[RFC updated PATCHES] Bug Translator 3016 : Error accessing members of anonymous structs / unions

[Prerna Saxena]

Hi Masami,
Thanks for letting me know..
It pointed me to an incorrect pointer reference that I had 
overlooked...Its funny why this was never uncovered in all test-runs I 
had on x86 & x86_64 :-)
Here's the updated patch...with this, your test script correctly throws 
a semantic error instead of causing SEGV.

Masami Hiramatsu wrote:
> Hi Prerna,
>
> Prerna Saxena wrote:
>> Agree, but making "die_mem" as the 6th arg will disturb the call flow.
>> This is because in each recursive call, the 6th arg is overwritten by 
>> a die which is pointed to by DW_AT_type attribute of the original 
>> attr_mem. If die_mem is re-used as 6th arg instead of a new variable, 
>> the old contents of die (in the parent recursive call) will also be 
>> lost as both die & die_mem point to the same location, (whose 
>> contents would be overwritten). This is not a problem if search in a 
>> branch  has succeeded-- but in case a search path fails and a new 
>> branch needs to be tried, this will deem it impossible.
>>
>> I agree with your concern about "temp_die_2" being local memory on 
>> the stack which may be reused, so I've fixed it by copying the 
>> contents of "temp_die_2" to "die_mem" in case of a successful match. 
>> This should take care of memory errors.
>
> Hmm, you seems right, but the below command still cause SEGV.
>
> $ stap -e 'probe 
> module("libsas").function("sas_ex_revalidate_domain"){print($port_dev->ex_dev->children)}' 
> -vp2
> Pass 1: parsed user script and 45 library script(s) in 
> 370usr/30sys/404real ms.
> Segmentation fault
>
> Would you run above command for testing & debugging?
>
> Thank you,
>
Thanks & regards,

-- 
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India 

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