run-make-fulldeps/c-link-to-rust-va-list-fn fails on aarch64-linux-gnu

[parched]

Running python2.7 ./x.py test --stage 2 on aarch64-linux-gnu I end up with the following failure

---- [run-make] run-make-fulldeps/c-link-to-rust-va-list-fn stdou
t ----                                                           
                                                                 
error: make failed                                               
status: exit code: 2                                             
command: "make"                                                  
stdout:                                                          
------------------------------------------                       
LD_LIBRARY_PATH="/usr/src/myapp/build/aarch64-unknown-linux-gnu/t
est/run-make-fulldeps/c-link-to-rust-va-list-fn/c-link-to-rust-va
-list-fn:/usr/src/myapp/build/aarch64-unknown-linux-gnu/stage2/li
b:/usr/src/myapp/build/aarch64-unknown-linux-gnu/stage0-bootstrap
-tools/aarch64-unknown-linux-gnu/release/deps:/usr/src/myapp/buil
d/aarch64-unknown-linux-gnu/stage0/lib:" '/usr/src/myapp/build/aa
rch64-unknown-linux-gnu/stage2/bin/rustc' --out-dir /usr/src/myap
p/build/aarch64-unknown-linux-gnu/test/run-make-fulldeps/c-link-t
o-rust-va-list-fn/c-link-to-rust-va-list-fn -L /usr/src/myapp/bui
ld/aarch64-unknown-linux-gnu/test/run-make-fulldeps/c-link-to-rus
t-va-list-fn/c-link-to-rust-va-list-fn  checkrust.rs             
cc -ffunction-sections -fdata-sections -fPIC test.c /usr/src/myap
p/build/aarch64-unknown-linux-gnu/test/run-make-fulldeps/c-link-t
o-rust-va-list-fn/c-link-to-rust-va-list-fn/libcheckrust.a -o /us
r/src/myapp/build/aarch64-unknown-linux-gnu/test/run-make-fulldep
s/c-link-to-rust-va-list-fn/c-link-to-rust-va-list-fn/test -lm -l
rt -ldl -lpthread 
LD_LIBRARY_PATH="/usr/src/myapp/build/aarch64-unknown-linux-gnu/t
est/run-make-fulldeps/c-link-to-rust-va-list-fn/c-link-to-rust-va
-list-fn:/usr/src/myapp/build/aarch64-unknown-linux-gnu/stage2/li
b/rustlib/aarch64-unknown-linux-gnu/lib:/usr/src/myapp/build/aarc
h64-unknown-linux-gnu/stage0-bootstrap-tools/aarch64-unknown-linu
x-gnu/release/deps:/usr/src/myapp/build/aarch64-unknown-linux-gnu
/stage0/lib:" /usr/src/myapp/build/aarch64-unknown-linux-gnu/test
/run-make-fulldeps/c-link-to-rust-va-list-fn/c-link-to-rust-va-li
st-fn/test                                                       
Makefile:4: recipe for target 'all' failed                       
                                                                 
------------------------------------------                       
stderr:                                                          
------------------------------------------                       
test: test.c:32: main: Assertion `test_rust(check_list_0, 0x01LL,
 0x02, 0x03LL) == 0' failed.                                     
Aborted (core dumped)                                            
make: *** [all] Error 134                                        
                                                                 
------------------------------------------

I was building this commit 9cd3bef

I haven't had the chance to debug it yet but I'll take a look when I get a chance.

cc @dlrobertson

[dlrobertson]

We rely on the LLVM implementation of va_arg for Aarch64 (unlike clang). I bet we'll have to manually implement it like we do for i686.

[dlrobertson]

BTW thanks for testing and reporting this!

[JamieCunliffe]

I had a brief conversation with @parched yesterday regarding this issue, and picking up the pull request that was opened. The following comment #62207 (review) about some platforms using the va_arg instruction and some using rust generated LLVM IR. Does the rust community now have a preference as to how to handle va_args as that comment was made almost a year ago?

I think there is more benefit in fixing up the va_arg instruction within LLVM. But I would like to get this issue fixed in a way that is approved by the rust community.

[dlrobertson]

I had a brief conversation with @parched yesterday regarding this issue, and picking up the pull request that was opened.

Awesome! Excited to see some interest in this. I've recently had some conversations with co-workers about work on this as well.

I think there is more benefit in fixing up the va_arg instruction within LLVM.

Do you mean within the rustc codegen or upstream LLVM?

[JamieCunliffe]

I think there is more benefit in fixing up the va_arg instruction within LLVM.

Do you mean within the rustc codegen or upstream LLVM?

I was thinking upstream LLVM.

I thought it would be best to raise the question here though as there didn't seem to be a decision on your comment about if rust was going to standardise it's approach to this, and if it is then which approach it would be.

[dlrobertson]

I was thinking upstream LLVM.

Last I checked there didn't seem to be much interest in this and it would require a quite large effort.

there didn't seem to be a decision on your comment about if rust was going to standardise it's approach to this, and if it is then which approach it would be.

IMHO a non-standarrd solution is better than a broken one 😄 My first implementation of Aarch64 variadics is broken, so I'd love to get something merged whether or not it is entirely standard. That being said, if we can implement this in codegen, I'd greatly prefer that.

[JamieCunliffe]

I have had a look at implementing this in rustc_codegen_llvm and started on this so if you want to assign it to me I'll continue on.