[LLVMdev] Redefining function

Conrado Miranda miranda.conrado at gmail.com
Fri Jan 29 11:50:59 PST 2010

Hi everybody.

I've just started learning about LLVM and didn't get too far studying the
I couldn't find the solution to my problem (if it has one) in the mailing
list or the source code. The problem is: how can I redefine a function
that's been called already by some other function?

Suppose I have 3 files, all compiled to bytecode through llvm-gcc (I think
it could be clang instead).

void do_print() { print(); }

void print() { printf("File2.c\n"); }

void print() { printf("File3.c\n"); }

Then, I have the main file compiled to executable like this:
int main() {
  // initialize and get context (not shown)
  Module *file1(LoadFile("file1.bc",Context));
  Module *file2(LoadFile("file2.bc",Context));
  Module *file3(LoadFile("file3.bc",Context));

  Linker::LinkModules(file1, file2, NULL);

  EngineBuilder builder(file1);
  ExecutionEngine *EE = builder.create();


  func = EE->FindFunctionNamed("do_print");
  EE->runFunction(func, std::vector<GenericValue>());

  //swap the definition of the function "print" from the one in File2.c to
  swap (file1, file2, file3);

  EE->runFunction(func, std::vector<GenericValue>());


  return 0;

I can get everything before the swap working (if I comment the rest, the
output is OK). I've tried to build the "swap" function many times but I
can't get it to work.
The expected output is:

If someone know how to do this or knows it's impossible, I would be very
thankful. I don't even know if this is the best way to do it.

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