Ah! I finally have a progress bar that doesn't stall the build!
- pipe size in Linux is only 8*512=4096 bytes
- pipe size is not setable
- when the feeding process spits out data faster than the eating
process can read it, then the feeding process stalls after 4KiB
of data sent to the pipe
- for us, the progress bar would spawn a sub-shell every line,
and the sub-shell would in turn spawn a 'date' command.
Which was sloooww as hell, and would cause some kind of a
starvation: the pipe was full most of the time, and the
feeding process was stalled all this time.

Now, we use internal variables and a little hack based onan offset
to determine the elapsed time. Much faster this way, but still
CPU-intensive.

 Trivial.  Still need to submit this.

 Index: gdb-6.1/gdb/tracepoint.c

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

 --- gdb-6.1.orig/gdb/tracepoint.c	2004-04-05 13:26:43.000000000 -0400

 +++ gdb-6.1/gdb/tracepoint.c	2004-04-05 13:26:45.000000000 -0400

 @@ -853,6 +853,8 @@ read_actions (struct tracepoint *t)

        else

  	line = gdb_readline (0);

 +      if (line == NULL || *line == EOF)

 +	break;

        linetype = validate_actionline (&line, t);

        if (linetype == BADLINE)

  	continue;		/* already warned -- collect another line */