From 32130635f623924f1aa19dda3054bab371d682b3 Mon Sep 17 00:00:00 2001
From: Marco Nelissen <marcone@google.com>
Date: Mon, 17 Dec 2012 10:28:20 -0800
Subject: [PATCH] Add NULL check to CallStack::toString

CallStack::toString() has a 0 default argument, which ends up getting
passed to strlen(), resulting in a crash.

Change-Id: If706aff8c400983670f49cdbb66e11191ac76e0e
---
 libs/utils/CallStack.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libs/utils/CallStack.cpp b/libs/utils/CallStack.cpp
index 18fd84f25..66fabebc4 100644
--- a/libs/utils/CallStack.cpp
+++ b/libs/utils/CallStack.cpp
@@ -118,7 +118,9 @@ String8 CallStack::toString(const char* prefix) const {
         char line[MAX_BACKTRACE_LINE_LENGTH];
         format_backtrace_line(i, &mStack[i], &symbols[i],
                 line, MAX_BACKTRACE_LINE_LENGTH);
-        str.append(prefix);
+        if (prefix) {
+            str.append(prefix);
+        }
         str.append(line);
         str.append("\n");
     }