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


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
________________________________________
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.
>>
>


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