Re: [Valgrind-users] how to trace an application

[Nicholas N. <nj...@cs...>]

On Sun, 1 Apr 2007, Nicholas Nethercote wrote:

>> What about making a new tool out of it?
>> It really would be _especially_ nice to print the function parameters with
>> correct types, using DWARF debug info.
>>
>> The call tracing can be extracted as a kind of a module which tools can
>> combine. The problem is that every such module could have its own
>> instrumentation requirements, and there could be conflicts combining
>> multiple instrumentations.
>>
>> Hmm... perhaps it would be enough for such modules to document their
>> instrumentation needs (such as "module X needs a helper call to y at start of
>> every BB" or "module X wants to scan the SB and insert an IR snippet
>> before every exit"), and let the tool author do the actual instrumentation
>> manually as it is done now.
>
> That would be very nice if it could be done in a clean way.  It's one of
> those things that could be useful in a range of contexts but is actually
> really hard to do well, because of all the weird cases (PLT, longjmp/setjmp,
> tail recursion, etc).

Thinking some more, it shouldn't be that hard.  You'd have events like 
"enter_function" and "exit_function", which would get passed the function 
name and start address.  (You'd have to make clear that 
enter_function/exit_function aren't always well-matched.)  It could be added 
in an instrumentation pass like the one used for the 
new_mem_stack/die_mem_stack events.

Nick