How to Invoke objcopy from the Command Line in Bazel Build?

[alugalashravankumar]

Hi all,

I’m trying to figure out how to invoke objcopy as part of a Bazel build from the command line.

For example, for strip we can run something like:
bazel build //examples/example1:example_c.stripped

Similarly, I want to invoke objcopy on the output binary.
Is there a standard or recommended way to achieve this in Bazel?

[trybka]

There isn't an implicit output like there is for .stripped, but you can create a genrule or a custom rule to achieve this.

$(OBJCOPY) is usually defined as a make variable¹ so it can be easily used in genrule commands.

Here's a simple example:

genrule(
    name = "libtestsharedlibrary_no_buildid",
    srcs = ["libtestsharedlibrary.so"],
    outs = ["libtestsharedlibrary_no_buildid.so"],
    cmd = "$(OBJCOPY) --remove-section .note.gnu.build-id $(SRCS) $(OUTS)",  # strip build-id
    toolchains = ["//tools/cpp:toolchain_type"],
)

The availability of objcopy is toolchain dependent.

Footnotes

1. https://bazel.build/reference/be/make-variables#custom_variables ↩