Re: [PATCH] Add CTF support to GDB [1/4] Add "-ctf" to tsave command

[Hui Zhu <teawater at gmail dot com>]

Hi Tom,

Thanks for your review.

On Fri, Jan 4, 2013 at 5:36 AM, Tom Tromey <tromey@redhat.com> wrote:
>>>>>> "Hui" == Hui Zhu <teawater@gmail.com> writes:
>
> Hui> +struct ctf_save_collect_s
> Hui> +{
> Hui> +  struct ctf_save_collect_s *next;
> Hui> +  char *str;
> Hui> +  char *ctf_str;
> Hui> +  int align_size;
> Hui> +  struct expression *expr;
> Hui> +  struct type *type;
> Hui> +  int is_ret;
> Hui> +};
>
>>> Like Hafiz said -- comments would be nice.
>
> Hui> I added some comments in the new patches.
>
> I looked at the new patches and did not see comments.  For example, I
> looked at this struct I quoted above.
>
> Every new structure, field, and function ought to have a comment.

OK.  I added comments for them in the new patch.

>
>
> Hui> +    case TYPE_CODE_ARRAY:
> Hui> +      for (; TYPE_CODE (type) == TYPE_CODE_ARRAY;
> Hui> +     type = TYPE_TARGET_TYPE (type))
> Hui> +  ;
>
> Tom> You probably want some check_typedef calls in there.
>
> Hui> Because typedef will be handle as a type in this part, so this part
> Hui> doesn't need check_typedef.
>
> That seems peculiar to me, but I don't really know CTF.
> In this case you need a comment, since the result will be non-obvious to
> gdb developers.
>
> Tom> check_typedef; though if your intent is to peel just a single layer,
> Tom> then it is a bit trickier -- I think the best you can do is always call
> Tom> it, then use TYPE_TARGET_TYPE if it is non-NULL or the result of
> Tom> check_typedef otherwise.
>
> Hui> If use check_typedef, this part will generate the define that
> Hui> different with the type descriptor of the code.
>
> You need to call check_typedef before you can even examine
> TYPE_TARGET_TYPE of a typedef.  This is what I meant by using it before
> using TYPE_TARGET_TYPE.  Otherwise with stubs I think you will see
> crashes -- check_typedef is what sets this field.
>
> If you then use TYPE_TARGET_TYPE and get NULL, you ought to instead use
> the result of check_typedef.  This means the stub had to resolve to a
> typedef in a different objfile.

I change it to following part:
    case TYPE_CODE_ARRAY:
      /* This part just to get the real name of this array.
         This part should keep typedef if it can.  */
      for (; TYPE_CODE (type) == TYPE_CODE_ARRAY;
	   type = TYPE_TARGET_TYPE (type) ? TYPE_TARGET_TYPE (type)
					  : check_typedef (type))
	;

>
> Hui> If use TYPE_TARGET_TYPE, it will generate following metadata:
> Hui> typedef char test_t1;
> Hui> typedef test_t1 test_t2;
> Hui> typedef test_t2 test_t3;
>
> I suppose there should be a test case doing this.

OK. I will write a test for all this function.

>
> Hui> +      case TYPE_CODE_PTR:
> Hui> +  align_size = TYPE_LENGTH (type);
> Hui> +  break;
>
> Tom> Surely the alignment rules are ABI dependent.
> Tom> I would guess that what you have will work in many cases, but definitely
> Tom> not all of them.
>
> Hui> All the type will be handle and record in function
> Hui> ctf_save_type_check_and_write.
> Hui> The size align will be handle in this function too.
>
> I don't think this really addresses the issue.
> Not all platforms use the alignment rules currently coded in
> ctf_save_type_check_and_write.  But maybe it doesn't matter.
>
> Hui> +    frame = get_current_frame ();
> Hui> +    if (!frame)
> Hui> +      error (_("get current frame fail"));
> Hui> +    frame = get_prev_frame (frame);
> Hui> +    if (!frame)
> Hui> +      error (_("get prev frame fail"));
> Tom>
> Tom> These messages could be improved.
>
> Actually, I don't think get_current_frame can return NULL, can it?
>
> For the second error, how about "could not find previous frame"?

Fixed.

>
> Hui> +      warning (_("\
> Hui> +Not save \"%s\" of tracepoint %d to ctf file because get its
> Hui> value fail: %s"),
> Hui> +         str, tps->tp->base.number, e.message);
> Tom>
> Tom> Likewise.
>
> Hui> Could you help me with this part?  :)
>
> How about "error saving tracepoint %d to CTF file %s: %s".

It is more better.  I updated them all.

>
> Tom> Although, this approach just seems weird, since it seems like you
> Tom> already have the symbol and you want its value; constructing and parsing
> Tom> an expression to get this is very roundabout.
> Tom>
> Tom> I'm not sure I really understand the goal here; but the parsing approach
> Tom> is particularly fragile if you have shadowing.
>
> Hui> Function ctf_save_collect_get will parse the collect string and add
> Hui> them to struct.
> Hui> Each tracepoint will call this function just once.
>
> Ok, I don't know the answer here.

I am sorry that this part is not very clear.  So I update the comments
of ctf_save_collect_get to:
/* Get var that want to collect from STR and put them to TPS->collect.
   This function will not be call when GDB add a new TP.  */

static void
ctf_save_collect_get (struct ctf_save_s *tcsp, struct ctf_save_tp_s *tps,
		      char *str)

How about this?

>
> Tom> Hmm, a lot of this code looks like code from tracepoint.c.
> Tom> I think it would be better to share the code if that is possible.
>
> Hui> I tried to share code with function add_local_symbols.  But it is not
> Hui> a big function and use different way to get block.
>
> I wonder why, and whether this means that the different ways of saving
> will in fact write out different data.

I added function add_local_symbols_1 for that.

>
> Hui> +    if (collect->expr)
> Hui> +      free_current_contents (&collect->expr);
>
> Tom> Why free_current_contents here?
> Tom> That seems weird.
>
> Hui> If this collect is $_ret, it will not have collect->expr.  Or maybe
> Hui> this collect will be free because when setup this collect get
> Hui> error.  So check it before free it.
>
> You can just write  xfree (collect->expr).
> You don't need a NULL check here.
> This applies to all those xfree calls.
>

OK.  Fixed.

I post a new version.  Please help me review it.

Thanks,
Hui

2013-01-08  Hui Zhu  <hui_zhu@mentor.com>

	* Makefile.in (REMOTE_OBS): Add ctf.o.
	(SFILES): Add ctf.c.
	(HFILES_NO_SRCDIR): Add ctf.h.
	* ctf.c, ctf.h: New files.
	* mi/mi-main.c (ctf.h): New include.
	(mi_cmd_trace_save): Add "-ctf".
	* tracepoint.c (ctf.h): New include.
	(collect_pseudocommand): Remove static.
	(trace_save_command): Add "-ctf".
	(_initialize_tracepoint): Ditto.
	* tracepoint.h (stack.h): New include.
	(collect_pseudocommand): Add extern.

Attachment: tsave-ctf.txt
Description: Text document