用sizeof()编写的任何内容都不会在C中执行

在C / C++中，sizeof()运算符用于查找日期类型或变量的大小。用sizeof()编写的表达式永远不会执行。

例子：

// C program to demonstrate that the
// expressions written in sizeof() are
// never executed
#include 
  
int main(){
      
    // The printf in sizeof is not executed
    // Only the return type of printf is 
    // considered and its size is evaluated
    // by sizeof,
    int a = sizeof(printf("hey"));
  
    printf("%d", a);
      
    return 0;
}

Output:
4

即使我们在sizeof()内分配一个值，更改也不会反映出来。

// One more C program to demonstrate that 
// the expressions written in sizeof() are
// never executed
#include 
  
int main() {
    int a = 5;
    int b = sizeof(a = 6);
    printf("a = %d,  b = %d\n", a, b);
    return 0;
}

Output:
a = 5, b = 4

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