The program is ill-formed (clang is right) per [dcl.spec.auto]/9: If the name of an entity with an undeduced placeholder type appears in an expression, the program is ill-formed. Once a non-discarded return statement has been seen in a function, however, the return type deduced from that statement can be used in the rest of the … Read more
Both (a) and (b) result in undefined behavior. It’s always undefined behavior to call a member function through a null pointer. If the function is static, it’s technically undefined as well, but there’s some dispute. The first thing to understand is why it’s undefined behavior to dereference a null pointer. In C++03, there’s actually a … Read more
1) What is a “callback hell” for someone who does not know javascript and node.js ? This other question has some examples of Javascript callback hell: How to avoid long nesting of asynchronous functions in Node.js The problem in Javascript is that the only way to “freeze” a computation and have the “rest of it” … Read more
It looks like http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-closed.html#526 addressed this problem (or something very similar to it) as a potential defect in the standard: 1) Parameters taken by const reference can be changed during execution of the function Examples: Given std::vector v: v.insert(v.begin(), v[2]); v[2] can be changed by moving elements of vector The proposed resolution was that this … Read more
When you add 1 to a pointer, the result is the location of the next object in a sequence of objects of the pointed-to type (i.e., an array). If p points to an int object, then p + 1 will point to the next int in a sequence. If p points to a 5-element array … Read more
At Lenexa meeting the issue got Immediate status with proposed resolution: This wording is relative to N4296. Change 23.3.3.4 [deque.modifiers]/5 to: -5- Complexity: The number of calls to the destructor of T is the same as the number of elements erased, but the number of calls to the assignment operator of T is no more … Read more
The issue here is pretty subtle. You would think that bar::bar() = default; would give you a compiler generated default constructor, and it does, but it is now considered user provided. [dcl.fct.def.default]/5 states: Explicitly-defaulted functions and implicitly-declared functions are collectively called defaulted functions, and the implementation shall provide implicit definitions for them ([class.ctor] [class.dtor], [class.copy.ctor], … Read more
The confusion is that C explicitly permits type-punning through a union, whereas C++ (c++11) has no such permission. c11 6.5.2.3 Structure and union members 95) If the member used to read the contents of a union object is not the same as the member last used to store a value in the object, the appropriate … Read more
What is color set to according to the standard? Answering with a quote from the C++11 and C++14 Standards: [expr.static.cast]/10 A value of integral or enumeration type can be explicitly converted to an enumeration type. The value is unchanged if the original value is within the range of the enumeration values (7.2). Otherwise, the resulting … Read more
The C11 standard says this, 6.8.5/6: An iteration statement whose controlling expression is not a constant expression,156) that performs no input/output operations, does not access volatile objects, and performs no synchronization or atomic operations in its body, controlling expression, or (in the case of a for statement) its expression-3, may be assumed by the implementation … Read more