关于NULL和nullptr 首先要明白一点: C语言中,NULL是指针,即#define NULL ((void *)0); C++中NULL是0 C 由于C中的NULL是void*类型的指针,所以允许: void* 指针赋值给int *和foo_t *的指针的时候,隐式转换成相应的类型。而如果换做一个C++编译器来编译的话是要出错的,因为C++是强类型的,void *是不能...
本节书摘来自华章计算机《C语言编程魔法书:基于C11标准》一书中的第1章,第1.3节,作者: 陈轶 更多章节内容可以访问云栖社区“华章计算机”公众号查看。 1.3 主流C语言编译器介绍 对于当前主流桌面操作系统而言,可使用Visual C++、GCC以及LLVM Clang这三大编译器。其中,Visual C++(简称MSVC)只能用于Windows操作系统;其余...
用nullptr代替NULL和0,可以使得重载函数的调用明确。 最后需要明确的是,一个int类型可以转化为NULL,但是nullptr不能由int类型转化而来,必须是一个指针类型。 template<typenameFuncType,typenameMuxType,typenamePtrType>//decltype(auto)是C++14的用法decltype(auto) lockAndCall(FuncType func, MuxType& mutex, PtrTyp...
当nullptr被传递给lockAndCall时,ptr的类型被推断为std::nullptr_t。当ptr传递给f3时,有一个从std::nullptr_t到Widget*的隐式转换,因为std::nullptr_t可以隐式地转换为所有指针类型。 模板类型推导为0和NULL推导出的的“错误”类型(即它们的真正的类型,而不是他们的fallback意义——作为一个空指针的代表)的这...
An Example of Null pointer in C Any pointer that contains a valid memory address can be made as aNULL pointerby assigning0. Example Here, firstlyptris initialized by the address ofnum, so it is not a NULL pointer, after that, we are assigning0to theptr, and then it will become a NU...
Use nullptr Instead of NULL This article will discuss the NULL keyword and the error of NULL undeclared in C++. ADVERTISEMENT the NULL Keyword in C+ The NULL is constant in C++, which is used to initialize a pointer variable with a value of 0. We can use NULL or 0 interchangeably. It...
#define NULL 0// since C++11#define NULL nullptr Notes In C, the macroNULLmay have the typevoid*, but that is not allowed in C++ because null pointer constants cannot have that type. Example Run this code #include <cstddef>#include <iostream>#include <type_traits>#include <typeinfo>clas...
In computer programming, null is both a value and a pointer. Null is a built-in constant that has a value of zero. It is the same as the character 0 used to terminate strings in C. Null can also be the value of apointer, which is the same as zero unless theCPUsupports a special...
a null pointer value is nullptr in C++/CLI. By the way, what type is Globals::administrativeData?Visual C++ MVPSunday, January 11, 2015 9:30 PMIs a custom class named AdministrativeData.Monday, January 12, 2015 3:08 PMOn 11/01/2015 19:58, Victorqedu123 wrote:...
really needs to explicitly point to nowhere, and not just an invalid address. For such cases, there exists a special value that any pointer type can take: thenull pointer value. This value can be expressed in C++ in two ways: either with an integer value of zero, or with thenullptr...