Avoid potential null dereference

In a log statement we were dereferencing a pointer that could
potentially be null. Add support for safely dereferencing a pointer
for ostreams.

Test: ./test.py --host
Bug: 67037140
Change-Id: Ibe04811883575902a9b2fe8a064f18de2b2cea7b

2 files changed, 20 insertions, 1 deletions

diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 9e0f515ba9..6381b2c356 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -8256,7 +8256,7 @@ class HParallelMove final : public HExpression<0> {
         DCHECK(!destination.OverlapsWith(move.GetDestination()))
             << "Overlapped destination for two moves in a parallel move: "
             << move.GetSource() << " ==> " << move.GetDestination() << " and "
-            << source << " ==> " << destination << " for " << *instruction;
+            << source << " ==> " << destination << " for " << SafePrint(instruction);
       }
     }
     moves_.emplace_back(source, destination, type, instruction);
diff --git a/libartbase/base/stl_util.h b/libartbase/base/stl_util.h
index 26b1de8b9b..4d4a686620 100644
--- a/libartbase/base/stl_util.h
+++ b/libartbase/base/stl_util.h
@@ -304,6 +304,25 @@ static inline IterationRange<FilterNull<InnerIter>> FilterOutNull(IterationRange
   return Filter(inner, NonNullFilter<typename InnerIter::value_type>());
 }
 
+template <typename Val>
+struct SafePrinter  {
+  const Val* val_;
+};
+
+template<typename Val>
+std::ostream& operator<<(std::ostream& os, const SafePrinter<Val>& v) {
+  if (v.val_ == nullptr) {
+    return os << "NULL";
+  } else {
+    return os << *v.val_;
+  }
+}
+
+template<typename Val>
+SafePrinter<Val> SafePrint(const Val* v) {
+  return SafePrinter<Val>{v};
+}
+
 }  // namespace art
 
 #endif  // ART_LIBARTBASE_BASE_STL_UTIL_H_