Selectively enable clippy::cast_sign_loss

This would have fixed bytecodealliance#7558 so try to head off future issues with that
by warning against this situation in a few crates. This lint is still
quite noisy though for Cranelift for example so it's not worthwhile at
this time to enable it for the whole workspace.

Cargo.toml

@@ -135,12 +135,16 @@ edition = "2021"
 rust-version = "1.72.0"
 
 [workspace.lints.rust]
+# Turn on some lints which are otherwise allow-by-default in rustc.
 unused_extern_crates = 'warn'
 trivial_numeric_casts = 'warn'
 unstable_features = 'warn'
 unused_import_braces = 'warn'
 
 [workspace.lints.clippy]
+# The default set of lints in Clippy is viewed as "too noisy" right now so
+# they're all turned off by default. Selective lints are then enabled below as
+# necessary.
 all = 'allow'
 
 [workspace.dependencies]

cranelift/entity/src/lib.rs

@@ -202,6 +202,7 @@ mod map;
 mod primary;
 mod set;
 mod sparse;
+mod unsigned;
 
 pub use self::boxed_slice::BoxedSlice;
 pub use self::iter::{Iter, IterMut};
@@ -211,6 +212,7 @@ pub use self::map::SecondaryMap;
 pub use self::primary::PrimaryMap;
 pub use self::set::EntitySet;
 pub use self::sparse::{SparseMap, SparseMapValue, SparseSet};
+pub use self::unsigned::Unsigned;
 
 /// A collection of tests to ensure that use of the different `entity_impl!` forms will generate
 /// `EntityRef` implementations that behave the same way.

cranelift/entity/src/unsigned.rs

@@ -0,0 +1,71 @@
+/// Helper trait used to add `unsigned()` methods to primitive signed integer
+/// types.
+///
+/// The purpose of this trait is to signal the intent that the sign bit of a
+/// signed integer is intended to be discarded and the value is instead
+/// understood to be a "bag of bits" where the conversion to an unsigned number
+/// is intended to be lossless. This can be used for example when converting a
+/// signed integer into a larger width with zero-extension.
+pub trait Unsigned {
+ /// The unsigned integer for this type which has the same width.
+ type Unsigned;
+
+ /// View this signed integer as an unsigned integer of the same width.
+ ///
+ /// All bits are preserved.
+ fn unsigned(self) -> Self::Unsigned;
+}
+
+impl Unsigned for i8 {
+ type Unsigned = u8;
+
+ #[inline]
+ fn unsigned(self) -> u8 {
+ self as u8
+ }
+}
+
+impl Unsigned for i16 {
+ type Unsigned = u16;
+
+ #[inline]
+ fn unsigned(self) -> u16 {
+ self as u16
+ }
+}
+
+impl Unsigned for i32 {
+ type Unsigned = u32;
+
+ #[inline]
+ fn unsigned(self) -> u32 {
+ self as u32
+ }
+}
+
+impl Unsigned for i64 {
+ type Unsigned = u64;
+
+ #[inline]
+ fn unsigned(self) -> u64 {
+ self as u64
+ }
+}
+
+impl Unsigned for i128 {
+ type Unsigned = u128;
+
+ #[inline]
+ fn unsigned(self) -> u128 {
+ self as u128
+ }
+}
+
+impl Unsigned for isize {
+ type Unsigned = usize;
+
+ #[inline]
+ fn unsigned(self) -> usize {
+ self as usize
+ }
+}

crates/environ/src/lib.rs

@@ -4,6 +4,7 @@
 //! linear memories.
 
 #![deny(missing_docs)]
+#![warn(clippy::cast_sign_loss)]
 
 mod address_map;
 mod builtin;

crates/environ/src/module_environ.rs

@@ -5,8 +5,8 @@ use crate::module::{
 use crate::{
  DataIndex, DefinedFuncIndex, ElemIndex, EntityIndex, EntityType, FuncIndex, GlobalIndex,
  GlobalInit, MemoryIndex, ModuleTypesBuilder, PrimaryMap, SignatureIndex, TableIndex,
- TableInitialValue, Tunables, TypeConvert, TypeIndex, WasmError, WasmFuncType, WasmHeapType,
- WasmResult, WasmType,
+ TableInitialValue, Tunables, TypeConvert, TypeIndex, Unsigned, WasmError, WasmFuncType,
+ WasmHeapType, WasmResult, WasmType,
 };
 use cranelift_entity::packed_option::ReservedValue;
 use std::borrow::Cow;
@@ -487,7 +487,7 @@ impl<'a, 'data> ModuleEnvironment<'a, 'data> {
  let table_index = TableIndex::from_u32(table_index.unwrap_or(0));
  let mut offset_expr_reader = offset_expr.get_binary_reader();
  let (base, offset) = match offset_expr_reader.read_operator()? {
- Operator::I32Const { value } => (None, value as u32),
+ Operator::I32Const { value } => (None, value.unsigned()),
  Operator::GlobalGet { global_index } => {
  (Some(GlobalIndex::from_u32(global_index)), 0)
  }
@@ -607,8 +607,8 @@ impl<'a, 'data> ModuleEnvironment<'a, 'data> {
  let memory_index = MemoryIndex::from_u32(memory_index);
  let mut offset_expr_reader = offset_expr.get_binary_reader();
  let (base, offset) = match offset_expr_reader.read_operator()? {
- Operator::I32Const { value } => (None, value as u64),
- Operator::I64Const { value } => (None, value as u64),
+ Operator::I32Const { value } => (None, value.unsigned().into()),
+ Operator::I64Const { value } => (None, value.unsigned()),
  Operator::GlobalGet { global_index } => {
  (Some(GlobalIndex::from_u32(global_index)), 0)
  }

crates/runtime/src/lib.rs

@@ -1,6 +1,7 @@
 //! Runtime library support for Wasmtime.
 
 #![deny(missing_docs)]
+#![warn(clippy::cast_sign_loss)]
 
 use anyhow::{Error, Result};
 use std::fmt;
@@ -240,7 +241,7 @@ pub fn page_size() -> usize {
 
  #[cfg(unix)]
  fn get_page_size() -> usize {
- unsafe { libc::sysconf(libc::_SC_PAGESIZE) as usize }
+ unsafe { libc::sysconf(libc::_SC_PAGESIZE).try_into().unwrap() }
  }
 }
 

crates/runtime/src/libcalls.rs

@@ -66,7 +66,7 @@ use std::mem;
 use std::ptr::{self, NonNull};
 use std::time::{Duration, Instant};
 use wasmtime_environ::{
- DataIndex, ElemIndex, FuncIndex, GlobalIndex, MemoryIndex, TableIndex, Trap,
+ DataIndex, ElemIndex, FuncIndex, GlobalIndex, MemoryIndex, TableIndex, Trap, Unsigned,
 };
 #[cfg(feature = "wmemcheck")]
 use wasmtime_wmemcheck::AccessError::{
@@ -233,7 +233,7 @@ unsafe fn table_grow(
  };
  Ok(match instance.table_grow(table_index, delta, element)? {
  Some(r) => r,
- None => -1_i32 as u32,
+ None => (-1_i32).unsigned(),
  })
 }
 

crates/runtime/src/traphandlers/macos.rs

@@ -31,7 +31,7 @@
 //! function declarations. Many bits and pieces are copied or translated from
 //! the SpiderMonkey implementation and it should pass all the tests!
 
-#![allow(non_snake_case)]
+#![allow(non_snake_case, clippy::cast_sign_loss)]
 
 use crate::traphandlers::{tls, wasmtime_longjmp};
 use mach::exception_types::*;

crates/runtime/src/vmcontext.rs

@@ -12,7 +12,7 @@ use std::ptr::NonNull;
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::u32;
 pub use vm_host_func_context::{VMArrayCallHostFuncContext, VMNativeCallHostFuncContext};
-use wasmtime_environ::{DefinedMemoryIndex, VMCONTEXT_MAGIC};
+use wasmtime_environ::{DefinedMemoryIndex, Unsigned, VMCONTEXT_MAGIC};
 
 /// A function pointer that exposes the array calling convention.
 ///
@@ -1038,7 +1038,7 @@ impl ValRaw {
  // `wasmtime` crate. Otherwise though all `ValRaw` constructors are
  // otherwise constrained to guarantee that the initial 64-bits are
  // always initialized.
- ValRaw::u64((i as u32).into())
+ ValRaw::u64(i.unsigned().into())
  }
 
  /// Creates a WebAssembly `i64` value
@@ -1112,13 +1112,13 @@ impl ValRaw {
  /// Gets the WebAssembly `i32` value
  #[inline]
  pub fn get_u32(&self) -> u32 {
- self.get_i32() as u32
+ self.get_i32().unsigned()
  }
 
  /// Gets the WebAssembly `i64` value
  #[inline]
  pub fn get_u64(&self) -> u64 {
- self.get_i64() as u64
+ self.get_i64().unsigned()
  }
 
  /// Gets the WebAssembly `f32` value

crates/wasi-common/src/lib.rs

@@ -50,6 +50,9 @@
 //! `WasiCtx::builder(...)` function. The
 //! `wasi_cap_std_sync::WasiCtxBuilder::new()` function uses this public
 //! interface to plug in its own implementations of each of these resources.
+
+#![warn(clippy::cast_sign_loss)]
+
 pub mod clocks;
 mod ctx;
 pub mod dir;

crates/wasi-common/src/snapshots/preview_1.rs

@@ -554,7 +554,9 @@ impl wasi_snapshot_preview1::WasiSnapshotPreview1 for WasiCtx {
  let whence = match whence {
  types::Whence::Cur => SeekFrom::Current(offset),
  types::Whence::End => SeekFrom::End(offset),
- types::Whence::Set => SeekFrom::Start(offset as u64),
+ types::Whence::Set => {
+ SeekFrom::Start(offset.try_into().map_err(|_| Error::invalid_argument())?)
+ }
  };
  let newoffset = self
  .table()

crates/wasi/src/lib.rs

@@ -7,6 +7,8 @@
 //! Individual snapshots are available through
 //! `wasmtime_wasi::snapshots::preview_{0, 1}::Wasi::new(&Store, Rc<RefCell<WasiCtx>>)`.
 
+#![warn(clippy::cast_sign_loss)]
+
 #[cfg(feature = "preview2")]
 pub mod preview2;
 

crates/wasi/src/preview2/preview1.rs

@@ -1565,7 +1565,9 @@ impl<
  let position = position.clone();
  drop(t);
  let pos = match whence {
- types::Whence::Set if offset >= 0 => offset as _,
+ types::Whence::Set if offset >= 0 => {
+ offset.try_into().map_err(|_| types::Errno::Inval)?
+ }
  types::Whence::Cur => position
  .load(Ordering::Relaxed)
  .checked_add_signed(offset)