You can put data definitions at the beginning of the switch body, but the compiler does not initialize auto and register variables at the beginning of a switch body. You can have declarations in the body of the switch statement.
You cannot use a switch statement to jump over initializations.
When the scope of an identifier with a variably modified type includes a case or default label of a switch statement, the entire switch statement is considered to be within the scope of that identifier. That is, the declaration of the identifier must precede the switch statement.
In C++, you cannot transfer control
over a declaration containing an explicit or implicit initializer
unless the declaration is located in an inner block that is completely
bypassed by the transfer of control. All declarations within the body
of a switch statement that contain initializers must be
contained in an inner block.