rust-lang / rust-lang/rust

`naked_asm!` does not accept assembly syntax that is accepted by `asm!`

Open
#147,267 9 comments 0 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

A-inline-assembly A-naked C-bug F-naked_functions T-compiler T-libs
Dominant language
Rust
Stars
119k
Forks
16.1k
PR merge metrics
PR metrics pending

Description

I tried this code:

extern "C" fn foo() {
    unsafe {
        core::arch::asm!("mov rax, QWORD PTR gs:[60h]");
    }
}

#[unsafe(naked)]
extern "C" fn foo2() {
    core::arch::naked_asm!("mov rax, QWORD PTR gs:[60h]")
}

I expected to see this happen: Both functions assemble correctly, as the only difference between the assembly statements is naked_asm! being used instead of asm!.

Instead, this happened: Assembly error in foo2:

error: <inline asm>:10:27: unknown token in expression
mov rax, QWORD PTR gs:[60h]
                          ^
Meta

rustc --version --verbose:

rustc 1.92.0-nightly (4645a7988 2025-09-17)
binary: rustc
commit-hash: 4645a7988177c286f61609cc667ecae4c571a2e8
commit-date: 2025-09-17
host: x86_64-pc-windows-msvc
release: 1.92.0-nightly
LLVM version: 21.1.1

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the minimal Rust reproducer in the issue and compare how asm! and naked_asm! handle the same assembly string on x86_64-pc-windows-msvc. Trace the compiler or LLVM path responsible for the differing expression parsing. Done means the shown naked_asm! statement assembles successfully without regressing existing behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
38/100

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.