sizeof | 易学教程

Checking the sizeof an integer type in the preprocessor

阅读更多关于 Checking the sizeof an integer type in the preprocessor

问题 How can I check the size of an unsigned in the preprocessor under g++? sizeof is out of the question since it is not defined when during preprocessing. 回答1: This may not be the most elegant method, but one thing that you may be able to leverage is UINT_MAX defined in "limits.h". That is, ... if UINT_MAX == 65535, then you would know that sizeof (unsigned) = 2 if UINT_MAX == 4294967295, then you would know that sizeof (unsigned) = 4. and so on. As I said, not elegant, but it should provide

在C语言中，double、long、unsigned、int、char类型数据所占字节数

阅读更多关于在C语言中，double、long、unsigned、int、char类型数据所占字节数

和机器字长及编译器有关系：所以，int，long int，short int的宽度都可能随编译器而异。但有几条铁定的原则（ANSI/ISO制订的）： 1 sizeof(short int)<=sizeof(int) 2 sizeof(int)<=sizeof(long int) 3 short int至少应为16位（2字节） 4 long int至少应为32位。 unsigned 是无符号的意思。例如： 16位编译器 char ：1个字节 char*(即指针变量): 2个字节 short int : 2个字节 int： 2个字节 unsigned int : 2个字节 float: 4个字节 double: 8个字节 long: 4个字节 long long: 8个字节 unsigned long: 4个字节 32位编译器 char ：1个字节 char*（即指针变量）: 4个字节（32位的寻址空间是2^32, 即32个bit，也就是4个字节。同理64位编译器） short int : 2个字节 int： 4个字节 unsigned int : 4个字节 float: 4个字节 double: 8个字节 long: 4个字节 long long: 8个字节 unsigned long: 4个字节 64位编译器 char ：1个字节 char*(即指针变量): 8个字节

在C语言中，double、long、unsigned、int、char类型数据所占字节数

阅读更多关于在C语言中，double、long、unsigned、int、char类型数据所占字节数

How does sizeof work for different data types when added and calculated? [duplicate]

阅读更多关于 How does sizeof work for different data types when added and calculated? [duplicate]

问题 This question already has answers here : What happens here? sizeof(short_int_variable + char_variable) (5 answers) Closed 5 years ago . #include <stdio.h> int main() { short int i = 20; char c = 97; printf("%d, %d, %d\n", sizeof(i), sizeof(c), sizeof(c + i)); return 0; } The output of this code is 2, 1, 4 According to me it should be 2, 1, 2 because char + short int is short int and size of short int is 2 . 回答1: According to C standard integral promotion rules, the type of the expression c +

find sizeof char array C++

阅读更多关于 find sizeof char array C++

问题 im trying to get the sizeof char array variable in a different function where it was initialize however cant get the right sizeof. please see code below int foo(uint8 *buffer){ cout <<"sizeof: "<< sizeof(buffer) <<endl; } int main() { uint8 txbuffer[13]={0}; uint8 uibuffer[4] = "abc"; uint8 rxbuffer[4] = "def"; uint8 l[2]="g"; int index = 1; foo(txbuffer); cout <<"sizeof after foo(): " <<sizeof(txbuffer) <<endl; return 0; } the output is: sizeof: 4 sizeof after foo(): 13 desired output is:

ping 实现设计---ICMP

阅读更多关于 ping 实现设计---ICMP

发送ICMP报文时，必须程序自己计算校验和，将它填入ICMP头部对应的域中。校验和的计算方法: 　　将数据以字为单位累加到一个双字中，如果数据长度为奇数，最后一个字节将被扩展到字，累加的结果是一个双字，最后将这个双字的高16位，低16位相加后取反，便得到了校验和。下面是checksum的计算校验和的代码： USHORT checksum(USHORT* buff, int size) { unsigned long cksum = 0; while(size>1) { cksum += *buff++; size -= sizeof(USHORT); } // 是奇数 if(size) { cksum += *(UCHAR*)buff; } // 将32位的chsum高16位和低16位相加，然后取反 cksum = (cksum >> 16) + (cksum & 0xffff); cksum += (cksum >> 16); return (USHORT)(~cksum); } Ping程序实例： Ping用来检查主机是否存在，是否可达。下面是Ping的执行步骤： 1 创建协议类型为IPPROTO_ICMP的原始套接字 2 创建并初始化ICMP封包 3 调用sendto函数向远程主机发送ICMP请求 4 调用recvfrom函数接收ICMP响应完整代码如下： /////

“sizeof” to know the size of an array doesn't work in a function in C [duplicate]

阅读更多关于 “sizeof” to know the size of an array doesn't work in a function in C [duplicate]

问题 This question already has answers here : Why isn't the size of an array parameter the same as within main? (13 answers) Closed 4 years ago . int main() { int laiArreglo[] = {5,8,2,3,1,4,6,9,2,10}, liElemento; printf("\nInsert the number: "); scanf("%d", &liElemento); ShowNumber(laiArreglo); return 0; } void ShowNumber(int laiArreglo[]) { int liContador; printf("\nNumbers: "); for (liContador = 0; liContador < sizeof (laiArreglo) / sizeof (int); liContador++) { printf("%d ", laiArreglo

sizeof argv[1] not working

阅读更多关于 sizeof argv[1] not working

问题 I'm really new to C and all I know is that the error is related to oldname and newname not be initialized #include <stdio.h> int main (int argc, char const *argv[]) { int result; int lengthOne; int lengthTwo; lengthOne = sizeof(argv[0]); lengthTwo= sizeof(argv[1]); char oldname[lengthOne] = argv[0]; char newname[lengthOne] = argv[1]; result = rename(oldname, newname); if (result == 0) { puts "File renamed"; } else { perror "ERROR: Could not rename file"; } return 0; } app.c: In function ‘main

Array length problem

阅读更多关于 Array length problem

问题 I was reading a csc placement paper where I read a question related to c language array's sizeof() operator. Answer was something else then i expected it to be. int DIMension(int array[]) { return sizeof(array )/ sizeof(int); } main() { int arr[10]; printf(“Array dimension is %d”, DIMension(arr)); } This program in c language prints 1 as the answer. Why is that happening? 回答1: Because int array[] is just a pointer and it's size is same as of int . I think you expected that size of arr will

11-enum,sizeof,typedef分析

阅读更多关于 11-enum,sizeof,typedef分析

注：博客中内容主要来自《狄泰软件学院》，博客仅当私人笔记使用。测试环境：Ubuntu 10.10 GCC版本：4.4.5 一、枚举类型的使用方法 1） enum 是C语言中的一种自定义类型 2） enum 值是可以根据需要自定义的整型值 3）第一个定义的 enum 值默认为0 4）默认情况下的 enum 值是在前一个定义值的基础上加1 5） enum 类型的变量只能取定义时的离散值 enum Color { GREEN, RED = 2, BLUE //实际为3 }; enum Color c = GREEN; printf("%d\n", c); 除了用自身成员赋值，还可以用其它数值赋值。二、枚举类型的特殊意义 1） enum 中定义的值是C语言中真正意义上的常量 2）在工程中 enum 多用于定义整型常量 enum //无名枚举，用于定义常量 { ARRAY_SIZE = 10, //定义数组大小 }; int array[ARRAY_SIZE] = {0}; //通过编译，证明是常量 int i = 0; for(i=0; i<ARRAY_SIZE; i++) { array[i] = i + 1; } 实例分析 enum的使用 11-1.c #include <stdio.h> enum //定义一个整型常量10 { ARRAY_SIZE = 10 /

订阅 sizeof