---

yaml
---
r: 236451
b: refs/heads/auto
c: 54c0231
h: refs/heads/master
i:
  236449: 9a0ca9f
  236447: 98871f6
v: v3

Author: ranma42

[refs]

@@ -8,7 +8,7 @@ refs/tags/release-0.3: b5f0d0f648d9a6153664837026ba1be43d3e2503
 refs/tags/release-0.3.1: 495bae036dfe5ec6ceafd3312b4dca48741e845b
 refs/tags/release-0.4: e828ea2080499553b97dfe33b3f4d472b4562ad7
 refs/tags/release-0.5: 7e3bcfbf21278251ee936ad53e92e9b719702d73
-refs/heads/auto: c7b84909b00dcf5f762778b4aa9783770c69416d
+refs/heads/auto: 54c0231b14a71a46e6607255d509457e0df0b8be
 refs/tags/release-0.6: b4ebcfa1812664df5e142f0134a5faea3918544c
 refs/tags/0.1: b19db808c2793fe2976759b85a355c3ad8c8b336
 refs/tags/0.2: 1754d02027f2924bed83b0160ee340c7f41d5ea1

branches/auto/src/libstd/panicking.rs

@@ -52,7 +52,6 @@ fn log_panic(obj: &(Any+Send), file: &'static str, line: u32,
     let prev = LOCAL_STDERR.with(|s| s.borrow_mut().take());
     match (prev, err.as_mut()) {
         (Some(mut stderr), _) => {
-            // FIXME: what to do when the thread printing panics?
             write(&mut *stderr);
             let mut s = Some(stderr);
             LOCAL_STDERR.with(|slot| {
@@ -71,6 +70,17 @@ pub fn on_panic(obj: &(Any+Send), file: &'static str, line: u32) {
         count
     });
 
+    // If this is the third nested call, on_panic triggered the last panic,
+    // otherwise the double-panic check would have aborted the process.
+    // Even if it is likely that on_panic was unable to log the backtrace,
+    // abort immediately to avoid infinite recursion, so that attaching a
+    // debugger provides a useable stacktrace.
+    if panics >= 3 {
+        util::dumb_print(format_args!("thread panicked while processing \
+                                       panic. aborting."));
+        unsafe { intrinsics::abort() }
+    }
+
     // If this is a double panic, make sure that we print a backtrace
     // for this panic. Otherwise only print it if logging is enabled.
     let log_backtrace = panics >= 2 || backtrace::log_enabled();