Win32调试API 注意内存泄漏

    最近学习 Win32调试API,  写了点程序, 又学到了一些东西.

    比如用 A.EXE 做 Debuger, B.EXE 做 Debuggee.

    一般的教程都象下面这样写 A.EXE:

    PROCESS_INFORMATION  pi;
    STARTUPINFO          si;
    DEBUG_EVENT          de;
    DWORD                dwContinueStatus;
    DWORD                dwExceptionNum=0;           // 异常次数

    GetStartupInfo(&si);
    CreateProcess("B.EXE", 0, 0, 0, 0, DEBUG_PROCESS, 0, 0, &si, &pi));

    while( WaitForDebugEvent(&de, INFINITE) )
    {
         dwContinueStatus = DBG_EXCEPTION_NOT_HANDLED;

         if (de.dwDebugEventCode == EXIT_PROCESS_DEBUG_EVENT)
         {
               break;                          // debugee 结束
          }
          else if (de.dwDebugEventCode == EXCEPTION_DEBUG_EVENT)
          {
               dwExceptionNum++;               // 第一次异常需要注意

               if (dwExceptionNum == 1) dwContinueStatus = DBG_CONTINUE;
          }
          ...

          ContinueDebugEvent(de.dwProcessId, de.dwThreadId, dwContinueStatus);
    }

    CloseHandle(pi.hThread);
    CloseHandle(pi.hProcess);

    上面的程序好象没问题. 但我在调试中发现, B.EXE 结束后,  只要 A.EXE 不关闭, B.EXE 就不能删除改名等,

    这说明 A.EXE 中打开了 B.EXE 的文件句柄, 但一直没有关闭. 经过反复研究, 终于找到了问题所在, 改写程序如下:

    while( WaitForDebugEvent(&de, INFINITE) )
    {
         dwContinueStatus = DBG_EXCEPTION_NOT_HANDLED;

         if (de.dwDebugEventCode == EXIT_PROCESS_DEBUG_EVENT)
         {
              break;                          // debugee 结束
         }
         else if (de.dwDebugEventCode == CREATE_PROCESS_DEBUG_EVENT)
        {
              // Handle to the process's image file
              CloseHandle(de.u.CreateProcessInfo.hFile);

              // Handle to the process
              CloseHandle(de.u.CreateProcessInfo.hProcess);

              // Handle to the initial thread of the process identified by the hProcess member
              CloseHandle(de.u.CreateProcessInfo.hThread);
         }
         else if (de.dwDebugEventCode == CREATE_THREAD_DEBUG_EVENT)
         {
              // Handle to the thread whose creation caused the debugging event
              CloseHandle(de.u.CreateThread.hThread);
          }
          else if (de.dwDebugEventCode == LOAD_DLL_DEBUG_EVENT)
         {
               // Handle to the loaded DLL
               CloseHandle(de.u.LoadDll.hFile);
          }
          else if (de.dwDebugEventCode == EXCEPTION_DEBUG_EVENT)
         {
               dwExceptionNum++;         // 第一次异常需要注意

               if (dwExceptionNum == 1) dwContinueStatus = DBG_CONTINUE;
          }
          ...

          ContinueDebugEvent(de.dwProcessId, de.dwThreadId, dwContinueStatus);
    }

    CloseHandle(pi.hThread);
    CloseHandle(pi.hProcess);

    原因就在于 CREATE_PROCESS_DEBUG_EVENT, CREATE_THREAD_DEBUG_EVENT, LOAD_DLL_DEBUG_EVENT 时会打开一些句柄,

    如果不使用这些句柄, 最好马上关闭.

    当然 A. EXE 关闭时, 这些句柄都会自动关闭, 但有些程序, debuger 创建在 Explorer, 就会造成内存泄露.

    具体细节请参考 MSDN.