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constify a couple thread_local statics #120976

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Mar 5, 2024
Merged

constify a couple thread_local statics #120976

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2 changes: 1 addition & 1 deletion compiler/rustc_data_structures/src/sync/worker_local.rs
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Expand Up @@ -42,7 +42,7 @@ pub struct Registry(Arc<RegistryData>);
thread_local! {
/// The registry associated with the thread.
/// This allows the `WorkerLocal` type to clone the registry in its constructor.
static REGISTRY: OnceCell<Registry> = OnceCell::new();
static REGISTRY: OnceCell<Registry> = const { OnceCell::new() };
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What is the benefit of doing this?

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according to the docs it can be more efficient to wrap in const
https://rust-lang.github.io/rust-clippy/master/index.html#/thread_local_initializer_can_be_made_const

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A more practical demonstration: https://godbolt.org/z/K1Yxe8193 (You can see that the first variant does lazy initialization and the second does not).

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Gotcha, I missed that this is a thread_local! particular thing.

}

struct ThreadData {
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4 changes: 2 additions & 2 deletions compiler/rustc_errors/src/markdown/term.rs
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Expand Up @@ -9,9 +9,9 @@ const DEFAULT_COLUMN_WIDTH: usize = 140;

thread_local! {
/// Track the position of viewable characters in our buffer
static CURSOR: Cell<usize> = Cell::new(0);
static CURSOR: Cell<usize> = const { Cell::new(0) };
/// Width of the terminal
static WIDTH: Cell<usize> = Cell::new(DEFAULT_COLUMN_WIDTH);
static WIDTH: Cell<usize> = const { Cell::new(DEFAULT_COLUMN_WIDTH) };
}

/// Print to terminal output to a buffer
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2 changes: 1 addition & 1 deletion library/proc_macro/src/bridge/client.rs
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Expand Up @@ -284,7 +284,7 @@ impl<'a> scoped_cell::ApplyL<'a> for BridgeStateL {

thread_local! {
static BRIDGE_STATE: scoped_cell::ScopedCell<BridgeStateL> =
scoped_cell::ScopedCell::new(BridgeState::NotConnected);
const { scoped_cell::ScopedCell::new(BridgeState::NotConnected) };
}

impl BridgeState<'_> {
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2 changes: 1 addition & 1 deletion library/proc_macro/src/bridge/server.rs
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Expand Up @@ -152,7 +152,7 @@ thread_local! {
/// This is required as the thread-local state in the proc_macro client does
/// not handle being re-entered, and will invalidate all `Symbol`s when
/// entering a nested macro.
static ALREADY_RUNNING_SAME_THREAD: Cell<bool> = Cell::new(false);
static ALREADY_RUNNING_SAME_THREAD: Cell<bool> = const { Cell::new(false) };
}

/// Keep `ALREADY_RUNNING_SAME_THREAD` (see also its documentation)
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