minor fixes

Author: pvdrz

src/helpers.rs

@@ -374,7 +374,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
     fn check_platform(&mut self, platform: &str, name: &str) -> InterpResult<'tcx> {
         if self.eval_context_mut().tcx.sess.target.target.target_os.to_lowercase() != platform {
             throw_unsup_format!(
-                "`{}` is only available in the `{}` platform",
+                "`{}` is only available on the `{}` platform",
                 name,
                 platform,
             )

src/shims/foreign_items.rs

@@ -179,8 +179,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
     }
 
     /// Emulates calling a foreign item using its name, failing if the item is not supported.
-    /// Returns Ok(false) if after calling this function, the call should return earlier instead of
-    /// going to the next block.
+    /// Returns `true` if the caller is expected to jump to the return block, and `false` if
+    /// jumping has already been taken care of.
     fn emulate_foreign_item_by_name(
         &mut self,
         link_name: &str,
@@ -315,35 +315,35 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 this.write_scalar(Scalar::from_int(result, Size::from_bits(32)), dest)?;
             }
 
-            "memchr" => {
+            "memrchr" => {
                 let ptr = this.read_scalar(args[0])?.not_undef()?;
                 let val = this.read_scalar(args[1])?.to_i32()? as u8;
                 let num = this.read_scalar(args[2])?.to_machine_usize(this)?;
-                let idx = this
+                if let Some(idx) = this
                     .memory
                     .read_bytes(ptr, Size::from_bytes(num))?
                     .iter()
-                    .position(|&c| c == val);
-                if let Some(idx) = idx {
-                    let new_ptr = ptr.ptr_offset(Size::from_bytes(idx as u64), this)?;
+                    .rev()
+                    .position(|&c| c == val)
+                {
+                    let new_ptr = ptr.ptr_offset(Size::from_bytes(num - idx as u64 - 1), this)?;
                     this.write_scalar(new_ptr, dest)?;
                 } else {
                     this.write_null(dest)?;
                 }
             }
 
-            "memrchr" => {
+            "memchr" => {
                 let ptr = this.read_scalar(args[0])?.not_undef()?;
                 let val = this.read_scalar(args[1])?.to_i32()? as u8;
                 let num = this.read_scalar(args[2])?.to_machine_usize(this)?;
-                if let Some(idx) = this
+                let idx = this
                     .memory
                     .read_bytes(ptr, Size::from_bytes(num))?
                     .iter()
-                    .rev()
-                    .position(|&c| c == val)
-                {
-                    let new_ptr = ptr.ptr_offset(Size::from_bytes(num - idx as u64 - 1), this)?;
+                    .position(|&c| c == val);
+                if let Some(idx) = idx {
+                    let new_ptr = ptr.ptr_offset(Size::from_bytes(idx as u64), this)?;
                     this.write_scalar(new_ptr, dest)?;
                 } else {
                     this.write_null(dest)?;

src/shims/foreign_items/posix/linux.rs

@@ -25,6 +25,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             }
 
             // Time related shims
+
+            // This is a POSIX function but it has only been tested on linux.
             "clock_gettime" => {
                 let result = this.clock_gettime(args[0], args[1])?;
                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
@@ -80,7 +82,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
     }
 }
 
-// Shims the posix 'getrandom()' syscall.
+// Shims the linux 'getrandom()' syscall.
 fn getrandom<'tcx>(
     this: &mut MiriEvalContext<'_, 'tcx>,
     args: &[OpTy<'tcx, Tag>],