Undefined behavior is stuff that is incorrect and must not happen (e.g. out of bounds access). Making it explicitly undefined helps writing efficient implementa

Undefined behavior is stuff that is incorrect and must not happen (e.g. out of bounds access). Making it explicitly undefined helps writing efficient implementations. So not only undefined behavior has not hindered the success of C++, it's probably one of the things contributing to its success, in particular its success in developing embedded and safety-critical systems. If you write a program for which correctness is particularly important (e.g. a safety-critical program), you must ensure, through tests, proofs, magic, etc. that you don't have any incorrect behavior. Which might be undefined, but again the problem is that it's incorrect, not that it's undefined. If you're flying at Mach 2 and an out-of-bounds read or write happens in your flight control software, it doesn't really matter that much whether you get "undefined behavior" (i.e. read or write "random" address), a panic, a log message, a popup window, etc. The safety is compromised by the fact that you did an incorrect operation, not that the operation is undefined. Now, if you want to write a music player or something like that, it does make sense to use a language like Python, Go, or whatever might give you more guarantees than C++, because realistically you're not going to write a proper test suite for it.