I believe in many cases in C, you would need to insert runtime checks (and I believe gcc/clang has a flag for inserting these when statically checking for it is

I believe in many cases in C, you would need to insert runtime checks (and I believe gcc/clang has a flag for inserting these when statically checking for it is infeasible). One such behavior which is considered undefined is signed integer overflow/underflow. Without this being undefined, some important loop optimizations would not be possible [1]. The blog link below has lots of information about undefined behavior from the perspective of a compiler implementer. [1] http://blog.llvm.org/2011/05/what-every-c-programmer-should-know.html http://blog.llvm.org/2011/05/what-every-c-programmer-should-...