Diversions are a facility in M4 for diverting text from the input stream into a holding buffer. There is a large number of diversion buffers in GNU M4, limited only by available memory. Text can be diverted into any one of these buffers and then `undiverted' back to the output (diversion number 0) at a later stage.
Text is diverted and undiverted using the
It is unlikely that you will want to use diversions in your own macros,
and it is difficult to do reliably without understanding the internals
of Autoconf. However, it is interesting to note that this is how