TraceError() with printf style insertions

void TraceError(int s, int v)
{
    int main_buf[2048];
    int buffer_pos; int string_pos; int q;
    for ( ; s[string_pos] != '%'; ++string_pos )
    {
        main_buf[buffer_pos] = s[string_pos];
    }
    //Now, we found an insertion token, so insert it

        //if ( s[string_pos] != '%' ) //copy the buffer text over to the buffer, until we find our token
        //{
        //  main_buf[buffer_pos] = s[string_pos];
        //  ++buffer_pos;
        //}
        //else //found a special token
        //{
    switch(s[string_pos+1])
    {
        case s:
        {
            ++buffer_pos;
            main_buf[buffer_pos+q+1] = ' '; //add a trailing space
            for ( q = 0; v[q]; ++q ) //until we reach NULL
            {
                main_buf[buffer_pos+q] = v[q];  //copy the string passed as a param
                                //over to the buffer
            }
            ++buffer_pos;
            main_buf[buffer_pos+q+1] = ' '; //add a trailing space
            ++buffer_pos; //set up the buffer for the next char
            break;

        }
        case f:
        {
            ++buffer_pos;
            main_buf[buffer_pos+q+1] = ' '; //add a trailing space
            int i_val[12];
            ftoa(i_val,v);
            for ( q = 0; i_val[q]; ++q )
            {
                main_buf[buffer_pos+q] = i_val[q];
            }
            main_buf[buffer_pos+q+1] = ' '; //add a trailing space
            ++buffer_pos; //set up the buffer for the next char
            break;

        }
        case d:
        {
            ++buffer_pos;
            main_buf[buffer_pos+q+1] = ' '; //add a trailing space
            int f_val[12];
            itoa(f_val,v);
            for ( q = 0; f_val[q] ; ++q )
            {
                main_buf[buffer_pos+q] = f_val[q];
            }
            main_buf[buffer_pos+q+1] = ' '; //add a trailing space
            ++buffer_pos; //set up the buffer for the next char
            break;

        }
        default: ++buffer_pos; break;
    }
    //we copied the insertion, so, resume the rest o the string:
    for ( ; s[string_pos]; ++string_pos ) //Until we reach NULL
    {
        //copy the rest of the string:
        main_buf[buffer_pos] = s[string_pos];
    }
        TraceS(main_buf); TraceNL();
    }