tree 0d0378b483a8586f688a5c35ca72fe414d4e2368
parent 4a164c8f55619e2bf79f9f62c86b8e4448c931d4
author David 'Digit' Turner <digit@google.com> 1605872700 +0100
committer Commit Bot <commit-bot@chromium.org> 1605905736 +0000

[rust] Fix command arguments for non-rust native dependencies.

The ninja Rust binary target writer did the following to generate
the command arguments set to 'rustc' for non-rust native library
dependencies (e.g. any native object file or shared library):

  1- Collect the ordered set of each dependency's directory,
     then write it as a series of `-Lnative=<dir>` arguments.

  2- For any dependency whose name begins with 'lib', write it
     as `-l<name>`, where <name> is the dependency's file name
     without a "lib" prefix and without a file extension.

  2- For non-"lib" dependencies, just use `-Clink-arg=<path>`
     instead.

However, while working on the Fuchsia build system, I found that rules 1
and 2 are both problematic:

  - Rule 1 means there is a possibility of linking the wrong library
    in the final binary. E.g. consider a dependency list like:

        dir1/libfoo.so
        dir2/libbar.so

    This gets translated into:

        -Lnative=dir1 -Lnative=dir2 -lfoo -lbar

    And if dir1/libbar.so happens to exist, it will be wrongly selected
    by the linker.

  - Rule 2 assumes the file extension is something like ".so", ".dylib"
    or ".a" , i.e. something the linker will look for automatically,
    however, in the Fuchsia build, we have to link against files named
    "libc.so.debug" and "libzircon.so.debug" (where the ".debug" prefix
    means these are the unstripped versions of the libraries). This
    ends up translated into:

      -Lnative=<dir2> -Lnative=<dir1> -lc.so -lzircon.so

    And the linker will look for libc.so.so and libzircon.so.so instead
    of the real files (and of course print an error message). Our
    current work-around is to create link scripts with this name that
    redirect to the real file, but this is ugly.

This CL simply fixes the issue by using `-Clink-arg=<path>` in all
cases. The `-Lnative=<dir>` arguments are still required to make
`#[link(...)]` directives work correctly.

Bug: 217
Change-Id: I5f7210300eea0effe3ed99b4f6aff5f07fb05518
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/10721
Commit-Queue: David Turner <digit@google.com>
Reviewed-by: Petr Hosek <phosek@google.com>
Reviewed-by: Brett Wilson <brettw@chromium.org>