[cfe-dev] Dissect and rewrite of function calls in expressions

[Marcel Schaible via cfe-dev]

I would think (in fact, I _KNOW_) that the compiler already does the 
transformation to temp1 = foo(42) and temp2 = foo(temp1) already. So 
it'd just be a case, at the LLVM-IR level at least, to insert some code 
to inspect temp1 and temp2.
>
Good hint. I'll check that.

> Of course, it may be a slightly more interesting challenge to find 
> your "interesting functions" (particularly if interesting functions 
> aren't a well defined set of functions) when looking at the LLVM-IR - 
> including the fact that for example member functions gets mangled 
> during compilation.
>
"Interesting functions" are marked by the developer.

> Also interesting/challenging is function pointers:
>
>     pf = foo;
>     var = 42 + pf(pf(42));
>
> Consider where pf is passed into the function you're currently looking 
> at, or comes from a table of function pointers, with a non-constant 
> determining the index into the table.
> A similar problem is of course virtual function calls - they are just 
> function pointer tables after all [but the table itself is the 
> variable part there, rather than the index, unless we're talking 
> virtual member function pointers, which isn't a common creature by any 
> means]

At the first shot I'll attack the trivial cases. So function pointer are 
on my list but come at a later point in time. Because the target are 
embedded devices, which in my case are programmed exclusively in plain "C"
I'll ignore for the moment vtables.

Anyway I would like to implement the dissecting of the expression my 
self with the clang frontend. Any hints on that?
--
Marcel