cpp/io/ostrstream/ostrstream

Constructs new output strstream and its underlying std.

@1@ Default-constructs the underlying std, which creates a dynamically growing buffer, and initializes the base class with the address of the strstreambuf member.

@2@ Initialized the base class with the address of the underlying std member, which is initialized in one of the two possible ways, both of which write to user-provided fixed-size array:
 * @a@ if the bit is not set in, constructs the buffer by calling . The behavior is undefined if there are less than  elements in the array whose first element is pointed to by
 * @b@ if the bit is set in, constructs the buffer by calling . The behavior is undefined if there are less than  elements in the array whose first element is pointed to by  or if the array does not contain a valid null-terminated character sequence.