No, those compilers would likely reject it, if I had activated c17 mode. But I did not -- so it worked. This is a real power of C and C++ -- each file gets its

No, those compilers would likely reject it, if I had activated c17 mode. But I did not -- so it worked. This is a real power of C and C++ -- each file gets its own mode. That K&R library you made in ancient time? C++98 classes? All still works and links to the modern stuff. You can be sure that whatever code you wrote today would still be usable, possibly with minor modifications, 20 years later. Sure, the compiler names and build systems will change, but the code would work.