1 files changed, 9 insertions, 8 deletions
diff --git a/lib/ubsan/ubsan_diag.cc b/lib/ubsan/ubsan_diag.cc
index bbe1e07390ad..742802b8f341 100644
--- a/lib/ubsan/ubsan_diag.cc
+++ b/lib/ubsan/ubsan_diag.cc
@@ -31,15 +31,16 @@ static void MaybePrintStackTrace(uptr pc, uptr bp) {
   // will definitely be called when we print the first diagnostics message.
   if (!flags()->print_stacktrace)
     return;
-  // We can only use slow unwind, as we don't have any information about stack
-  // top/bottom.
-  // FIXME: It's better to respect "fast_unwind_on_fatal" runtime flag and
-  // fetch stack top/bottom information if we have it (e.g. if we're running
-  // under ASan).
-  if (StackTrace::WillUseFastUnwind(false))
-    return;
+
+  uptr top = 0;
+  uptr bottom = 0;
+  bool request_fast_unwind = common_flags()->fast_unwind_on_fatal;
+  if (request_fast_unwind)
+    __sanitizer::GetThreadStackTopAndBottom(false, &top, &bottom);
+
   BufferedStackTrace stack;
-  stack.Unwind(kStackTraceMax, pc, bp, 0, 0, 0, false);
+  stack.Unwind(kStackTraceMax, pc, bp, nullptr, top, bottom,
+               request_fast_unwind);
   stack.Print();
 }