va_copy — porting to visual C++?

Question

A previous question showed a nice way of printing to a string. The answer involved va_copy:

std::string format (const char *fmt, ...);
{
   va_list ap;
   va         


        

Answer 1

You should be able to get away with just doing a regular assignment:

va_list apcopy = ap;

It's technically non-portable and undefined behavior, but it will work with most compilers and architectures. In the x86 calling convention, va_lists are just pointers into the stack and are safe to copy.