diff options
| -rw-r--r-- | clippy_lints/src/casts/cast_possible_wrap.rs | 94 | ||||
| -rw-r--r-- | clippy_lints/src/casts/mod.rs | 7 | ||||
| -rw-r--r-- | tests/ui/cast.rs | 8 | ||||
| -rw-r--r-- | tests/ui/cast.stderr | 118 |
4 files changed, 187 insertions, 40 deletions
diff --git a/clippy_lints/src/casts/cast_possible_wrap.rs b/clippy_lints/src/casts/cast_possible_wrap.rs index 28ecdea7ea0..f77d7821539 100644 --- a/clippy_lints/src/casts/cast_possible_wrap.rs +++ b/clippy_lints/src/casts/cast_possible_wrap.rs @@ -1,41 +1,89 @@ -use clippy_utils::diagnostics::span_lint; -use clippy_utils::ty::is_isize_or_usize; use rustc_hir::Expr; -use rustc_lint::LateContext; +use rustc_lint::{LateContext, LintContext}; use rustc_middle::ty::Ty; use super::{utils, CAST_POSSIBLE_WRAP}; +// this should be kept in sync with the allowed bit widths of `usize` and `isize` +const ALLOWED_POINTER_SIZES: [u64; 3] = [16, 32, 64]; + +// whether the lint should be emitted, and the required pointer size, if it matters +#[derive(Copy, Clone, Debug, PartialEq, Eq)] +enum EmitState { + NoLint, + LintAlways, + LintOnPtrSize(u64), +} + pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) { if !(cast_from.is_integral() && cast_to.is_integral()) { return; } - let arch_64_suffix = " on targets with 64-bit wide pointers"; - let arch_32_suffix = " on targets with 32-bit wide pointers"; - let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed(); + // emit a lint if a cast is: + // 1. unsigned to signed + // and + // 2. either: + // 2a. between two types of constant size that are always the same size + // 2b. between one target-dependent size and one constant size integer, + // and the constant integer is in the allowed set of target dependent sizes + // (the ptr size could be chosen to be the same as the constant size) + + if cast_from.is_signed() || !cast_to.is_signed() { + return; + } + let from_nbits = utils::int_ty_to_nbits(cast_from, cx.tcx); let to_nbits = utils::int_ty_to_nbits(cast_to, cx.tcx); - let (should_lint, suffix) = match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) { - (true, true) | (false, false) => (to_nbits == from_nbits && cast_unsigned_to_signed, ""), - (true, false) => (to_nbits <= 32 && cast_unsigned_to_signed, arch_32_suffix), - (false, true) => ( - cast_unsigned_to_signed, - if from_nbits == 64 { - arch_64_suffix + let should_lint = match (cast_from.is_ptr_sized_integral(), cast_to.is_ptr_sized_integral()) { + (true, true) => { + // casts between two ptr sized integers are trivially always the same size + // so do not depend on any specific pointer size to be the same + EmitState::LintAlways + }, + (true, false) => { + // the first type is `usize` and the second is a constant sized signed integer + if ALLOWED_POINTER_SIZES.contains(&to_nbits) { + EmitState::LintOnPtrSize(to_nbits) + } else { + EmitState::NoLint + } + }, + (false, true) => { + // the first type is a constant sized unsigned integer, and the second is `isize` + if ALLOWED_POINTER_SIZES.contains(&from_nbits) { + EmitState::LintOnPtrSize(from_nbits) + } else { + EmitState::NoLint + } + }, + (false, false) => { + // the types are both a constant known size + // and do not depend on any specific pointer size to be the same + if from_nbits == to_nbits { + EmitState::LintAlways } else { - arch_32_suffix - }, + EmitState::NoLint + } + }, + }; + + let message = match should_lint { + EmitState::NoLint => return, + EmitState::LintAlways => format!("casting `{cast_from}` to `{cast_to}` may wrap around the value"), + EmitState::LintOnPtrSize(ptr_size) => format!( + "casting `{cast_from}` to `{cast_to}` may wrap around the value on targets with {ptr_size}-bit wide pointers", ), }; - if should_lint { - span_lint( - cx, - CAST_POSSIBLE_WRAP, - expr.span, - &format!("casting `{cast_from}` to `{cast_to}` may wrap around the value{suffix}",), - ); - } + cx.struct_span_lint(CAST_POSSIBLE_WRAP, expr.span, message, |diag| { + if let EmitState::LintOnPtrSize(16) = should_lint { + diag + .note("`usize` and `isize` may be as small as 16 bits on some platforms") + .note("for more information see https://doc.rust-lang.org/reference/types/numeric.html#machine-dependent-integer-types") + } else { + diag + } + }); } diff --git a/clippy_lints/src/casts/mod.rs b/clippy_lints/src/casts/mod.rs index d2166872d93..0ac6ef6496a 100644 --- a/clippy_lints/src/casts/mod.rs +++ b/clippy_lints/src/casts/mod.rs @@ -118,9 +118,10 @@ declare_clippy_lint! { declare_clippy_lint! { /// ### What it does /// Checks for casts from an unsigned type to a signed type of - /// the same size. Performing such a cast is a 'no-op' for the compiler, - /// i.e., nothing is changed at the bit level, and the binary representation of - /// the value is reinterpreted. This can cause wrapping if the value is too big + /// the same size, or possibly smaller due to target dependent integers. + /// Performing such a cast is a 'no-op' for the compiler, i.e., nothing is + /// changed at the bit level, and the binary representation of the value is + /// reinterpreted. This can cause wrapping if the value is too big /// for the target signed type. However, the cast works as defined, so this lint /// is `Allow` by default. /// diff --git a/tests/ui/cast.rs b/tests/ui/cast.rs index a86b85706a3..60a0eabf55b 100644 --- a/tests/ui/cast.rs +++ b/tests/ui/cast.rs @@ -41,6 +41,14 @@ fn main() { 1u32 as i32; 1u64 as i64; 1usize as isize; + 1usize as i8; // should not wrap, usize is never 8 bits + 1usize as i16; // wraps on 16 bit ptr size + 1usize as i32; // wraps on 32 bit ptr size + 1usize as i64; // wraps on 64 bit ptr size + 1u8 as isize; // should not wrap, isize is never 8 bits + 1u16 as isize; // wraps on 16 bit ptr size + 1u32 as isize; // wraps on 32 bit ptr size + 1u64 as isize; // wraps on 64 bit ptr size // Test clippy::cast_sign_loss 1i32 as u32; -1i32 as u32; diff --git a/tests/ui/cast.stderr b/tests/ui/cast.stderr index 65ecf1aa37a..de29af78ef3 100644 --- a/tests/ui/cast.stderr +++ b/tests/ui/cast.stderr @@ -215,20 +215,110 @@ error: casting `usize` to `isize` may wrap around the value LL | 1usize as isize; | ^^^^^^^^^^^^^^^ -error: casting `i32` to `u32` may lose the sign of the value +error: casting `usize` to `i8` may truncate the value + --> $DIR/cast.rs:44:5 + | +LL | 1usize as i8; // should not wrap, usize is never 8 bits + | ^^^^^^^^^^^^ + | + = help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ... +help: ... or use `try_from` and handle the error accordingly + | +LL | i8::try_from(1usize); // should not wrap, usize is never 8 bits + | ~~~~~~~~~~~~~~~~~~~~ + +error: casting `usize` to `i16` may truncate the value + --> $DIR/cast.rs:45:5 + | +LL | 1usize as i16; // wraps on 16 bit ptr size + | ^^^^^^^^^^^^^ + | + = help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ... +help: ... or use `try_from` and handle the error accordingly + | +LL | i16::try_from(1usize); // wraps on 16 bit ptr size + | ~~~~~~~~~~~~~~~~~~~~~ + +error: casting `usize` to `i16` may wrap around the value on targets with 16-bit wide pointers + --> $DIR/cast.rs:45:5 + | +LL | 1usize as i16; // wraps on 16 bit ptr size + | ^^^^^^^^^^^^^ + | + = note: `usize` and `isize` may be as small as 16 bits on some platforms + = note: for more information see https://doc.rust-lang.org/reference/types/numeric.html#machine-dependent-integer-types + +error: casting `usize` to `i32` may truncate the value on targets with 64-bit wide pointers --> $DIR/cast.rs:46:5 | +LL | 1usize as i32; // wraps on 32 bit ptr size + | ^^^^^^^^^^^^^ + | + = help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ... +help: ... or use `try_from` and handle the error accordingly + | +LL | i32::try_from(1usize); // wraps on 32 bit ptr size + | ~~~~~~~~~~~~~~~~~~~~~ + +error: casting `usize` to `i32` may wrap around the value on targets with 32-bit wide pointers + --> $DIR/cast.rs:46:5 + | +LL | 1usize as i32; // wraps on 32 bit ptr size + | ^^^^^^^^^^^^^ + +error: casting `usize` to `i64` may wrap around the value on targets with 64-bit wide pointers + --> $DIR/cast.rs:47:5 + | +LL | 1usize as i64; // wraps on 64 bit ptr size + | ^^^^^^^^^^^^^ + +error: casting `u16` to `isize` may wrap around the value on targets with 16-bit wide pointers + --> $DIR/cast.rs:49:5 + | +LL | 1u16 as isize; // wraps on 16 bit ptr size + | ^^^^^^^^^^^^^ + | + = note: `usize` and `isize` may be as small as 16 bits on some platforms + = note: for more information see https://doc.rust-lang.org/reference/types/numeric.html#machine-dependent-integer-types + +error: casting `u32` to `isize` may wrap around the value on targets with 32-bit wide pointers + --> $DIR/cast.rs:50:5 + | +LL | 1u32 as isize; // wraps on 32 bit ptr size + | ^^^^^^^^^^^^^ + +error: casting `u64` to `isize` may truncate the value on targets with 32-bit wide pointers + --> $DIR/cast.rs:51:5 + | +LL | 1u64 as isize; // wraps on 64 bit ptr size + | ^^^^^^^^^^^^^ + | + = help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ... +help: ... or use `try_from` and handle the error accordingly + | +LL | isize::try_from(1u64); // wraps on 64 bit ptr size + | ~~~~~~~~~~~~~~~~~~~~~ + +error: casting `u64` to `isize` may wrap around the value on targets with 64-bit wide pointers + --> $DIR/cast.rs:51:5 + | +LL | 1u64 as isize; // wraps on 64 bit ptr size + | ^^^^^^^^^^^^^ + +error: casting `i32` to `u32` may lose the sign of the value + --> $DIR/cast.rs:54:5 + | LL | -1i32 as u32; | ^^^^^^^^^^^^ error: casting `isize` to `usize` may lose the sign of the value - --> $DIR/cast.rs:48:5 + --> $DIR/cast.rs:56:5 | LL | -1isize as usize; | ^^^^^^^^^^^^^^^^ error: casting `i64` to `i8` may truncate the value - --> $DIR/cast.rs:115:5 + --> $DIR/cast.rs:123:5 | LL | (-99999999999i64).min(1) as i8; // should be linted because signed | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -240,7 +330,7 @@ LL | i8::try_from((-99999999999i64).min(1)); // should be linted because sig | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ error: casting `u64` to `u8` may truncate the value - --> $DIR/cast.rs:127:5 + --> $DIR/cast.rs:135:5 | LL | 999999u64.clamp(0, 256) as u8; // should still be linted | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -252,7 +342,7 @@ LL | u8::try_from(999999u64.clamp(0, 256)); // should still be linted | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ error: casting `main::E2` to `u8` may truncate the value - --> $DIR/cast.rs:148:21 + --> $DIR/cast.rs:156:21 | LL | let _ = self as u8; | ^^^^^^^^^^ @@ -264,7 +354,7 @@ LL | let _ = u8::try_from(self); | ~~~~~~~~~~~~~~~~~~ error: casting `main::E2::B` to `u8` will truncate the value - --> $DIR/cast.rs:149:21 + --> $DIR/cast.rs:157:21 | LL | let _ = Self::B as u8; | ^^^^^^^^^^^^^ @@ -272,7 +362,7 @@ LL | let _ = Self::B as u8; = note: `-D clippy::cast-enum-truncation` implied by `-D warnings` error: casting `main::E5` to `i8` may truncate the value - --> $DIR/cast.rs:185:21 + --> $DIR/cast.rs:193:21 | LL | let _ = self as i8; | ^^^^^^^^^^ @@ -284,13 +374,13 @@ LL | let _ = i8::try_from(self); | ~~~~~~~~~~~~~~~~~~ error: casting `main::E5::A` to `i8` will truncate the value - --> $DIR/cast.rs:186:21 + --> $DIR/cast.rs:194:21 | LL | let _ = Self::A as i8; | ^^^^^^^^^^^^^ error: casting `main::E6` to `i16` may truncate the value - --> $DIR/cast.rs:200:21 + --> $DIR/cast.rs:208:21 | LL | let _ = self as i16; | ^^^^^^^^^^^ @@ -302,7 +392,7 @@ LL | let _ = i16::try_from(self); | ~~~~~~~~~~~~~~~~~~~ error: casting `main::E7` to `usize` may truncate the value on targets with 32-bit wide pointers - --> $DIR/cast.rs:215:21 + --> $DIR/cast.rs:223:21 | LL | let _ = self as usize; | ^^^^^^^^^^^^^ @@ -314,7 +404,7 @@ LL | let _ = usize::try_from(self); | ~~~~~~~~~~~~~~~~~~~~~ error: casting `main::E10` to `u16` may truncate the value - --> $DIR/cast.rs:256:21 + --> $DIR/cast.rs:264:21 | LL | let _ = self as u16; | ^^^^^^^^^^^ @@ -326,7 +416,7 @@ LL | let _ = u16::try_from(self); | ~~~~~~~~~~~~~~~~~~~ error: casting `u32` to `u8` may truncate the value - --> $DIR/cast.rs:264:13 + --> $DIR/cast.rs:272:13 | LL | let c = (q >> 16) as u8; | ^^^^^^^^^^^^^^^ @@ -338,7 +428,7 @@ LL | let c = u8::try_from(q >> 16); | ~~~~~~~~~~~~~~~~~~~~~ error: casting `u32` to `u8` may truncate the value - --> $DIR/cast.rs:267:13 + --> $DIR/cast.rs:275:13 | LL | let c = (q / 1000) as u8; | ^^^^^^^^^^^^^^^^ @@ -349,5 +439,5 @@ help: ... or use `try_from` and handle the error accordingly LL | let c = u8::try_from(q / 1000); | ~~~~~~~~~~~~~~~~~~~~~~ -error: aborting due to 41 previous errors +error: aborting due to 51 previous errors |