Re: [RFA] Displaced stepping just enable in non-stop mode

[teawater <teawater@gmail.com>]

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Hi Pedro,

Thanks for your example, I make a new patch for infrun.c and other for manual.

2008-10-10  Hui Zhu  <teawater@gmail.com>

	Displaced stepping can be set to
	auto (enable in non-stop mode), on, off.

	* infrun.c (can_use_displaced_stepping): Change type to const
	char pointer.
	(can_use_displaced_stepping_auto): New string.
	(can_use_displaced_stepping_on): New string.
	(can_use_displaced_stepping_off): New string.
	(can_use_displaced_stepping_enum): New array.
	(show_can_use_displaced_stepping): In auto mode, also show the
	current effect of the option.
	(use_displaced_stepping): Return non-zero if displaced stepping
 	is auto, and can be used with GDBARCH, and in non-stop mode.
	Return non-zero if displaced stepping is on, and can be used
	with GDBARCH.
	(_initialize_infrun): "can-use-displaced-stepping" function
	change to add_setshow_enum_cmd.

2008-10-10  Hui Zhu  <teawater@gmail.com>

	* gdb.texinfo (can-use-displaced-stepping) Describe the auto mode
	setting, and make it the default.


Thanks,
Hui

On Thu, Oct 9, 2008 at 22:49, Pedro Alves <pedro@codesourcery.com> wrote:
> Hi,
>
> Thanks for doing this.
>
> On Wednesday 08 October 2008 07:10:43, teawater wrote:
>
>> -int can_use_displaced_stepping = 1;
>> +const char can_use_displaced_stepping_auto[] = "auto";
>> +const char can_use_displaced_stepping_on[] = "on";
>> +const char can_use_displaced_stepping_off[] = "off";
>> +const char *can_use_displaced_stepping_enum[] =
>> +{
>> +  can_use_displaced_stepping_auto,
>> +  can_use_displaced_stepping_on,
>> +  can_use_displaced_stepping_off,
>> +  NULL,
>> +};
>> +const char *can_use_displaced_stepping = can_use_displaced_stepping_auto;
>
> Could you make these static while you're at it, please?  It was just missed
> in the old boolean setting.
>
>>  static void
>>  show_can_use_displaced_stepping (struct ui_file *file, int from_tty,
>>                                  struct cmd_list_element *c,
>> @@ -567,12 +579,16 @@ Debugger's willingness to use displaced
>>  "breakpoints is %s.\n"), value);
>
> Could you update this function to show what effect the auto setting
> is currently having?  See breakpoint.c:show_always_inserted_mode for
> an example.
>
>>  }
>>
>> -/* Return non-zero if displaced stepping is enabled, and can be used
>> +/* Return non-zero if displaced stepping is auto, and can be used
>> +   with GDBARCH, and in non-stop mode.
>> +   Return non-zero if displaced stepping is on, and can be used
>>     with GDBARCH.  */
>>  static int
>>  use_displaced_stepping (struct gdbarch *gdbarch)
>>  {
>> -  return (can_use_displaced_stepping
>> +  return (((can_use_displaced_stepping == can_use_displaced_stepping_auto
>> +           && non_stop)
>> +          || can_use_displaced_stepping == can_use_displaced_stepping_on)
>>           && gdbarch_displaced_step_copy_insn_p (gdbarch));
>>  }
>>
>> @@ -4857,11 +4873,14 @@ function is skipped and the step command
>>                            show_step_stop_if_no_debug,
>>                            &setlist, &showlist);
>>
>> -  add_setshow_boolean_cmd ("can-use-displaced-stepping", class_maintenance,
>> +  add_setshow_enum_cmd ("can-use-displaced-stepping", class_maintenance,
>> +                          can_use_displaced_stepping_enum,
>>                            &can_use_displaced_stepping, _("\
>>  Set debugger's willingness to use displaced stepping."), _("\
>>  Show debugger's willingness to use displaced stepping."), _("\
>> -If zero, gdb will not use displaced stepping to step over\n\
>> +If auto, gdb will auto use displaced stepping if it need (in non-stop mode).\n\
>> +If on, gdb will use displaced stepping if such is supported by the target.\n\
>> +If off, gdb will not use displaced stepping to step over\n\
>>  breakpoints, even if such is supported by the target."),
>
> This also needs to be updated in the manual.  I'd suggest borrowing the text
> from breakpoint.c's "always-inserted" command description to make it a
> bit more descriptive, and mention which mode is the default.  Should mostly
> be a matter of copy-paste, I think.
>
> --
> Pedro Alves
>

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--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,23 @@
+2008-10-10  Hui Zhu  <teawater@gmail.com>
+
+	Displaced stepping can be set to
+	auto (enable in non-stop mode), on, off.
+
+	* infrun.c (can_use_displaced_stepping): Change type to const
+	char pointer.
+	(can_use_displaced_stepping_auto): New string.
+	(can_use_displaced_stepping_on): New string.
+	(can_use_displaced_stepping_off): New string.
+	(can_use_displaced_stepping_enum): New array.
+	(show_can_use_displaced_stepping): In auto mode, also show the
+	current effect of the option.
+	(use_displaced_stepping): Return non-zero if displaced stepping
+ 	is auto, and can be used with GDBARCH, and in non-stop mode.
+	Return non-zero if displaced stepping is on, and can be used
+	with GDBARCH.
+	(_initialize_infrun): "can-use-displaced-stepping" function
+	change to add_setshow_enum_cmd.
+
 2008-10-09  Pedro Alves  <pedro@codesourcery.com>
 
 	* remote.c (remote_wait): Rename to...
--- a/infrun.c
+++ b/infrun.c
@@ -553,26 +553,50 @@ static CORE_ADDR displaced_step_original
 /* Saved contents of copy area.  */
 static gdb_byte *displaced_step_saved_copy;
 
-/* When this is non-zero, we are allowed to use displaced stepping, if
-   the architecture supports it.  When this is zero, we use
+/* When this is auto, we are allowed to use displaced stepping,
+   If the architecture supports it and in non-stop mode.
+   When this is on, we are allowed to use displaced stepping, if
+   the architecture supports it.  When this is off, we use
    traditional the hold-and-step approach.  */
-int can_use_displaced_stepping = 1;
+static const char can_use_displaced_stepping_auto[] = "auto";
+static const char can_use_displaced_stepping_on[] = "on";
+static const char can_use_displaced_stepping_off[] = "off";
+static const char *can_use_displaced_stepping_enum[] =
+{
+  can_use_displaced_stepping_auto,
+  can_use_displaced_stepping_on,
+  can_use_displaced_stepping_off,
+  NULL,
+};
+static const char *can_use_displaced_stepping =
+  can_use_displaced_stepping_auto;
 static void
 show_can_use_displaced_stepping (struct ui_file *file, int from_tty,
 				 struct cmd_list_element *c,
 				 const char *value)
 {
-  fprintf_filtered (file, _("\
-Debugger's willingness to use displaced stepping to step over "
-"breakpoints is %s.\n"), value);
+  if (can_use_displaced_stepping == can_use_displaced_stepping_auto)
+    {
+      fprintf_filtered (file, _("\
+Debugger's willingness to use displaced stepping to step over " "breakpoints is %s (currently %s).\n"), value, non_stop ? "on" : "off");
+    }
+  else
+    {
+      fprintf_filtered (file, _("\
+Debugger's willingness to use displaced stepping to step over " "breakpoints is %s.\n"), value);
+    }
 }
 
-/* Return non-zero if displaced stepping is enabled, and can be used
+/* Return non-zero if displaced stepping is auto, and can be used
+   with GDBARCH, and in non-stop mode.
+   Return non-zero if displaced stepping is on, and can be used
    with GDBARCH.  */
 static int
 use_displaced_stepping (struct gdbarch *gdbarch)
 {
-  return (can_use_displaced_stepping
+  return (((can_use_displaced_stepping == can_use_displaced_stepping_auto
+	    && non_stop)
+	   || can_use_displaced_stepping == can_use_displaced_stepping_on)
 	  && gdbarch_displaced_step_copy_insn_p (gdbarch));
 }
 
@@ -4857,11 +4881,14 @@ function is skipped and the step command
 			   show_step_stop_if_no_debug,
 			   &setlist, &showlist);
 
-  add_setshow_boolean_cmd ("can-use-displaced-stepping", class_maintenance,
+  add_setshow_enum_cmd ("can-use-displaced-stepping", class_maintenance,
+			   can_use_displaced_stepping_enum,
 			   &can_use_displaced_stepping, _("\
 Set debugger's willingness to use displaced stepping."), _("\
 Show debugger's willingness to use displaced stepping."), _("\
-If zero, gdb will not use displaced stepping to step over\n\
+If auto, gdb will auto use displaced stepping if it need (in non-stop mode).\n\
+If on, gdb will use displaced stepping if such is supported by the target.\n\
+If off, gdb will not use displaced stepping to step over\n\
 breakpoints, even if such is supported by the target."),
 			   NULL,
 			   show_can_use_displaced_stepping,

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--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2008-10-10  Hui Zhu  <teawater@gmail.com>
+
+	* gdb.texinfo (can-use-displaced-stepping) Describe the auto mode
+	setting, and make it the default.
+
 2008-10-06  Doug Evans  <dje@google.com>
 
 	* gdb.texinfo (set debug dwarf2-die): Document it.
--- a/gdb.texinfo
+++ b/gdb.texinfo
@@ -23935,16 +23935,25 @@ Shared library events.
 
 @kindex maint set can-use-displaced-stepping
 @kindex maint show can-use-displaced-stepping
-@cindex displaced stepping support
-@cindex out-of-line single-stepping
-@item maint set can-use-displaced-stepping
-@itemx maint show can-use-displaced-stepping
-Control whether or not @value{GDBN} will do @dfn{displaced stepping}
-if the target supports it.  The default is on.  Displaced stepping is
-a way to single-step over breakpoints without removing them from the
-inferior, by executing an out-of-line copy of the instruction that was
-originally at the breakpoint location.  It is also known as
-out-of-line single-stepping.
+@table @code
+@item maint set can-use-displaced-stepping on
+If the target supports it.  Gdb behaves are single-step over
+breakpoints without removing them from the inferior, by executing
+an out-of-line copy of the instruction that was originally at the
+breakpoint location.  It is also known as out-of-line single-stepping.
+
+@item maint set can-use-displaced-stepping off
+Gdb behaves are single-step over breakpoints with removing them from
+the inferior.
+
+@cindex non-stop mode, and @code{breakpoint always-inserted}
+@item maint set can-use-displaced-stepping auto
+This is the default mode.  If @value{GDBN} is controlling the inferior
+in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
+@code{can-use-displaced-stepping} mode is on.  If @value{GDBN} is
+controlling the inferior in all-stop mode, @value{GDBN} behaves as if
+@code{can-use-displaced-stepping} mode is off.
+@end table
 
 @kindex maint check-symtabs
 @item maint check-symtabs