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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,85 @@ | ||
| use crate::rustc_target::abi::LayoutOf; | ||
| use crate::utils::span_lint_and_then; | ||
| use if_chain::if_chain; | ||
| use rustc::mir::interpret::ConstValue; | ||
| use rustc::ty::{self, ConstKind}; | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir::{Item, ItemKind}; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_session::{declare_tool_lint, impl_lint_pass}; | ||
| use rustc_span::{BytePos, Pos, Span}; | ||
| use rustc_typeck::hir_ty_to_ty; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// **What it does:** Checks for large `const` non-scalar types (ie: array) 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. | ||
| /// | ||
| /// **Known problems:** None. | ||
| /// | ||
| /// **Example:** | ||
| /// ```rust,ignore | ||
| /// // Bad | ||
| /// pub const a = [0u32; 1_000_000]; | ||
| /// | ||
| /// // Good | ||
| /// pub static a = [0u32; 1_000_000]; | ||
| /// ``` | ||
| pub NON_SCALAR_CONST, | ||
| perf, | ||
| "large non-scalar const variable may cause performance overhead" | ||
| } | ||
|
|
||
| pub struct NonScalarConst { | ||
| maximum_allowed_size: u64, | ||
| } | ||
|
|
||
| impl NonScalarConst { | ||
| #[must_use] | ||
| pub fn new(maximum_allowed_size: u64) -> Self { | ||
| Self { maximum_allowed_size } | ||
| } | ||
| } | ||
|
|
||
| impl_lint_pass!(NonScalarConst => [NON_SCALAR_CONST]); | ||
|
|
||
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonScalarConst { | ||
| fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'_>) { | ||
| if_chain! { | ||
| if !item.span.from_expansion(); | ||
| if let ItemKind::Const(hir_ty, _) = &item.kind; | ||
| let ty = hir_ty_to_ty(cx.tcx, hir_ty); | ||
| if let ty::Array(element_type, cst) = ty.kind; | ||
| if let ConstKind::Value(val) = cst.val; | ||
| if let ConstValue::Scalar(element_count) = val; | ||
| if let Ok(element_count) = element_count.to_machine_usize(&cx.tcx); | ||
| if let Ok(element_size) = cx.layout_of(element_type).map(|l| l.size.bytes()); | ||
| if self.maximum_allowed_size < element_count * element_size; | ||
|
|
||
| then { | ||
| let hi_pos = item.ident.span.lo() - BytePos::from_usize(1); | ||
| let sugg_span = Span::new( | ||
| hi_pos - BytePos::from_usize("const".len()), | ||
| hi_pos, | ||
| item.span.ctxt(), | ||
| ); | ||
| span_lint_and_then( | ||
| cx, | ||
| NON_SCALAR_CONST, | ||
| sugg_span, | ||
| "large array defined as const", | ||
| |db| { | ||
| db.span_suggestion( | ||
| item.span, | ||
| "make this a static item", | ||
| "static".to_string(), | ||
| Applicability::MachineApplicable, | ||
| ); | ||
| } | ||
| ); | ||
| } | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,34 @@ | ||
| #![warn(clippy::non_scalar_const)] | ||
|
|
||
| #[derive(Clone, Copy)] | ||
| pub struct S { | ||
| pub data: [u64; 32], | ||
| } | ||
|
|
||
| // Should lint | ||
| pub(crate) const FOO_PUB_CRATE: [u32; 1_000_000] = [0u32; 1_000_000]; | ||
| pub const FOO_PUB: [u32; 1_000_000] = [0u32; 1_000_000]; | ||
| const FOO: [u32; 1_000_000] = [0u32; 1_000_000]; | ||
|
|
||
| // Good | ||
| pub(crate) const G_FOO_PUB_CRATE: [u32; 1_000] = [0u32; 1_000]; | ||
| pub const G_FOO_PUB: [u32; 1_000] = [0u32; 1_000]; | ||
| const G_FOO: [u32; 1_000] = [0u32; 1_000]; | ||
|
|
||
| fn main() { | ||
| // Should lint | ||
| pub const BAR_PUB: [u32; 1_000_000] = [0u32; 1_000_000]; | ||
| const BAR: [u32; 1_000_000] = [0u32; 1_000_000]; | ||
| pub const BAR_STRUCT_PUB: [S; 5_000] = [S { data: [0; 32] }; 5_000]; | ||
| const BAR_STRUCT: [S; 5_000] = [S { data: [0; 32] }; 5_000]; | ||
| pub const BAR_S_PUB: [Option<&str>; 200_000] = [Some("str"); 200_000]; | ||
| const BAR_S: [Option<&str>; 200_000] = [Some("str"); 200_000]; | ||
|
|
||
| // Good | ||
| pub const G_BAR_PUB: [u32; 1_000] = [0u32; 1_000]; | ||
| const G_BAR: [u32; 1_000] = [0u32; 1_000]; | ||
| pub const G_BAR_STRUCT_PUB: [S; 500] = [S { data: [0; 32] }; 500]; | ||
| const G_BAR_STRUCT: [S; 500] = [S { data: [0; 32] }; 500]; | ||
| pub const G_BAR_S_PUB: [Option<&str>; 200] = [Some("str"); 200]; | ||
| const G_BAR_S: [Option<&str>; 200] = [Some("str"); 200]; | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,66 @@ | ||
| error: large array defined as const | ||
| --> $DIR/non_scalar_const.rs:9:12 | ||
| | | ||
| LL | pub(crate) const FOO_PUB_CRATE: [u32; 1_000_000] = [0u32; 1_000_000]; | ||
| | -----------^^^^^----------------------------------------------------- help: make this a static item: `static` | ||
| | | ||
| = note: `-D clippy::non-scalar-const` implied by `-D warnings` | ||
|
|
||
| error: large array defined as const | ||
| --> $DIR/non_scalar_const.rs:10:5 | ||
| | | ||
| LL | pub const FOO_PUB: [u32; 1_000_000] = [0u32; 1_000_000]; | ||
| | ----^^^^^----------------------------------------------- help: make this a static item: `static` | ||
|
|
||
| error: large array defined as const | ||
| --> $DIR/non_scalar_const.rs:11:1 | ||
| | | ||
| LL | const FOO: [u32; 1_000_000] = [0u32; 1_000_000]; | ||
| | ^^^^^------------------------------------------- | ||
| | | | ||
| | help: make this a static item: `static` | ||
|
|
||
| error: large array defined as const | ||
| --> $DIR/non_scalar_const.rs:20:9 | ||
| | | ||
| LL | pub const BAR_PUB: [u32; 1_000_000] = [0u32; 1_000_000]; | ||
| | ----^^^^^----------------------------------------------- help: make this a static item: `static` | ||
|
|
||
| error: large array defined as const | ||
| --> $DIR/non_scalar_const.rs:21:5 | ||
| | | ||
| LL | const BAR: [u32; 1_000_000] = [0u32; 1_000_000]; | ||
| | ^^^^^------------------------------------------- | ||
| | | | ||
| | help: make this a static item: `static` | ||
|
|
||
| error: large array defined as const | ||
| --> $DIR/non_scalar_const.rs:22:9 | ||
| | | ||
| LL | pub const BAR_STRUCT_PUB: [S; 5_000] = [S { data: [0; 32] }; 5_000]; | ||
| | ----^^^^^----------------------------------------------------------- help: make this a static item: `static` | ||
|
|
||
| error: large array defined as const | ||
| --> $DIR/non_scalar_const.rs:23:5 | ||
| | | ||
| LL | const BAR_STRUCT: [S; 5_000] = [S { data: [0; 32] }; 5_000]; | ||
| | ^^^^^------------------------------------------------------- | ||
| | | | ||
| | help: make this a static item: `static` | ||
|
|
||
| error: large array defined as const | ||
| --> $DIR/non_scalar_const.rs:24:9 | ||
| | | ||
| LL | pub const BAR_S_PUB: [Option<&str>; 200_000] = [Some("str"); 200_000]; | ||
| | ----^^^^^------------------------------------------------------------- help: make this a static item: `static` | ||
|
|
||
| error: large array defined as const | ||
| --> $DIR/non_scalar_const.rs:25:5 | ||
| | | ||
| LL | const BAR_S: [Option<&str>; 200_000] = [Some("str"); 200_000]; | ||
| | ^^^^^--------------------------------------------------------- | ||
| | | | ||
| | help: make this a static item: `static` | ||
|
|
||
| error: aborting due to 9 previous errors | ||
|
|