在使用Visual Studio 2010进行调试时，访问冲突读取位置的第一次机会异常

Question

我努力抓住遗留代码访问违规继续获取：

First-chance exception at 0x57e77e1c in YouTubeLocal.exe: 0xC0000005: Access violation reading location 0x0000000c.

我的堆栈看起来像这样：

    Qt5Guid.dll!57e77e1c()  
    [Frames below may be incorrect and/or missing, no symbols loaded for Qt5Guid.dll]   
    Qt5Guid.dll!57e75604()  
    Qt5Guid.dll!57ed520b()  
    Qt5Guid.dll!57dcf18b()  
>   msvcr100d.dll!_unlock(int locknum=0x00000004)  Line 375 C
    msvcr100d.dll!_heap_alloc_dbg_impl(unsigned int nSize=0x00000040, int nBlockUse=0x00000001, const char * szFileName=0x00000000, int nLine=0x00000000, int * errno_tmp=0x0015cb70)  Line 507 + 0x7 bytes C++
    msvcr100d.dll!_heap_alloc_dbg_impl(unsigned int nSize=0x00000040, int nBlockUse=0x00000001, const char * szFileName=0x00000000, int nLine=0x00000000, int * errno_tmp=0x0015cb70)  Line 504 + 0xc bytes C++
    msvcr100d.dll!_nh_malloc_dbg_impl(unsigned int nSize=0x00000040, int nhFlag=0x00000000, int nBlockUse=0x00000001, const char * szFileName=0x00000000, int nLine=0x00000000, int * errno_tmp=0x0015cb70)  Line 239 + 0x19 bytes  C++
    msvcr100d.dll!_nh_malloc_dbg(unsigned int nSize=0x00000002, int nhFlag=0x0015cbdc, int nBlockUse=0x0015cbc8, const char * szFileName=0x0015cbb0, int nLine=0x0015cbc8)  Line 302 + 0x1d bytes   C++
    Qt5Cored.dll!533b0628()     
    Qt5Cored.dll!53388046()     
    Qt5Cored.dll!5335f56b()     
    Qt5Cored.dll!535e74c4()     
    Qt5Cored.dll!536f7198()     
    Qt5Widgetsd.dll!53aa4aea()  
    kernel32.dll!778bc3d4()     
    msvcr100d.dll!_unlock(int locknum=0x00000004)  Line 375 C
    msvcr100d.dll!_free_dbg(void * pUserData=0x53a4b300, int nBlockUse=0x019757a0)  Line 1270 + 0x7 bytes   C++
    msvcr100d.dll!_free_dbg(void * pUserData=0x53a4b300, int nBlockUse=0x019757a0)  Line 1267 + 0xc bytes   C++
    01b4bd40()  
    kernel32.dll!778bc3d4()     
    msvcr100d.dll!_free_base(void * pBlock=0x0015d060)  Line 50 + 0x13 bytes    C
    018a4a84()  
    kernel32.dll!778bc3d4()     
    msvcr100d.dll!_free_base(void * pBlock=0x57c49736)  Line 50 + 0x13 bytes    C
    0015d140()  
    feeefeee()  

调试器在此文件中停止（mlock.c）

/***
* _unlock - Release multi-thread lock
*
*Purpose:
*       Note that it is legal for a thread to aquire _EXIT_LOCK1
*       multiple times.
*
*Entry:
*       locknum = number of the lock to release
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/

void __cdecl _unlock (
        int locknum
        )
{
        /*
         * leave the critical section.
         */
        LeaveCriticalSection( _locktable[locknum].lock );
}

我找不到发生访问冲突的行。如何捕获导致异常的行？

更新： 这是我的解决方案：Microsoft Application Verifier

Answer 1

尝试添加一些宏，在释放内存后将指针设置为NULL。在使用这样的指针之前，还可以尝试添加一些断言或类似的东西。有了这个，你应该能够很快找到错误。