Arduino 类层次结构、字符串和内存泄漏

Question

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

我先发布我的代码，然后我会指出似乎出现内存泄漏的位置。

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());
}

问题似乎出在 State.hi 我在 cmets 中标记了点

#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（字符串状态名已注释）

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

取消注释属性字符串 statusName 时的内存泄漏

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

感谢您的时间建议。希望你能帮助我。

Answer 1

好像是析构函数的问题，

我根据您的代码发布了一个实现..

#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

这是我与你的主要结果：

...

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

...

Answer 2

免责声明：我想将其发布为评论，而不是答案，因为在我看来，它并不能解决问题，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，但无论如何我会为您发布它们）

1. 不要把函数实现放在头文件里：用cpp文件存放函数实现，头文件存放原型
2. 继承的目的是重用您已经拥有的大部分代码。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，您可以这样使用它：

/* 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;
};

那么释放还有一个小问题：如果new失败，你会在下一个delete遇到问题。要解决这个问题，您可以执行类似的操作（我还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;
    }
}

也就是说......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。

至于你的明确问题，我不知道库函数是如何工作的。在开始了解为什么会发生这种泄漏之前，我会尝试弄清楚这是否真的是泄漏。因此，启动修改后的程序（在删除之前进行测试并打印 no more memory 字符串）并让它运行，直到库告诉您它内存不足。如果它稳定或达到 0 并且不打印，这是一个库问题。另一方面，如果程序停止打印字符串，那就是泄漏。

附注：让小型微控制器过于频繁地执行分配和解除分配不是一个好习惯，因为它的内存有限。进行测试，因为如果存在真正的泄漏，也许应该对其进行更多调查，但是对于您的应用程序，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：修改答案我发现您的changeStatus 函数返回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（实际上你正在返回一个指针而不是什么）。但我不确定。