Print backtrace instead of panicking

Author: Aaron1011

src/libstd/alloc.rs

@@ -202,15 +202,15 @@ pub fn take_alloc_error_hook() -> fn(Layout) {
 /// This lives in `libstd` so that we can call `dumb_print`.
 ///
 /// This hook prints out a message like the default error hook,
-/// but then panics to generate a backtrace. If we are completely
-/// out of memory, panicking and/or backtrace generation may fail:
+/// and then attempts to print a backtrace (without panicking).
+/// If we are completely out of memory, backtrace generation may fail:
 /// this is fine, since the backtrace is best-effort only. We
 /// are guaranteed to print the actual error message, though.
 #[doc(hidden)]
 #[unstable(feature = "alloc_internals", issue = "0")]
 pub fn rustc_alloc_error_hook(layout: Layout) {
     dumb_print(format_args!("memory allocation of {} bytes failed. backtrace:", layout.size()));
-    panic!();
+    dumb_print(format_args!("{:?}", crate::backtrace::Backtrace::capture()));
 }
 
 fn default_alloc_error_hook(layout: Layout) {