http://sourceware.org/ml/gdb-patches/2016-03/msg00013.html

Subject: [PATCH 1/2] Fix PR gdb/19676: Disable displaced stepping if /proc not mounted

On GNU/Linux archs that support displaced stepping, if /proc is not

mounted, GDB gets stuck not able to step past breakpoints:

 (gdb) c

 Continuing.

 dl_main (phdr=<optimized out>, phnum=<optimized out>, user_entry=<optimized out>, auxv=<optimized out>) at rtld.c:2163

 2163      LIBC_PROBE (init_complete, 2, LM_ID_BASE, r);

 Cannot find AT_ENTRY auxiliary vector entry.

 (gdb) c

 Continuing.

 dl_main (phdr=<optimized out>, phnum=<optimized out>, user_entry=<optimized out>, auxv=<optimized out>) at rtld.c:2163

 2163      LIBC_PROBE (init_complete, 2, LM_ID_BASE, r);

 Cannot find AT_ENTRY auxiliary vector entry.

 (gdb)

That's because GDB can't figure out where the scratch pad is.

This is a regression introduced by the earlier changes to make the

Linux native target always work in non-stop mode.

This commit makes GDB detect the case and fallback to stepping over

breakpoints in-line.

gdb/ChangeLog:

2016-03-01  Pedro Alves  <pedro@cascais.lan>

	PR gdb/19676

	* infrun.c (displaced_step_prepare): Also disable displaced

	stepping on NOT_SUPPORTED_ERROR.

	* linux-tdep.c (linux_displaced_step_location): If reading auxv

	fails, throw NOT_SUPPORTED_ERROR instead of generic error.

---

 gdb/infrun.c     | 3 ++-

 gdb/linux-tdep.c | 3 ++-

 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/gdb/infrun.c b/gdb/infrun.c

index 3e8c9e0..696105d 100644

--- a/gdb/infrun.c

+++ b/gdb/infrun.c

@@ -1894,7 +1894,8 @@ displaced_step_prepare (ptid_t ptid)

     {

       struct displaced_step_inferior_state *displaced_state;

-      if (ex.error != MEMORY_ERROR)

+      if (ex.error != MEMORY_ERROR

+	  && ex.error != NOT_SUPPORTED_ERROR)

 	throw_exception (ex);

       if (debug_infrun)

diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c

index 555c302..f197aa7 100644

--- a/gdb/linux-tdep.c

+++ b/gdb/linux-tdep.c

@@ -2426,7 +2426,8 @@ linux_displaced_step_location (struct gdbarch *gdbarch)

      location.  The auxiliary vector gets us the PowerPC-side entry

      point address instead.  */

   if (target_auxv_search (&current_target, AT_ENTRY, &addr) <= 0)

-    error (_("Cannot find AT_ENTRY auxiliary vector entry."));

+    throw_error (NOT_SUPPORTED_ERROR,

+		 _("Cannot find AT_ENTRY auxiliary vector entry."));

   /* Make certain that the address points at real code, and not a

      function descriptor.  */

-- 

2.5.0

http://sourceware.org/ml/gdb-patches/2016-03/msg00014.html

Subject: [PATCH 2/2] Fix PR gdb/19676: Internal error in linux-thread.db.c if /proc not mounted

If /proc is not mounted, GDB fails an assertion in find_new_threads_once:

 Continuing.

 /home/pedro/gdb/mygit/src/gdb/linux-thread-db.c:1249: internal-error: find_new_threads_once: Assertion `!target_has_execution' failed.

 A problem internal to GDB has been detected,

 further debugging may prove unreliable.

 Quit this debugging session? (y or n)

That was supposed to catch misuses of td_ta_thr_iter, which is unsafe

for live debugging.  However, if /proc is not mounted, we still

fallback to using it.

I didn't bother with a warning, because GDB already prints several

others related to failing to open /proc files.

gdb/ChangeLog:

2016-03-01  Pedro Alves  <pedro@cascais.lan>

	PR gdb/19676

	* linux-thread-db.c (try_thread_db_load_1): Leave

	info->td_ta_thr_iter_p NULL iff debugging a live process and we

	have /proc access.

	(find_new_threads_once): Assert that we have a non-NULL

	info->td_ta_thr_iter_p instead of checking whether the target has

	execution.

---

 gdb/linux-thread-db.c | 16 ++++++++++------

 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/gdb/linux-thread-db.c b/gdb/linux-thread-db.c

index 1eb457d..ce60beb 100644

--- a/gdb/linux-thread-db.c

+++ b/gdb/linux-thread-db.c

@@ -564,7 +564,6 @@ try_thread_db_load_1 (struct thread_db_info *info)

   /* These are essential.  */

   CHK (TDB_VERBOSE_DLSYM (info, td_ta_map_lwp2thr));

-  CHK (TDB_VERBOSE_DLSYM (info, td_ta_thr_iter));

   CHK (TDB_VERBOSE_DLSYM (info, td_thr_validate));

   CHK (TDB_VERBOSE_DLSYM (info, td_thr_get_info));

@@ -572,10 +571,6 @@ try_thread_db_load_1 (struct thread_db_info *info)

   TDB_DLSYM (info, td_thr_tls_get_addr);

   TDB_DLSYM (info, td_thr_tlsbase);

-#undef TDB_VERBOSE_DLSYM

-#undef TDB_DLSYM

-#undef CHK

-

   /* It's best to avoid td_ta_thr_iter if possible.  That walks data

      structures in the inferior's address space that may be corrupted,

      or, if the target is running, may change while we walk them.  If

@@ -587,6 +582,15 @@ try_thread_db_load_1 (struct thread_db_info *info)

      currently on core targets, as it uses ptrace directly.  */

   if (target_has_execution

       && linux_proc_task_list_dir_exists (ptid_get_pid (inferior_ptid)))

+    info->td_ta_thr_iter_p = NULL;

+  else

+    CHK (TDB_VERBOSE_DLSYM (info, td_ta_thr_iter));

+

+#undef TDB_VERBOSE_DLSYM

+#undef TDB_DLSYM

+#undef CHK

+

+  if (info->td_ta_thr_iter_p == NULL)

     {

       struct lwp_info *lp;

       int pid = ptid_get_pid (inferior_ptid);

@@ -1246,7 +1250,7 @@ find_new_threads_once (struct thread_db_info *info, int iteration,

   data.new_threads = 0;

   /* See comment in thread_db_update_thread_list.  */

-  gdb_assert (!target_has_execution);

+  gdb_assert (info->td_ta_thr_iter_p != NULL);

   TRY

     {

-- 

2.5.0

http://sourceware.org/ml/gdb-patches/2016-03/msg00246.html

Subject: [patch] Suggest running gdbserver for a PID in container

--azLHFNyN32YCQGCU

Content-Type: text/plain; charset=us-ascii

Content-Disposition: inline

Hi,

currently

	gdb -p <pid from a container>

will print:

	warning: Target and debugger are in different PID namespaces; thread lists and other data are likely unreliable

BTW it is a bit lost in all the other messages.  Full screen output is in:

	https://sourceware.org/bugzilla/show_bug.cgi?id=19828

It correctly states the problem but it does not say how to solve it.

Is at least this little suggestion OK?

Originally I wanted to suggest also the Docker "-p 1234:1234" parameter but

I see the containers are more general topic than just Docker (even LxC etc.).

According to Gary future GDBs should be able to work even without gdbserver.

But currently gdbserver is still required.

Thanks,

Jan

--azLHFNyN32YCQGCU

Content-Type: text/plain; charset=us-ascii

Content-Disposition: inline; filename=1

gdb/ChangeLog

2016-03-15  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* linux-thread-db.c (check_pid_namespace_match): Extend the message.

diff --git a/gdb/linux-thread-db.c b/gdb/linux-thread-db.c

index 1eb457d..21166bf 100644

--- a/gdb/linux-thread-db.c

+++ b/gdb/linux-thread-db.c

@@ -1020,7 +1020,8 @@ check_pid_namespace_match (void)

 	{

 	  warning (_ ("Target and debugger are in different PID "

 		      "namespaces; thread lists and other data are "

-		      "likely unreliable"));

+		      "likely unreliable.  "

+		      "Connect to gdbserver inside the container."));

 	}

     }

 }

--azLHFNyN32YCQGCU--

commit fef3cb9f3aa84018d10866f89228ae3f23e5ca7e

Author: Jan Kratochvil <jan.kratochvil@redhat.com>

Date:   Wed Apr 6 15:57:08 2016 +0200

    Print the "file" command suggestion in exec_file_locate_attach

    currently:

    	$ gdbserver-7.9 :1234 true &

    	$ gdb -q -ex 'target remote :1234' # that -q is not relevant here

    	Remote debugging using :1234

    	warning: Could not load vsyscall page because no executable was specified

    	try using the "file" command first.

    	0x00007ffff7ddcc80 in ?? ()

    	(gdb) b main

    	No symbol table is loaded.  Use the "file" command.

    	Make breakpoint pending on future shared library load? (y or [n]) _

    Provide more suggestive message to use the "file" command.

    gdb/ChangeLog

    2016-04-06  Jan Kratochvil  <jan.kratochvil@redhat.com>

    	    Pedro Alves  <palves@redhat.com>

    	* exec.c (exec_file_locate_attach): Print warning for unsupported

    	target_pid_to_exec_file.

    	* symfile-mem.c (add_vsyscall_page): Remove the "file" command

    	message part.

### a/gdb/ChangeLog

### b/gdb/ChangeLog

## -1,3 +1,11 @@

+2016-04-06  Jan Kratochvil  <jan.kratochvil@redhat.com>

+	    Pedro Alves  <palves@redhat.com>

+

+	* exec.c (exec_file_locate_attach): Print warning for unsupported

+	target_pid_to_exec_file.

+	* symfile-mem.c (add_vsyscall_page): Remove the "file" command

+	message part.

+

 2016-04-04  Simon Marchi  <simon.marchi@ericsson.com>

 	* cli/cli-decode.c (help_cmd_list): Fix function doc and remove

--- a/gdb/exec.c

+++ b/gdb/exec.c

@@ -151,7 +151,13 @@ exec_file_locate_attach (int pid, int from_tty)

   /* Try to determine a filename from the process itself.  */

   exec_file = target_pid_to_exec_file (pid);

   if (exec_file == NULL)

-    return;

+    {

+      warning (_("No executable has been specified and target does not "

+		 "support\n"

+		 "determining executable automatically.  "

+		 "Try using the \"file\" command."));

+      return;

+    }

   /* If gdb_sysroot is not empty and the discovered filename

      is absolute then prefix the filename with gdb_sysroot.  */

--- a/gdb/symfile-mem.c

+++ b/gdb/symfile-mem.c

@@ -214,8 +214,7 @@ add_vsyscall_page (struct target_ops *target, int from_tty)

 	  format should fix this.  */

 	{

 	  warning (_("Could not load vsyscall page "

-		     "because no executable was specified\n"

-		     "try using the \"file\" command first."));

+		     "because no executable was specified"));

 	  return;

 	}

       args.bfd = bfd;

commit 2ef34d11f61d79dcb152713aa059051d8cd3295d

Author: Markus Metzger <markus.t.metzger@intel.com>

Date:   Fri Feb 5 09:32:53 2016 +0100

    btrace: fix PR gdb/19829

    This is a backport of

    33b4777ca1b7 btrace, frame: fix crash in get_frame_type

    a038fa3e14a4 stack: check frame_unwind_caller_id

    2f3ef606b912 frame: add skip_tailcall_frames

    In skip_artificial_frames we repeatedly call get_prev_frame_always until we get

    a non-inline and non-tailcall frame assuming that there must be such a frame

    eventually.

    For record targets, however, we may have a frame chain that consists only of

    artificial frames.  This leads to a crash in get_frame_type when dereferencing a

    NULL frame pointer.

    Change skip_artificial_frames and skip_tailcall_frames to return NULL in such a

    case and modify each caller to cope with a NULL return.

    In frame_unwind_caller_pc and frame_unwind_caller_arch, we simply assert that

    the returned value is not NULL.  Their caller was supposed to check

    frame_unwind_caller_id before calling those functions.

    In other cases, we thrown an error.

    In infcmd further move the skip_tailcall_frames call to the forward-stepping

    case since we don't need a frame for reverse execution and we don't want to fail

    because of that.  Reverse-finish does make sense for a tailcall frame.

    gdb/

    	* frame.h (skip_tailcall_frames): New.

    	* infcmd.c (finish_command): Call skip_tailcall_frames.

    	* frame.c (skip_artificial_frames): Return NULL if only artificial frames

    	are found.  Update comment.

    	(frame_pop): Call skip_tailcall_frames.

    	(frame_unwind_caller_id): Handle NULL return.

    	(frame_unwind_caller_pc, frame_unwind_caller_arch): Assert that

    	skip_artificial_frames does not return NULL.

    	(frame_pop): Add an error if only tailcall frames are found.

    	* infcmd.c (finish_command): Move skip_tailcall_frames call into forward-

    	execution case.  Add an error if only tailcall frames are found.

    	* stack.c (frame_info): Check frame_unwind_caller_id.

    testsuite/

    	* gdb.btrace/tailcall-only.exp: New.

    	* gdb.btrace/tailcall-only.c: New.

    	* gdb.btrace/x86_64-tailcall-only.S: New.

    	* gdb.btrace/i686-tailcall-only.S: New.

### a/gdb/ChangeLog

### b/gdb/ChangeLog

## -1,3 +1,19 @@

+2016-03-17  Markus Metzger  <markus.t.metzger@intel.com>

+

+	PR gdb/19829

+	* frame.h (skip_tailcall_frames): New.

+	* infcmd.c (finish_command): Call skip_tailcall_frames.

+	* frame.c (skip_artificial_frames): Return NULL if only artificial

+	frames are found.  Update comment.

+	(frame_pop): Call skip_tailcall_frames.

+	(frame_unwind_caller_id): Handle NULL return.

+	(frame_unwind_caller_pc, frame_unwind_caller_arch): Assert that

+	skip_artificial_frames does not return NULL.

+	(frame_pop): Add an error if only tailcall frames are found.

+	* infcmd.c (finish_command): Move skip_tailcall_frames call into

+	forward-execution case.  Add an error if only tailcall frames are found.

+	* stack.c (frame_info): Check frame_unwind_caller_id.

+

 2016-03-15  Pedro Alves  <palves@redhat.com>

 	PR gdb/19676

--- a/gdb/frame.c

+++ b/gdb/frame.c

@@ -420,7 +420,8 @@ fprint_frame (struct ui_file *file, struct frame_info *fi)

 /* Given FRAME, return the enclosing frame as found in real frames read-in from

    inferior memory.  Skip any previous frames which were made up by GDB.

-   Return the original frame if no immediate previous frames exist.  */

+   Return FRAME if FRAME is a non-artificial frame.

+   Return NULL if FRAME is the start of an artificial-only chain.  */

 static struct frame_info *

 skip_artificial_frames (struct frame_info *frame)

@@ -428,12 +429,34 @@ skip_artificial_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).  This is safe, because as these frames

-     are made up by GDB, there must be a real frame in the chain

-     below.  */

+     sets a backtrace limit).

+

+     Note that for record targets we may get a frame chain that consists

+     of artificial frames only.  */

   while (get_frame_type (frame) == INLINE_FRAME

 	 || get_frame_type (frame) == TAILCALL_FRAME)

-    frame = get_prev_frame_always (frame);

+    {

+      frame = get_prev_frame_always (frame);

+      if (frame == NULL)

+	break;

+    }

+

+  return frame;

+}

+

+/* See frame.h.  */

+

+struct frame_info *

+skip_tailcall_frames (struct frame_info *frame)

+{

+  while (get_frame_type (frame) == TAILCALL_FRAME)

+    {

+      /* Note that for record targets we may get a frame chain that consists of

+	 tailcall frames only.  */

+      frame = get_prev_frame (frame);

+      if (frame == NULL)

+	break;

+    }

   return frame;

 }

@@ -496,6 +519,9 @@ frame_unwind_caller_id (struct frame_info *next_frame)

      requests the frame ID of "main()"s caller.  */

   next_frame = skip_artificial_frames (next_frame);

+  if (next_frame == NULL)

+    return null_frame_id;

+

   this_frame = get_prev_frame_always (next_frame);

   if (this_frame)

     return get_frame_id (skip_artificial_frames (this_frame));

@@ -869,7 +895,14 @@ frame_unwind_pc (struct frame_info *this_frame)

 CORE_ADDR

 frame_unwind_caller_pc (struct frame_info *this_frame)

 {

-  return frame_unwind_pc (skip_artificial_frames (this_frame));

+  this_frame = skip_artificial_frames (this_frame);

+

+  /* We must have a non-artificial frame.  The caller is supposed to check

+     the result of frame_unwind_caller_id (), which returns NULL_FRAME_ID

+     in this case.  */

+  gdb_assert (this_frame != NULL);

+

+  return frame_unwind_pc (this_frame);

 }

 int

@@ -972,8 +1005,10 @@ frame_pop (struct frame_info *this_frame)

   /* Ignore TAILCALL_FRAME type frames, they were executed already before

      entering THISFRAME.  */

-  while (get_frame_type (prev_frame) == TAILCALL_FRAME)

-    prev_frame = get_prev_frame (prev_frame);

+  prev_frame = skip_tailcall_frames (prev_frame);

+

+  if (prev_frame == NULL)

+    error (_("Cannot find the caller frame."));

   /* Make a copy of all the register values unwound from this frame.

      Save them in a scratch buffer so that there isn't a race between

@@ -2561,7 +2596,14 @@ frame_unwind_arch (struct frame_info *next_frame)

 struct gdbarch *

 frame_unwind_caller_arch (struct frame_info *next_frame)

 {

-  return frame_unwind_arch (skip_artificial_frames (next_frame));

+  next_frame = skip_artificial_frames (next_frame);

+

+  /* We must have a non-artificial frame.  The caller is supposed to check

+     the result of frame_unwind_caller_id (), which returns NULL_FRAME_ID

+     in this case.  */

+  gdb_assert (next_frame != NULL);

+

+  return frame_unwind_arch (next_frame);

 }

 /* Gets the language of FRAME.  */

--- a/gdb/frame.h

+++ b/gdb/frame.h

@@ -820,5 +820,10 @@ extern int frame_unwinder_is (struct frame_info *fi,

 extern enum language get_frame_language (struct frame_info *frame);

+/* Return the first non-tailcall frame above FRAME or FRAME if it is not a

+   tailcall frame.  Return NULL if FRAME is the start of a tailcall-only

+   chain.  */

+

+extern struct frame_info *skip_tailcall_frames (struct frame_info *frame);

 #endif /* !defined (FRAME_H)  */

--- a/gdb/infcmd.c

+++ b/gdb/infcmd.c

@@ -2000,11 +2000,6 @@ finish_command (char *arg, int from_tty)

       return;

     }

-  /* Ignore TAILCALL_FRAME type frames, they were executed already before

-     entering THISFRAME.  */

-  while (get_frame_type (frame) == TAILCALL_FRAME)

-    frame = get_prev_frame (frame);

-

   /* Find the function we will return from.  */

   sm->function = find_pc_function (get_frame_pc (get_selected_frame (NULL)));

@@ -2031,7 +2026,16 @@ finish_command (char *arg, int from_tty)

   if (execution_direction == EXEC_REVERSE)

     finish_backward (sm);

   else

-    finish_forward (sm, frame);

+    {

+      /* Ignore TAILCALL_FRAME type frames, they were executed already before

+	 entering THISFRAME.  */

+      frame = skip_tailcall_frames (frame);

+

+      if (frame == NULL)

+	error (_("Cannot find the caller frame."));

+

+      finish_forward (sm, frame);

+    }

 }

--- a/gdb/stack.c

+++ b/gdb/stack.c

@@ -1509,27 +1509,32 @@ frame_info (char *addr_exp, int from_tty)

   wrap_here ("    ");

   printf_filtered ("saved %s = ", pc_regname);

-  TRY

-    {

-      caller_pc = frame_unwind_caller_pc (fi);

-      caller_pc_p = 1;

-    }

-  CATCH (ex, RETURN_MASK_ERROR)

+  if (!frame_id_p (frame_unwind_caller_id (fi)))

+    val_print_unavailable (gdb_stdout);

+  else

     {

-      switch (ex.error)

+      TRY

 	{

-	case NOT_AVAILABLE_ERROR:

-	  val_print_unavailable (gdb_stdout);

-	  break;

-	case OPTIMIZED_OUT_ERROR:

-	  val_print_not_saved (gdb_stdout);

-	  break;

-	default:

-	  fprintf_filtered (gdb_stdout, _("<error: %s>"), ex.message);

-	  break;

+	  caller_pc = frame_unwind_caller_pc (fi);

+	  caller_pc_p = 1;

 	}

+      CATCH (ex, RETURN_MASK_ERROR)

+	{

+	  switch (ex.error)

+	    {

+	    case NOT_AVAILABLE_ERROR:

+	      val_print_unavailable (gdb_stdout);

+	      break;

+	    case OPTIMIZED_OUT_ERROR:

+	      val_print_not_saved (gdb_stdout);

+	      break;

+	    default:

+	      fprintf_filtered (gdb_stdout, _("<error: %s>"), ex.message);

+	      break;

+	    }

+	}

+      END_CATCH

     }

-  END_CATCH

   if (caller_pc_p)

     fputs_filtered (paddress (gdbarch, caller_pc), gdb_stdout);

### a/gdb/testsuite/ChangeLog

### b/gdb/testsuite/ChangeLog

## -1,3 +1,11 @@

+2016-03-17  Markus Metzger  <markus.t.metzger@intel.com>

+

+	PR gdb/19829

+	* gdb.btrace/tailcall-only.exp: New.

+	* gdb.btrace/tailcall-only.c: New.

+	* gdb.btrace/x86_64-tailcall-only.S: New.

+	* gdb.btrace/i686-tailcall-only.S: New.

+

 2016-02-16  Don Breazeal  <donb@codesourcery.com>

 	PR remote/19496

--- /dev/null

+++ b/gdb/testsuite/gdb.btrace/i686-tailcall-only.S

@@ -0,0 +1,447 @@

+/* This testcase is part of GDB, the GNU debugger.

+

+   Copyright 2016 Free Software Foundation, Inc.

+

+   This program is free software; you can redistribute it and/or modify

+   it under the terms of the GNU General Public License as published by

+   the Free Software Foundation; either version 3 of the License, or

+   (at your option) any later version.

+

+   This program is distributed in the hope that it will be useful,

+   but WITHOUT ANY WARRANTY; without even the implied warranty of

+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+   GNU General Public License for more details.

+

+   You should have received a copy of the GNU General Public License

+   along with this program.  If not, see <http://www.gnu.org/licenses/>.

+

+

+   This file has been generated using:

+   gcc -m32 -march=i686 -S -O2 -dA -g tailcall-only.c -o i686-tailcall-only.S

+ */

+

+	.file	"tailcall-only.c"

+	.text

+.Ltext0:

+	.p2align 4,,15

+	.type	bar_1, @function

+bar_1:

+.LFB0:

+	.file 1 "tailcall-only.c"

+	# tailcall-only.c:22

+	.loc 1 22 0

+	.cfi_startproc

+# BLOCK 2 freq:10000 seq:0

+# PRED: ENTRY [100.0%]  (FALLTHRU)

+	# tailcall-only.c:24

+	.loc 1 24 0

+	movl	$42, %eax

+# SUCC: EXIT [100.0%]

+	ret

+	.cfi_endproc

+.LFE0:

+	.size	bar_1, .-bar_1

+	.p2align 4,,15

+	.type	bar, @function

+bar:

+.LFB1:

+	# tailcall-only.c:28

+	.loc 1 28 0

+	.cfi_startproc

+# BLOCK 2 freq:10000 seq:0

+# PRED: ENTRY [100.0%]  (FALLTHRU)

+	# tailcall-only.c:29

+	.loc 1 29 0

+	jmp	bar_1

+# SUCC: EXIT [100.0%]  (ABNORMAL,SIBCALL)

+.LVL0:

+	.cfi_endproc

+.LFE1:

+	.size	bar, .-bar

+	.p2align 4,,15

+	.type	foo_1, @function

+foo_1:

+.LFB2:

+	# tailcall-only.c:34

+	.loc 1 34 0

+	.cfi_startproc

+# BLOCK 2 freq:10000 seq:0

+# PRED: ENTRY [100.0%]  (FALLTHRU)

+	# tailcall-only.c:35

+	.loc 1 35 0

+	jmp	bar

+# SUCC: EXIT [100.0%]  (ABNORMAL,SIBCALL)

+.LVL1:

+	.cfi_endproc

+.LFE2:

+	.size	foo_1, .-foo_1

+	.p2align 4,,15

+	.type	foo, @function

+foo:

+.LFB3:

+	# tailcall-only.c:40

+	.loc 1 40 0

+	.cfi_startproc

+# BLOCK 2 freq:10000 seq:0

+# PRED: ENTRY [100.0%]  (FALLTHRU)

+	# tailcall-only.c:41

+	.loc 1 41 0

+	jmp	foo_1

+# SUCC: EXIT [100.0%]  (ABNORMAL,SIBCALL)

+.LVL2:

+	.cfi_endproc

+.LFE3:

+	.size	foo, .-foo

+	.section	.text.startup,"ax",@progbits

+	.p2align 4,,15

+	.globl	main

+	.type	main, @function

+main:

+.LFB4:

+	# tailcall-only.c:46

+	.loc 1 46 0

+	.cfi_startproc

+# BLOCK 2 freq:10000 seq:0

+# PRED: ENTRY [100.0%]  (FALLTHRU)

+	# tailcall-only.c:49

+	.loc 1 49 0

+	call	foo

+.LVL3:

+	# tailcall-only.c:50

+	.loc 1 50 0

+	addl	$1, %eax

+.LVL4:

+# SUCC: EXIT [100.0%]

+	# tailcall-only.c:53

+	.loc 1 53 0

+	ret

+	.cfi_endproc

+.LFE4:

+	.size	main, .-main

+	.text

+.Letext0:

+	.section	.debug_info,"",@progbits

+.Ldebug_info0:

+	.long	0xd5	# Length of Compilation Unit Info

+	.value	0x4	# DWARF version number

+	.long	.Ldebug_abbrev0	# Offset Into Abbrev. Section

+	.byte	0x4	# Pointer Size (in bytes)

+	.uleb128 0x1	# (DIE (0xb) DW_TAG_compile_unit)

+	.long	.LASF1	# DW_AT_producer: "GNU C 4.8.3 20140911 (Red Hat 4.8.3-9) -m32 -march=i686 -g -O2"

+	.byte	0x1	# DW_AT_language

+	.long	.LASF2	# DW_AT_name: "tailcall-only.c"

+	.long	.LASF3	# DW_AT_comp_dir: ""

+	.long	.Ldebug_ranges0+0	# DW_AT_ranges