VC++ com编程错误之0xC0000005: 读取位置 0xfeeefef6 时发生访问冲突

调用COM+，能够得到想要的结果，在执行最后return 0这句之后就报错。

报错位置在 comip.h

void _Release() throw()

{

if (m_pInterface != NULL) {

m_pInterface->Release(); // 在这里报的错

}

}

我自己在遇到这个问题时，将 m_pInterface->Release(); 注释掉程序不再报错。

网上一些其他的方法：

1.m_pInterface->Release() 改成 m_pInterface = NULL 出自http://topic.csdn.net/u/20091120/16/8a9c8d91-9a39-416b-8d8d-8c2cd2a71d3e.html

2.程序中实现的时候：ptr->Release();改成ptr.Release()；出自http://topic.csdn.net/u/20091120/16/8a9c8d91-9a39-416b-8d8d-8c2cd2a71d3e.html

3.有一种说法是范围问题。个人还不是很懂。详见：http://stackoverflow.com/questions/2653797/why-does-couninitialize-cause-an-error-on-exit

这个方法试了一下，也是可以的。具体见以下说明。

I'm working on a C++ application to read some data from an Excel file. I've got it working, but I'm confused about one part. Here's the code (simplified to read only the first cell).

//Mostly copied from http://www.codeproject.com/KB/wtl/WTLExcel.aspx 
#import "c:\Program Files\Common Files\Microsoft Shared\OFFICE11\MSO.DLL"
#import "c:\Program Files\Common Files\Microsoft Shared\VBA\VBA6\VBE6EXT.OLB"
#import "C:\Program Files\Microsoft Office\Office11\excel.exe" rename ("DialogBox","ExcelDialogBox") rename("RGB","ExcelRGB") rename("CopyFile", "ExcelCopyFile") rename("ReplaceText", "ExcelReplaceText") exclude("IFont", "IPicture")

_variant_t varOption((long) DISP_E_PARAMNOTFOUND, VT_ERROR);

int _tmain(int argc, _TCHAR* argv[])
{
DWORD dwCoInit = 0;
CoInitializeEx(NULL, dwCoInit);
Excel::_ApplicationPtr pExcel;
pExcel.CreateInstance(_T("Excel.Application"));
Excel::_WorkbookPtr pBook;
pBook = pExcel->Workbooks->Open("c:\\test.xls", varOption, varOption, varOption, varOption, varOption, varOption, varOption, varOption, varOption, varOption, varOption, varOption);
Excel::_WorksheetPtr pSheet = pBook->Sheets->Item[1];
Excel::RangePtr pRange = pSheet->GetRange(_bstr_t(_T("A1")));
_variant_t vItem = pRange->Value2;
printf(_bstr_t(vItem.bstrVal));
pBook->Close(VARIANT_FALSE);
pExcel->Quit();
//CoUninitialize();
return 0;
}

I had to comment out the call to CoUninitialize for the program to work. When CoUninitialize is uncommented, I get an access violation in the _Release function in comip.h on program exit.

Here's the code from comip.h, for what it's worth.

void _Release() throw()
{
if (m_pInterface != NULL) {
m_pInterface->Release();
}
}

I'm not very experienced with COM programming, so there's probably something obvious I'm missing.

Why does the call to CoUninitialize cause an exception?

What are the consequences of not calling CoUninitialize?

Am I doing something completely wrong here?

ANSWER！

The problem you are having is one of scope. The short answer is to move the CoInit and CoUninit into an outer scope from the Ptrs. For example:

//Mostly copied from http://www.codeproject.com/KB/wtl/WTLExcel.aspx 
#import "c:\Program Files\Common Files\Microsoft Shared\OFFICE11\MSO.DLL"
#import "c:\Program Files\Common Files\Microsoft Shared\VBA\VBA6\VBE6EXT.OLB"
#import "C:\Program Files\Microsoft Office\Office11\excel.exe" rename ("DialogBox","ExcelDialogBox") rename("RGB","ExcelRGB") rename("CopyFile", "ExcelCopyFile") rename("ReplaceText", "ExcelReplaceText") exclude("IFont", "IPicture")

_variant_t varOption((long) DISP_E_PARAMNOTFOUND, VT_ERROR);

int _tmain(int argc, _TCHAR* argv[])
{
DWORD dwCoInit = 0;
CoInitializeEx(NULL, dwCoInit);
{
Excel::_ApplicationPtr pExcel;
pExcel.CreateInstance(_T("Excel.Application"));
Excel::_WorkbookPtr pBook;
pBook = pExcel->Workbooks->Open("c:\\test.xls", varOption, varOption, varOption, varOption, varOption, varOption, varOption, varOption, varOption, varOption, varOption, varOption);
Excel::_WorksheetPtr pSheet = pBook->Sheets->Item[1];
Excel::RangePtr pRange = pSheet->GetRange(_bstr_t(_T("A1")));
_variant_t vItem = pRange->Value2;
printf(_bstr_t(vItem.bstrVal));
pBook->Close(VARIANT_FALSE);
pExcel->Quit();
}
CoUninitialize();
return 0;
}

The longer answer is that the Ptrs destructors (which calls Release) are being called on exit from main. This is after CoUnit which, basically, shuts down the communication channel between your app and the COM object.

What are the consequences of not calling CoUnit? For short lived in-process COM servers, there really isn't any negative consequence.