161–170 of 246 posts
I had to fight through school and university in India with my teachers who believed these were legit questions to ask in written exams. Can't 100% blame them since almost all standard-issue textbooks had them and claimed they'd give predictable output. I thought the same until I noticed the weirdness when running them across different compilers and after I read about UB, sequence points and similar quirks in books th…
Earlier quoted context omitted.
IMO, The only reasonable answer if asked this in an interview is “I would not write code where I have to know the answer to this question” These sorts of things are neat trivia to learn about things like sequence points but 99.9% of the time if it matters in your codebase you're writing something unmaintainable.
> IMO, The only reasonable answer if asked this in an interview is “I would not write code where I have to know the answer to this question” That's half of a reasonable answer. The other half is "but I do know the answer so if I see it when reviewing or working on someone else's code I can flag it or rewrite it, and explain to them why it is bad".
> The other half is "but I do know the answer
If you claim to know the answer you've made a grave mistake and fooled yourself.
If you ran the code in a compiler and used that to conclude "this is the answer" rather than "this is an answer" then now is a great time to learn how easy it is to fool yourself. You just need you ask yourself what assumptions you made. I'll wager you assumed all compilers process this line in the same way.
Or just RTFA, or Susam's, as that's exactly what they are about. They explain why this is undefined behavior.
| The first principle is that you must not fool yourself — and you are the easiest person to fool.
- FeynmanEarlier quoted context omitted.
I don't see the name "thaumasiotes" at that link, nor do I see anything relevant to the code in the title. The behavior of "int a = 5; a = a++ + ++a;" is undefined. There is no guarantee of a numeric result, because there is no guarantee of anything .
It's only the order of evaluation that is undefined.
A conforming implementation could reject it at compile time, or generate code that traps, or generate code that set a to 137, or, in principle, generate code that reformats your hard drive. Some of these behaviors are unlikely, but none are forbidden by the language standard.
I am, thankfully, out of this craziness now but it was fun solving ton of such puzzles from Yashavant Kanetkar books while preparing for campus hiring interviews back in 2000. "Test Your C Skills" in particular. Fun times. https://www.scribd.com/document/235004757/Test-Your-C-Skills...
"Test Your C Skills" is a published book by Yashavant Kanetkar, apparently published in 2005, and still available in paperback. The document you linked to appears to be a scan of a printed copy of that book, and is almost certainly in violation of copyright. The cover and the title and copyright pages are notably missing.
Earlier quoted context omitted.
No it isn't. You don't need to know the answer to know that it is bad code. The very fact that it isn't clear shows that.
Right, the feedback I'd expect in a code review interview is something like "This is unclear or wrong, write what you actually meant". That's the feedback I would want, and it's the feedback I give to my colleagues in reviews. Actually I tend to be too verbose, so you might get a full paragraph explaining what the ISO document says and that you shouldn't assume it does whatever it is your compiler says. My actual fee…
> Actually I tend to be too verbose, so you might get a full paragraph explaining what the ISO document
Verbosity isn't bad. Not everything needs to be a fucking tweet
You should start here:
https://c-faq.com/expr/evalorder2.html
I cannot recommend the C FAQ enough. It is written in an accessible way and contains proper references to textbooks and standards.
Disclosure: I was one of the contributors.