+ // Do nothing if PrettyStackTraceHead is uninitialized. This can only happen
+ // if a shutdown occurred after we created the PrettyStackTraceEntry. That
+ // does occur in the following idiom:
+ //
+ // PrettyStackTraceProgram X(...);
+ // llvm_shutdown_obj Y;
+ //
+ // Without this check, we may end up removing ourselves from the stack trace
+ // after PrettyStackTraceHead has already been destroyed.
+ if (!PrettyStackTraceHead.isConstructed())
+ return;
+
+ assert(PrettyStackTraceHead->get() == this &&