Re: [PATCH 10/14] rust: add a build.rs script for tests

From: Ezekiel Newren <ezekielnewren@gmail.com>
Date: Oct 29, 2025, 22:10 UTC
Message-ID: <CAH=ZcbBYRiceXQ-9FNq0aK0WzN4nDhqonaoafweStC37mx7JBA@mail.gmail.com>
In-Reply-To: <xmqqms59acak.fsf@gitster.g>

On Wed, Oct 29, 2025 at 10:43 AM Junio C Hamano <gitster@pobox.com> wrote:

Show 30 quoted lines

>
> "brian m. carlson" <sandals@crustytoothpaste.net> writes:
>
> > Cargo uses the build.rs script to determine how to compile and link a
> > binary.  The only binary we're generating, however, is for our tests,
> > but in a future commit, we're going to link against libgit.a for some
> > functionality and we'll need to make sure the test binaries are
> > complete.
>
> OK.
>
> > -$(RUST_LIB): Cargo.toml $(RUST_SOURCES)
> > +$(RUST_LIB): Cargo.toml $(RUST_SOURCES) $(XDIFF_LIB) $(LIB_FILE) $(REFTABLE_LIB)
> >       $(QUIET_CARGO)cargo build $(CARGO_ARGS)
> > ...
> > +fn main() {
> > +    println!("cargo::rustc-link-search=.");
> > +    println!("cargo::rustc-link-search=reftable");
> > +    println!("cargo::rustc-link-search=xdiff");
> > +    println!("cargo::rustc-link-lib=git");
> > +    println!("cargo::rustc-link-lib=reftable");
> > +    println!("cargo::rustc-link-lib=z");
> > +    println!("cargo::rustc-link-lib=xdiff");
> > +}
>
> Hmm, I recall Ezekiel earlier arguing to roll reftable and xdiff
> libraries into libgit.a as it is a lot more cumbersome to have to
> link with multiple libraries (sorry, I may be misremembering and do
> not have reference handy), but if the above is all it takes to link
> with these, perhaps it is not such a huge deal?

I think Brian might have written this before my series was merged in.

> I am a bit confused.
>
> XDIFF_LIB and REFTABLE_LIB are gone from Makefile on 'master'
> already.  Perhaps we should revert earlier series from him?

I don't think we should revert my series. Brian should delete certain lines like so:

 fn main() {
     println!("cargo::rustc-link-search=.");
-    println!("cargo::rustc-link-search=reftable");
-    println!("cargo::rustc-link-search=xdiff");
     println!("cargo::rustc-link-lib=git");
-    println!("cargo::rustc-link-lib=reftable");
     println!("cargo::rustc-link-lib=z");
-    println!("cargo::rustc-link-lib=xdiff");
 }

Also the makefile needs to add the flag -fPIC or -fPIE when compiling with Rust.