> If you need mkstemp you have have two options: either you restrict > your program to run only on platforms that include it, or you > implement your own version. In either case there is *zero* advantage > of finding out at build time whatever your system includes it or not.
What if there is different APIs on different systems? Example is clone/rfork. With configure you can choose one of them at compile time. And even if you want, you can't implement your own version in userspace.
