[PATCH 5/7] range stepping: New command 'maint set range stepping'

[Yao Qi <yao@codesourcery.com>]

On 03/18/2013 11:45 AM, Eli Zaretskii wrote:
>> Don't have any special reasons to do this.  The range stepping should be
>> >always on if target supports, and it can be turned off for some
>> >"maintenance purpose", so I set this command as a maintenance
>> >command.
> What would be the possible reasons to turn this feature off?
>
> Once we have the reasons, we could try thinking whether or not they
> are limited to GDB maintenance.

Range-stepping is useful to speed up some operations, so users don't
have to turn it off.  The reason turning it off could be that the
remote stub has a bug in supporting range stepping, so we have to
disable it in GDB side.

I considered to name the command to "set remote range-stepping", but
range-stepping is not specific to remote target, and it can be
implemented on native target as well.  So "set remote range-stepping"
is not a good choice.  I also considered "set range-stepping", but
unable to find a reasonable place for documentation on it.  In V2, I
don't update the command name.

gdb:

2013-04-11  Yao Qi  <yao@codesourcery.com>

	* remote.c (use_range_stepping): New.
	(remote_vcont_probe): Set 'use_range_stepping' if the remote
	target supports range stepping.
	(append_resumption): Use 'vCont;r' packet if 'use_range_stepping'
	is true.
	(maint_show_range_stepping): New.
	(maint_set_range_stepping): New.
	(_initialize_remote): Call add_setshow_boolean_cmd to register
	commands 'maint set range-stepping' and
	'maint show range-stepping'.

gdb/doc:

2013-04-11  Yao Qi  <yao@codesourcery.com>

	* gdb.texinfo (Maintenance Commands): Document commands
	'maint set range-stepping' and 'maint show range-stepping' and
	convenience variable '$range_stepping_counter'.
---
 gdb/doc/gdb.texinfo |   10 ++++++++
 gdb/remote.c        |   64 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 73 insertions(+), 1 deletions(-)

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index bf7e25e..9292b94 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -35620,6 +35620,16 @@ data in a @file{gmon.out} file, be sure to move it to a safe location.
 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
 compiled with the @samp{-pg} compiler option.
 
+@kindex maint set range-stepping
+@kindex maint show range-stepping
+@cindex range-stepping
+@item maint set range-stepping
+@itemx maint show range-stepping
+@vindex $range_stepping_counter
+Control whether to do stepping in an address range.  The debugger convenience
+variable @samp{$range_stepping_counter} contains the number of range stepping
+@value{GDBN} has performed.
+
 @kindex maint set show-debug-regs
 @kindex maint show show-debug-regs
 @cindex hardware debug registers
diff --git a/gdb/remote.c b/gdb/remote.c
index a063698..7022275 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -260,6 +260,10 @@ struct support_v_cont
   int r;
 };
 
+/* A flag on GDB is willing to use range-stepping or not.  */
+
+static int use_range_stepping = 0;
+
 /* Description of the remote protocol state for the currently
    connected target.  This is per-target state, and independent of the
    selected architecture.  */
@@ -4652,6 +4656,7 @@ remote_vcont_probe (struct remote_state *rs)
       support_C = 0;
       rs->support_vCont.t = 0;
       rs->support_vCont.r = 0;
+      use_range_stepping = 0;
       while (p && *p == ';')
 	{
 	  p++;
@@ -4666,7 +4671,10 @@ remote_vcont_probe (struct remote_state *rs)
 	  else if (*p == 't' && (*(p + 1) == ';' || *(p + 1) == 0))
 	    rs->support_vCont.t = 1;
 	  else if (*p == 'r' && (*(p + 1) == ';' || *(p + 1) == 0))
-	    rs->support_vCont.r = 1;
+	    {
+	      rs->support_vCont.r = 1;
+	      use_range_stepping = 1;
+	    }
 
 	  p = strchr (p, ';');
 	}
@@ -4713,6 +4721,8 @@ append_resumption (char *p, char *endp,
 
       pc = regcache_read_pc (get_thread_regcache (ptid));
       if (rs->support_vCont.r /* Target supports step range.  */
+	  /* GDB is willing to do range stepping.  */
+	  && use_range_stepping
 	  /* Can't do range stepping for all threads of a process
 	     'pPID.-1'.  */
 	  && !(remote_multi_process_p (rs) && ptid_is_pid (ptid))
@@ -11697,6 +11707,45 @@ remote_upload_trace_state_variables (struct uploaded_tsv **utsvp)
   return 0;
 }
 
+static void
+maint_show_range_stepping (struct ui_file *file, int from_tty,
+			   struct cmd_list_element *c,
+			   const char *value)
+{
+  fprintf_filtered (file,
+		    _("Debugger's willingness to do range-stepping "
+		      "is %s.\n"), value);
+}
+
+static void
+maint_set_range_stepping (char *ignore_args, int from_tty,
+			  struct cmd_list_element *c)
+{
+  /* Check range stepping is supported when turns it on.  */
+  if (use_range_stepping)
+    {
+      if (remote_desc != NULL)
+	{
+	  struct remote_state *rs = get_remote_state ();
+
+	  if (remote_protocol_packets[PACKET_vCont].support == PACKET_SUPPORT_UNKNOWN)
+	    remote_vcont_probe (rs);
+
+	  if (remote_protocol_packets[PACKET_vCont].support == PACKET_DISABLE
+	      || !rs->support_vCont.r)
+	    {
+	      use_range_stepping = 0;
+	      error (_("Range stepping is not supported"));
+	    }
+	}
+      else
+	{
+	  use_range_stepping = 0;
+	  error (_("Range stepping is not supported"));
+	}
+    }
+}
+
 void
 _initialize_remote (void)
 {
@@ -12094,6 +12143,19 @@ Set the remote pathname for \"run\""), _("\
 Show the remote pathname for \"run\""), NULL, NULL, NULL,
 				   &remote_set_cmdlist, &remote_show_cmdlist);
 
+  add_setshow_boolean_cmd ("range-stepping", class_maintenance,
+			   &use_range_stepping, _("\
+Enable or disable range-stepping."), _("\
+Show whether range-stepping is enabled."), _("\
+If On, GDB will tell the target to do stepping a range of address.\n\
+This will speed up stepping a line of source file.\n\
+If off, GDB will not use it, even if such is supported by the \n\
+target"),
+			   maint_set_range_stepping,
+			   maint_show_range_stepping,
+			   &maintenance_set_cmdlist,
+			   &maintenance_show_cmdlist);
+
   /* Eventually initialize fileio.  See fileio.c */
   initialize_remote_fileio (remote_set_cmdlist, remote_show_cmdlist);
 
-- 
1.7.7.6