[RFA] Make "bt N" print correct number of frames when using a frame filter

[Pedro Alves]

On 07/14/2017 07:56 PM, Tom Tromey wrote:
>>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:
> 
> Pedro> Can you expand on the need for the PRINT_MORE_FRAMES flag and
> Pedro> having it based on from_tty?  I assume that your first made
> Pedro> the printing unconditional, but then for some reason decided
> Pedro> against it?
> 
> I think my reason was just to have it parallel the no-frame-filter code
> in stack.c:
> 
>       /* If we've stopped before the end, mention that.  */
>       if (fi && from_tty)
> 	printf_filtered (_("(More stack frames follow...)\n"));
> 
> I don't know why this code is conditional on from_tty, but that seemed
> like a separate decision.

OK.  I found that was added here:

 +Tue Oct  2 11:20:02 1990  John Gilmore  (gnu at cygint)
 +
 +       * stack.c (backtrace_command):  Skip "more stack frames follow"
 +       unless interactive.

Funny enough, around the same time the preloading of symbols
was added.  See:

$ git diff 831c851165e1^..bd5635a1 -- stack.c

@@ -493,6 +515,28 @@ backtrace_command (count_exp)
   else
     count = -1;
 
+  if (info_verbose)
+    {
+      struct partial_symtab *ps;
+      
+      /* Read in symbols for all of the frames.  Need to do this in
+        a separate pass so that "Reading in symbols for xxx" messages
+        don't screw up the appearance of the backtrace.  Also
+        if people have strong opinions against reading symbols for
+        backtrace this may have to be an option.  */
+      i = count;
+      for (frame = trailing;
+          frame != NULL && i--;
+          frame = get_prev_frame (frame))
+       {
+         QUIT;
+         fi = get_frame_info (frame);
+         ps = find_pc_psymtab (fi->pc);
+         if (ps)
+           (void) PSYMTAB_TO_SYMTAB (ps);      /* Force syms to come in */
+       }
+    }
+
   for (i = 0, frame = trailing;
        frame && count--;
        i++, frame = get_prev_frame (frame))
@@ -503,7 +547,7 @@ backtrace_command (count_exp)
     }
 
   /* If we've stopped before the end, mention that.  */
-  if (frame)
+  if (frame && from_tty)
     printf_filtered ("(More stack frames follow...)\n");
 }
 ^L

Thanks,
Pedro Alves