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Disable compilation of Atomic64 code in metric.rs if there's no Atomic64 #188

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Disable compilation of Atomic64 code in metric.rs if there's no Atomic64 #188

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2 changes: 2 additions & 0 deletions src/metric.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,8 @@
//! of these components can choose what metrics they’re interested in and also
//! can add their own custom metrics without the need to maintain forks.

#![cfg(target_has_atomic = "64")]
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This would result in a compilation error when this condition is not true.

To implement this, it should be on https://github.com/rust-vmm/vmm-sys-util/blob/main/src/lib.rs#L21 like:

#[cfg(target_has_atomic = "64")]
pub mod metric;

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Well, it doesn't result in compilation error: see https://buildd.debian.org/status/package.php?p=rust-vmm-sys-util&suite=sid - it compiled fine on all platforms where previously this caused an error. I guess it will result in compilation error of crates which use this one, as there will be no implementation for the declared functionality.

But I must admit: I know nothing about rust. It's the 2nd day since I looked at what rust actually is, what I suggest is just something I've seen being used elsewhere. I've no idea if this is a correct solution or not.

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Writing #![cfg(target_has_atomic = "64")] (notice the !) is equivalent to:

#[cfg(target_has_atomic = "64")] pub mod metric;

We can still have it as @JonathanWoollett-Light suggested even if they're equivalent because it is making it a bit more obvious that the whole module is excluded from compilation on targets that don't support atomic64.


use std::sync::atomic::{AtomicU64, Ordering};

/// Abstraction over the common metric operations.
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