# [`std::runtime::posix::atomic`](/silk/docs/std/runtime-posix-atomic/)

[`std::runtime::posix::atomic`](/silk/docs/std/runtime-posix-atomic/) is the hosted POSIX implementation module for
[`std::runtime::atomic`](/silk/docs/std/runtime-atomic/).

This module is implementation-facing and should not be imported directly by
ordinary user code.

## Behavior

The module exposes `ext` declarations for runtime symbols implemented in
[`src/silk_rt_atomic.c`](https://github.com/oro-computer/silk/blob/master/src/silk_rt_atomic.c), then re-exports narrow wrappers for
[`std::runtime::atomic`](/silk/docs/std/runtime-atomic/).

The runtime symbols use native compiler atomic builtins for:

- `u64` load/store,
- `u64` swap,
- `u64` fetch-add/fetch-sub,
- `u64` compare-exchange,
- thread fences.

Invalid memory-order combinations are a checker error at the public
[`std::atomic`](/silk/docs/std/atomic/) layer. Runtime helpers still sanitize invalid load/store/failure
orders to a conservative sequentially consistent operation so malformed
low-level direct calls do not lower to ordinary non-atomic memory access.