An Example of Using CrashRpt API

The following example shows how to use CrashRpt API functions and structures to enable crash reporting support in a console C++ application. We use console application for simplicity, but in general the application may be WinAPI/MFC/ATL/WTL based, as well. For additional information on CrashRpt API functions and structures, please refer to Using CrashRpt API.

First create a console Win32 application and call it MyApp. Then configure the MyApp application as described in Configuring Your Project's Build Settings.

Let's assume the case when MyApp application has two threads. The first thread, the application thread, will be the main one. The main() function will be executed in this thread and interaction with user will also be performed in this thread. The second thread, the worker thread, is typically used when some time-consuming computational work is to be done without blocking the application thread.

The MyApp application will create a log file that will be included in error report on crash. The log file is typically helpful when debugging a crash.

Let's create the code template.

#include <windows.h>
#include <stdio.h>
#include <tchar.h>

FILE* g_hLog = NULL; // Global handle to the application log file

// The following function writes an entry to the log file
void log_write(LPCTSTR szFormat, ...)
{
  if (g_hLog == NULL) 
    return; // Log file seems to be closed

  va_list args;
  va_start(args); 
  _vftprintf_s(g_hLog, szFormat, args);
  fflush(g_hLog);
}

// Thread procedure
DWORD WINAPI ThreadProc(LPVOID lpParam)
{
  log_write(_T("Entering the thread proc\n"));

  // Define the infinite loop where some processing will be done 
  for(;;)
  {
    // There is a hidden error somewhere inside of the loop...
    int* p = NULL;
    *p = 13; // This results in Access Violation
  }    
   
  log_write(_T("Leaving the thread proc\n"));

  return 0;
}

int _tmain(int argc, _TCHAR* argv[])
{
  // Open log file
  errno_t err = _tfopen_s(&g_hLog, _T("log.txt"), _T("wt"));
  if(err!=0 || g_hLog==NULL)
  {
    _tprintf_s(_T("Error opening log.txt\n"));
    return 1; // Couldn't open log file
  }

  log_write(_T("Started successfully\n"));

  // Create the worker thread
  HANDLE hWorkingThread = CreateThread(NULL, 0, 
           ThreadProc, (LPVOID)NULL, 0, NULL);

  log_write(_T("Created working thread\n"));

  // There is a hidden error in the main() function
  // Call of _tprintf_s with NULL parameter
  TCHAR* szFormatString = NULL;
  _tprintf_s(szFormatString);

  // Wait until the worker thread is exited
  WaitForSingleObject(hWorkingThread, INFINITE);

  log_write(_T("Working thread has exited\n"));

  // Close the log file
  if(g_hLog!=NULL)
  {
    fclose(g_hLog);
    g_hLog = NULL;// Clean up handle
  }

  // Exit
  return 0;
}

We intentionally inserted the code that would cause an exception in both threads. In real-life programs such a code always exists, even when you test your application very carefully.

To enable crash reporting support in the application, we need to include CrashRpt header in the beginning of the code:

// Include CrashRpt Header 
#include "CrashRpt.h"

Next, we define the crash callback function and call it CrashCallback(). The crash callback function will be called by CrashRpt when crash occurs, so we will be able to close the handle to log file. For more information on crash callback, see the the PFNCRASHCALLBACK() prototype.

// Define the callback function that will be called on crash
int CALLBACK CrashCallback(CR_CRASH_CALLBACK_INFO* pInfo)
{  
  // The application has crashed!

  // Close the log file here
  // to ensure CrashRpt is able to include it into error report
  if(g_hLog!=NULL)
  {
    fclose(g_hLog);
    g_hLog = NULL;// Clean up handle
  }

  // Return CR_CB_DODEFAULT to generate error report
  return CR_CB_DODEFAULT;
}

Because we have a multi-threaded application, we need to use some CrashRpt Functions to set exception handlers for the worker thread. In this example, we use the crInstallToCurrentThread2() and crUninstallFromCurrentThread() functions to set exception handlers in the beginning of the thread procedure and unset them in the end of the thread procedure, respectively.

// Thread procedure
DWORD WINAPI ThreadProc(LPVOID lpParam)
{
  // Install exception handlers for this thread
  crInstallToCurrentThread2(0);

  ...

  // Unset exception handlers before exiting the thread
  crUninstallFromCurrentThread();    

  return 0;
}    

Next, in the beginning of the main() function, we initialize the CrashRpt library and install the exception handlers for the entire process with the help of crInstall() function and pass configuration information to it through the CR_INSTALL_INFO structure. If something goes wrong, we can check the last error message with the crGetLastErrorMsg() function.

int _tmain(int argc, _TCHAR* argv[])
{  
  // Define CrashRpt configuration parameters
  CR_INSTALL_INFO info;  
  memset(&info, 0, sizeof(CR_INSTALL_INFO));  
  info.cb = sizeof(CR_INSTALL_INFO);    
  info.pszAppName = _T("MyApp");  
  info.pszAppVersion = _T("1.0.0");  
  info.pszEmailSubject = _T("MyApp 1.0.0 Error Report");  
  info.pszEmailTo = _T("myapp_support@hotmail.com");    
  info.pszUrl = _T("http://myapp.com/tools/crashrpt.php");  
  info.uPriorities[CR_HTTP] = 3;  // First try send report over HTTP 
  info.uPriorities[CR_SMTP] = 2;  // Second try send report over SMTP  
  info.uPriorities[CR_SMAPI] = 1; // Third try send report over Simple MAPI    
  // Install all available exception handlers
  info.dwFlags |= CR_INST_ALL_POSSIBLE_HANDLERS;
  // Restart the app on crash 
  info.dwFlags |= CR_INST_APP_RESTART; 
  info.dwFlags |= CR_INST_SEND_QUEUED_REPORTS; 
  info.pszRestartCmdLine = _T("/restart");
  // Define the Privacy Policy URL 
  info.pszPrivacyPolicyURL = _T("http://myapp.com/privacypolicy.html"); 
  
  // Install crash reporting
  int nResult = crInstall(&info);    
  if(nResult!=0)  
  {    
    // Something goes wrong. Get error message.
    TCHAR szErrorMsg[512] = _T("");        
    crGetLastErrorMsg(szErrorMsg, 512);    
    _tprintf_s(_T("%s\n"), szErrorMsg);    
    return 1;
  } 

Next, we want to set the crash callback function by calling crSetCrashCallback().

  // Set crash callback function
  crSetCrashCallback(CrashCallback, NULL);

Next, we want to add our error log file to the crash report. We do this with the crAddFile2() function.

  // Add our log file to the error report
  crAddFile2(_T("log.txt"), NULL, _T("Log File"), CR_AF_MAKE_FILE_COPY);    

When the app crashes, we can include the screen shot to the crash report. We do this with the crAddScreenshot2() function.

  // We want the screenshot of the entire desktop is to be added on crash
  crAddScreenshot2(CR_AS_VIRTUAL_SCREEN, 0);   

The following code adds a named property to the crash description XML file (see the crAddProperty() function). The property tells what graphics adapter is installed on end user's computer (for simplicity, it is hardcoded, but you usually determine adapter's model dynamically using Windows Management Instrumentation, shortly WMI).

  // Add a named property that means what graphics adapter is
  // installed on end user's machine
  crAddProperty(_T("VideoCard"), _T("nVidia GeForce 8600 GTS"));

In the end of the main() function, we uninitialize CrashRpt and unset the exception handlers using the crUninstall() function.

  // Uninitialize CrashRpt before exiting the main function
  crUninstall();

Below we have it all in one piece of code:

#include <windows.h>
#include <stdio.h>
#include <tchar.h>
// Include CrashRpt Header 
#include "CrashRpt.h"

FILE* g_hLog = NULL; // Global handle to the application log file

// Define the callback function that will be called on crash
int CALLBACK CrashCallback(CR_CRASH_CALLBACK_INFO* pInfo)
{  
  // The application has crashed!

  // Close the log file here
  // to ensure CrashRpt is able to include it into error report
  if(g_hLog!=NULL)
  {
    fclose(g_hLog);
    g_hLog = NULL;// Clean up handle
  }

  // Return CR_CB_DODEFAULT to generate error report
  return CR_CB_DODEFAULT;
}

// The following function writes an entry to the log file
void log_write(LPCTSTR szFormat, ...)
{
  if (g_hLog == NULL) 
    return; // Log file seems to be closed

  va_list args; 
  va_start(args); 
  _vftprintf_s(g_hLog, szFormat, args);
  fflush(g_hLog);
}

// Thread procedure
DWORD WINAPI ThreadProc(LPVOID lpParam)
{
  // Install exception handlers for this thread
  crInstallToCurrentThread2(0);

  log_write(_T("Entering the thread proc\n"));

  // Define the infinite loop where some processing will be done 
  for(;;)
  {
    // There is a hidden error somewhere inside of the loop...
    int* p = NULL;
    *p = 13; // This results in Access Violation
  }    
   
  log_write(_T("Leaving the thread proc\n"));

  // Unset exception handlers before exiting the thread
  crUninstallFromCurrentThread();    

  return 0;
}

int _tmain(int argc, _TCHAR* argv[])
{  
  // Define CrashRpt configuration parameters
  CR_INSTALL_INFO info;  
  memset(&info, 0, sizeof(CR_INSTALL_INFO));  
  info.cb = sizeof(CR_INSTALL_INFO);    
  info.pszAppName = _T("MyApp");  
  info.pszAppVersion = _T("1.0.0");  
  info.pszEmailSubject = _T("MyApp 1.0.0 Error Report");  
  info.pszEmailTo = _T("myapp_support@hotmail.com");    
  info.pszUrl = _T("http://myapp.com/tools/crashrpt.php");  
  info.uPriorities[CR_HTTP] = 3;  // First try send report over HTTP 
  info.uPriorities[CR_SMTP] = 2;  // Second try send report over SMTP  
  info.uPriorities[CR_SMAPI] = 1; // Third try send report over Simple MAPI    
  // Install all available exception handlers
  info.dwFlags |= CR_INST_ALL_POSSIBLE_HANDLERS;
  // Restart the app on crash 
  info.dwFlags |= CR_INST_APP_RESTART; 
  info.dwFlags |= CR_INST_SEND_QUEUED_REPORTS; 
  info.pszRestartCmdLine = _T("/restart");
  // Define the Privacy Policy URL 
  info.pszPrivacyPolicyURL = _T("http://myapp.com/privacypolicy.html"); 
  
  // Install crash reporting
  int nResult = crInstall(&info);    
  if(nResult!=0)  
  {    
    // Something goes wrong. Get error message.
    TCHAR szErrorMsg[512] = _T("");        
    crGetLastErrorMsg(szErrorMsg, 512);    
    _tprintf_s(_T("%s\n"), szErrorMsg);    
    return 1;
  } 

  // Set crash callback function
  crSetCrashCallback(CrashCallback, NULL);

  // Add our log file to the error report
  crAddFile2(_T("log.txt"), NULL, _T("Log File"), CR_AF_MAKE_FILE_COPY);    

  // We want the screenshot of the entire desktop is to be added on crash
  crAddScreenshot2(CR_AS_VIRTUAL_SCREEN, 0);   

  // Add a named property that means what graphics adapter is
  // installed on user's machine
  crAddProperty(_T("VideoCard"), _T("nVidia GeForce 8600 GTS"));

  // The main code follows...

  // Open log file
  errno_t err = _tfopen_s(&g_hLog, _T("log.txt"), _T("wt"));
  if(err!=0 || g_hLog==NULL)
  {
    _tprintf_s(_T("Error opening log.txt\n"));
    return 1; // Couldn't open log file
  }

  log_write(_T("Started successfully\n"));

  // Create the worker thread
  HANDLE hWorkingThread = CreateThread(NULL, 0, 
           ThreadProc, (LPVOID)NULL, 0, NULL);

  log_write(_T("Created working thread\n"));

  // There is a hidden error in the main() function
  // Call of _tprintf_s with NULL parameter
  TCHAR* szFormatString = NULL;
  _tprintf_s(szFormatString);

  // Wait until the worker thread is exited
  WaitForSingleObject(hWorkingThread, INFINITE);

  log_write(_T("Working thread has exited\n"));

  // Close the log file
  if(g_hLog!=NULL)
  {
    fclose(g_hLog);
    g_hLog = NULL;// Clean up handle
  }

  // Uninitialize CrashRpt before exiting the main function
  crUninstall();

  // Exit
  return 0;
}

Do not forget to add CrashRptXXXX.lib file to the list of input libraries of your project (XXXX is the placeholder for the version of CrashRpt). For additional info, see Configuring Your Project's Build Settings.

Before running the application, you should place the following files to the directory where your application executable file is located (for additional information, see Preparing to Software Release):

• CrashRptXXXX.dll (here and below XXXX should be replaced with the actual version of CrashRpt)
• CrashSenderXXXX.exe
• dbghelp.dll
• crashrpt_lang.ini

When files have been copied, run the application. As error occurs, you should be able to see an error report window (for additional information, see About an Error Report)

Further reading: Internationalization Support.