Document how to bring non-source tree absolute paths into your workspace.

[sertel]

Bugs: what's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

I'm trying to configure a simple C++ project with the following BUILD:

cc_binary(
    name = "my-llvm-project",
    srcs = glob(["*.cc"]),
    copts = ["-I/usr/inlcude/llvm-6.0/include"],
)

The error is:

The include path '/usr/inlcude/llvm-6.0/include' references a path outside of the execution root.

I also tried to use includes instead:

cc_binary(
    name = "my-llvm-project",
    srcs = glob(["*.cc"]),
    includes = ["/usr/inlcude/llvm-6.0/include"],
)

Bazel says:

in includes attribute of cc_binary rule //main:my-llvm-project: ignoring invalid absolute path '/usr/inlcude/llvm-6.0/include'

Even if I declare llvm as a library:

cc_library(
    name = "llvm-dep",
    hdrs = glob(["/usr/include/llvm-6.0/include/*.h",
    "/usr/include/llvm-6.0/include/**/*.h"]),
)

cc_binary(
    name = "my-llvm-project",
    srcs = glob(["*.cc"]),
    deps = ["llvm-dep"]
)

I get the following error message:

pattern cannot be absolute

If there is a preferred way of doing this in bazel then it should be in the docs.

What operating system are you running Bazel on?

Ubuntu LTS 18.04 (bionic) on the following kernel: Linux 4.4.0-17763-Microsoft (WSL)

What's the output of bazel info release?

release 0.27.1

If bazel info release returns "development version" or "(@non-git)", tell us how you built Bazel.

I used the binary installer as described here: https://docs.bazel.build/versions/master/install-ubuntu.html#install-with-installer-ubuntu

Have you found anything relevant by searching the web?

This issue might be related: https://github.com/bazelbuild/bazel/issues/3239

[sertel]

I finally found this post: https://groups.google.com/forum/#!searchin/bazel-discuss/cc_library$20includes%7Csort:date/bazel-discuss/lsbxZxNjJQw/NKb7f_eJBwAJ It suggests to set up a local repository:

WORKSPACE:

new_local_repository(
    name = "llvm",
    path = "/usr/lib/llvm-6.0/include",
    build_file_content = """
package(default_visibility = ["//visibility:public"])
cc_library(
    name = "headers",
    hdrs = glob(["**/*.h"])
)
"""
)

BUILD:

package(default_visibility = ["//visibility:public"])

cc_binary(
    name = "my-llvm-project",
    srcs = glob(["*.cc"]),
    copts = ["-Iexternal/llvm"],
    deps = ["@llvm//:headers"]
)

I leave the issue open nevertheless because it would really be great to find this trivial use case on the documentation website. It would have been a great help for me.

[aiuto]

I changed the title to highlight that this is really a knowledge transfer problem. PTAL.

[brianjenkins94]

Is creating a repository the generally accepted solution? Feels like there's still a documentation gap -- if not a knowledge gap here.

[github-actions[bot]]

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[hzeller]

Is there a documentation in the meantime ? It would be good if bazel would emit an actionable error message, i.e. have a link to an explanation and how to fix or work-around.

The more people start using systems that expose includes in content-hash-derived paths (such as NixOS), being able to direct bazel to accept system headers in in paths outside its sandboxed comfort-zone is important.