c ++ char * + std :: vector内存泄漏 [英] c++ char* + std::vector memory leak

问题描述

以下代码从磁盘读取一个大对象集合（95G的压缩对象，通过WriteObject流化器解压缩），并将其内容作为字符串打印。

对象.cxx：

  std :: vector< char> ObjectHandler :: GetObject（const std :: string& path）
 {
 TFile * file = new TFile（path.c_str（））; 
 
 //如果文件未找到或为空
 if（file-> IsZombie（））{
 cout< 找不到该对象在<路径<< endl; 
} 
 
 //从根文件获取AliCDBEntry 
 AliCDBEntry * entry =（AliCDBEntry *）file-> Get（AliCDBEntry）; 
 
 //创建一个输出缓冲区
 TBufferFile * buffer = new TBufferFile（TBuffer :: kWrite）; 
 
 //将AliCDBEntry对象流式并序列化到缓冲区
 buffer-> WriteObject（（const TObject *）entry）; 
 
 //获取缓冲区的指针
 char * pointer = buffer-> Buffer（）; 
 
 //将对象存储到引用的向量
 std :: vector< char> vector（pointer，pointer + buffer-> Length（））; 
 
 //释放打开的文件
删除文件; 
 
删除缓冲区; 
 
 return vector; 
} 
  

main.cxx：

  ObjectHandler objHandler; 
 boost :: filesystem :: path dataPath（/ tmp）; 
 boost :: filesystem :: recursive_directory_iterator endIterator; 
 
 if（boost :: filesystem :: exists（dataPath）&& boost :: filesystem :: is_directory（dataPath））{
 for（static boost :: filesystem :: recursive_directory_iterator directoryIterator（dataPath）; directoryIterator！= endIterator; 
 ++ directoryIterator）{
 if（boost :: filesystem :: is_regular_file（directoryIterator-> status（）））{
 
 cout < directoryIterator-> path（）。string（）<< endl; 
 std :: vector< char> vector = objHandler.GetObject（directoryIterator-> path（）。string（））; 
 cout<<载体< endl; 
} 
} 
} 
  

正确的方法来实现这个方法？

2）这段代码是泄漏的，我怀疑是 char *指针

em>是由 ObjectHandler :: GetObject（）方法返回的实际 std :: vector 。我用下面的代码测试了实现：

  struct sysinfo sys_info; 
 
 sysinfo（& sys_info）; 
 
 cout<< Total：<< sys_info.totalram *（unsigned long long）sys_info.mem_unit / 1024< Free：<< sys_info.freeram *（unsigned long long）sys_info.mem_unit / 1024< endl; 
  

，并且空闲ram连续减少，直到它达到0并且程序被终止。

解决方案

内存泄漏是一个可以包含几个内容的术语;取决于你跟谁交谈。
一个是新的不匹配删除。
另一个，经常查看，是仍然引用和范围内，但只是没有使用或需要的内存。

如果你不使用profiller ，那么你不能确定你有什么，但是因为你有一个大的向量被传递，我们不知道你用它做什么，你可以做的第二，没有人会看到。 / p>

The following code is reading a big object collection (95G of compressed objects that are uncompressed via the WriteObject streamer) from disk and prints their content as strings.

object.cxx:

std::vector<char> ObjectHandler::GetObject(const std::string& path)
{
  TFile *file = new TFile(path.c_str());

  // If file was not found or empty
  if (file->IsZombie()) {
    cout << "The object was not found at " << path << endl;
  }

  // Get the AliCDBEntry from the root file
  AliCDBEntry *entry = (AliCDBEntry*)file->Get("AliCDBEntry");

  // Create an outcoming buffer
  TBufferFile *buffer = new TBufferFile(TBuffer::kWrite);

  // Stream and serialize the AliCDBEntry object to the buffer
  buffer->WriteObject((const TObject*)entry);

  // Obtain a pointer to the buffer
  char *pointer = buffer->Buffer();

  // Store the object to the referenced vector
  std::vector<char> vector(pointer, pointer + buffer->Length());

  // Release the open file
  delete file;

  delete buffer;

  return vector;
}

main.cxx:

ObjectHandler objHandler;
boost::filesystem::path dataPath("/tmp");
boost::filesystem::recursive_directory_iterator endIterator;

if (boost::filesystem::exists(dataPath) && boost::filesystem::is_directory(dataPath)) {
  for (static boost::filesystem::recursive_directory_iterator directoryIterator(dataPath); directoryIterator != endIterator;
     ++directoryIterator) {
    if (boost::filesystem::is_regular_file(directoryIterator->status())) {

      cout << directoryIterator->path().string() << endl;
      std::vector<char> vector = objHandler.GetObject(directoryIterator->path().string());
      cout << vector << endl;
      }
   }
}

1) Is calling by value the correct way to implement this method? Am i doing additional copies that could be avoided if calling by reference?

2) This code is leaking and i am suspecting that either the char *pointer is to blame, or the actual std::vector that is returned by the ObjectHandler::GetObject() method. I've tested the implementation with the following code:

struct sysinfo sys_info;

sysinfo (&sys_info);

cout << "Total: " << sys_info.totalram *(unsigned long long)sys_info.mem_unit / 1024 << " Free: " << sys_info.freeram *(unsigned long long)sys_info.mem_unit/ 1024 << endl;

and the free ram is continuously reduced, until it reaches 0 and the program is killed.

解决方案

"Memory Leak" is a term that can encompass a few things; depending on who you talk to. One is a new without matching delete. The other, often looked over, is memory that's still referenced and in scope, but just not used or needed.

If you don't use a profiller, then you can't be sure which you have, but since you've a large vector being passed around, and we don't know what you do with it, you could be doing the 2nd and no one would ever see.

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