sizeof&strlen 详述

sizeof vs strlen。

用于字符串引发的bug

char text[] = "abcdef";
size_t s1 = sizeof(text);   // is 6 
size_t s2 = strlen(text);   // is 7

const char* text2 = "abcdef";
size_t s3 = sizeof(text2); // is platform-dependent
size_t s4 = strlen(text2); // is 6

sizeof() 是个什么瓜皮

sizeof() is a unary operator or compiletime expression that calculates the amount of the memory occupied by a variables. Return unsigned int.

用法1(C)

#include <stdio.h> // C language
#define my_sizeof(type) (char*)(&type+1)-(char*)(&type)
int main()
{
    double x;
    printf("%ld", my_sizeof(x));  // is 8
    getchar();
    return 0;
}

用法2

sizeof(variable-name)
sizeof(expression)
sizeof(type)

strlen()又是什么玩意

strlen is a predefined function, which is defined in a header file known as string.h

用法1

strlen(const char* str)