Add comments to the helpers

Author: tiif

src/shims/unix/fd.rs

@@ -647,8 +647,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         Ok(())
     }
 
-    /// This function write bytes to the user supplied buffer and write the total number of bytes
-    /// written to the dest place. (TODO: fix phrasing later, this function might change)
+    /// This function either writes to the user supplied buffer and to dest place, or return error.
     fn read_byte_helper(
         &mut self,
         buf: Pointer,
@@ -680,6 +679,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         }
     }
 
+    /// This function either writes the number of written bytes to dest place or return error.
     fn write_byte_helper(
         &mut self,
         result: io::Result<usize>,