minicore.md

minicore test auxiliary: using core stubs

[tests/auxiliary/minicore.rs][minicore] is a test auxiliary for ui/codegen/assembly test suites. It provides core stubs for tests that need to build for cross-compiled targets but do not need/want to run.

A test can use [minicore] by specifying the //@ add-core-stubs directive. Then, mark the test with #![feature(no_core)] + #![no_std] + #![no_core]. Due to Edition 2015 extern prelude rules, you will probably need to declare minicore as an extern crate.

Due to the no_std + no_core nature of these tests, //@ add-core-stubs implies and requires that the test will be built with -C panic=abort. Unwinding panics are not supported.

If you find a core item to be missing from the [minicore] stub, consider adding it to the test auxiliary if it's likely to be used or is already needed by more than one test.

Please note that [`minicore`] is only intended for `core` items, and explicitly **not** `std` or `alloc` items because `core` items are applicable to a wider range of tests.

Example codegen test that uses minicore

//@ add-core-stubs
//@ revisions: meow bark
//@[meow] compile-flags: --target=x86_64-unknown-linux-gnu
//@[meow] needs-llvm-components: x86
//@[bark] compile-flags: --target=wasm32-unknown-unknown
//@[bark] needs-llvm-components: webassembly

#![crate_type = "lib"]
#![feature(no_core)]
#![no_std]
#![no_core]

extern crate minicore;
use minicore::*;

struct Meow;
impl Copy for Meow {} // `Copy` here is provided by `minicore`

// CHECK-LABEL: meow
#[unsafe(no_mangle)]
fn meow() {}