On Thu, 2010-08-26 at 18:16 -0700, Jeff Saremi wrote:
> I'm hoping someone here could take the time to outline what I need to do (i'm
> not looking for code but if you point me to some i'd appreciate it).
>
> I'd like to track an object from the it's created until it's destroyed (in
> C++). And then see if a certain method of it is called or not. To keep it
> short we can limit this to one function at the beginning of which an object
> gets created and at the end of it the object goes out of scope.
> And i'm guessing this can be done via one a pass at the right time. I guess
> before gimplification or being converted to RTL and such.
I am not sure that is easily feasible. I would believe it is impossible.
Within the compiler (or inside a GCC plugin, or inside a GCC extension
coded in MELT), you probably are able change/inspect C++ classes & every
other declaration any compiler is tracking. You are also able to find
every occurrence of variables containing a pointer to such classes.
However, you are apparently willing to track a single *instance* of such
a class, and this instance is in the execution of the compiled program
[not inside the compiler]. This means that you are able to deal with all
the aliasing & pointer equivalence issues (a task known to be
impossible). How can the compiler surely know that pointer p in [a
particular instruction of] method YourClass::foo() is never (or
sometimes, or always) pointing to the same instance -in the running
process of the compiled program- as pointer q in method yourclass::bar()
Or perhaps my English is so weak that I misunderstood you. If that is
the case, apologies.
Or maybe you want to instrument your compiler so that for every code
emitted for method yourclass::gee() you add a first block which checks
that the this reciever is not a given pointer.
In other words & C++ parlance, you could (this is doable, but not
trivial) hack the compiler so that at the start of every method (i.e.
member function in C++) the equivalent of the following C++ code has
been magically added
extern "C" YourClass* hunted_yourclass_pointer;
extern "C" void some_error_routine(void);
if (this == hunted_yourclass_pointer)
some_error_routine();
But I am not sure you want to do that.
Cheers.
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Basile STARYNKEVITCH http://starynkevitch.net/Basile/
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