Rustdoc failure in `armv7` targets with `-neon` with `target_feature(enable = "neon")`

[sayantn]

I tried this code:

#![feature(arm_target_feature)]

#[target_feature(enable = "neon")]
unsafe fn foo() {}

This always compiles, but in armv7 targets that have -neon target-feature, running rustdoc on it produces the error

error: target feature `neon` cannot be toggled with `#[target_feature]`: unsound on hard-float targets because it changes float ABI
 --> bug.rs:3:18
  |
5 | #[target_feature(enable = "neon")]
  |

even if the target has +soft-float (e.g armv7-unknown-linux-gnueabi).

rustc --version --verbose:

rustc 1.85.0-nightly (9e136a30a 2024-12-19)
binary: rustc
commit-hash: 9e136a30a965bf4e63f03095c57df7257bf96fd6
commit-date: 2024-12-19
host: x86_64-unknown-linux-gnu
release: 1.85.0-nightly
LLVM version: 19.1.6

Related: #133417

[jieyouxu]

Hi @sayantn, could you elaborate on how exactly you ran rustdoc (e.g. flags, configs)?

[sayantn]

I typically use cargo doc --target armv7-unknown-linux-gnueabihf, but rustdoc --target armv7-unknown-linux-gnueabihf --crate-type=lib bug.rs also reproduces the issue. No extra flags or anything needed, just a nightly toolchain