Fix LruCache, allow std:string caching

The default initalization for mNullValue uses 0 which is in the case of
a std::string TValue will invoke the contructor with undefined behavior
parameter.

Using an empty uniform initialization {} addresses the problem.

Test: Already tested in lrucache_test.cpp
Bug: 257127748
Change-Id: I37420ce8a16c99f3014538a0208d7e113870b1c7

libutils/LruCache_test.cpp

@@ -29,6 +29,8 @@ typedef const char* StringValue;
 struct ComplexKey {
     int k;
 
+    explicit ComplexKey() : k(0) { instanceCount += 1; }
+
     explicit ComplexKey(int k) : k(k) {
         instanceCount += 1;
     }
@@ -57,6 +59,8 @@ ssize_t ComplexKey::instanceCount = 0;
 struct ComplexValue {
     int v;
 
+    explicit ComplexValue() : v(0) { instanceCount += 1; }
+
     explicit ComplexValue(int v) : v(v) {
         instanceCount += 1;
     }
@@ -83,10 +87,9 @@ struct KeyWithPointer {
 
 struct KeyFailsOnCopy : public ComplexKey {
     public:
-    KeyFailsOnCopy(const KeyFailsOnCopy& key) : ComplexKey(key) {
-        ADD_FAILURE();
-    }
-    KeyFailsOnCopy(int key) : ComplexKey(key) { }
+      KeyFailsOnCopy() : ComplexKey() {}
+      KeyFailsOnCopy(const KeyFailsOnCopy& key) : ComplexKey(key) { ADD_FAILURE(); }
+      KeyFailsOnCopy(int key) : ComplexKey(key) {}
 };
 
 } // namespace

libutils/include/utils/LruCache.h

@@ -161,12 +161,12 @@ public:
 // Implementation is here, because it's fully templated
 template <typename TKey, typename TValue>
 LruCache<TKey, TValue>::LruCache(uint32_t maxCapacity)
-    : mSet(new LruCacheSet())
-    , mListener(nullptr)
-    , mOldest(nullptr)
-    , mYoungest(nullptr)
-    , mMaxCapacity(maxCapacity)
-    , mNullValue(0) {
+    : mSet(new LruCacheSet()),
+      mListener(nullptr),
+      mOldest(nullptr),
+      mYoungest(nullptr),
+      mMaxCapacity(maxCapacity),
+      mNullValue{} {
     mSet->max_load_factor(1.0);
 };