On Sun, Feb 18, 2024 at 05:12:28PM +0100, Christophe JAILLET wrote: > 2 issues related to incorrect available space in the output buffer > computation may lead to some extra memory allocation. > > > First: vsnprintf() takes the size of the buffer, *including* the space for > the trailing null. > > But printbuf_remaining() returns the number of characters we can print > to the output buffer, *excluding* the terminating null. > > So, use printbuf_remaining_size(), which includes the space for the > terminating null. > > > Second: if the return value of vsnprintf() is greater than or equal to the > passed size, the resulting string is truncated. > So, in order to see if some extra space is needed, the check needs to be > changed.
btw, the patch was suspect to begin with in cases where off-by-one errors are difficult to avoid, but harmless in one direction - just over allocate.
