---

yaml
---
r: 236575
b: refs/heads/tmp
c: 54c0231
h: refs/heads/master
i:
  236573: 2e4d11e
  236571: 6047e9e
  236567: 12989c3
  236559: bb20390
  236543: cbd7f6e
v: v3

Author: ranma42

[refs]

@@ -25,7 +25,7 @@ refs/tags/0.11.0: e1247cb1d0d681be034adb4b558b5a0c0d5720f9
 refs/tags/0.12.0: f0c419429ef30723ceaf6b42f9b5a2aeb5d2e2d1
 refs/heads/beta: d2e13e822a73e0ea46ae9e21afdd3155fc997f6d
 refs/tags/1.0.0-alpha: e42bd6d93a1d3433c486200587f8f9e12590a4d7
-refs/heads/tmp: c7b84909b00dcf5f762778b4aa9783770c69416d
+refs/heads/tmp: 54c0231b14a71a46e6607255d509457e0df0b8be
 refs/tags/1.0.0-alpha.2: 4c705f6bc559886632d3871b04f58aab093bfa2f
 refs/tags/homu-tmp: f859507de8c410b648d934d8f5ec1c52daac971d
 refs/tags/1.0.0-beta: 8cbb92b53468ee2b0c2d3eeb8567005953d40828

branches/tmp/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();