[RFA v3 13/13] Remove verbose code from backtrace command

[Tom Tromey <tom@tromey.com>]

In https://sourceware.org/ml/gdb-patches/2017-06/msg00741.html,
Pedro asks:

> Doesn't the "info verbose on" bit affect frame filters too?

The answer is that yes, it could.  However, it's not completely
effective, because the C code can't guess how many frames might need
to be unwound to satisfy the request -- a frame filter will request as
many frames as it needs.

Also, I tried removing this code from backtrace, and I think the
result is better without it.  In particular, now the expansion line
occurs just before the frame that caused the expansion, like:

    (gdb) bt no-filters
    #0  0x00007ffff576cecd in poll () from /lib64/libc.so.6
    Reading in symbols for ../../binutils-gdb/gdb/event-loop.c...done.
    #1  0x00000000007ecc33 in gdb_wait_for_event (block=1)
	at ../../binutils-gdb/gdb/event-loop.c:772
    #2  0x00000000007ec006 in gdb_do_one_event ()
	at ../../binutils-gdb/gdb/event-loop.c:347
    #3  0x00000000007ec03e in start_event_loop ()
	at ../../binutils-gdb/gdb/event-loop.c:371
    Reading in symbols for ../../binutils-gdb/gdb/main.c...done.
    #4  0x000000000086693d in captured_command_loop (
	Reading in symbols for ../../binutils-gdb/gdb/exceptions.c...done.
    data=0x0) at ../../binutils-gdb/gdb/main.c:325

So, I am proposing this patch to simply remove this code.

gdb/ChangeLog
2018-03-23  Tom Tromey  <tom@tromey.com>

	* stack.c (backtrace_command_1): Remove verbose code.
---
 gdb/ChangeLog |  4 ++++
 gdb/stack.c   | 18 ------------------
 2 files changed, 4 insertions(+), 18 deletions(-)

diff --git a/gdb/stack.c b/gdb/stack.c
index 427b182c7f..9fdc9eece2 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -1780,24 +1780,6 @@ backtrace_command_1 (const char *count_exp, frame_filter_flags flags,
 	  count = -1;
 	}
 
-      if (info_verbose)
-	{
-	  /* 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 (fi = trailing; fi != NULL && i--; fi = get_prev_frame (fi))
-	    {
-	      CORE_ADDR pc;
-
-	      QUIT;
-	      pc = get_frame_address_in_block (fi);
-	      expand_symtab_containing_pc (pc, find_pc_mapped_section (pc));
-	    }
-	}
-
       for (i = 0, fi = trailing; fi && count--; i++, fi = get_prev_frame (fi))
 	{
 	  QUIT;
-- 
2.13.6