Alignment fix

Author: guitargeek

math/vecops/inc/ROOT/RVec.hxx

@@ -143,8 +143,8 @@ public:
    // and we prefer the smaller Size_T to reduce the size of each RVec object.
    using Size_T = int32_t;
 
-   void *fBeginX;
 protected:
+   void *fBeginX;
    /// Always >= 0.
    // Type is signed only for consistency with fCapacity.
    Size_T fSize = 0;
@@ -213,7 +213,9 @@ class R__CLING_PTRCHECK(off) SmallVectorTemplateCommon : public SmallVectorBase
    /// SmallVectorStorage is properly-aligned even for small-size of 0.
    void *getFirstEl() const
    {
-      return const_cast<void *>(reinterpret_cast<const void *>(reinterpret_cast<const char *>(this) +
+      // get the SmallVectorBase subobject inside RVec
+      auto *base = static_cast<const SmallVectorBase *>(this);
+      return const_cast<void *>(reinterpret_cast<const void *>(reinterpret_cast<const char *>(base) +
                                                                offsetof(SmallVectorAlignmentAndSize<T>, FirstEl)));
    }
    // Space after 'FirstEl' is clobbered, do not add any instance vars after it.