Last round involved a randomized solution for problem E, and some pretests were aimed against std's rand() function. This caused a big dispute among contestants. It was questioned whether doing this type of tests was fair or necessary, since passing them depends merely on specific language knowledge, not actual problem-solving skills. Contest coordinators counter-argued that participants would've gotten hacked if it hadn't been for these pretests. They also stated that it's one's responsibility to know their favorite language when using it on a round. Since both sides had valid points.
The fact is, this controversy was really caused because of a technical property within C++ (and codeforces, partly), which many people had no clue existed. This is just an example of the fact that languages and their functioning in CF will sometimes have non-intuitive and unexpected properties, which may screw our performance in a contest. In other words, we are constantly exposed to bumping into another of these hidden behaviors, making the mentioned round hardly the last time something like this happens.
That's why I thought: We should have a list of the main language-specific issues that could annoy us during contests. Just a brief enumeration of not-so-fun facts about languages, such that, if not known, could break our solutions or get us hacked. Making a brief list available for the community, and exposing it to participants before a round could prevent a lot of trouble. If a problem could make you bump into one of these weird language issues, contest coordinators could safely assume we know about them and not get into an ethical debate whether it's fair to include tests against it. Also, contestants would be safe from losing rating to specific language knowledge. In other words, we could prevent issues like the last round's with the least amount of effort.
