large_stack_frames: print total size and largest component.
Instead of just saying “this function's stack frame is big”, report: * the (presumed) size of the frame * the size and type of the largest local contributing to that size * the configurable limit that was exceeded (once)
This commit is contained in:
Kevin Reid
parent
124e68bef8
commit
01646457a9
@ -1,10 +1,12 @@
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use std::ops::AddAssign;
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use std::{fmt, ops};
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use clippy_utils::diagnostics::span_lint_and_note;
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use clippy_utils::diagnostics::span_lint_and_then;
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use clippy_utils::fn_has_unsatisfiable_preds;
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use clippy_utils::source::snippet_opt;
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use rustc_hir::def_id::LocalDefId;
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use rustc_hir::intravisit::FnKind;
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use rustc_hir::{Body, FnDecl};
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use rustc_lexer::is_ident;
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::impl_lint_pass;
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use rustc_span::Span;
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@ -108,25 +110,37 @@ pub fn exceeds_limit(self, limit: u64) -> bool {
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}
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}
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impl AddAssign<u64> for Space {
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fn add_assign(&mut self, rhs: u64) {
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if let Self::Used(lhs) = self {
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match lhs.checked_add(rhs) {
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Some(sum) => *self = Self::Used(sum),
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None => *self = Self::Overflow,
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impl fmt::Display for Space {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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Space::Used(1) => write!(f, "1 byte"),
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Space::Used(n) => write!(f, "{n} bytes"),
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Space::Overflow => write!(f, "over 2⁶⁴-1 bytes"),
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}
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}
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}
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impl ops::Add<u64> for Space {
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type Output = Self;
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fn add(self, rhs: u64) -> Self {
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match self {
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Self::Used(lhs) => match lhs.checked_add(rhs) {
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Some(sum) => Self::Used(sum),
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None => Self::Overflow,
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},
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Self::Overflow => self,
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}
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}
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}
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impl<'tcx> LateLintPass<'tcx> for LargeStackFrames {
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fn check_fn(
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&mut self,
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cx: &LateContext<'tcx>,
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_: FnKind<'tcx>,
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fn_kind: FnKind<'tcx>,
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_: &'tcx FnDecl<'tcx>,
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_: &'tcx Body<'tcx>,
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span: Span,
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entire_fn_span: Span,
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local_def_id: LocalDefId,
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) {
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let def_id = local_def_id.to_def_id();
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@ -138,22 +152,68 @@ fn check_fn(
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let mir = cx.tcx.optimized_mir(def_id);
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let param_env = cx.tcx.param_env(def_id);
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let mut frame_size = Space::Used(0);
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let sizes_of_locals = || {
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mir.local_decls.iter().filter_map(|local| {
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let layout = cx.tcx.layout_of(param_env.and(local.ty)).ok()?;
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Some((local, layout.size.bytes()))
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})
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};
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for local in &mir.local_decls {
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if let Ok(layout) = cx.tcx.layout_of(param_env.and(local.ty)) {
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frame_size += layout.size.bytes();
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}
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}
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let frame_size = sizes_of_locals().fold(Space::Used(0), |sum, (_, size)| sum + size);
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if frame_size.exceeds_limit(self.maximum_allowed_size) {
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span_lint_and_note(
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let limit = self.maximum_allowed_size;
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if frame_size.exceeds_limit(limit) {
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// Point at just the function name if possible, because lints that span
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// the entire body and don't have to are less legible.
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let fn_span = match fn_kind {
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FnKind::ItemFn(ident, _, _) | FnKind::Method(ident, _) => ident.span,
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FnKind::Closure => entire_fn_span,
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};
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span_lint_and_then(
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cx,
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LARGE_STACK_FRAMES,
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span,
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"this function allocates a large amount of stack space",
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None,
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"allocating large amounts of stack space can overflow the stack",
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fn_span,
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&format!("this function may allocate {frame_size} on the stack"),
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|diag| {
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// Point out the largest individual contribution to this size, because
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// it is the most likely to be unintentionally large.
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if let Some((local, size)) = sizes_of_locals().max_by_key(|&(_, size)| size) {
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let local_span: Span = local.source_info.span;
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let size = Space::Used(size); // pluralizes for us
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let ty = local.ty;
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// TODO: Is there a cleaner, robust way to ask this question?
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// The obvious `LocalDecl::is_user_variable()` panics on "unwrapping cross-crate data",
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// and that doesn't get us the true name in scope rather than the span text either.
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if let Some(name) = snippet_opt(cx, local_span)
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&& is_ident(&name)
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{
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// If the local is an ordinary named variable,
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// print its name rather than relying solely on the span.
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diag.span_label(
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local_span,
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format!("`{name}` is the largest part, at {size} for type `{ty}`"),
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);
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} else {
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diag.span_label(
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local_span,
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format!("this is the largest part, at {size} for type `{ty}`"),
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);
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}
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}
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// Explain why we are linting this and not other functions.
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diag.note(format!(
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"{frame_size} is larger than Clippy's configured `stack-size-threshold` of {limit}"
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));
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// Explain why the user should care, briefly.
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diag.note_once(
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"allocating large amounts of stack space can overflow the stack \
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and cause the program to abort",
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);
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},
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);
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}
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}
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@ -10,7 +10,7 @@ fn f() {
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let _x = create_array::<1000>();
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}
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fn f2() {
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//~^ ERROR: this function allocates a large amount of stack space
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//~^ ERROR: this function may allocate 1001 bytes on the stack
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let _x = create_array::<1001>();
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}
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@ -1,13 +1,14 @@
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error: this function allocates a large amount of stack space
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--> tests/ui-toml/large_stack_frames/large_stack_frames.rs:12:1
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error: this function may allocate 1001 bytes on the stack
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--> tests/ui-toml/large_stack_frames/large_stack_frames.rs:12:4
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LL | / fn f2() {
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LL | |
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LL | | let _x = create_array::<1001>();
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LL | | }
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| |_^
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LL | fn f2() {
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| ^^
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LL |
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LL | let _x = create_array::<1001>();
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| -- `_x` is the largest part, at 1001 bytes for type `[u8; 1001]`
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= note: allocating large amounts of stack space can overflow the stack
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= note: 1001 bytes is larger than Clippy's configured `stack-size-threshold` of 1000
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= note: allocating large amounts of stack space can overflow the stack and cause the program to abort
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= note: `-D clippy::large-stack-frames` implied by `-D warnings`
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= help: to override `-D warnings` add `#[allow(clippy::large_stack_frames)]`
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@ -1,3 +1,5 @@
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//@ normalize-stderr-test: "\b10000(08|16|32)\b" -> "100$$PTR"
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//@ normalize-stderr-test: "\b2500(060|120)\b" -> "250$$PTR"
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#![allow(unused, incomplete_features)]
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#![warn(clippy::large_stack_frames)]
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#![feature(unsized_locals)]
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@ -23,8 +25,7 @@ fn default() -> Self {
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}
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fn many_small_arrays() {
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//~^ ERROR: this function allocates a large amount of stack space
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//~| NOTE: allocating large amounts of stack space can overflow the stack
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//~^ ERROR: this function may allocate
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let x = [0u8; 500_000];
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let x2 = [0u8; 500_000];
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let x3 = [0u8; 500_000];
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@ -34,17 +35,21 @@ fn many_small_arrays() {
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}
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fn large_return_value() -> ArrayDefault<1_000_000> {
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//~^ ERROR: this function allocates a large amount of stack space
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//~| NOTE: allocating large amounts of stack space can overflow the stack
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//~^ ERROR: this function may allocate 1000000 bytes on the stack
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Default::default()
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}
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fn large_fn_arg(x: ArrayDefault<1_000_000>) {
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//~^ ERROR: this function allocates a large amount of stack space
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//~| NOTE: allocating large amounts of stack space can overflow the stack
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//~^ ERROR: this function may allocate
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black_box(&x);
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}
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fn has_large_closure() {
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let f = || black_box(&[0u8; 1_000_000]);
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//~^ ERROR: this function may allocate
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f();
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}
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fn main() {
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generic::<ArrayDefault<1_000_000>>();
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}
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@ -1,42 +1,42 @@
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error: this function allocates a large amount of stack space
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--> tests/ui/large_stack_frames.rs:25:1
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error: this function may allocate 250$PTR bytes on the stack
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--> tests/ui/large_stack_frames.rs:27:4
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LL | / fn many_small_arrays() {
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LL | |
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LL | |
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LL | | let x = [0u8; 500_000];
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... |
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LL | | black_box((&x, &x2, &x3, &x4, &x5));
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LL | | }
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| |_^
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LL | fn many_small_arrays() {
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| ^^^^^^^^^^^^^^^^^
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...
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LL | let x5 = [0u8; 500_000];
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| -- `x5` is the largest part, at 500000 bytes for type `[u8; 500000]`
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= note: allocating large amounts of stack space can overflow the stack
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= note: 250$PTR bytes is larger than Clippy's configured `stack-size-threshold` of 512000
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= note: allocating large amounts of stack space can overflow the stack and cause the program to abort
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= note: `-D clippy::large-stack-frames` implied by `-D warnings`
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= help: to override `-D warnings` add `#[allow(clippy::large_stack_frames)]`
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error: this function allocates a large amount of stack space
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--> tests/ui/large_stack_frames.rs:36:1
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error: this function may allocate 1000000 bytes on the stack
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--> tests/ui/large_stack_frames.rs:37:4
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LL | / fn large_return_value() -> ArrayDefault<1_000_000> {
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LL | |
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LL | |
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LL | | Default::default()
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LL | | }
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| |_^
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LL | fn large_return_value() -> ArrayDefault<1_000_000> {
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| ^^^^^^^^^^^^^^^^^^ ----------------------- this is the largest part, at 1000000 bytes for type `ArrayDefault<1000000>`
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= note: allocating large amounts of stack space can overflow the stack
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= note: 1000000 bytes is larger than Clippy's configured `stack-size-threshold` of 512000
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error: this function allocates a large amount of stack space
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--> tests/ui/large_stack_frames.rs:42:1
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error: this function may allocate 100$PTR bytes on the stack
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--> tests/ui/large_stack_frames.rs:42:4
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LL | / fn large_fn_arg(x: ArrayDefault<1_000_000>) {
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LL | |
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LL | |
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LL | | black_box(&x);
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LL | | }
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| |_^
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LL | fn large_fn_arg(x: ArrayDefault<1_000_000>) {
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| ^^^^^^^^^^^^ - `x` is the largest part, at 1000000 bytes for type `ArrayDefault<1000000>`
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= note: allocating large amounts of stack space can overflow the stack
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= note: 100$PTR bytes is larger than Clippy's configured `stack-size-threshold` of 512000
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error: aborting due to 3 previous errors
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error: this function may allocate 100$PTR bytes on the stack
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--> tests/ui/large_stack_frames.rs:48:13
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LL | let f = || black_box(&[0u8; 1_000_000]);
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| ^^^^^^^^^^^^^^----------------^
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| |
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| this is the largest part, at 1000000 bytes for type `[u8; 1000000]`
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= note: 100$PTR bytes is larger than Clippy's configured `stack-size-threshold` of 512000
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error: aborting due to 4 previous errors
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