cpp/language/constant initialization

Sets the initial values of the variables to a compile-time constant.

Explanation
If a static variable is constant-initialized (see below), constant initialization is performed instead of zero initialization before all other initializations.

A variable or temporary object is constant-initialized if
 * either it has an or its  results in some initialization being performed, and
 * its initialization is a.

The effects of constant initialization are the same as the effects of the corresponding initialization, except that it's guaranteed that it is complete before any other initialization of a static object begins, and it may be performed at compile time.