[LLVMdev] Unit testing with random input using JIT

[Reid Kleckner]

If you know the prototype of f, you can just use getPointerToFunction
and cast the result:

// Let F be an llvm::Function* referring to 'f'.
void (*f)(int*) = (void (*)(int*))JIT->getPointerToFunction(F);
int a;
f(&a);
// read a

I haven't compiled this, it's a guess at the usage from memory.

Reid

On Fri, Feb 11, 2011 at 12:55 PM, Vu Le <vmle at ucdavis.edu> wrote:
> Suppose I want to test the function f with zero.
> f(int *t){
>   *t = 2
> }
> What I did was that I create a wrapper
> void Wrapper(){
>   int a = 1;
>   int *b = &a;
>   f(b);
>   // now I want to print the value of b
>   // but I don't know how
> }
>
> Thanks.
> Vu
> On Thu, Feb 10, 2011 at 6:56 PM, Reid Kleckner <reid.kleckner at gmail.com>
> wrote:
>>
>> Not sure what you mean here.  If you have a copy of that pointer in
>> the caller of the wrapper function, you should be able to follow it to
>> recover the modified value as normal.
>>
>> Reid
>>
>> On Thu, Feb 10, 2011 at 9:20 PM, Vu Le <vmle at ucdavis.edu> wrote:
>> > Hi Reid,
>> > If an argument is a pointer and the function changes the value it
>> > pointed
>> > to,
>> > do you know how to get that updated value after executing the wrapper
>> > function?
>> >
>> > Thanks.
>> > Vu
>> >
>> > On Tue, Jan 11, 2011 at 2:40 PM, Reid Kleckner <reid.kleckner at gmail.com>
>> > wrote:
>> >>
>> >> On Tue, Jan 11, 2011 at 1:41 PM, Vu Le <vmle at ucdavis.edu> wrote:
>> >> > Hi,
>> >> > I want to implement a tool that probes a function with several input
>> >> > and
>> >> > records all the return output.
>> >> > The function might have more than 1 return value (by reference
>> >> > parameters).
>> >> >
>> >> > Does ExecutionEngine::runFunction() support function call with
>> >> > complex
>> >> > argument type?
>> >> > If not, I guess that I have to create a wrapper function, prepare all
>> >> > the
>> >> > data, and call the original function.
>> >> > Am I on the right track?
>> >>
>> >> For functions with complicated parameters and return values,
>> >> runFunction will generate a wrapper function that calls the function
>> >> with the right arguments.  This is fairly expensive and leaks memory
>> >> if called more than once for the same function.  If the type of the
>> >> function is known, you can just use getPointerToFunction, cast that,
>> >> and call it from C.
>> >>
>> >> If it's not known but you want to call it many times with different
>> >> arguments, you could generate a wrapper function responsible for
>> >> unpacking your own datastructure describing the arguments and calling
>> >> the function you are testing with those arguments.  Seems like you are
>> >> on the right track there.
>> >>
>> >> Reid
>> >
>> >
>
>