c++ - Access Violation when calling LockFileEx() -

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i have filemapping class allows me lock file exclusive use process using win32 api function lockfileex().

bool filemapping::lockfile(bool wait) {     if (isfilelocked())         return true;      // want exclusive lock.     dword flags = lockfile_exclusive_lock;      // if don't want thread block, have set appropriate flag.     if (!wait)         flags |= lockfile_fail_immediately;      m_isfilelocked = lockfileex(m_filedesc, flags, 0, (dword) m_mappinglength, (dword) (((uint64_t) m_mappinglength) >> 32), null);     return m_isfilelocked; }

whenever lockfileex() call access violation:

unhandled exception @ 0x7466c2ec in tftpserver.exe: 0xc0000005:
access violation reading location 0x00000008.

the file handle m_filedesc valid handle (mapping file memory handle works) , m_mappinglength size_t containing length of mapped file portion in bytes.

does have idea how fix this?

your last argument null, while should pointer overlapped structure. error reading location 0x00000008 corresponds documented requirement that:

you must initialize hevent member valid handle or zero.

given hevent member comes after 2 pointers, in 32 bit compilation it'd 8 bytes beginning of structure. lockfileex trying read hevent member, , crashes.


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