Don't initialize POD types with memset(0)

This is dangerous as at least pointers to member objects/data
are not always zero initialized.

Change-Id: I1250e101ab73cd816694315fc9130f4d486b9feb
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/corelib/global/qglobal.cpp

@@ -3970,10 +3970,8 @@ bool qunsetenv(const char *varName)
 
     \list
     \li \c Q_PRIMITIVE_TYPE specifies that \a Type is a POD (plain old
-       data) type with no constructor or destructor, or else a type where
-       every bit pattern is a valid object; memset()ting memory to zero
-       creates a value-initialized instance of the type; and memcpy()ing
-       creates a valid independent copy of an object.
+       data) type with no constructor or destructor, or else a type memcpy()ing
+       creates a valid independent copy of the object.
     \li \c Q_RELOCATABLE_TYPE specifies that \a Type has a constructor
        and/or a destructor but can be moved in memory using \c
        memcpy().

src/corelib/tools/qarraydataops.h

@@ -83,8 +83,11 @@ public:
         Q_ASSERT(newSize > this->size);
         Q_ASSERT(newSize - this->size <= this->freeSpaceAtEnd());
 
-        ::memset(static_cast<void *>(this->end()), 0, (newSize - this->size) * sizeof(T));
+        T *where = this->end();
         this->size = qsizetype(newSize);
+        const T *e = this->end();
+        while (where != e)
+            *where++ = T();
     }
 
     void copyAppend(const T *b, const T *e) noexcept
@@ -675,7 +678,6 @@ protected:
     using DataPointer = QArrayDataPointer<T>;
 
 public:
-    // using QGenericArrayOps<T>::appendInitialize;
     // using QGenericArrayOps<T>::copyAppend;
     // using QGenericArrayOps<T>::moveAppend;
     // using QGenericArrayOps<T>::truncate;