libsnprintfv provides a free and portable implementation of the printf family of functions, including support for the extensions in GNU libc (such as dprintf) and for passing variable lists of arguments not only through va_list, but also creating them by the program at run-time. libsnprintfv provides support for adding new format specifiers in a way that is source-code compatible with that of GNU libc, but more powerful.
We do not expect to make any release of libsnprintfv as a separate package. Instead, we hope to integrate it into gnulib.