Tracking Issue: Translation nightly features

[TheDan64]

This is the tracking issue for generated code which requires nightly to run:

• ~Assembly - asm - https://github.com/rust-lang/rust/issues/29722~ asm! stabilized since 1.59.0
• Intrinsics for atomic operations - core_intrinsics - Unlikely to ever be stabilized itself, no tracking issue
• ~Ptr to ptr offset calculation - ptr_wrapping_offset_from - https://github.com/rust-lang/rust/issues/41079~ wrapping_offset_from removed and offset_from added in 1.47.0, still const unstable.
• Labels for breaks in relooper - label_break_value - https://github.com/rust-lang/rust/issues/48594
• Opaque extern types - extern_types - https://github.com/rust-lang/rust/issues/43467
• Thread Local variables - thread_local - https://github.com/rust-lang/rust/issues/29594
• ~Cast const ptr to usize - const_raw_ptr_to_usize_cast - https://github.com/rust-lang/rust/issues/51910~ const_raw_ptr_to_usize_cast removed, no longer needed either, and impossible in C as well
• ~Cast const slice to pointer - const_slice_as_ptr~ - [].as_ptr() const since 1.32.0
• C-compatible variadic functions - c_variadics - https://github.com/rust-lang/rust/issues/44930
• ~Libc types - libc~ - Now generating Cargo.toml files which use the libc crate

[rinon]

Since libc is on crates.io and rustc errors when we use the internal version, we should drop that off the list of nightly features.

[bjorn3]

Intrinsics for atomic operations - core_intrinsics - Unlikely to ever be stabilized itself, no tracking issue

Maybe cast the pointer from say *mut u64 to *mut AtomicU64 and then use the normal AtomicU64 methods on it.

[panstromek]

Note about ptr_offset_from stabilization:

Method wrapping_offset_from (which is often used in c2rust output) has been deprecated since 1.46 and it is being removed in ptr_offset_from stabilization PR: https://github.com/rust-lang/rust/pull/74238

[chrysn]

Assembly is now tracked at https://github.com/rust-lang/rust/issues/70173 -- but without any plan for stabilization; see #306. Unless the asm transpilation is significantly reworked (to produce Rust asm rather than llvm_asm), this now falls in the "unlikely to be stabilized" category.

[OvermindDL1]

Method wrapping_offset_from (which is often used in c2rust output) has been deprecated since 1.46 and it is being removed in ptr_offset_from stabilization PR: rust-lang/rust#74238

And looks like it's entirely gone now, says the feature doesn't exist and the wrapping_offset_from call no longer exists in the source.

[fanninpm]

And looks like it's entirely gone now, says the feature doesn't exist and the wrapping_offset_from call no longer exists in the source.

It was removed in August.

[XVilka]

I think it worth to pin this issue, otherwise it's easy to miss and one of the most important, imho.

[kkysen]

A bunch of these features have since been stabilized or removed:

• asm! is stabilized since 1.59.0: core::arch::asm!
• wrapping_offset_from was removed but offset_from was added in 1.47.0. It is const unstable.
• const_raw_ptr_to_usize_cast was removed since it is unsafe at compile time. Why do we need this? You can't const cast a pointer to an integer in C either, even if the pointer was originally cast from an integer: https://godbolt.org/z/xKrhfG7z6. These are errors because they try to be variable-length array declarations:

#include <stdint.h>

int a[(uintptr_t) (char *) 0];
int b[(uintptr_t) ""];

• const_slice_as_ptr works on stable now: [].as_ptr() has been const since 1.32.0.

[pitaj]

It appears that core_intrinsics is also used for rotate_left and rotate_right. Is there a reason these can't just use the inherent methods instead?

[mewmew]

• [x] Labels for breaks in relooper - label_break_value - https://github.com/rust-lang/rust/issues/48594

the feature label_break_value has been stable since 1.65.0 and no longer requires an attribute to enable

ref: https://github.com/rust-lang/rust/pull/99332

Thus, #![feature(label_break_value)] can be removed from transpiled code output.