cpp/io/basic stringbuf/overflow

Appends the character to the output character sequence.

If is the end-of-file indicator, then there is no character to append. The function does nothing and returns an unspecified value other than.

Otherwise, if the output sequence has a write position available or this function can successfully make a write position available, then calls and returns.

This function can make a write position available if the std is open for output : in this case, it reallocates (or initially allocates) the buffer big enough to hold the entire current buffer plus at least one more character. If the std is also open for input, then also increases the size of the get area by moving egptr to point just past the new write position.

Return value
to indicate failure, if the character  was successfully appended, or some value other than  if called with  as the argument.