Static rustc_lint_defs::builtin::BAD_ASM_STYLE

pub static BAD_ASM_STYLE: &Lint

The bad_asm_style lint detects the use of the .intel_syntax and .att_syntax directives.

Example

#[cfg(target_arch="x86_64")]
use std::arch::asm;

fn main() {
    #[cfg(target_arch="x86_64")]
    unsafe {
        asm!(
            ".att_syntax",
            "movq %{0}, %{0}", in(reg) 0usize
        );
    }
}

This will produce:

warning: avoid using `.att_syntax`, prefer using `options(att_syntax)` instead
 --> src/main.rs:8:14
  |
8 |             ".att_syntax",
  |              ^^^^^^^^^^^
  |
  = note: `#[warn(bad_asm_style)]` on by default

Explanation

On x86, asm! uses the intel assembly syntax by default. While this can be switched using assembler directives like .att_syntax, using the att_syntax option is recommended instead because it will also properly prefix register placeholders with % as required by AT&T syntax.