Question

这是有问题的功能：

#include        <cstdlib>
#include    <string>
#include    <iostream>
#include        <unistd.h>
#include        <pthread.h>
#include        "Train.h"
#include        "Platform.h"

const int   NUM_TRAINS      = 4; 
const int   NUM_NORTHERNLY_TRAINS   = NUM_TRAINS / 2;
const int   NUM_SOUTHERNLY_TRAINS   = NUM_TRAINS - NUM_NORTHERNLY_TRAINS;
const int       NUM_LOOPS       = 16;
const char* TRAIN_NAME_ARRAY[NUM_TRAINS]
                = { "Thomas the Tank-Engine",
                    "Percy the Small Engine",
                    "California Zephyr",
                    "Tokaido Shinkansen"
                  };
const int   TRAIN_TRANSIT_TIME_MSECS[NUM_TRAINS]
                = { 10000,  // Thomas
                    10000,  // Percy
                     5000,  // CA Zephyr
                     1000   // Bullet train
                   };

Platform    northBoundPlatform("North-bound Platform");
Platform    southBoundPlatform("South-bound Platform");

void*   initiallyNorthernly (void* vPtr)
{
  Train* id = ((Train*)vPtr);
  for  (int i = 0;  i < NUM_LOOPS;  i++)
  {
    northBoundPlatform.arrive(id);
    northBoundPlatform.leave();
    pause();
    southBoundPlatform.arrive(id);
    southBoundPlatform.leave();
    pause();
  }
  return((void*)id);
}


void*   initiallySouthernly (void* vPtr)
{
  Train* id = (Train*)vPtr;     
  for  (int i = 0;  i < NUM_LOOPS;  i++)
  {
    southBoundPlatform.arrive(id);
    southBoundPlatform.leave();
    pause();
    northBoundPlatform.arrive(id);
    northBoundPlatform.leave();
    pause();
  }
  return((void*)id);

}   


int     main    ()
{
  pthread_t     tidArray[NUM_TRAINS];
  Train*    trainArray[NUM_TRAINS];
  pthread_t     tidArray2[NUM_NORTHERNLY_TRAINS];
  Train*        trainArray2[NUM_NORTHERNLY_TRAINS];
  pthread_t     tidArray3[NUM_SOUTHERNLY_TRAINS];
  Train*        trainArray3[NUM_SOUTHERNLY_TRAINS];

  for  (int i = 0;  i < NUM_TRAINS;  i++)
   { trainArray[i] = new    Train(TRAIN_NAME_ARRAY[i],TRAIN_TRANSIT_TIME_MSECS[i]);
   }
    int trainInd      = 0;


  for (int i = 0; i < NUM_NORTHERNLY_TRAINS; i++)
  { 
    pthread_create(&tidArray2[i], NULL, initiallyNorthernly,&trainArray2[i]);
  }

  for (int i = 0; i < NUM_SOUTHERNLY_TRAINS; i++)
  {
     pthread_create(&tidArray3[i], NULL, initiallySouthernly,&trainArray3[i]);
  }

  for  (int i = 0;  i < NUM_TRAINS;  i++) 
  {     
     trainArray[i] = NULL;

  //  Wait for all Train threads.  Also, get the pointers to the Train objects
  //  and delete() them because they were created by 'new'
     pthread_join(tidArray[i], (void**)&trainInd);
     pthread_join(tidArray2[i],(void**)&trainInd);
     pthread_join(tidArray3[i],(void**)&trainInd);
  }
  return(EXIT_SUCCESS);
}

以下是相应的头文件：

Train.h

class   Train
{

  std::string   name_;


  int       pauseTimeUsecs_;

public :

  Train     (const std::string& newName,
         int            newPauseTimeUsecs
        )
  {
    name_       = newName;
    pauseTimeUsecs_ = newPauseTimeUsecs;
    std::cout << getName() << " leaving the trainyard.\n";
  }


  ~Train    ()
  {
    std::cout << getName() << " going back to the trainyard\n";
  }

  const std::string&
        getName ()
            const
  { return(name_); }


  void      pause   ()
            const
  {
    usleep(pauseTimeUsecs_);
  }

};

Platform.h

class   Platform
{

  std::string       name_;


  Train*        trainPtr_;

  pthread_mutex_t  mutexLock_;
  pthread_cond_t    notEmptyCond_;
  pthread_cond_t    notFullCond_;
public :

  Platform      (const std::string& newName
        )
  {
    name_   = newName;
    trainPtr_   = NULL;
    pthread_mutex_init(&mutexLock_,NULL);
    pthread_cond_init(&notEmptyCond_,NULL);
    pthread_cond_init(&notFullCond_,NULL);
  }

  //  PURPOSE:  To release resources.  No parameters.  No return value.
  ~Platform     ()
  {
    pthread_mutex_destroy(&mutexLock_);
    pthread_cond_destroy(&notEmptyCond_);
    pthread_cond_destroy(&notFullCond_);
  }


  const std::string&
        getName ()
            const
  {
    return(name_);
  }


  Train*    getTrainPtr
            ()
            const
  {
    return(trainPtr_);
  }


  void      arrive  (Train* newTrainPtr
            )
  {
    pthread_mutex_lock(&mutexLock_);
    while  (getTrainPtr() != NULL)
    {
      std::cout << getTrainPtr()->getName()
        << " is at " << getName()
        << ", "      << newTrainPtr->getName()
        << " must wait.\n";
      usleep(10) + rand() % 10;
      pthread_cond_wait(&notFullCond_,&mutexLock_);
    }

    std::cout << newTrainPtr->getName() << " arriving at " << getName()     << "\n";

    trainPtr_   = newTrainPtr;

    usleep(10 + rand() % 10);
    pthread_mutex_unlock(&mutexLock_);
    pthread_cond_signal(&notEmptyCond_);
  }


  Train*    leave   ()
  {
    pthread_mutex_lock(&mutexLock_);
    while  (getTrainPtr() == NULL)
    {
      std::cout << "No train at " << getName() << "!\n";
      usleep(10 + rand() % 10);
      pthread_cond_wait(&notEmptyCond_,&mutexLock_);
    }

    Train*  toReturn    = getTrainPtr();

    std::cout << toReturn->getName() << " leaving " << getName() << "\n";

    usleep(10 + rand() % 10);
    trainPtr_ = NULL;
    pthread_cond_signal(&notFullCond_);
    pthread_mutex_unlock(&mutexLock_);
    return(toReturn);
  }

};

使用gdb运行后，当我调用northBoundPlatform（Platform对象）时出现分段错误。该函数的目标是使vPtr指向的训练对象到达Northern平台的到达（），在northernPlatform留下（），在train对象上的pause（），在southBoundPlatform的到达（），离开（）到southBoundPlatform，再次对该对象执行pause（），最后返回指向所使用的火车的指针。

我不确定我是否正确地将vPtr投射到Train *中导致分段错误。如有必要，我可以提供其余的主要代码。任何帮助表示赞赏。

Answer 1

你的main（）函数为每个NUM_NORTHERNLY_TRAINS都有两个for循环，使用initialNorthernly和initialSouthernly，但是第二个循环应该用NUM_SOUTHERNLY_TRAINS循环。

处理导致C ++中的分段错误的指针

1 个答案: