> Why not disallow undefined behavior and instead have the compiler emit ... You can't "disallow" all undefined behavior in C without fundamentally changing th

> Why not disallow undefined behavior and instead have the compiler emit ... You can't "disallow" all undefined behavior in C without fundamentally changing the language to something different (Which would also likely make it useless for it's intended use-case). Some of the details related to undefined behavior are simply not possible for the compiler to detect without extra information, hence why they are undefined. `Rust` has the same thing, you can invoke undefined behavior anywhere in the program through use of `unsafe` anywhere else. And Ex. How is the compiler supposed to determine if a particular function is ever called with a `NULL` parameter? How does it know if a particular signed addition may overflow? How does it know if two parameters to a function alias in an invalid way? How does it know if a particular pointer lacks a `const` and is actually backed by read-only memory? And most importantly, how does it determine all of this at compile time? With that not all undefined behavior-based optimizations are unexpected or warrant a warning or error (In-fact, I would say at the very least the majority of them don't). Undefined behavior is much more complicated then just dead-code removal. Even then though, you don't always want dead-code removal warned about - Imagine getting a warning about every inline function or macro that results in some dead-code. To be clear, I'm not saying there aren't obvious problems that have come from this approach, and I think some of the choices for undefined-behavior are clear mistakes now even though they made some sense in the 80s or 90s (And some of those can usually be turned off, thankfully). And I think there are also some additions that could be made to the language that could solve a lot of the existing problems (Like non-null pointers, or fat pointers, though I'm not exactly holding my breath...), but the existence of undefined-behavior is not in-and-of-itself the actual problem with the language, and "disallowing" it outright is simply not possible. I would actually wager undefined-behavior exists in some form in a lot more languages than you'd expect, just less documented. Rust certainly still has it, despite it's numerous safety-focused features. And even if you add things like fat pointers to C that would clearly reduce possible out-of-bounds mistakes, the language would still need to provide some way to create one from a size and a pointer, and that still allows for undefined-behavior cases to happen - my point being, while adding such a thing is still clearly better, it does not actually remove the undefined-behavior possibility.