Objects with the auto storage class specifier have automatic storage duration. Each time a block is entered, storage for auto objects defined in that block is made available. When the block is exited, the objects are no longer available for use. An object declared with no linkage specification and without the static storage class specifier has automatic storage duration.
If an auto object is defined within a function that is recursively invoked, memory is allocated for the object at each invocation of the block.