Re: [PING][PATCH 0/2] Improved variable object invalidation in GDB

[Saqlain Raza <saqlain_raza@mentor.com>]

Ping !

For reference, the patch is available in:

https://sourceware.org/ml/gdb-patches/2019-10/msg00557.html

Testcase:

https://sourceware.org/ml/gdb-patches/2019-10/msg00558.html

Thanks,
Saqlain

On 11/7/19 12:50 PM, Saqlain Raza wrote:
> Hi Luis,
>
> Thanks you very much for taking a look and sorry for the delay in 
> response.
>
>> Before reviewing the patch itself, could you please expand, with more 
>> detail, what the use case is for this particular fix? 
> Can you please review the test-case submitted in 
> https://sourceware.org/ml/gdb-patches/2019-10/msg00558.html if that 
> somewhat clarifies the use-case ?
>
> For examining, changing or updating the values of expression, a GDB/MI 
> Variable object of the expression using "-var-create" is made and 
> later is checked for changes using "-var-update". Now, the problem is 
> that the memory contents of a global symbol (being monitored via the 
> expression) are changed but in response to "-var-update", it replies 
> with the empty change list "changelist=[]" where as changes are now 
> expected in change list (due to changed memory contents). This happens 
> after a symbol file removal takes place.
>
> GDB traces for Variable object creation and update before symbol file 
> is removed:
>
> 565,916 104-var-create --thread-group i1 - * ((NODE*)0xbc834)->next
> 565,924 %"Sending packet: $mbc838,4#35..."
> 565,924 %"Ack\n"
> 565,924 %"Packet received: 4cca0b00\n"
> 565,925 104^done,name="var14",numchild="3",value="0xbca4c 
> <Control_Array+536>",type="struct NODE_\
> STRUCT *",has_more="0"
>
> 573,325 141-var-update 1 var14
> 573,334 %"Sending packet: $mbc838,4#35..."
> 573,334 %"Ack\n"
> 573,334 %"Packet received: 4cca0b00\n"
> 573,334 141^done,changelist=[]
>
> GDB traces generated when symbol file has been removed:
>
> 589,422 184-var-update 1 var14
> 589,431 %"Sending packet: $mbc838,4#35..."
> 589,431 %"Ack\n"
> 589,431 %"Packet received: 64cc0b00\n" <----- Memory contents did change.
> 589,431 184^done,changelist=[]  <------- Changelist still empty.
>
> Thanks,
> Saqlain
>
> On 10/22/19 5:53 PM, Luis Machado wrote:
>> Hi,
>>
>> Before reviewing the patch itself, could you please expand, with more 
>> detail, what the use case is for this particular fix?
>>
>> It seems to be the same patch Taimoor sent a while ago, so in order 
>> to improve its chances of getting accepted, it would be nice to have 
>> a bit more background.
>>
>> In particular, adding varobj bits to objfiles.[c] is a bit strange. 
>> Varobj access seems to be restricted to core varobj implementations 
>> and language support only.
>>
>> It may be a sign that something more fundamental is missing, like an 
>> interface of some kind, an observer or a notification.
>>
>> Better understanding the use case will allow us to determine 
>> where/how exactly this should be fixed.
>>
>> Luis
>>
>> On 10/17/19 7:03 AM, Raza, Saqlain wrote:
>>> Hi,
>>> This patch series improves variable object invalidation in GDB.
>>>
>>> This is a followup to the patch series submission made in 
>>> https://sourceware.org/ml/gdb-patches/2015-04/msg00598.html . This 
>>> problem still holds in the latest GDB master.
>>>
>>> Raza, Saqlain (2):
>>>    Fix varobj updation after symbol removal
>>>    Testsuite for varobj updation after symbol removal
>>>
>>>   gdb/ChangeLog                              |  13 ++
>>>   gdb/objfiles.c                             |  19 ++
>>>   gdb/testsuite/ChangeLog                    |  11 +
>>>   gdb/testsuite/gdb.mi/mi-var-invalidate.exp |  68 ++++++
>>>   gdb/testsuite/gdb.mi/sym-file-lib.c        |  28 +++
>>>   gdb/testsuite/gdb.mi/sym-file-loader.c     | 355 
>>> +++++++++++++++++++++++++++++
>>>   gdb/testsuite/gdb.mi/sym-file-loader.h     | 101 ++++++++
>>>   gdb/testsuite/gdb.mi/sym-file-main.c       |  86 +++++++
>>>   gdb/varobj.c                               |  35 +++
>>>   gdb/varobj.h                               |   4 +
>>>   10 files changed, 720 insertions(+)
>>>   create mode 100644 gdb/testsuite/gdb.mi/sym-file-lib.c
>>>   create mode 100644 gdb/testsuite/gdb.mi/sym-file-loader.c
>>>   create mode 100644 gdb/testsuite/gdb.mi/sym-file-loader.h
>>>   create mode 100644 gdb/testsuite/gdb.mi/sym-file-main.c
>>>