📜  sizeof运算符的操作数

📅  最后修改于: 2021-05-30 14:42:37             🧑  作者: Mango

sizeof运算符用于返回其操作数的大小(以字节为单位)。此运算符始终在其操作数之前。操作数可以是数据类型或表达式。让我们通过适当的示例来看看这两个操作数。

  1. type-name :必须在括号中指定类型名称。
    sizeof(type - name)
    

    让我们看一下代码:

    C
    #include  
    int main() 
    { 
        printf("%lu\n", sizeof(char)); 
        printf("%lu\n", sizeof(int)); 
        printf("%lu\n", sizeof(float)); 
        printf("%lu", sizeof(double));
        return 0; 
    }


    C++
    #include  
    using namespace std; 
      
    int main() 
    { 
        cout << sizeof(char)<<"\n"; 
        cout << sizeof(int)<<"\n"; 
        cout << sizeof(float)<<"\n"; 
        cout << sizeof(double)<<"\n"; 
        return 0; 
    }


    C
    #include 
      
    int main()
    {
        int i = 5;
        int int_size = sizeof(i++);
      
        // Displaying the size of the operand
        printf("\n size of i = %d", int_size);
      
        // Displaying the value of the operand
        printf("\n Value of i = %d", i);
      
        getchar();
        return 0;
    }


    C++
    #include 
    using namespace std;
      
    int main()
    {
        int i = 5;
        int int_size = sizeof(i++);
      
        // Displaying the size of the operand
        cout << "\n size of i = " << int_size;
      
        // Displaying the value of the operand
        cout << "\n Value of i = " << i;
      
        return 0;
    }
      
    // This code is contributed by SHUBHAMSINGH10


    输出:
    1
    4
    4
    8
    
  2. expression :可以在带括号或不带括号的情况下指定表达式。
    // First type
    sizeof expression
      
    // Second type
    sizeof(expression)
    

    该表达式仅用于获取操作数的类型,而不用于求值。例如,下面的代码将i的值打印为5,并将ia的大小打印

    C

    #include 
      
    int main()
    {
        int i = 5;
        int int_size = sizeof(i++);
      
        // Displaying the size of the operand
        printf("\n size of i = %d", int_size);
      
        // Displaying the value of the operand
        printf("\n Value of i = %d", i);
      
        getchar();
        return 0;
    }
    

    C++

    #include 
    using namespace std;
      
    int main()
    {
        int i = 5;
        int int_size = sizeof(i++);
      
        // Displaying the size of the operand
        cout << "\n size of i = " << int_size;
      
        // Displaying the value of the operand
        cout << "\n Value of i = " << i;
      
        return 0;
    }
      
    // This code is contributed by SHUBHAMSINGH10
    
    输出:
    size of i = 4
     Value of i = 5
    

参考:
http://www.gnu.org/software/gnu-c-manual/gnu-c-manual.html#The-sizeof-Operator

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