async functions are disallowed (because `-> impl Trait` is not supported). `const` entry functions are allowed, nonsecure-call functions must be function pointers, which cannot be evaluated during constant evaluation.
cmse: disallow `impl Trait` in `cmse-nonsecure-entry` return types
tracking issue: https://github.com/rust-lang/rust/issues/75835
fixes https://github.com/rust-lang/rust/issues/147242
Refactors some logic to be more robust in the future, and then disallows `impl Trait` as a return type for the cmse ABIs.
The `is_valid_cmse_output_layout` function disallows `union` values like before. That is not entirely correct, but preserves the current behavior. Some additional logic is needed for `union` values (and any types where parts may be uninitialized) that I'll tackle in a later PR.
can be reviewed commit-by-commit.
r? types
cmse: fix 'region variables should not be hashed'
tracking issue: https://github.com/rust-lang/rust/issues/81391
fixes https://github.com/rust-lang/rust/issues/131639
Some background: the `cmse-nonsecure-call` calling convention is used for a call from "secure" to "non-secure" code. To make sure that "non-secure" cannot read any secrets, restrictions are put on the signatures of functions with this calling convention: they can only use 4 arguments for passing arguments, and one register for passing a result. No arguments are passed via the stack, and all other registers are cleared before the call.
We check during `hir_ty_lowering` that the signature follows these rules. We do that by determining and then inspecting the layout of the type. That works well overall, but can run into asserts when the type itself is ill-formed. This PR fixes one such case.
I believe that the fix here, just erasing the regions, is the right shape, but there may be some nuance that I'm missing.
r? types
Split out the `extern_system_varargs` feature
After the stabilization PR was opened, `extern "system"` functions were added to `extended_varargs_abi_support`. This has a number of questions regarding it that were not discussed and were somewhat surprising. It deserves to be considered as its own feature, separate from `extended_varargs_abi_support`.
Tracking issue:
- https://github.com/rust-lang/rust/issues/136946
After the stabilization PR was opened, `extern "system"` functions were
added to `extended_varargs_abi_support`. This has a number of questions
regarding it that were not discussed and were somewhat surprising.
It deserves to be considered as its own feature, separate from
`extended_varargs_abi_support`.
```
error[E0610]: `{integer}` is a primitive type and therefore doesn't have fields
--> $DIR/attempted-access-non-fatal.rs:7:15
|
LL | let _ = 2.l;
| ^
|
help: if intended to be a floating point literal, consider adding a `0` after the period and a `f64` suffix
|
LL - let _ = 2.l;
LL + let _ = 2.0f64;
|
```
