dtrace discuss - May 2009 - How to trace the parameters of C++ class ?

Hi

If we''d trace an input parameter, which is infact an C++ class , such
as
TextItem, anyway we could trace the contents inside the TextItem ?

Example, it has a member named string, we''d get the contents of
TextItem.string.
Any advice?

Wynne

When the compiler passes an aggregate (class, struct, union, array, 
etc.) to a function it will always pass a pointer (the difference 
between passing by value, ref, or pointer is just language semantics). 
Given that, you should be able to typedef the struct in dtrace and then 
reference ((TextItem*) argN)->string (remember arg0 is the this pointer 
if it''s a member function).

I don''t know whether dtrace can handle member function declarations (it
certainly can''t call them!), so you may need to declare a struct type 
which shadows all the data members of TextItem.

Ryan

wynne wang wrote:
> Hi
>
> If we''d trace an input parameter, which is infact an C++ class ,
such as
> TextItem, anyway we could trace the contents inside the TextItem ?
>
> Example, it has a member named string, we''d get the contents of
> TextItem.string.
> Any advice?
>
> Wynne
>
> _______________________________________________
> dtrace-discuss mailing list
> dtrace-discuss at opensolaris.org
>

Oh, yeah -- make sure to copyin() first so you can actually access the 
memory...

Ryan

Ryan Johnson wrote:
> When the compiler passes an aggregate (class, struct, union, array, 
> etc.) to a function it will always pass a pointer (the difference 
> between passing by value, ref, or pointer is just language semantics). 
> Given that, you should be able to typedef the struct in dtrace and 
> then reference ((TextItem*) argN)->string (remember arg0 is the this 
> pointer if it''s a member function).
>
> I don''t know whether dtrace can handle member function
declarations
> (it certainly can''t call them!), so you may need to declare a
struct
> type which shadows all the data members of TextItem.
>
> Ryan
>
> wynne wang wrote:
>> Hi
>>
>> If we''d trace an input parameter, which is infact an C++ class
, such as
>> TextItem, anyway we could trace the contents inside the TextItem ?
>>
>> Example, it has a member named string, we''d get the contents
of
>> TextItem.string.
>> Any advice?
>>
>> Wynne
>>
>> _______________________________________________
>> dtrace-discuss mailing list
>> dtrace-discuss at opensolaris.org
>>   
>
> _______________________________________________
> dtrace-discuss mailing list
> dtrace-discuss at opensolaris.org