Re: [PATCH 2/2] rust: enable default uwtable and ignore arm no_std test

Sunil Kumar Dora
2025-12-24T04:03:58Z

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Hi Randy,

On 12/23/2025 4:10 AM, Randy MacLeod wrote:
> On 2025-12-22 4:38 a.m., Yash.Shinde@windriver.com wrote:
>> From: Hemanth Kumar M D<hemanth.250302@gmail.com>
>>
>> Rust 1.92.0 adds new test that require unwind table support to be
>> enabled by default. Set `default-uwtable = true` in the generated
>> target spec to match upstream behavior.
>>
>> ref:https://github.com/rust-lang/rust/commit/fe66eaa67acc47525db6f13cf97d54780d87b805
>>
>> Also ignore the no_std simple-runs UI test on ARM targets. The test
>> fails with panic=abort due to a known unwind table issue on 32-bit ARM
>>
>> https://github.com/rust-lang/rust/issues/146996
>
> Okay and I'm glad to see the upstream issues linked.
>
> Should we make some of these tspec decisions set-able by well-informed
> users?
>
> Maybe they can already do that using this horridly named "FEATURES"
> variable.
> (rename to RUST_FEATURES maybe ?)
>
The existing FEATURES variables in the .bbclass is currently used for
low-level CPU instructions.
As you suggested, RUST_FEATURE variable will allow us to keep H/W tuning
separate from
high-level compiler policy. I will discuss with team.
>
>
> For example, this bug:
>
> Unable to produce a Rust static binary with TCLIBC=musl (oe-core/master)
> https://bugzilla.yoctoproject.org/show_bug.cgi?id=16076
>
Although the bug report did not include a specific recipe, I used
ripgrep as a reference
to validate the issue and was able to build a fully static musl binary.

I found that changing *tspec['dynamic-linking']* from *true *to *false
*in the .bbclass alone was not enough
to produce static binary. The problem had two parts.

First, at the target specification level, rust-target-config.bbclass
forces dynamic-linking to true.
Because of this, the compiler assumes the target is dynamic and ignores
requests for static linking.
As a result, it still produces a dynamic PIE binary that depends on the
musl dynamic loader (ld-musl.so).

Second, at the linker wrapper level, *target-rust-ccld* enforces dynamic
linking by default.
It automatically adds flags such as*-Wl,-Bdynamic* and *-pie*. This
conflicts with the compiler’s static intent
and causes it to pick shared libraries from the sysroot, which leads to
the error
“*attempted static linking of dynamic object*”.

To work around this and meet static musl requirements, I applied
recipe-specific changes to bypass the wrapper’s
enforcement and handle circular dependencies and crate-level leakage.
With these adjustments, the final link correctly uses static archives
instead of falling back to shared objects.

I will update the bug report with these findings.
>
>
> seems to be due to hard-coding dynamic-linking to True below just
> after your:
>
> + tspec['default-uwtable'] = True
>
>
> change.
>
> I've CCed Nick in case you guys have a quick work-around to enable
> static linking.
>
> ../Randy
>
>> Signed-off-by: Hemanth Kumar M D<hemanth.250302@gmail.com>
>> Signed-off-by: Yash Shinde<Yash.Shinde@windriver.com>
>> ---
>> meta/classes-recipe/rust-target-config.bbclass | 1 +
>> .../rust/files/rust-oe-selftest.patch | 12 ++++++++++++
>> 2 files changed, 13 insertions(+)
>>
>> diff --git a/meta/classes-recipe/rust-target-config.bbclass b/meta/classes-recipe/rust-target-config.bbclass
>> index 33a290412e..2a06c4ae8b 100644
>> --- a/meta/classes-recipe/rust-target-config.bbclass
>> +++ b/meta/classes-recipe/rust-target-config.bbclass
>> @@ -418,6 +418,7 @@ def rust_gen_target(d, thing, wd, arch):
>> tspec['llvm-floatabi'] = "soft"
>> elif fpu == "hard":
>> tspec['llvm-floatabi'] = "hard"
>> + tspec['default-uwtable'] = True
>> tspec['dynamic-linking'] = True
>> tspec['executables'] = True
>> tspec['linker-is-gnu'] = True
>> diff --git a/meta/recipes-devtools/rust/files/rust-oe-selftest.patch b/meta/recipes-devtools/rust/files/rust-oe-selftest.patch
>> index b39b326455..d1fba81612 100644
>> --- a/meta/recipes-devtools/rust/files/rust-oe-selftest.patch
>> +++ b/meta/recipes-devtools/rust/files/rust-oe-selftest.patch
>> @@ -254,3 +254,15 @@ index a3562f2fd93..d4e52ed91be 100644
>> fn linux_hwcap2_aarch64() {
>> let file =
>> concat!(env!("CARGO_MANIFEST_DIR"), "/src/detect/test_data/linux-hwcap2-aarch64.auxv");
>> +diff --git a/tests/ui/no_std/simple-runs.rs b/tests/ui/no_std/simple-runs.rs
>> +index af44dfe..e6674e5 100644
>> +--- a/tests/ui/no_std/simple-runs.rs
>> ++++ b/tests/ui/no_std/simple-runs.rs
>> +@@ -2,6 +2,7 @@
>> +
>> + //@ run-pass
>> + //@ compile-flags: -Cpanic=abort
>> ++//@ ignore-arm FIXME(#146996)
>> + //@ ignore-wasm different `main` convention
>> +
>> + #![feature(lang_items)]
>
>
> --
> # Randy MacLeod
> # Wind River Linux

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