llvm dev - Nov 2013 - [LLVMdev] get source-level function signature?

Hi,

I want to get source-level function signature by using metadata and 
debug info descriptors, but it seems that the return type is only 
available if it's a primitive type. For example, for the following code:

int *foo(struct ST *s) {
   return &s[1].Z.B[5][13];
}

I get empty string as the return type when I use the getReturnTypeName() 
function of DISubprogram. However, if I change the return type to
"int"
and the corresponding code, I get the "int" type.

I took a look at the implementation of the function, which is the following:

     /// getReturnTypeName - Subprogram return types are encoded either as
     /// DIType or as DICompositeType.
     StringRef getReturnTypeName() const {
       DICompositeType DCT(getFieldAs<DICompositeType>(7));
       if (DCT.Verify()) {
         DIArray A = DCT.getTypeArray();
         DIType T(A.getElement(0));
         return T.getName();
       }
       DIType T(getFieldAs<DIType>(7));
       return T.getName();
     }

I also tried to get the types of parameters by changing the index of 
A.getElement() and noticed the same issue, namely, the types seem to 
work only with primitive types like "int."

My questions are:

(1) Is it possible to get source-level function signature by using 
metadata? For example, for the function

int* convert(unsigned *u)
{
   return (int*) u;
}

I'd like to get its type as "(unsigned int *) -> int*" not the
llvm
type: (i32*) -> i32*.

(2) When the above function is declared as

extern int* convert(unsigned *u);

Can I still get the source-level signature? It seems to me that the list 
of subprograms in the compile unit metadata only contains functions 
defined in the unit.

My examples use pointers, but in general I'd like to get any derived or 
composite types.

Thanks very much,
Lewis

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