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


On Mon, Feb 4, 2013 at 11:33 PM, Abid, Hafiz <Hafiz_Abid@mentor.com> wrote:
> Hi Hui,
> I tested the latest patch. I get some build error due to uninitialized local variables.
> ../../gdb/gdb/ctf.c: In function ‘ctf_save_collect_get_1’:
> ../../gdb/gdb/ctf.c:636:21: error: ‘type’ may be used uninitialised in this function [-Werror=uninitialized]
> ../../gdb/gdb/ctf.c: In function ‘ctf_save_collect_get’:
> ../../gdb/gdb/ctf.c:734:28: error: ‘pc’ may be used uninitialised in this function [-Werror=uninitialized]
> ../../gdb/gdb/ctf.c: In function ‘ctf_save_tp_find’:
> ../../gdb/gdb/ctf.c:823:7: error: ‘pc’ may be used uninitialised in this function [-Werror=uninitialized]
> ../../gdb/gdb/ctf.c: In function ‘ctf_save’:
> ../../gdb/gdb/ctf.c:1323:33: error: ‘content’ may be used uninitialised in this function [-Werror=uninitialized]
> ../../gdb/gdb/ctf.c:1307:56: error: ‘val’ may be used uninitialised in this function [-Werror=uninitialized]
>
> After fixing that, I can see that array and while-stepping are working OK. As I understand, bitfields are not yet supported in babeltrace. So that takes care of most of the issues I reported.
>
> Regards,
> Abid


Hi Abid,

Thanks for your help.  I just post a new version that fixed these issues.

Best,
Hui

2013-02-05  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.
	* breakpoint.c (tracepoint_count): Remove static.
	* 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.

> ________________________________________
> From: Hui Zhu [teawater@gmail.com]
> Sent: Wednesday, January 23, 2013 1:32 PM
> To: Abid, Hafiz
> Cc: Tom Tromey; Zhu, Hui; gdb-patches@sourceware.org
> Subject: Re: [PATCH] Add CTF support to GDB [1/4] Add "-ctf" to tsave command
>
> Hi Abid,
>
> I post a new version according to your comments.
>
> Following part have the reply for your comments.
>
> Thanks,
> Hui
>
> 2013-01-23  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.
>         * breakpoint.c (tracepoint_count): Remove static.
>         * 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.
>
> On Fri, Jan 18, 2013 at 10:29 PM, Hafiz Abid Qadeer
> <hafiz_abid@mentor.com> wrote:
>> On 18/01/13 01:16:24, Hui Zhu wrote:
>>>
>>> Hi Abid,
>>>
>>> Thanks for your review.
>>>
>>> On Mon, Jan 14, 2013 at 10:27 PM, Abid, Hafiz <Hafiz_Abid@mentor.com>
>>> wrote:
>>> > Hi Hui,
>>> > I tested your patch and found a few problems. I used 'tsave -ctf output'
>>> > and then used babeltrace to get a text dump of the output.
>>> >
>>> > 1. In case of array, the tracing results are off by one.
>>> > 2. Struct members values are not shown correctly in case of bitfields.
>>>
>>> Could you give me some example about this 2 issues?
>>> And I just fixed some type issue with while-stepping.  I think maybe
>>> they were fixed in the new patch.
>>>
>> I made an array of size 5 and gave it elements values from 5 to 9. I
>> collected this array in trace. After trace was finished, GDB will show
>> correct values of all the array elements. But in babeltrace, the first
>> element would have value of 6 and last will have a garbage value. So it
>> looked that values are off by one index.
>>
>> For bitfield, I had a structure like this and I observed that value of b was
>> not correct in babeltrace.
>> struct test_main
>> {
>>         int a;
>>         int b: 16;
>>         int c: 16;
>> };
>>
>> I will send you my test application offline.
>
> Thanks.  This issue is because old patch doesn't support bitfields.  I
> add them in the new patch.  But babeltrace doesn't support gcc
> bitfields.  So I didn't update test for bitfields.
>
>>
>>
>>> > 3. When I use while-stepping on tracepoints actions, I see some error in
>>> > the babeltrace.
>>>
>>> Fixed.  And I think it is a good idea for test.  So I updated test for
>>> this issue.
>>>
>>> > 4. It looks that TYPE_CODE_FLT is not supported which cause the
>>> > following warning when I use collect $reg on the tracepoint actions.
>>> > "warning: error saving tracepoint 2 "$st0" to CTF file: type is not
>>> > support."
>>>
>>> Yes.  current patch is still not support all the type of GDB.
>>>
>>> >
>>> > Below are some comments on the code. I see many tab characters in the
>>> > patch. It may be problem in my editor but something to keep an eye on.
>>> >
>>> >>+#define CTF_PACKET_SIZE               4096
>>> > It may be my ignorance but is this size sufficient? Should it be
>>> > possible to increase the limit using some command?
>>>
>>> Yes, add a command to change current ctf_packet_size is a good idea.
>>> Do you mind I add it after CTF patch get commit?  Then we can keep
>>> focus on the current function of CTF patch.
>>
>> I dont have any problem with fixed size. I was just giving an idea that you
>> may want to implement in future.
>>
>>
>>>
>>> >
>>> >>+  /* This is the content size of current packet.  */
>>> >>+  size_t content_size;
>>> > ...
>>> >>+  /* This is the content size of current packet and event that is
>>> >>+     being written to file.
>>> >>+     Check size use it.  */
>>> >>+  size_t current_content_size;
>>> > I don't fully understand the difference between these 2 variables.
>>> > Probably they need a more helpful comment.
>>> >
>>>
>>> I update it to:
>>>   /* This is the temp value of CONTENT_SIZE when GDB write a event to
>>>      CTF file.
>>>      If this event save success, CURRENT_CONTENT_SIZE will set to
>>>      CONTENT_SIZE.  */
>>>   size_t current_content_size;
>>>
>>> >> +error saving tracepoint %d \"%s\" to CTF file: type is not support."),
>>> > 'supported' instead of 'support'.
>>>
>>> Fixed.
>>>
>>> >
>>> >>+            sprintf (regname, "$%s", name);
>>> >>+  sprintf (file_name, "%s/%s", dirname, CTF_METADATA_NAME);
>>> >>+  sprintf (file_name, "%s/%s", dirname, CTF_DATASTREAM_NAME);
>>> > Please use xsnprintf. There are also a bunch of snprintf calls in this
>>> > file.
>>>
>>> The size of file_name is alloca as the right size for both this
>>> string.  So I think this part doesn't need xsnprintf.
>>>   file_name = alloca (strlen (dirname) + 1
>>>                       + strlen (CTF_DATASTREAM_NAME) + 1);
>>> >
>>> >>+                  case '$':
>>> >>+                    collect->ctf_str
>>> >>+                        = ctf_save_metadata_change_char
>>> >> (collect->ctf_str,
>>> >>+                                                         i, "dollar");
>>> > This will change expression like $eip in gdb to dollar_eip in ctf. Does
>>> > CTF forbid these characters?
>>>
>>> No.
>>
>> In that case, the question will be why we do this change from $eip to
>> dollar_eip.
>
> Oops,  sorry for my mistake.  CTF doesn't support this char like $ or
> something else.
>
>>
>>
>>>
>>> >
>>> >>+static void
>>> >>+tsv_save_do_loc_arg_collect (const char *print_name,
>>> >>+                           struct symbol *sym,
>>> >>+                           void *cb_data)
>>> >>+{
>>> >>+  struct loc_arg_collect_data *p = cb_data;
>>> >>+  char *name;
>>> >>+
>>> >>+  name = alloca (strlen (print_name) + 1);
>>> >>+  strcpy (name, print_name);
>>> >>+  ctf_save_collect_get_1 (p->tcsp, p->tps, name);
>>> >>+}
>>> > Is there any real need to make a copy of the print_name? I think it can
>>> > be passed directly to the ctf_save_collect_get_1.
>>>
>>> This is because print_name is a const but ctf_save_collect_get_1's
>>> argument name need to be a string that is not a const.
>>> Added comments for that.
>>
>> You probably would have done a cast or perhaps ctf_save_collect_get_1's
>> argument can be changed to const.
>>
>
> Fixed.
>
>>
>>>
>>> >
>>> >>+ tmp = alloca (strlen (collect->ctf_str) + 30);
>>> >>+        strcpy (tmp, collect->ctf_str);
>>> >>+        while (1)
>>> >>+          {
>>> >>+            struct ctf_save_collect_s *collect2;
>>> >>+            int i = 0;
>>> >>+
>>> >>+            for (collect2 = tps->collect; collect2;
>>> >>+                 collect2 = collect2->next)
>>> >>+              {
>>> >>+                if (collect2->ctf_str
>>> >>+                    && strcmp (collect2->ctf_str, tmp) == 0)
>>> >>+                  break;
>>> >>+              }
>>> >>+            if (collect2 == NULL)
>>> >>+              break;
>>> >>+
>>> >>+            snprintf (tmp, strlen (collect->ctf_str) + 30,
>>> >>+                      "%s_%d", collect->ctf_str, i++);
>>> >>+          }
>>> > What is the purpose of this loop? It only writes a new string in the tmp
>>> > local variable which is not used after the loop.
>>>
>>> Fixed.
>>>
>>> >
>>> >>+\"%s\" of tracepoint %d rename to \"%s\" in CTF file."),
>>> > I think 'is renamed' will be better instead of rename here.
>>>
>>> Fixed.
>>>
>>> >
>>> >>+        if (try_count > 1 || 4 + 4 + 4 == tcs.content_size)
>>> > what is the significance of this 4 + 4 + 4
>>>
>>> Change it to CONTENT_HEADER_SIZE
>>>
>>> >
>>> >>+traceframe %d of tracepoint %d need save data that bigger than packet
>>> >> size %d.\n\
>>> > should be "needs to save data that is bigger than the packet size"
>>>
>>> Fixed.
>>>
>>> >
>>> >>+traceframe %d is dropped because try to get the value of \"%s\" got
>>> >> error: %s"),
>>> > This probably needs to re-phrased.
>>>
>>> Fixed.
>>>
>>> >
>>> > Also many comments can be improved grammatically. This will make them
>>> > easier to understand. Please let me know if I need any help there.
>>> >
>>> > Thanks,
>>> > Abid
>>>
>>> Post a new version according to your comments.
>>>
>>> Thanks,
>>> Hui
>>>
>>> 2013-01-18  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.
>>>         * breakpoint.c (tracepoint_count): Remove static.
>>>         * 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.
>>>
>>> >
>>> > ________________________________________
>>> > From: gdb-patches-owner@sourceware.org
>>> > [gdb-patches-owner@sourceware.org] on behalf of Hui Zhu [teawater@gmail.com]
>>> > Sent: Monday, January 14, 2013 5:18 AM
>>> > To: Tom Tromey
>>> > Cc: Zhu, Hui; gdb-patches@sourceware.org
>>> > Subject: Re: [PATCH] Add CTF support to GDB [1/4] Add "-ctf" to tsave
>>> > command
>>> >
>>> > Hi Tom,
>>> >
>>> > I found a bug when I use test to test this patch.
>>> > So I post a new version to fix this bug.
>>> > The change of this patch is change the same type check to:
>>> > static void
>>> > ctf_save_type_define_write (struct ctf_save_s *tcsp, struct type *type)
>>> > {
>>> >   struct ctf_save_type_s *t;
>>> >
>>> >   for (t = tcsp->type; t; t = t->next)
>>> >     {
>>> >       if (t->type == type
>>> >           || (TYPE_NAME (t->type) && TYPE_NAME (type)
>>> >               && strcmp (TYPE_NAME (t->type), TYPE_NAME (type)) == 0))
>>> >         return;
>>> >     }
>>> >
>>> > Thanks,
>>> > Hui
>>> >
>>> > On Tue, Jan 8, 2013 at 9:40 AM, Hui Zhu <teawater@gmail.com> wrote:
>>> >> 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


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