pass clippy::cast_sign_loss and clippy::cast_possible_wrap

Author: RalfJung

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

@@ -24,7 +24,12 @@
     clippy::derive_hash_xor_eq,
     clippy::too_many_arguments
 )]
-#![warn(rust_2018_idioms, clippy::cast_lossless)]
+#![warn(
+    rust_2018_idioms,
+    clippy::cast_possible_wrap, // unsigned -> signed
+    clippy::cast_sign_loss, // signed -> unsigned
+    clippy::cast_lossless,
+)]
 
 extern crate rustc_apfloat;
 extern crate rustc_ast;

src/shims/env.rs

@@ -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

@@ -526,8 +526,12 @@ 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)]
+                let val = val as u8;
+
                 if let Some(idx) = this
                     .read_bytes_ptr(ptr, Size::from_bytes(num))?
                     .iter()
@@ -543,8 +547,12 @@ 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)]
+                let val = val as u8;
+
                 let idx = this
                     .read_bytes_ptr(ptr, Size::from_bytes(num))?
                     .iter()

src/shims/unix/fs.rs

@@ -776,7 +776,9 @@ 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) {
@@ -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

@@ -102,7 +102,7 @@ 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,
                 )?;
             }