On Wed, 18 Dec 2013 17:15:30 +0000, Mark Lawrence wrote: > On 18/12/2013 08:18, Steven D'Aprano wrote: >> >> The C99 standard lists 191 different kinds of undefined behavior, >> including what happens when there is an unmatched ' or " on a line of >> source code. >> >> No compile-time error, no run-time error, just blindingly fast and >> correct (according to the standard) code that does the wrong thing. >> >> > Plenty of compile-time warnings depending on the compiler, which the > CPython core devs take a great deal of trouble to eliminate on every > buildbot.
Correct. The *great deal of trouble* part is important. Things which are the responsibility of the language and compiler in (say) Java, D, Rust, Go, etc. are the responsibility of the programmer with C. I mention these languages as they are all intended to be safer languages than C while still being efficient. Whether they succeed or not is another question. Now, I wish to be absolutely clear. There are certain programming areas where squeezing out every last iota of performance is important, and to do so may require making some compromises on correctness or safety. I find the C standard's position on undefined behaviour to be irresponsible, but, hey, maybe it is justified on the basis that C is a systems language intended for use in writing performance-critical operating system kernels, device drivers and similar. It's fine for Python to promise that nothing you do will ever cause a segfault, but for a language used to write kernels and device drivers, you probably want something more powerful and less constrained. But why is so much non-performance critical code written in C? Why so many user-space applications? History has shown us that the decision to prefer efficiency-by-default rather than correctness-by-default has been a disaster for software safety and security. C language practically is the embodiment of premature optimization: the language allows compilers to silently throw your code away in order to generate efficient code by default, whether you need it or not. -- Steven -- https://mail.python.org/mailman/listinfo/python-list
