variable arguments in c++ with different datatypes

please read through the following code

#define  INT    0
#define  CHAR   1
#define  FLOAT  2
#define  DOUBLE 3

int createKey(int keySize,vector<int> &types, ...){ 
    va_list varlist;
    va_start(varlist,types.size());

    int intKey;
    float floatKey;
    char charKey;
    double doubleKey;

    char *key = (char*)malloc(keySize);
    int offset = 0;

    for(int i=0;i<types.size();i++){
        switch(types[i]){
            case INT:
                intKey = va_arg(varlist,int);
                memcpy(&key[offset],&intKey,sizeof(int));
                offset += sizeof(int);
            break;

            case CHAR:
                charKey = va_arg(varlist,char);
                memcpy(&key[offset],&charKey,sizeof(char));
                offset += sizeof(char);
            break;

            case FLOAT:
                floatKey = va_arg(varlist,float);
                memcpy(&key[offset],&floatKey,sizeof(float));
                offset += sizeof(float);
            break;

            case DOUBLE:
                doubleKey = va_arg(varlist,double);
                memcpy(&key[offset],&doubleKey,sizeof(double));
                offset += sizeof(double);
            break;

        }
        va_end(varlist);
    }

    int testIntKey;
    char testCharKey;
    float testFloatKey;
    double testDoubleKey;

    offset = 0;

    for(int i=0;i<types.size();i++) {
        switch(types[i]){
            case INT:
                memcpy(&testIntKey,&key[offset],sizeof(int));
                cout<<testIntKey<<endl;
                offset += sizeof(int);
            break;

            case CHAR:
                memcpy(&testCharKey,&key[offset],sizeof(char));
                cout<<testCharKey<<endl;
                offset += sizeof(char);

            break;

            case FLOAT:
                memcpy(&testFloatKey,&key[offset],sizeof(float));
                cout<<testFloatKey<<endl;
                offset += sizeof(float);
            break;

            case DOUBLE:
                memcpy(&testDoubleKey,&key[offset],sizeof(double));
                cout<<testDoubleKey<<endl;
                offset += sizeof(double);
            break;
        }
    }

}

In the above code, I am trying to create a key that is a combination of one or more of the datatypes(int,char,float,double)...I used ellipses as i donot know the number of arguments that may be passed to createKey(). Now the above code when compiled shows the following warnings..

varargsTest.cpp: In function ‘int createKey(int, std::vector<int, std::allocator<int> >&, ...)’:
varargsTest.cpp:20: warning: second parameter of ‘va_start’ not last named argument
varargsTest.cpp:39: warning: ‘char’ is promoted to ‘int’ when passed through ‘...’
varargsTest.cpp:39: note: (so you should pass ‘int’ not ‘char’ to ‘va_arg’)
varargsTest.cpp:39: note: if this code is reached, the program will abort
varargsTest.cpp:45: warning: ‘float’ is promoted to ‘double’ when passed through ‘...’
varargsTest.cpp:45: note: if this code is reached, the program will abort

and when i run the program with the following ..

int main()
{
    vector<int> types;

    types.push_back(INT);
    types.push_back(CHAR);
    types.push_back(INT);

    createKey(9,types,85,'s',97);

}

I get Illegal instruction.

How could this problem be solved...Is this the right approach to handle these kind of problems?