string? wstring? std::string is a basic_string templated on a char, and std::wstring on a wchar_t. char vs. wchar_t char is supposed to hold a character, usually an 8-bit character. wchar_t is supposed to hold a wide character, and then, things get tricky: On Linux, a wchar_t is 4 bytes, while on Windows, it’s 2 bytes. … Read more
The do … while and if … else are there to make it so that a semicolon after your macro always means the same thing. Let’s say you had something like your second macro. #define BAR(X) f(x); g(x) Now if you were to use BAR(X); in an if … else statement, where the bodies of … Read more
1. “What is it?” While std::move() is technically a function – I would say it isn’t really a function. It’s sort of a converter between ways the compiler considers an expression’s value. 2. “What does it do?” The first thing to note is that std::move() doesn’t actually move anything. It changes an expression from being … Read more
There are two widely-used memory allocation techniques: automatic allocation and dynamic allocation. Commonly, there is a corresponding region of memory for each: the stack and the heap. Stack The stack always allocates memory in a sequential fashion. It can do so because it requires you to release the memory in the reverse order (First-In, Last-Out: … Read more
A declaration introduces an identifier and describes its type, be it a type, object, or function. A declaration is what the compiler needs to accept references to that identifier. These are declarations: extern int bar; extern int g(int, int); double f(int, double); // extern can be omitted for function declarations class foo; // no extern … Read more
It declares an rvalue reference (standards proposal doc). Here’s an introduction to rvalue references. Here’s a fantastic in-depth look at rvalue references by one of Microsoft’s standard library developers. CAUTION: the linked article on MSDN (“Rvalue References: C++0x Features in VC10, Part 2”) is a very clear introduction to Rvalue references, but makes statements about … Read more
Language features: Templates and Generic Code Template argument deduction for class templates Like how functions deduce template arguments, now constructors can deduce the template arguments of the class http://wg21.link/p0433r2 http://wg21.link/p0620r0 http://wg21.link/p0512r0 template <auto> Represents a value of any (non-type template argument) type. Non-type template arguments fixes template<template<class…>typename bob> struct foo {} ( Folding + … … Read more
The rules (which did not change in C++11): Reserved in any scope, including for use as implementation macros: identifiers beginning with an underscore followed immediately by an uppercase letter identifiers containing adjacent underscores (or “double underscore”) Reserved in the global namespace: identifiers beginning with an underscore Also, everything in the std namespace is reserved. (You … Read more
C++98 and C++03 This answer is for the older versions of the C++ standard. The C++11 and C++14 versions of the standard do not formally contain ‘sequence points’; operations are ‘sequenced before’ or ‘unsequenced’ or ‘indeterminately sequenced’ instead. The net effect is essentially the same, but the terminology is different. Disclaimer : Okay. This answer … Read more
Let’s get pedantic, because there are differences that can actually affect your code’s behavior. Much of the following is taken from comments made to an “Old New Thing” article. Sometimes the memory returned by the new operator will be initialized, and sometimes it won’t depending on whether the type you’re newing up is a POD … Read more