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RE: [PATCH v2 2/3] frame: use get_prev_frame_always in skip_tailcall_frames
- From: "Metzger, Markus T" <markus dot t dot metzger at intel dot com>
- To: Joel Brobecker <brobecker at adacore dot com>
- Cc: "palves at redhat dot com" <palves at redhat dot com>, "gdb-patches at sourceware dot org" <gdb-patches at sourceware dot org>
- Date: Mon, 8 Feb 2016 08:14:09 +0000
- Subject: RE: [PATCH v2 2/3] frame: use get_prev_frame_always in skip_tailcall_frames
- Authentication-results: sourceware.org; auth=none
- References: <1454681922-2228-1-git-send-email-markus dot t dot metzger at intel dot com> <1454681922-2228-2-git-send-email-markus dot t dot metzger at intel dot com> <20160207130057 dot GE20874 at adacore dot com>
> -----Original Message-----
> From: Joel Brobecker [mailto:brobecker@adacore.com]
> Sent: Sunday, February 7, 2016 2:01 PM
> To: Metzger, Markus T <markus.t.metzger@intel.com>
> Cc: palves@redhat.com; gdb-patches@sourceware.org
> Subject: Re: [PATCH v2 2/3] frame: use get_prev_frame_always in
> skip_tailcall_frames
Hi Joel,
Thanks for your review.
> > Following the practice in skip_artificial_frames, also use
> > get_prev_frame_always instead of get_prev_frame in
> > skip_tailcall_frames.
> >
> > 2016-02-05 Markus Metzger <markus.t.metzger@intel.com>
> >
> > gdb/
> > * frame.c (skip_tailcall_frames): Call get_prev_frame_always.
>
> This seems OK; but would you be able to create a testcase for this?
I modified an existing test case to cover the changes. GDB dies with the modified
test and without the changes to skip_tailcall_frames. This also showed another place
where we want to use get_prev_frame_always.
Here's the modified version of this patch:
commit d426b734a965ef21d03bf7ed30f20be7d7ed31fa
Author: Markus Metzger <markus.t.metzger@intel.com>
Date: Fri Feb 5 09:39:05 2016 +0100
frame: use get_prev_frame_always in skip_tailcall_frames and finish_command
Following the practice in skip_artificial_frames, also use get_prev_frame_always
instead of get_prev_frame in skip_tailcall_frames and in finish_command.
2016-02-08 Markus Metzger <markus.t.metzger@intel.com>
gdb/
* frame.c (skip_tailcall_frames): Call get_prev_frame_always.
* infcmd.c (finish_command): Call get_prev_frame_always.
testsuite/
* gdb.arch/amd64-tailcall-ret.exp: Set backtrace limit.
diff --git a/gdb/frame.c b/gdb/frame.c
index b7832c7..6ab8834 100644
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -443,8 +443,12 @@ skip_artificial_frames (struct frame_info *frame)
struct frame_info *
skip_tailcall_frames (struct frame_info *frame)
{
+ /* Note we use get_prev_frame_always, and not get_prev_frame. The
+ latter will truncate the frame chain, leading to this function
+ unintentionally returning a null_frame_id (e.g., when the user
+ sets a backtrace limit). */
while (get_frame_type (frame) == TAILCALL_FRAME)
- frame = get_prev_frame (frame);
+ frame = get_prev_frame_always (frame);
return frame;
}
diff --git a/gdb/infcmd.c b/gdb/infcmd.c
index 930dc61..e98f6f5 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -1958,7 +1958,10 @@ finish_command (char *arg, int from_tty)
/* Done with ARGS. */
do_cleanups (args_chain);
- frame = get_prev_frame (get_selected_frame (_("No selected frame.")));
+ /* Note we use get_prev_frame_always, and not get_prev_frame. The latter
+ will truncate the frame chain, leading to this function unintentionally
+ throwing an error (e.g., when the user sets a backtrace limit). */
+ frame = get_prev_frame_always (get_selected_frame (_("No selected frame.")));
if (frame == 0)
error (_("\"finish\" not meaningful in the outermost frame."));
diff --git a/gdb/testsuite/gdb.arch/amd64-tailcall-ret.exp b/gdb/testsuite/gdb.arch/amd64-tailcall-ret.exp
index 2642cdd..0334b54 100644
--- a/gdb/testsuite/gdb.arch/amd64-tailcall-ret.exp
+++ b/gdb/testsuite/gdb.arch/amd64-tailcall-ret.exp
@@ -36,6 +36,11 @@ if ![runto_main] {
gdb_breakpoint "g"
gdb_continue_to_breakpoint "g" ".* v = 2;"
+# Severely limit the back trace. The limit should be ignored for "return"
+# and "finish" commands.
+#
+gdb_test "set backtrace limit 1"
+
gdb_test "return" { f \(\); /\* second \*/} "return" \
{Make g return now\? \(y or n\) } "y"
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