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

[Patrick Steinhardt <ps@pks.im>]

On Mon, Oct 27, 2025 at 12:44:00AM +0000, brian m. carlson wrote:
> diff --git a/Makefile b/Makefile
> index 7e5a735ca6..7c36302717 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -2948,7 +2948,7 @@ scalar$X: scalar.o GIT-LDFLAGS $(GITLIBS)
>  $(LIB_FILE): $(LIB_OBJS)
>  	$(QUIET_AR)$(RM) $@ && $(AR) $(ARFLAGS) $@ $^
>  
> -$(RUST_LIB): Cargo.toml $(RUST_SOURCES)
> +$(RUST_LIB): Cargo.toml $(RUST_SOURCES) $(XDIFF_LIB) $(LIB_FILE) $(REFTABLE_LIB)
>  	$(QUIET_CARGO)cargo build $(CARGO_ARGS)

We have recently removed the separare xdiff and reftable libraries, so
it shouldn't be necessary to have these anymore.

But one thing I'm curious about: don't we have a circular dependency
between the Rust and C library now? I guess that's somewhat expected, as
we'll want to call Rust from C and vice versa. But on the Meson side I
think we need to adjust our logic so that we don't pull the Rust library
into libgit.a to break this cycle.

> diff --git a/build.rs b/build.rs
> new file mode 100644
> index 0000000000..136d58c35a
> --- /dev/null
> +++ b/build.rs
> @@ -0,0 +1,21 @@
> +// This program is free software; you can redistribute it and/or modify
> +// it under the terms of the GNU General Public License as published by
> +// the Free Software Foundation: version 2 of the License, dated June 1991.
> +//
> +// This program is distributed in the hope that it will be useful,
> +// but WITHOUT ANY WARRANTY; without even the implied warranty of
> +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +// GNU General Public License for more details.
> +//
> +// You should have received a copy of the GNU General Public License along
> +// with this program; if not, see <https://www.gnu.org/licenses/>.
> +
> +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");
> +}

How do we ensure that the correct libraries are linked here? E.g. for
libz, if there are multiple such libraries, which one gets precedence?

Patrick