Put breakpoint inside ast_read(), in channel.c:1372 ** NOT REACHED **

=======================
Put bkpt inside ast_playtones_start(), in indications.c:214 (call to ast_activate_generator() )
TAKEN:

Breakpoint 2, ast_playtones_start (chan=0x8132b20, vol=0,
    playlst=0xbe3fd77c "!697+1336/1000|!0/100", interruptible=0) at indications.c:214
214             if (ast_activate_generator(chan, &playtones, &d)) {

Firstly, this parses the playlist in its thrd parameter and parses it to build 
d (a struct playtones_def )...

		d.items[d.nitems].freq1    = freq1;
		d.items[d.nitems].freq2    = freq2;
		d.items[d.nitems].duration = time;
		d.items[d.nitems].modulate = modulate;
		d.nitems++;

This calls ast_activate_generator (channel.c:849) passing it d as third parameter.
This allocates chan->generatordata (a (struct playtones_state *) using 
gen->alloc which really is playtones_alloc()):

chan->generatordata = gen->alloc(chan, params)

So, chan->generatordata now points to a struct playtones_state whose fields 
reppos, nitems and items are set to the ones of the same names in params:

(gdb) print ((struct playtones_state *)chan->generatordata)->reppos
$17 = -1
(gdb) print ((struct playtones_state *)chan->generatordata)->nitems
$16 = 2
(gdb) print *(struct playtones_state *)chan->generatordata
$9 = {vol = 8192, reppos = -1, nitems = 2, items = 0x80f4900, npos = 0, pos = 0, origwfmt = 4,
  f = {frametype = 0, subclass = 0, datalen = 0, samples = 0, mallocd = 0, offset = 0,
    src = 0x0, data = 0x0, delivery = {tv_sec = 0, tv_usec = 0}, prev = 0x0, next = 0x0},
  offset = '\000' <repeats 63 times>, data = {0 <repeats 4000 times>}}

(gdb) print ((struct playtones_state *)chan->generatordata)->items[0]
$14 = {freq1 = 697, freq2 = 1336, duration = 1000, modulate = 0}
(gdb) print ((struct playtones_state *)chan->generatordata)->items[1]
$15 = {freq1 = 0, freq2 = 0, duration = 100, modulate = 0}

It also sets the chan->generator field to gen (a struct made of pointers to playtones_alloc(),
playtones_release() and playtones_generator() ), 

Calls to ast_prod(chan) and ast_settimeout(chan, 160, generator_force, chan) have
no significant effects because, respectively, chan is already up (chan->_state == AST_STATE_UP)
and ZAPTEL_OPTIMIZATIONS is undefined, so that the timer can't be used.


==============

So, the problem is that the generator is correctly initialized, but never run 
because ast_read is never called. NOTE: that should be done by ast_safe_sleep
if called for a delay > 0:

channel.c:554:
   int ast_safe_sleep(struct ast_channel *chan, int ms)
   {
	   struct ast_frame *f;
	   while(ms > 0) {
		   ms = ast_waitfor(chan, ms);
		   if (ms <0)
			   return -1;
		   if (ms > 0) {
			   f = ast_read(chan); <=========
			   if (!f)
				   return -1;
			   ast_frfree(f);
		   }
	   }
	   return 0;
   }

==========

With SendDTMF, on the other hand, ast_safe_sleep() is called, but it finds 
chan->generator and chan->generatordata == NULL :-( This is because (??) it's
called to process a "w" at app.c:283: interdigit pauses are processed directly
through calls to the underlying ast_waitfor().