[LLVMdev] printf decleration

[Ryan M. Lefever]

Ok, I think I figured it out.  I talked to someone, and we figured out 
that when I make a call to printf with a constant string, I need to make 
a global variable and use getElementPtr to reference it.  The modified 
call for accessing the printf is:

   /* m is Module*, f is Function*, i is Instruction* */
   Constant* constStr = ConstantArray::get("test\n");
   GlobalVariable* gv = new GlobalVariable
     (constStr->getType(), true, GlobalValue::InternalLinkage, constStr,
      "", m);
   std::vector<Constant*> geplist;
   geplist.push_back(ConstantUInt::get(Type::UIntTy,0));
   geplist.push_back(ConstantUInt::get(Type::UIntTy,0));
   Constant* gep = ConstantExpr::getGetElementPtr(gv,geplist);

   std::vector<Value*> args;
   args.push_back(gep);

   new CallInst(f, args, "", i);

Ryan M. Lefever wrote:
> I am writing a pass where I need to make a function deceleration for 
> printf.  Below is the code I'm trying to use.
> 
> -----
> bool MyPass::runOnModule(Module &m) {
>   vector<const Type*> args;
>   args.push_back(PointerType::get(Type::SByteTy));
>   Function* f = m.getOrInsertFunction("printf",
>        FunctionType::get(Type::IntTy, args, true));
> -----
> 
> When I insert a call instruction to printf, I am using the following code:
> 
> -----
>   /* i an Instruction*, and f is the Function* from above */
>   std::vector<Value*> args;
>   args.push_back(ConstantArray::get("test"));
> 
>   new CallInst(f, args, "", i);
> -----
> 
> However, when my pass is run with opt it complains:
> 
> -----
> Call parameter type does not match function signature!
> [5 x sbyte] c"test\00"
>  sbyte* call int (sbyte*, ...)* %printf( [5 x sbyte] c"test\00" )  ;
> <int>:0 [#uses=0]
> -----
> 
> Does anyone know what the problem is?
> 
> Thanks,
> Ryan
> 

-- 
Ryan M. Lefever  [217.333.7231]  [http://www.ews.uiuc.edu/~lefever]