Add comment for the flag diff check

pvdrz · pvdrz · commit 1c64f29811db · 2019-10-11T03:55:18.000-05:00
diff --git a/src/shims/fs.rs b/src/shims/fs.rs
@@ -107,6 +107,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             if let Some(FileHandle { flag: old_flag, .. }) =
                 this.machine.file_handler.handles.get_mut(&fd)
             {
+                // Check that the only difference between the old flag and the current flag is
+                // exactly the `FD_CLOEXEC` value.
                 if flag ^ *old_flag == fd_cloexec {
                     *old_flag = flag;
                 } else {

Original file line number	Diff line number	Diff line change
`@@ -107,6 +107,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx`
`107`	`107`	`if let Some(FileHandle { flag: old_flag, .. }) =`
`108`	`108`	`this.machine.file_handler.handles.get_mut(&fd)`
`109`	`109`	`{`
	`110`	`+ // Check that the only difference between the old flag and the current flag is`
	`111`	+ // exactly the `FD_CLOEXEC` value.
`110`	`112`	`if flag ^ *old_flag == fd_cloexec {`
`111`	`113`	`*old_flag = flag;`
`112`	`114`	`} else {`