Re: [PATCH v2] rust: respect CARGO_BUILD_TARGET when locating build output

[Junio C Hamano <gitster@pobox.com>]

James Le Cuirot <chewi@gentoo.org> writes:

> 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>
> ---
>
>> Nowhere in the above description I see mention of meson, but the
>> patch is only to cargo-meson that is referenced by src/meson.build
>> which invites a few questions:
>>
>>  * Does "make" work fine without any change similar to this?
>>
>>  * Shouldn't the commit title say "meson" somewhere if this change
>>    is only for "meson" driven build?
>
> Good point. I hadn't realised that Make is still supported. I have now
> amended the Makefile and tested both the native and cross cases.
>
>  Makefile           | 4 ++--
>  src/cargo-meson.sh | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 1cec251..5cd5889 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -940,9 +940,9 @@ TEST_SHELL_PATH = $(SHELL_PATH)
>  LIB_FILE = libgit.a
>
>  ifdef DEBUG
> -RUST_TARGET_DIR = target/debug
> +RUST_TARGET_DIR = target/$(CARGO_BUILD_TARGET)/debug
>  else
> -RUST_TARGET_DIR = target/release
> +RUST_TARGET_DIR = target/$(CARGO_BUILD_TARGET)/release
>  endif

This seems to be based on a bit stale codebase.  Specifically you
would want to build on top of post-924dfced6b (Makefile: support
universal macOS builds via RUST_TARGETS, 2026-07-08) version of
Makefile.

>
>  ifeq ($(uname_S),Windows)
> diff --git a/src/cargo-meson.sh b/src/cargo-meson.sh
> index 75f3cd1..3a558aa 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/${CARGO_BUILD_TARGET-}/$BUILD_TYPE/$LIBNAME" "$BUILD_DIR/libgitcore.a" >/dev/null 2>&1

When CARGO_BUILD_TARGET is not defined, this leaves double slashes
in the resujlting pathname, which may not be incorrect per-se, but
still is not what you meant to say, which is probably a lot closer
to

    ${CARGO_BUILD_TARGET+$CARGO_BUILD_TARGET/}



>  then
> -	cp "$BUILD_DIR/$BUILD_TYPE/$LIBNAME" "$BUILD_DIR/libgitcore.a"
> +	cp "$BUILD_DIR/${CARGO_BUILD_TARGET-}/$BUILD_TYPE/$LIBNAME" "$BUILD_DIR/libgitcore.a"
>  fi
> --
> 2.55.0