Clippy lints / Performance
Clippy lint · Performance · checked with Clippy 0.1.99
clippy::large_const_arrays: Checks for large const arrays that should be defined as static instead
What it meansChecks for large const arrays that should be defined as static instead. It is in the performance group and warns by default.
Does it matter?
Performance: const variables are inlined upon use. Static items result in only one instance and has a fixed location in memory.
Code that could be written to run faster. Warns by default.
How to fix it
Clippy can fix this one for you: run cargo clippy --fix (add --allow-dirty if you have uncommitted changes). Review the diff before you commit.
Flagged
pub const a = [0u32; 1_000_000];
Write this instead
pub static a = [0u32; 1_000_000];
Turn it off, or on
Allow it where it does not fit your code, as narrowly as you can:
On one item
#[allow(clippy::large_const_arrays)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
large_const_arrays = "allow"One run
cargo clippy -- -A clippy::large-const-arraysThe [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.
Settings in clippy.toml
array-size-threshold: The maximum allowed size for arrays on the stack
Clippy's own documentation
What it does
Checks for large const arrays that should
be defined as static instead.
Why is this bad?
Performance: const variables are inlined upon use. Static items result in only one instance and has a fixed location in memory.
Example
pub const a = [0u32; 1_000_000];
Use instead:
pub static a = [0u32; 1_000_000];
Configuration
-
array-size-threshold: The maximum allowed size for arrays on the stack(default:
16384)
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
Related lints
- large_enum_variantlarge size difference between variants
- extend_with_drainuse of `extend` instead of `append` for adding the full range of a second vector
- format_in_format_argsDetects format! within the arguments of another macro that does formatting such as format! itself, write! or println!
- iter_overeager_clonedChecks for usage of _.cloned().<func>() where call to .cloned() can be postponed
- manual_cleartruncating to zero length
- manual_containsusing `contains()` instead of `iter().any()` is more efficient
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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