讀書心得 - C++ Primer (5th Edition) - Chapter 2 (4) - 常用詞彙

 常用詞彙

• bind
  Associating a name with a given entity so that uses of the name are uses of the underlying entity. For example, a reference is a name that is bound to an object.
• compound type
  A type that is defined in terms of another type.
• const
  Type qualifier used to define objects that may not be changed. const objects must be initialized, because there is no way to give them a value after they are defined.
• declaration
  Asserts the existence of a variable, function, or type defined elsewhere. Names may not be used until they are defined or declared.
• definition
  Allocates storage for a variable of a specified type and optionally initializes the variable. Names may not be used until they are defined or declared.
• const pointer
  Pointer that is const.
• pointer to const
  Pointer that can hold the address of a const object. A pointer to const may not be used to change the value of the object to which it points.
• reference to const
  A reference that may not change the value of the object to which it refers. A reference to const may be bound to a const object, a nonconst object, or the result of an expression.
• const reference
  因為 reference 本身不是 object 所以不能用 const 修飾，所以口語上跟 reference to const 同義。
• undefined
  Usage for which the language does not specify a meaning. Knowingly or unknowingly relying on undefined behavior is a great source of hard-to-track runtime errors, security problems, and portability problems.(例如給 unsigned char 賦值 256)
• word
  The natural unit of integer computation on a given machine. Usually a word is large enough to hold an address. On a 32-bit machine a word is typically 4 bytes.

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Programmer Interview - stack v.s. heap

 stack v.s. heap

• 與 threads 的互動

  在一個 multi-threaded 的程式中，每個 thread 都各自擁有一個 stack，但共享一個 heap。

• object 可以儲存在 heap，而非 stack

  在 c++ 可以使用 new，來將 object 實體儲存在 heap。

      void foo () {
          // myClass, myPointer 儲存在 stack
          // myPointer 所指向的 tempClass object 則儲存在 heap
          // function 結束 myClass, myPointer 則會與 stack 一起 remove
          // 而 myPointer 所指向的 tempClass 不會，所以下 delete
          tempClass myClass;
          tempClass *myPointer = new tempClass();
          delete myPointer;
      }

Java 或 .NET 可以透過 garbage collection 來作到 delete myPointer; 的效果。

• stack 跟 heap 的大小
  stack 大小是固定的，有某些語言可以增加其大小。若 stack 不夠則會造成 stackoverflow (ex 無限遞迴)。heap 大小則是靠 OS 給的。

參考資料 :

1. difference-between-stack-and-heap

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