From cc35b5e7246672b0768a14d4e004c76026dcf84c Mon Sep 17 00:00:00 2001
From: Jakob Stoklund Olesen <jolesen@mozilla.com>
Date: Tue, 12 Sep 2017 08:59:35 -0700
Subject: [PATCH] Flush the debug trace file after each dbg!().

When debugging code built with panic=about, the debug trace buffer is
not flushed on a panic and important messages are lost.

This does slow down debug tracing a bit, but this is still better than
unbuffered or line buffered I/O since the dbg!() macro can write out
many lines like a whole function.
---
 lib/cretonne/src/dbg.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/cretonne/src/dbg.rs b/lib/cretonne/src/dbg.rs
index 0ac03f4c4f..9bd5500e3c 100644
--- a/lib/cretonne/src/dbg.rs
+++ b/lib/cretonne/src/dbg.rs
@@ -63,7 +63,11 @@ thread_local! {
 ///
 /// This is for use by the `dbg!` macro.
 pub fn writeln_with_format_args(args: fmt::Arguments) -> io::Result<()> {
-    WRITER.with(|rc| writeln!(*rc.borrow_mut(), "{}", args))
+    WRITER.with(|rc| {
+        let mut w = rc.borrow_mut();
+        writeln!(*w, "{}", args)?;
+        w.flush()
+    })
 }
 
 /// Open the tracing file for the current thread.