Support for pointers with asm_const · Issue #128464 · rust-lang/rust (original) (raw)
Inline assembly supports an unstable feature called asm_const with tracking issue #93332 that lets you pass constants to inline assembly. However, it only supports integer types. This issue is a feature request to support raw pointers with asm_const.
This would enable code such as the following:
#![feature(const_refs_to_static)] #![feature(asm_const)] use core::arch::asm; use core::ptr::addr_of; use core::ffi::c_void;
trait Helper { const MY_PTR: *const c_void; }
fn my_asm_wrapper<T: Helper>() { unsafe { asm!("mov {},eax", const T::MY_PTR) }; }
extern "C" { static FOO: usize; }
struct HelperForPassingPointerAsConstGeneric {} impl Helper for HelperForPassingPointerAsConstGeneric { const MY_PTR: *const c_void = addr_of!(FOO).cast(); }
fn main() { my_asm_wrapper::(); }
Currently, the above code would require you to convert my_asm_wrapper into a macro_rules! so that you can write out the path to the global using the sym operand. Supporting this would be useful for the Rust for Linux project, as implementing support for static keys requires a long list of workarounds at the moment.