Arduino class 层次结构、字符串和内存泄漏

Question

下午好，我正在开始一个新的 Arduino 项目 1.6.10 IDE 版本。但是当我使用基于 class 的结构时遇到了一些内存泄漏问题。

我先post我的代码，然后我会指出似乎出现内存泄漏的地方。

mainSketchFile.

#include <Ethernet.h>
#include <MemoryFree.h>
#include "Constants.h"
#include "State.h"



StateFactory CurrentStateFactory;

void setup() {

  pinMode(BUZZER,OUTPUT);
  Serial.begin(9600);
  Serial.println("START");
  delay(1000);

}

void loop() {

  Serial.print(F("Free RAM = ")); 
  Serial.println(freeMemory(), DEC);  // print how much RAM is available.
  CurrentStateFactory.changeStatus(1);
  Serial.println(CurrentStateFactory.getCurrentState()->getNumber());
  CurrentStateFactory.changeStatus(2);
  Serial.println(CurrentStateFactory.getCurrentState()->getNumber());
}

问题好像出在State.h我在评论里标出了重点

#ifndef State_h
#define State_h

/////////////////// STATE/////////////////////////

class MachineState{
  public: 
    virtual int getNumber();
  protected:

};

/////////////////////ACTIVE FULL/////////////////////////////////
class ActiveFull : public MachineState
{
  public:
      ActiveFull();
      virtual int getNumber();
  private:
      String statusName; //<----- PROBLRM SEEMS TO BE HERE WHEN COMMENTED NO MEMORY LEAK APPEN
      int number;
};

ActiveFull::ActiveFull(){
  this->number=1;
};


int ActiveFull::getNumber(){
  return this->number;
}

////////////////////////////// ACTIVE EMPTY ////////////////////
class ActiveEmpty : public MachineState
{
  public:
      ActiveEmpty();
      virtual int getNumber();
  protected:
      String statusName;//<----- PROBLRM SEEMS TO BE HERE WHEN COMMENTED NO MEMORY LEAK APPEN
      int number;
};

ActiveEmpty::ActiveEmpty(){
   this->number=2;
};

int ActiveEmpty::getNumber(){
  return this->number;
}


//////////////////FACTORY/////////////////////////////


class StateFactory{
    private:
      MachineState *currentState;
    public: 
      StateFactory();
      void *changeStatus(int choice); // factory
      MachineState *getCurrentState();
  };

StateFactory::StateFactory(){
  MachineState *var1=new ActiveFull();
  this->currentState=var1; 
}

MachineState *StateFactory::getCurrentState(){
  return this->currentState; 
 }


void *StateFactory::changeStatus(int choice)
{
 delete  this->currentState;  // to prevent memory leak
  if (choice == 1){
      MachineState *var1=new ActiveFull();
      this->currentState=var1;
    }
  else if (choice == 2){
      MachineState *var1=new ActiveEmpty;
      this->currentState=var1;
    }
  else{
      MachineState *var1=new ActiveEmpty;
      this->currentState=var1;
    }
}

#endif

我使用库来跟踪内存使用情况，这是草图的输出：

没有内存泄漏（String statusName 已注释）

Free RAM = 7897
1
2
Free RAM = 7897
1
2
Free RAM = 7897
1
2
Free RAM = 7897
1
2
Free RAM = 7897
1
2
Free RAM = 7897
1
2
Free RAM = 7897
1
2
Free RAM = 7897
1
2
Free RAM = 7897
1
2

属性 String statusName 取消注释时内存泄漏

Free RAM = 6567
1
2
Free RAM = 6559
1
2
Free RAM = 6551
1
2
Free RAM = 6543
1
2
Free RAM = 6535
1
2
Free RAM = 6527
1
2

感谢您的宝贵时间。希望你能帮助我。

Answer 1

免责声明：我想 post 这是评论，而不是答案，因为在我看来它不能解决问题，而只是提供建议。然后我需要一些代码块，所以我需要答案功能。

好吧，恕我直言，您的代码需要一些改进（或者这可能只是因为您减少了它，但无论如何我都会 post 为您改进）

不要将函数实现放在头文件中：使用cpp文件存储函数实现，使用头文件存储原型
继承的目的是重用你们已经共有的大部分代码。所以有很多不同的变量是没有意义的；最好以不同的方式声明它们。

例如你可以这样使用它：

/* File State.h */

class MachineState{
    public: 
        int getNumber();
    protected:
        String statusName;
        int number;
};

/////////////////////ACTIVE FULL/////////////////////////////////
class ActiveFull : public MachineState
{
    public:
        ActiveFull();
};

////////////////////////////// ACTIVE EMPTY ////////////////////
class ActiveEmpty : public MachineState
{
    public:
        ActiveEmpty();
};

/* File State.cpp */

int MachineState::getNumber(){
    return this->number;
}

ActiveEmpty::ActiveEmpty(){
    this->number=1;
};

ActiveEmpty::ActiveEmpty(){
    this->number=2;
};

或者，如果您不必更改数字的值（因此您不需要真正的变量）

/* File State.h */

class MachineState{
    public: 
        virtual int getNumber() = 0;
    protected:
        String statusName;
};

/////////////////////ACTIVE FULL/////////////////////////////////
class ActiveFull : public MachineState
{
    public:
        virtual int getNumber();
};

////////////////////////////// ACTIVE EMPTY ////////////////////
class ActiveEmpty : public MachineState
{
    public:
        virtual int getNumber();
};

/* File State.cpp */

int ActiveEmpty::getNumber(){
    return 1;
};

int ActiveEmpty::getNumber(){
    return 2;
};

然后有一个关于释放的小问题：如果 new 失败，你会在下一个 delete 遇到问题。要解决这个问题，您可以这样做（我也稍微缩短了您的代码）

void *StateFactory::changeStatus(int choice)
{
    if (this->currentState) // If it was correctly allocated
        delete this->currentState;  // to prevent memory leak
    switch (choice)
    {
    case 1:
        this->currentState = new ActiveFull();
        break;
    case 2: // case 2 can be removed since it is identical to default
        this->currentState = new ActiveEmpty();
        break;
    default:
        this->currentState = new ActiveEmpty();
        break;
    }
}

就是说...好吧，我会这样修改循环：

void printCurrentStateNumber()
{
    if (CurrentStateFactory.getCurrentState())
        Serial.println(CurrentStateFactory.getCurrentState()->getNumber());
    else
        Serial.println("No more memory");
}

void loop() {
    Serial.print(F("Free RAM = ")); 
    Serial.println(freeMemory(), DEC);  // print how much RAM is available.
    CurrentStateFactory.changeStatus(1);
    printCurrentStateNumber();
    CurrentStateFactory.changeStatus(2);
    printCurrentStateNumber();
}

这是为了测试状态是否创建成功。

至于你的显式问题，我不知道库函数是如何工作的。在开始理解为什么会出现这种泄漏之前，我会尝试弄清楚这是否真的是泄漏。所以启动修改后的程序（在删除之前进行测试并打印不再有内存字符串）并让它运行直到库告诉你它运行内存不足。如果它稳定或达到 0 并且不打印，则说明是库问题。另一方面，如果程序停止打印字符串，那就是泄漏。

旁注：让小型微控制器过于频繁地执行分配和释放不是一个好习惯，因为它的内存有限。进行测试，因为如果存在真正的泄漏，也许应该进行更多调查，但对于您的应用程序，我建议您考虑永久分配对象的两个实例，然后根据您之前传递给它的值使用它们 - 显然如果只有几个派生类)，像这样：

/* In the header file */
#define NUM_OF_STATES 2

class StateFactory{
private:
    MachineState states[NUM_OF_STATES];
public: 
    StateFactory();
    void changeStatus(int choice); // factory
    MachineState *getCurrentState();
private:
    int currentIdx;
};

/* In the source file */

StateFactory::StateFactory()
{
    states[0] = new ActiveFull();
    states[1] = new ActiveEmpty();
    this->currentIdx = 0;
}

MachineState *StateFactory::getCurrentState(){
    return states[this->currentIdx];
}

void StateFactory::changeStatus(int choice)
{
    switch (choice)
    {
    case 1:
        this->currentIdx = 0;
        break;
    case 2: // case 2 can be removed since it is identical to default
        this->currentIdx = 1;
        break;
    default:
        this->currentIdx = 1;
        break;
    }
}

最后注意：修改答案后我发现您的 changeStatus 函数 returns 是 void * 而不是 void。你绝对应该解决这个问题，也许事情会得到解决（事实上你返回的是一个指针而不是什么都没有）。但我不确定。

Answer 2

好像是析构函数的问题，

我post一个基于你的代码的实现..

#ifndef State_h
#define State_h


/* MachineState Class */
class MachineState{
  public:
  virtual void test() = 0;
     MachineState(){
        number = 0;
        statusName = "NULL";
     }
     virtual ~MachineState(){
      Serial.println("Destroy base");
     }
     void setNumber(int n){
      number =  n;
     }
     void setStatusName(String some){
      statusName = some;
     }
     String getStatusName(){
      return statusName;
     }
     int getNumber(){
      return number;
     }
     virtual void print()const{
      Serial.println("Class MS");
     }
  protected:
      String statusName;
      int number;

};


/* ActiveFull Class */
class ActiveFull : public MachineState{
  public:
      ActiveFull(){
        x = "Class AF";
        setNumber(1);
      }
      void print()const{
        Serial.println("Class AF"); 
      }
      void test(){}
      ~ActiveFull(){
       Serial.println("Destroy AF");
      }
  private:
    String x;
};


/* ActiveEmpty Class */
class ActiveEmpty : public MachineState
{
  public:
      void print()const{
        Serial.println("Class EE"); 
      }
      ActiveEmpty(){
        x = "Class EE";
        setNumber(2);
      }
      void test(){}
      ~ActiveEmpty(){
          Serial.println("Destroy EE");
      }
  private:
    String x;
};

/* StateFactory Class */
class StateFactory{
    private:
      MachineState *currentState;
    public: 
      StateFactory();
      ~StateFactory(){
        Serial.println("Ho distrutto StateFactory");
      }
      void changeStatus(int choice); // factory
      MachineState *getCurrentState();
  };

StateFactory::StateFactory(){
  this->currentState=new ActiveFull(); 
}

MachineState *StateFactory::getCurrentState(){
  return this->currentState; 
 }


void StateFactory::changeStatus(int choice){
  if(this->currenState)
     delete  this->currentState;
  if (choice == 1){
      currentState = new ActiveFull();
    }
  else if (choice == 2){
      currentState = new ActiveEmpty();
    }
  else{
      currentState = new ActiveEmpty();
    }
}

#endif

这是我对你的主要结果：

...

2
Class EE
Free RAM = 7751
Destroy EE
Destroy base
1
Class AF
Destroy AF
Destroy base
2
Class EE
Free RAM = 7751
Destroy EE
Destroy base
1
Class AF
Destroy AF
Destroy base

...

Arduino class 层次结构、字符串和内存泄漏

Arduino class hierarchy, Strings and memory leak

c++

string

memory-leaks

arduino

class-hierarchy