SymEnumSourceFiles get incomplete file names

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C++

Win32

debugging

I was tring to use SymEnumSourceFiles to get the file name within the debugging module.But the file name as a parameter in the callback function seems incomplete. e.g. A file named"c:\\program files\\test\\test.cpp" only showed "c:\\program fi" in the FileName part of the PSOURCEFILE type parameter, and that's very wired.
Here is my code:

    struct foo
{
    static BOOL CALLBACK run( PSOURCEFILE pSourceFile, PVOID UserContext)
    {
        static TCHAR szFileName[MAX_PATH] = _T("");
        if (_tcscmp(szFileName, pSourceFile->FileName))
        {
            _tcscpy(szFileName, pSourceFile->FileName);
        }
        return TRUE;
    }
};

    HANDLE hCurrentProcess = GetCurrentProcess();
SymInitialize(hCurrentProcess, NULL, FALSE);
DWORD64 BaseOfDll = SymLoadModule64(hCurrentProcess,
                                        NULL,
                                       (LPCSTR)_bstr_t(lpszFile),
                                        NULL,0,0);
if(!SymEnumSourceFiles(hCurrentProcess, BaseOfDll, NULL, foo::run, (PVOID)pCallBack))
{
    ATLTRACE(_T(__FUNCTION__) _T(" error:0x%x\n"), GetLastError());
}
SymUnloadModule64(hCurrentProcess, BaseOfDll);
SymCleanup(hCurrentProcess);

Can anyone tell me where I go wrong please?
PS. When I simply replace SymEnumSourceFiles with SymEnumLines and change the callback function, the file name I got is correct.