One of the new features in C++20 is Down with typename. In C++17, you had to provide the typename keyword in nearly all† dependent contexts to disambiguate a type from a value. But in C++20, this rule is relaxed a lot. In all contexts where you need to have a type, the typename keyword is … Read more
Both are correct. 20.8.9.1.2 forwards to 20.8.2 to describe the requirements and the effect of your call to bind. 20.8.2 is: 20.8.2 Requirements [func.require] 1 Define INVOKE(f, t1, t2, …, tN) as follows: — (t1.*f)(t2, …, tN) when f is a pointer to a member function of a class T and t1 is an object … Read more
First of all, you assume that sizeof(long) == sizeof(int) == sizeof(float). This is not always true, and totally unspecified (platform dependent). Actually, this is true on my Windows using clang-cl and wrong on my Linux using the same 64-bit machine. Different compilers on the same OS/machine can give different results. A static assert is at … Read more
Assuming no UB, are 5 of the 8 possible and not the 3 unexpected ones? especially is valid input possible with error indicator set? Speaking specifically to the provisions of the standard, I’m inclined to agree with your analysis: Few functions are specified to clear the error indicator of a stream, and fgetc() is not … Read more
This is CWG 232. That issue might seem like it’s mainly about dereferencing a null pointer but it’s fundamentally about what it means to simply dereference something that doesn’t point to an object. There is no explicit language rule about this case. One of the examples in the issue is: Similarly, dereferencing a pointer to … Read more
I find it easier (if maybe not 100% precise) to think of lvalue-s as real objects and rvalue-s as the value stored in the object. The expression x is an lvalue expression that refers to the object x defined in the first line, but when used as the right hand side of an assignment to … Read more
Unfortunately, as of N3936 (C++14 final draft), no standard provided random distribution has a requirement like this. And it’s easy to see why. There are many valid ways of writing a distribution function. Some better than others. And algorithms for even something as basic as the normal distribution are getting better and are the subject … Read more
The designers of the C language decided that it should not be possible to assign arrays by value. At the time this seemed a sensible decision (early 1970s) – memory and processor speed were very limited and they considered that having a = b; make a and b both refer to the same array was … Read more
C++98/03 Impossible. String can be copy on write so it needs to handle all reads and writes. C++11/14 In [string.require]: The char-like objects in a basic_string object shall be stored contiguously. That is, for any basic_string object s, the identity &*(s.begin() + n) == &*s.begin() + n shall hold for all values of n such … Read more
The fact that it is indeterminate not only means that it is unpredictable at the first read, it also means that it is not guaranteed to be stable. This means that reading the same uninitialized variable twice is not guaranteed to produce the same value. For this reason you cannot really “determine” that value by … Read more