Why llvm::FunctionType(Type*, bool) has bool if by definition it doesn't take parameters?

Question

One definition of FunctionType *FunctionType::get is:

FunctionType *FunctionType::get(Type *Result, bool  isVarArg)   

The documentation says:

Create a FunctionType taking no parameters.

When are we going to use the bool isVarArg parameter to indicate that the number of arguments is variable if the type has no parameters?

Answer 1

The reason for this is that variable arguments are treated differently by LLVM than fixed/positional parameters. No fixed parameters (the kind that would appear in ArrayRef<Type *> llvm::FunctionType::params () const) are what the docs mean by "no parameters", so varargs are exempt.

If you check the note for getNumParams(), it says:

Return the number of fixed parameters this function type requires. This does not consider varargs.