gdb.base/breakpoint-in-ro-region.exp regression on sss targets (PR gdb/22583)

As Maciej reported at
<https://sourceware.org/ml/gdb-patches/2017-12/msg00212.html>, this
commit:

 commit d930703d68ae160ddfe8ebe5fdcf416fb6090e1e
 Date: Thu Nov 16 18:44:43 2017 +0000
 Subject: Don't ever Quit out of resume

caused regressions on software single-set targets, specifically:

 FAIL: gdb.base/breakpoint-in-ro-region.exp: always-inserted off: auto-hw off: single-step breakpoint is not left behind
 FAIL: gdb.base/breakpoint-in-ro-region.exp: always-inserted off: auto-hw on: single-step breakpoint is not left behind
 FAIL: gdb.base/breakpoint-in-ro-region.exp: always-inserted on: auto-hw off: step in ro region (cannot insert hw break)
 FAIL: gdb.base/breakpoint-in-ro-region.exp: always-inserted on: auto-hw off: single-step breakpoint is not left behind
 FAIL: gdb.base/breakpoint-in-ro-region.exp: always-inserted on: auto-hw on: single-step breakpoint is not left behind

and indeed detailed logs indicate a breakpoint is left lingering, e.g.:

 (gdb) PASS: gdb.base/breakpoint-in-ro-region.exp: always-inserted off: auto-hw off: step in ro region (cannot insert sw break)
 maint info breakpoints 0
 Num     Type           Disp Enb Address    What
 0       sw single-step keep y   0x00400774 in main at [...]/gdb/testsuite/gdb.base/breakpoint-in-ro-region.c:24 inf 1 thread 1
	 stop only in thread 1
 (gdb) FAIL: gdb.base/breakpoint-in-ro-region.exp: always-inserted off: auto-hw off: single-step breakpoint is not left behind

vs:

 (gdb) PASS: gdb.base/breakpoint-in-ro-region.exp: always-inserted off: auto-hw off: step in ro region (cannot insert sw break)
 maint info breakpoints 0
 No breakpoint or watchpoint matching '0'.
 (gdb) PASS: gdb.base/breakpoint-in-ro-region.exp: always-inserted off: auto-hw off: single-step breakpoint is not left behind

as at commit d930703d68ae^.

Before commit d930703d68ae, we had a cleanup installed in 'resume'
that would delete single-step breakpoints on error:

  /* Resuming.  */

  /* Things to clean up if we QUIT out of resume ().  */
  static void
  resume_cleanups (void *ignore)
  {
    if (!ptid_equal (inferior_ptid, null_ptid))
     delete_single_step_breakpoints (inferior_thread ());

    normal_stop ();
  }

That whole function was removed by d930703d68ae mainly to eliminate
the normal_stop call:

~~~~
    Note that the exception called from within resume ends up calling
    normal_stop via resume_cleanups.  That's very borked though, because
    normal_stop is going to re-handle whatever was the last reported
    event, possibly even re-running a hook stop...
~~~~

But as the regression shows, removing resume_cleanups completely went
a bit too far, as the delete_single_step_breakpoints call is still
necessary.

So fix the regression by reinstating the
delete_single_step_breakpoints call on error.  However, since we're
trying to eliminate cleanups, restore it in a different form (using
TRY/CATCH).

Tested on x86-64 GNU/Linux both top of master and on top of a series
that implements software single-step on x86.

gdb/ChangeLog:
2018-01-11  Pedro Alves  <palves@redhat.com>

	PR gdb/22583
	* infrun.c (resume): Rename to ...
	(resume_1): ... this.
	(resume): Reimplement as wrapper around resume_1.

2 files changed, 37 insertions, 3 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 8edb782f08..d40b914823 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,12 @@
 2018-01-11  Pedro Alves  <palves@redhat.com>
 
+	PR gdb/22583
+	* infrun.c (resume): Rename to ...
+	(resume_1): ... this.
+	(resume): Reimplement as wrapper around resume_1.
+
+2018-01-11  Pedro Alves  <palves@redhat.com>
+
 	PR remote/22597
 	* remote.c (remote_parse_stop_reply): Default to the last-set
 	general thread instead of to 'magic_null_ptid'.
diff --git a/gdb/infrun.c b/gdb/infrun.c
index 7e8d8da588..7d6aa7d069 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -2355,10 +2355,11 @@ do_target_resume (ptid_t resume_ptid, int step, enum gdb_signal sig)
 }
 
 /* Resume the inferior.  SIG is the signal to give the inferior
-   (GDB_SIGNAL_0 for none).  */
+   (GDB_SIGNAL_0 for none).  Note: don't call this directly; instead
+   call 'resume', which handles exceptions.  */
 
-void
-resume (enum gdb_signal sig)
+static void
+resume_1 (enum gdb_signal sig)
 {
   struct regcache *regcache = get_current_regcache ();
   struct gdbarch *gdbarch = regcache->arch ();
@@ -2730,6 +2731,32 @@ resume (enum gdb_signal sig)
   do_target_resume (resume_ptid, step, sig);
   tp->resumed = 1;
 }
+
+/* Resume the inferior.  SIG is the signal to give the inferior
+   (GDB_SIGNAL_0 for none).  This is a wrapper around 'resume_1' that
+   rolls back state on error.  */
+
+void
+resume (gdb_signal sig)
+{
+  TRY
+    {
+      resume_1 (sig);
+    }
+  CATCH (ex, RETURN_MASK_ALL)
+    {
+      /* If resuming is being aborted for any reason, delete any
+	 single-step breakpoint resume_1 may have created, to avoid
+	 confusing the following resumption, and to avoid leaving
+	 single-step breakpoints perturbing other threads, in case
+	 we're running in non-stop mode.  */
+      if (inferior_ptid != null_ptid)
+	delete_single_step_breakpoints (inferior_thread ());
+      throw_exception (ex);
+    }
+  END_CATCH
+}
+
 
 /* Proceeding.  */