Re: [OE-core] [PATCH v2 2/2] cargo-cross-canadian: Use SDK's flags during target linking

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

On Wed, 2022-07-20 at 15:11 -0300, Otavio Salvador wrote:
> 
> 
> Em qua., 20 de jul. de 2022 às 14:21, Richard Purdie
> <richard.purdie@linuxfoundation.org> escreveu:
> > I've done a bit more work on this and the more I dig, the more I
> > think
> > we have some issues we need to sort with taking a step back and
> > checking some assumptions.
> > 
> > What I'm lacking is a good way to test the resulting rust
> > toolchain.
> > Would someone with some rust knowledge be able to add something to
> > meta/lib/oeqa/sdk/cases/ which tested rust in the SDK?
> > 
> > If someone can add some rust tests in the SDK, I think I might have
> > an
> > idea of what the patches look like to properly fix the rust
> > toolchain
> > there.
> > 
> 
> 
> Ok, I will send you a test case shortly. 

Thanks.

Just to share what I'm thinking, I think we need to add a nativesdk to
llvm-rust like this:

diff --git a/meta/recipes-devtools/rust/rust-llvm.inc b/meta/recipes-devtools/rust/rust-llvm.inc
index 9baad12dc8e..625eb570416 100644
--- a/meta/recipes-devtools/rust/rust-llvm.inc
+++ b/meta/recipes-devtools/rust/rust-llvm.inc
@@ -47,6 +47,13 @@ EXTRA_OECMAKE:append:class-target = "\
     -DLLVM_CONFIG_PATH=${STAGING_LIBDIR_NATIVE}/llvm-rust/bin/llvm-config \
 "
 
+EXTRA_OECMAKE:append:class-nativesdk = "\
+    -DCMAKE_CROSSCOMPILING:BOOL=ON \
+    -DLLVM_BUILD_TOOLS=OFF \
+    -DLLVM_TABLEGEN=${STAGING_LIBDIR_NATIVE}/llvm-rust/bin/llvm-tblgen \
+    -DLLVM_CONFIG_PATH=${STAGING_LIBDIR_NATIVE}/llvm-rust/bin/llvm-config \
+"
+
 # The debug symbols are huge here (>2GB) so suppress them since they
 # provide almost no value. If you really need them then override this
 INHIBIT_PACKAGE_DEBUG_SPLIT = "1"
@@ -68,4 +75,4 @@ FILES:${PN}-staticdev =+ "${libdir}/llvm-rust/*/*.a"
 FILES:${PN} += "${libdir}/libLLVM*.so.* ${libdir}/llvm-rust/lib/*.so.* ${libdir}/llvm-rust/bin"
 FILES:${PN}-dev += "${datadir}/llvm ${libdir}/llvm-rust/lib/*.so ${libdir}/llvm-rust/include ${libdir}/llvm-rust/share ${libdir}/llvm-rust/lib/cmake"
 
-BBCLASSEXTEND = "native"
+BBCLASSEXTEND = "native nativesdk"

and then I think rust-cross-canadian can either copy in or create a
json file just like rust-cross does. Unlike gcc there is no target
specific cross compiler for rust as far as I can tell.

The crosssdk recipe also looks a bit suspect and I'm not sure that
entirely makes sense now or is needed. I guess it might be if we had
rust applications we needed to compile for the sdk itself but we don't
have any of those yet?

Cheers,

Richard