Only load LOCAL_STREAMS if they are being used

2020-10-22 03:22:13 -07:00
parent d0d0e78208
commit db15596c57
1 changed files with 5 additions and 0 deletions
--- a/library/std/src/io/stdio.rs
+++ b/library/std/src/io/stdio.rs
@@ -963,6 +963,11 @@ pub fn set_print(sink: Option<Box<dyn LocalOutput>>) -> Option<Box<dyn LocalOutp
 }

 pub(crate) fn clone_io() -> (Option<Box<dyn LocalOutput>>, Option<Box<dyn LocalOutput>>) {
+    // Don't waste time when LOCAL_{STDOUT,STDERR} are definitely None.
+    if !LOCAL_STREAMS.load(Ordering::Relaxed) {
+        return (None, None);
+    }
+
    LOCAL_STDOUT.with(|stdout| {
        LOCAL_STDERR.with(|stderr| {
            (