Handling of OUT function arguments for "apitrace trim"

[Carl Worth]

José,

As I coded up some preliminary support for "apitrace trim" I tried to
verify that I could read a trace in and then write an identical trace
back out again.

I found that the traces I generated were slightly different in byte
content, but identical according to "apitrace dump".

My code to write out a function looks like this:

    unsigned __call = writer.beginEnter(call->sig);
    for (unsigned i = 0; i < call->args.size(); ++i) {
        writer.beginArg(i);
        _visit(call->args[i]);
        writer.endArg();
    }
    writer.endEnter();
    writer.beginLeave(__call);
    if (call->ret) {
        writer.beginReturn();
        _visit(call->ret);
        writer.endReturn();
    }
    writer.endLeave();

This causes a result that's different from the original trace because
the original trace puts some of the argument values inside the "Leave"
block rather than inside the "Enter" block, (for those arguments that
are marked as OUT arguments in the specs).

As far as I can see, the current code doesn't hold on to the information
for which arguments are OUT arguments, so I wouldn't be able to generate
an identical trace without augmenting something there.

But then again, the current parser is also throwing away the information
of which arguments are OUT arguments. So it occurs to me that no code
using the current parser can even care whether the arguments are in the
Leave or Enter blocks, (as long as they have the correct value).

So I'm looking for your advice. Shall I go ahead with code like the
above for the trim case? Or shall we extend the parser to identify which
arguments are OUT arguments so that I can put those into the Leave
block?

-Carl

-- 
carl.d.worth at intel.com
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