enable clippy lints against integer casts

src/intptrcast.rs

@@ -230,6 +230,7 @@ impl<'mir, 'tcx> GlobalStateInner {
 
         // Wrapping "addr - base_addr"
         let dl = ecx.data_layout();
+        #[allow(clippy::cast_possible_wrap)] // we want to wrap here
         let neg_base_addr = (base_addr as i64).wrapping_neg();
         Some((
             alloc_id,

src/lib.rs

@@ -9,7 +9,7 @@
 #![feature(is_some_with)]
 #![feature(nonzero_ops)]
 #![feature(local_key_cell_methods)]
-#![warn(rust_2018_idioms)]
+// Configure clippy and other lints
 #![allow(
     clippy::collapsible_else_if,
     clippy::collapsible_if,
@@ -24,6 +24,13 @@
     clippy::derive_hash_xor_eq,
     clippy::too_many_arguments
 )]
+#![warn(
+    rust_2018_idioms,
+    clippy::cast_possible_wrap, // unsigned -> signed
+    clippy::cast_sign_loss, // signed -> unsigned
+    clippy::cast_lossless,
+    clippy::cast_possible_truncation,
+)]
 
 extern crate rustc_apfloat;
 extern crate rustc_ast;

src/shims/backtrace.rs

@@ -171,9 +171,11 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             );
         }
 
-        let lineno: u32 = lo.line as u32;
+        // `u32` is not enough to fit line/colno, which can be `usize`. It seems unlikely that a
+        // file would have more than 2^32 lines or columns, but whatever, just default to 0.
+        let lineno: u32 = u32::try_from(lo.line).unwrap_or(0);
         // `lo.col` is 0-based - add 1 to make it 1-based for the caller.
-        let colno: u32 = lo.col.0 as u32 + 1;
+        let colno: u32 = u32::try_from(lo.col.0 + 1).unwrap_or(0);
 
         let dest = this.force_allocation(dest)?;
         if let ty::Adt(adt, _) = dest.layout.ty.kind() {

src/shims/env.rs

@@ -202,7 +202,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         let env_block_ptr = this.read_pointer(env_block_op)?;
         let result = this.deallocate_ptr(env_block_ptr, None, MiriMemoryKind::Runtime.into());
         // If the function succeeds, the return value is nonzero.
-        Ok(result.is_ok() as i32)
+        Ok(i32::from(result.is_ok()))
     }
 
     fn setenv(
@@ -459,7 +459,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         // The reason we need to do this wacky of a conversion is because
         // `libc::getpid` returns an i32, however, `std::process::id()` return an u32.
         // So we un-do the conversion that stdlib does and turn it back into an i32.
-
+        #[allow(clippy::cast_possible_wrap)]
         Ok(std::process::id() as i32)
     }
 

src/shims/foreign_items.rs

@@ -82,8 +82,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             let align = this.min_align(size, kind);
             let ptr = this.allocate_ptr(Size::from_bytes(size), align, kind.into())?;
             if zero_init {
-                // We just allocated this, the access is definitely in-bounds.
-                this.write_bytes_ptr(ptr.into(), iter::repeat(0u8).take(size as usize)).unwrap();
+                // We just allocated this, the access is definitely in-bounds and fits into our address space.
+                this.write_bytes_ptr(
+                    ptr.into(),
+                    iter::repeat(0u8).take(usize::try_from(size).unwrap()),
+                )
+                .unwrap();
             }
             Ok(ptr.into())
         }
@@ -526,8 +530,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             "memrchr" => {
                 let [ptr, val, num] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
                 let ptr = this.read_pointer(ptr)?;
-                let val = this.read_scalar(val)?.to_i32()? as u8;
+                let val = this.read_scalar(val)?.to_i32()?;
                 let num = this.read_scalar(num)?.to_machine_usize(this)?;
+                // The docs say val is "interpreted as unsigned char".
+                #[allow(clippy::cast_sign_loss, clippy::cast_possible_truncation)]
+                let val = val as u8;
+
                 if let Some(idx) = this
                     .read_bytes_ptr(ptr, Size::from_bytes(num))?
                     .iter()
@@ -543,8 +551,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             "memchr" => {
                 let [ptr, val, num] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
                 let ptr = this.read_pointer(ptr)?;
-                let val = this.read_scalar(val)?.to_i32()? as u8;
+                let val = this.read_scalar(val)?.to_i32()?;
                 let num = this.read_scalar(num)?.to_machine_usize(this)?;
+                // The docs say val is "interpreted as unsigned char".
+                #[allow(clippy::cast_sign_loss, clippy::cast_possible_truncation)]
+                let val = val as u8;
+
                 let idx = this
                     .read_bytes_ptr(ptr, Size::from_bytes(num))?
                     .iter()

src/shims/intrinsics/mod.rs

@@ -117,10 +117,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 let byte_count = ty_layout.size.checked_mul(count, this).ok_or_else(|| {
                     err_ub_format!("overflow computing total size of `{intrinsic_name}`")
                 })?;
-                this.write_bytes_ptr(
-                    ptr,
-                    iter::repeat(val_byte).take(byte_count.bytes() as usize),
-                )?;
+                this.write_bytes_ptr(ptr, iter::repeat(val_byte).take(byte_count.bytes_usize()))?;
             }
 
             // Floating-point operations

src/shims/tls.rs

@@ -73,7 +73,7 @@ impl<'tcx> TlsData<'tcx> {
         self.keys.try_insert(new_key, TlsEntry { data: Default::default(), dtor }).unwrap();
         trace!("New TLS key allocated: {} with dtor {:?}", new_key, dtor);
 
-        if max_size.bits() < 128 && new_key >= (1u128 << max_size.bits() as u128) {
+        if max_size.bits() < 128 && new_key >= (1u128 << max_size.bits()) {
             throw_unsup_format!("we ran out of TLS key space");
         }
         Ok(new_key)

src/shims/unix/fs.rs

@@ -776,15 +776,17 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
         // We cap the number of read bytes to the largest value that we are able to fit in both the
         // host's and target's `isize`. This saves us from having to handle overflows later.
-        let count = count.min(this.machine_isize_max() as u64).min(isize::MAX as u64);
+        let count = count
+            .min(u64::try_from(this.machine_isize_max()).unwrap())
+            .min(u64::try_from(isize::MAX).unwrap());
         let communicate = this.machine.communicate();
 
         if let Some(file_descriptor) = this.machine.file_handler.handles.get_mut(&fd) {
             trace!("read: FD mapped to {:?}", file_descriptor);
             // We want to read at most `count` bytes. We are sure that `count` is not negative
             // because it was a target's `usize`. Also we are sure that its smaller than
-            // `usize::MAX` because it is a host's `isize`.
-            let mut bytes = vec![0; count as usize];
+            // `usize::MAX` because it is bounded by the host's `isize`.
+            let mut bytes = vec![0; usize::try_from(count).unwrap()];
             // `File::read` never returns a value larger than `count`,
             // so this cannot fail.
             let result =
@@ -827,7 +829,9 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
         // We cap the number of written bytes to the largest value that we are able to fit in both the
         // host's and target's `isize`. This saves us from having to handle overflows later.
-        let count = count.min(this.machine_isize_max() as u64).min(isize::MAX as u64);
+        let count = count
+            .min(u64::try_from(this.machine_isize_max()).unwrap())
+            .min(u64::try_from(isize::MAX).unwrap());
         let communicate = this.machine.communicate();
 
         if let Some(file_descriptor) = this.machine.file_handler.handles.get(&fd) {

src/shims/windows/dlsym.rs

@@ -84,7 +84,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                     } else {
                         io::stderr().write(buf_cont)
                     };
-                    res.ok().map(|n| n as u32)
+                    // We write at most `n` bytes, which is a `u32`, so we cannot have written more than that.
+                    res.ok().map(|n| u32::try_from(n).unwrap())
                 } else {
                     throw_unsup_format!(
                         "on Windows, writing to anything except stdout/stderr is not supported"
@@ -102,7 +103,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 // Return whether this was a success. >= 0 is success.
                 // For the error code we arbitrarily pick 0xC0000185, STATUS_IO_DEVICE_ERROR.
                 this.write_scalar(
-                    Scalar::from_i32(if written.is_some() { 0 } else { 0xC0000185u32 as i32 }),
+                    Scalar::from_u32(if written.is_some() { 0 } else { 0xC0000185u32 }),
                     dest,
                 )?;
             }

src/shims/windows/foreign_items.rs

@@ -116,7 +116,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 // Initialize with `0`.
                 this.write_bytes_ptr(
                     system_info.ptr,
-                    iter::repeat(0u8).take(system_info.layout.size.bytes() as usize),
+                    iter::repeat(0u8).take(system_info.layout.size.bytes_usize()),
                 )?;
                 // Set selected fields.
                 let word_layout = this.machine.layouts.u16;

src/stacked_borrows/item.rs

@@ -22,7 +22,7 @@ impl Item {
         assert!(tag.0.get() <= TAG_MASK);
         let packed_tag = tag.0.get();
         let packed_perm = perm.to_bits() << PERM_SHIFT;
-        let packed_protected = (protected as u64) << PROTECTED_SHIFT;
+        let packed_protected = u64::from(protected) << PROTECTED_SHIFT;
 
         let new = Self(packed_tag | packed_perm | packed_protected);