Re: [PATCH v2 1/2] rust: pick a GCC-compatible Cargo target under MSYS2/MinGW

[James Le Cuirot <chewi@gentoo.org>]

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On Fri, 2026-09-11 at 14:09 -0700, Junio C Hamano wrote:
> "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
> writes:
> 
> > @@ -993,6 +993,7 @@ endif
> >  ifndef DEBUG
> >  CARGO_ARGS += --release
> >  endif
> > +CARGO_ARGS += $(if $(CARGO_TARGET),--target $(CARGO_TARGET))
> 
> Should this use CARGO_BUILD_TARGET (instead of CARGO_TARGET) to
> match what the officially supported Cargo environment variable is
> called?  It would also help us work better with the changes from the
> jc/rust-cargo-build-target topic.
> 
> Thanks.

Yes, without explicitly setting --target at all. This is how Gentoo Linux
supports cross-compiling of its Rust packages. Just avoid setting
CARGO_BUILD_TARGET (or passing --target) when you're not cross-compiling. It
will cause Cargo to behave differently, even if you give the native tuple. For
example, RUSTFLAGS is normally applied to both the build host binaries and the
target host binaries, but when an explicit target is set, RUSTFLAGS is only
applied to the target host binaries.

Regards,
Chewi

> Author: James Le Cuirot <chewi@gentoo.org>
> Date:   Thu Sep 10 11:20:14 2026 +0100
> 
>     rust: respect CARGO_BUILD_TARGET when locating build output
>     
>     When cross-compiling, Cargo always writes to a target-tuple subdirectory
>     determined by CARGO_BUILD_TARGET, even when it matches the native tuple.
>     The build looked in $BUILD_DIR/$BUILD_TYPE directly, so it failed to
>     locate the freshly built library.
>     
>     Respect CARGO_BUILD_TARGET in the output path so the correct artifact
>     is located.
>     
>     Signed-off-by: James Le Cuirot <chewi@gentoo.org>
>     Signed-off-by: Junio C Hamano <gitster@pobox.com>
> 
> diff --git a/Makefile b/Makefile
> index d4b775953d..f0ca2e4f72 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -959,7 +959,7 @@ RUST_LIB_NAME = gitcore.lib
>  else
>  RUST_LIB_NAME = libgitcore.a
>  endif
> -RUST_LIB = target/$(RUST_BUILD_CONFIG)/$(RUST_LIB_NAME)
> +RUST_LIB = target/$(if $(CARGO_BUILD_TARGET),$(CARGO_BUILD_TARGET)/)$(RUST_BUILD_CONFIG)/$(RUST_LIB_NAME)
>  endif
>  
>  GITLIBS = common-main.o $(LIB_FILE)
> diff --git a/src/cargo-meson.sh b/src/cargo-meson.sh
> index 75f3cd1265..83c7e7b79b 100755
> --- a/src/cargo-meson.sh
> +++ b/src/cargo-meson.sh
> @@ -38,7 +38,7 @@ then
>  	exit $RET
>  fi
>  
> -if ! cmp "$BUILD_DIR/$BUILD_TYPE/$LIBNAME" "$BUILD_DIR/libgitcore.a" >/dev/null 2>&1
> +if ! cmp "$BUILD_DIR/${CARGO_BUILD_TARGET:+$CARGO_BUILD_TARGET/}$BUILD_TYPE/$LIBNAME" "$BUILD_DIR/libgitcore.a" >/dev/null 2>&1
>  then
> -	cp "$BUILD_DIR/$BUILD_TYPE/$LIBNAME" "$BUILD_DIR/libgitcore.a"
> +	cp "$BUILD_DIR/${CARGO_BUILD_TARGET:+$CARGO_BUILD_TARGET/}$BUILD_TYPE/$LIBNAME" "$BUILD_DIR/libgitcore.a"
>  fi

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