Re: [OE-core] [PATCH] rust: Use llvm-config from native llvm-rust on rust target builds

[Richard Purdie <richard.purdie@linuxfoundation.org>]

On Sat, 2024-01-13 at 21:58 -0800, Khem Raj wrote:
> target rust recipe builds ( cross compile ) calls llvm-config from
> target sysroot which works ok as long as C++ runtime it needs is
> available on build host e.g. libstdc++ etc. which is commonly the
> case, however when using clang and llvm runtime this falters since
> it should be using libc++ from native sysroot and if this does not
> exist on build machine this fails to find libc++ shared object and
> llvm-config fails to run. This ensures that llvm-config version in
> use is correctly relocated and can use shared libraries from native
> sysroot correctly. Adding ORIGIN to sysroot will look for the .so in
> same dir as the binary and there is the libc++.so.1 copied in place
> 
> Fixes rust build with clang compiler.
> 
> > /mnt/b/yoe/master/build/tmp/work/riscv64-yoe-linux/rust/1.74.1/recipe-sysroot/usr/lib/llvm-rust/bin/llvm-config: error while loading shared libraries: libc++.so.1: cannot open shared object file: No such file or director
> y
> > thread 'main' panicked at llvm.rs:551:19:
> > command did not execute successfully: "/mnt/b/yoe/master/build/tmp/work/riscv64-yoe-linux/rust/1.74.1/recipe-sysroot/usr/lib/llvm-rust/bin/llvm-config" "--version"
> > expected success, got: exit status: 127
> 
> Signed-off-by: Khem Raj <raj.khem@gmail.com>
> ---
>  meta/recipes-devtools/rust/rust_1.74.1.bb | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/meta/recipes-devtools/rust/rust_1.74.1.bb b/meta/recipes-devtools/rust/rust_1.74.1.bb
> index 30543ada7db..2dffe009827 100644
> --- a/meta/recipes-devtools/rust/rust_1.74.1.bb
> +++ b/meta/recipes-devtools/rust/rust_1.74.1.bb
> @@ -198,9 +198,13 @@ rust_runx () {
>      # Copy the natively built llvm-config into the target so we can run it. Horrible,
>      # but works!
>      if [ ${RUST_ALTERNATE_EXE_PATH_NATIVE} != ${RUST_ALTERNATE_EXE_PATH} -a ! -f ${RUST_ALTERNATE_EXE_PATH} ]; then
> -        mkdir -p `dirname ${RUST_ALTERNATE_EXE_PATH}`
> +        tgtdir=`dirname ${RUST_ALTERNATE_EXE_PATH}`
> +        mkdir -p ${tgtdir}
>          cp ${RUST_ALTERNATE_EXE_PATH_NATIVE} ${RUST_ALTERNATE_EXE_PATH}
> -        chrpath -d ${RUST_ALTERNATE_EXE_PATH}
> +        if [ -e ${STAGING_LIBDIR_NATIVE}/libc++.so.1 ]; then
> +            cp ${STAGING_LIBDIR_NATIVE}/libc++.so.1 ${tgtdir}/
> +        fi
> +        chrpath -r \$ORIGIN ${RUST_ALTERNATE_EXE_PATH}
>      fi
>  
>      oe_cargo_fix_env

Copying a native library into the target sysroot goes beyond what I'm
comfortable with even for this horrible hack with llvm-config.

Since it seems to be finding it by RPATH, can you not just add an RPATH
to the native sysroot in the binary?

Cheers,

Richard