[LLVMdev] Function Arguments

Matt Masten mmasten at lanl.gov
Wed Aug 18 17:08:14 PDT 2010


I have a question about setting up arguments for function declarations 
and calls.  I have two parameters that I would like to pass to a 
function.  One is an integer and the other is a string of characters.  I 
would like to somehow associate the character string with a pointer that 
I can pass to the function, just like I've shown here for the integer.  
The following is the code I'm working with so far:

// Declare the function as external
vector<const Type*> runTimeFuncArgs;
runTimeFuncArgs.push_back(Type::getInt32Ty(getGlobalContext()));  // int 
type, first arg
str.length() + 1)); // 2nd arg as an array
FunctionType *runTimeFuncType = 
FunctionType::get(Type::getInt32Ty(getGlobalContext()), runTimeFuncArgs, 
Function *runTimeFunc = Function::Create(runTimeFuncType, 
Function::ExternalLinkage, "myfunc", F.getParent());

// Call the function
vector <Value *> params;
int num = 0;
params.push_back(ConstantArray::get(getGlobalContext(), str, true));
CallInst::Create(runTimeFunc, params.begin(), params.end(), "", 

However, this doesn't quite give me what I want.  Instead of passing in 
the entire array by value, I would like to somehow associate "str" with 
a char* and then use that as the parameter to the function.  I wasn't 
able to find an example of this in the documentation and was wondering 
if you could point me in the right direction.  I'm guessing there's a 
simple solution to this that I have somehow overlooked.



More information about the llvm-dev mailing list