Initialization Order of Class Data Members

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The order is the order they appear in the class definition – this is from section 12.6.2 of the C++ Standard:

5 Initialization shall proceed in the
following order:

— First, and only for
the constructor of the most derived
class as described below, virtual base
classes shall be initialized in the
order they appear on a depth-first
left-to-right traversal of the
directed acyclic graph of base
classes, where “left-to-right” is the
order of appearance of the base class
names in the derived class
base-specifier-list.

— Then, direct
base classes shall be initialized in
declaration order as they appear in
the base-specifier-list (regardless of
the order of the mem-initializers).

— Then, nonstatic data members shall be
initialized in the order they were
declared in the class definition
(again regardless of the order of the
mem-initializers).

— Finally, the body
of the constructor is executed. [Note:
the declaration order is mandated to
ensure that base and member subobjects
are destroyed in the reverse order of
initialization. ]

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