技術標籤：指標資料結構c++java棧

• 

• 功能：以位元組位單位，返回一個表示式或一個數據型別所佔的位元組數

• 返回值型別：是size_t型別

• sizeof有無括號：

• • sizeof不加括號，後面不可以直接跟資料型別

  • sizeof加括號，後面既可以跟表示式也可以跟資料型別

• 注意事項

• • 對引用型別執行sizeof運算得到被引用物件所佔空間的大小

  • 對指標執行sizeof運算得到指標本身所佔空間大小

  • 對解引用指標執行sizeof運算得到指標指向指向的物件所佔空間的大小，指標不需有效

  • 對陣列執行sizeof運算得到整個陣列所佔空間的大小，等價於對陣列中所有的元素各執行一次sizeof運算並將結果求和。注意，sizeof運算不會把陣列轉換指標來處理

  • 對string物件或vector物件執行sizeof運算只返回該型別固定部分的大小，不會計算物件中的元素佔用了多少空間

  二話不說，來看程式碼：

  #include <iostream>
  #include <string>
  using namespace std;
  int main(){
    int a = 12;
    short int b = 12;
    float   c = 12.0f;
    double  d = 12.333;
    long  int e = 123;
          long long int  f = 1233;
    char ch = '0';
    
    cout << sizeof a << ","  << sizeof b << ","  << sizeof c << ","  << sizeof d << ","  << sizeof e << ","  << sizeof f << ","  << sizeof ch <<endl;
  
  
    uint8_t   ua = 1;
    uint16_t  ub = 2;
     uint32_t  uc = 3;
    uint64_t  ud = 4;
  
  
    cout << sizeof ua << ","  << sizeof ub << ","  << sizeof uc << ","  << sizeof ud <<endl;
  
  
    char* pa = &ch;
    int*  pb = &a;
    
    cout <<sizeof pa << ","  << sizeof pb <<endl;  
    uint32_t& p = uc;
    cout << sizeof p <<endl;
          
          int   array[10];
    cout << sizeof array <<endl;
  
  
    string  s = "hello world";
    string  s_empty; 
    cout << sizeof s << ","  << sizeof s_empty << endl;
    return 0;
  }