedanese]

@achew22 does this work for you:

https://github.com/kubernetes/kubernetes/blob/v1.7.0-alpha.4/cmd/kubeadm/BUILD#L11-L22

[achew22]

Woo! That fixed it. Thanks for the help!