[PATCH 1/2] [gdbserver] assert on step if !can_hardware_single_step

[Yao Qi <qiyaoltc@gmail.com>]

From: Yao Qi <yao.qi@linaro.org>

GDB sends vCont;s by mistake to GDBserver on arm target which doesn't
have single step at all.  However, it is hard to find the problem from
the debugging log.  With this patch applied, the problem is easy to
identify, like:

(gdb) PASS: gdb.threads/non-stop-fair-events.exp: signal_thread=2: switch to thread 6 to step it
step&^M
(gdb) PASS: gdb.threads/non-stop-fair-events.exp: signal_thread=2: set 6 thread stepping
thread /home/yao/SourceCode/gnu/gdb/git/gdb/gdbserver/linux-low.c:3686: A problem internal to GDBserver has been detected.^M
linux_resume_one_lwp_throw: Assertion `step == 0' failed.

gdb/gdbserver:

2015-04-02  Yao Qi  <yao.qi@linaro.org>

	* linux-low.c (linux_resume_one_lwp_throw): Assert on step.
---
 gdb/gdbserver/linux-low.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index e4c5420..bc6ab1ae 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -3682,6 +3682,9 @@ linux_resume_one_lwp_throw (struct lwp_info *lwp,
   if (the_low_target.prepare_to_resume != NULL)
     the_low_target.prepare_to_resume (lwp);
 
+  if (!can_hardware_single_step ())
+    gdb_assert (step == 0);
+
   regcache_invalidate_thread (thread);
   errno = 0;
   lwp->stepping = step;
-- 
1.9.1