From 7ac4154643a952fed1d942adcb78e27b17ad41dd Mon Sep 17 00:00:00 2001
From: Markus Westerlind <markus.westerlind@distilnetworks.com>
Date: Mon, 17 Feb 2020 08:09:34 +0100
Subject: [PATCH] perf: Buffer stderr when writing json errors/warnings

Since `stderr` is unbuffered, writing out json messages actually take up
about ~10%/0.1s of the runtime of the `inflate` benchmark.

cc #64413
---
 src/librustc_errors/json.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/librustc_errors/json.rs b/src/librustc_errors/json.rs
index ffdff6acec5..f0cfd815a2c 100644
--- a/src/librustc_errors/json.rs
+++ b/src/librustc_errors/json.rs
@@ -48,7 +48,7 @@ pub fn stderr(
         macro_backtrace: bool,
     ) -> JsonEmitter {
         JsonEmitter {
-            dst: Box::new(io::stderr()),
+            dst: Box::new(io::BufWriter::new(io::stderr())),
             registry,
             sm: source_map,
             pretty,
-- 
2.44.0