通常来说,null表示虚无&不确定,在不同的实现中对null的定义相似。最早在Codd提出关系模型的最早的paper里,就引入了NULL。 先看不同语言对于null的处理: c++的NULL c++中NULL是一个宏,是一个空指针常量,如果将NULL扩展为常数,那么这个数是0,类型为int,也就是说常数0既是整型常量,也是空指针常量(cpp 11中引入...
//null.cpp#include<iostream>intmain(void){charp[] ="12345";int*a = (void*)p;return0; } 编译: $ g+ -o null null.cpp null.cpp: In function 'int main()': null.cpp:5:17: error: invalid conversion from 'void*' to 'int*' [-fpermissive] int *a = (void*)p; 所以不能将NUL...
//null.cpp#include<iostream>intmain(void){char p[]="12345";int*a=(void*)p;return0;} 编译: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 $ g+-onullnull.cppnull.cpp:Infunction'int main()':null.cpp:5:17:error:invalid conversionfrom'void*'to'int*'[-fpermissive]int*a=(void*)...
这两个应用程序是相同的(Peer 2对等程序),但是有两个实例正在运行并试图进行通信。我的错误发生在reader = new ObjectInputSream(cliIn)上,我被抛出了一个SocketTimeoutException (这本身就很奇怪,我希望在read()上,而不是在装饰我的流的时候下面是我试图做的事情。clientSocket.setSoTime 浏览2提问于201...
The NULL keyword is declared a constant in different header files like iostream, stdio, or cstddef. You can include any of these to resolve this error. #include <iostream> int main() { int* p = NULL; return 0; } The above code executes without an error because NULL is also defined...
$ g+ -o null null.cpp null.cpp: In function 'int main()': null.cpp:5:17: error: invalid conversion from 'void*' to 'int*' [-fpermissive] int *a = (void*)p; 所以不能将NULL定义为(void*)0。 nullptr nullptr并非整型类别,甚至也不是指针类型,但是能转换成任意指针类型。nullptr的实际...
In C++, we can initialize a pointer by assigning the value ‘0’ or the literal ‘nullptr’. Note: Modern C++ suggests that we should not initialize the pointers to 0. It can lead to different results when we do function overloading. In this method, we will check if the pointer is...
[原创]安卓U3D逆向从Assembly-CSharp到il2cpp vivado使用时出现的问题及解决办法(一) 不是吧阿sir,你这业务太熟了吧,震惊面试官第八年! 基于MSM 的tomcat session 共享 LNMP架构(三) tomcat老是运行之前被我删除的web项目,导致报错 搭建基于docker的elk平台来分析java日志 ...
cppreference：http://www.cplusplus.com/doc/tutorial/cppreference 是一个免费网站，基本上提供了所有的...
thetime(NULL)Function in C++ Thetime()function with a parameter NULL,time(NULL), returns the current calendar time in seconds since 1 January 1970. Null is a built-in constant whose value is0and a pointer similar to0unless the CPU supports a special bit pattern for a Null pointer. ...