library/core/src/arch.rs

#![doc = include_str!("../../stdarch/crates/core_arch/src/core_arch_docs.md")]

#[allow(
    // some targets don't have anything to reexport, which
    // makes the `pub use` unused and unreachable, allow
    // both lints as to not have `#[cfg]`s
    //
    // cf. https://github.com/rust-lang/rust/pull/116033#issuecomment-1760085575
    unused_imports,
    unreachable_pub
)]
#[stable(feature = "simd_arch", since = "1.27.0")]
pub use crate::core_arch::arch::*;

/// Inline assembly.
///
/// Refer to [Rust By Example] for a usage guide and the [reference] for
/// detailed information about the syntax and available options.
///
/// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html
/// [reference]: https://doc.rust-lang.org/nightly/reference/inline-assembly.html
#[stable(feature = "asm", since = "1.59.0")]
#[rustc_builtin_macro]
pub macro asm("assembly template", $(operands,)* $(options($(option),*))?) {
    /* compiler built-in */
}

/// Inline assembly used in combination with `#[naked]` functions.
///
/// Refer to [Rust By Example] for a usage guide and the [reference] for
/// detailed information about the syntax and available options.
///
/// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html
/// [reference]: https://doc.rust-lang.org/nightly/reference/inline-assembly.html
#[stable(feature = "naked_functions", since = "1.88.0")]
#[rustc_builtin_macro]
pub macro naked_asm("assembly template", $(operands,)* $(options($(option),*))?) {
    /* compiler built-in */
}

/// Module-level inline assembly.
///
/// Refer to [Rust By Example] for a usage guide and the [reference] for
/// detailed information about the syntax and available options.
///
/// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html
/// [reference]: https://doc.rust-lang.org/nightly/reference/inline-assembly.html
#[stable(feature = "global_asm", since = "1.59.0")]
#[rustc_builtin_macro]
pub macro global_asm("assembly template", $(operands,)* $(options($(option),*))?) {
    /* compiler built-in */
}

/// Compiles to a target-specific software breakpoint instruction or equivalent.
///
/// This will typically abort the program. It may result in a core dump, and/or the system logging
/// debug information. Additional target-specific capabilities may be possible depending on
/// debuggers or other tooling; in particular, a debugger may be able to resume execution.
///
/// If possible, this will produce an instruction sequence that allows a debugger to resume *after*
/// the breakpoint, rather than resuming *at* the breakpoint; however, the exact behavior is
/// target-specific and debugger-specific, and not guaranteed.
///
/// If the target platform does not have any kind of debug breakpoint instruction, this may compile
/// to a trapping instruction (e.g. an undefined instruction) instead, or to some other form of
/// target-specific abort that may or may not support convenient resumption.
///
/// The precise behavior and the precise instruction generated are not guaranteed, except that in
/// normal execution with no debug tooling involved this will not continue executing.
///
/// - On x86 targets, this produces an `int3` instruction.
/// - On aarch64 targets, this produces a `brk #0xf000` instruction.
// When stabilizing this, update the comment on `core::intrinsics::breakpoint`.
#[unstable(feature = "breakpoint", issue = "133724")]
#[inline(always)]
pub fn breakpoint() {
    core::intrinsics::breakpoint();
}

/// The `core::arch::return_address!()` macro returns a pointer with an address that corresponds to the caller of the function that invoked the `return_address!()` macro.
/// The pointer has no provenance, as if created by `core::ptr::without_provenance`. It cannot be used to read memory (other than ZSTs).
///
/// The value returned by the macro depends highly on the architecture and compiler (including any options set).
/// In particular, it is allowed to be wrong (particularly if inlining is involved), or even contain a nonsense value.
/// The result of this macro must not be relied upon for soundness or correctness, only for debugging purposes.
///
/// As a best effort, if a useful value cannot be determined (for example, due to limitations on the current codegen),
/// this macro tries to return a null pointer instead of nonsense (this cannot be relied upon for correctness, however).
///
/// Formally, this function returns a pointer with a non-deterministic address and no provenance.
///
/// This is equivalent to the gcc `__builtin_return_address(0)` intrinsic (other forms of the intrinsic are not supported).
/// Because the operation can be always performed by the compiler without crashing or causing undefined behaviour, invoking the macro is a safe operation.
///
/// ## Example
/// ```
/// #![feature(return_address)]
///
/// # fn run_test() {
/// let addr = core::arch::return_address!();
/// println!("Caller is {addr:p}");
/// # }
/// # #[cfg(not(miri))] // FIXME: Figure out how to make miri work before stabilizing this macro
/// # run_test()
/// ```
#[unstable(feature = "return_address", issue = "154966")]
#[allow_internal_unstable(core_intrinsics)]
pub macro return_address() {{ core::intrinsics::return_address() }}