警告 C6269：操作顺序可能不正确：取消引用被忽略

Question

我在 vs 2010 上对 c++ 代码运行代码分析 我在这些线上收到错误

va_arg(argList, TCHAR_ARG);
va_arg(argList, int*);

警告 C6269：操作顺序可能不正确：取消引用被忽略

在这两行上收到警告的原因是什么？

我在 Switch case

case 'C':
case 'C'|_atltmpFORCE_ANSI:
case 'C'|_atltmpFORCE_UNICODE:
case 'o';
case 'p':
case 'n':

完整代码上遇到错误

inline void CXString::FormatV(LPCTSTR lpszFormat, va_list argList)
{
    va_list argListSave = argList;

    // make a guess at the maximum length of the resulting string
    int nMaxLen = 0;
    for (LPCTSTR lpsz = lpszFormat; *lpsz != '\0'; lpsz = CharNext(lpsz))
    {
        // handle '%' character, but watch out for '%%'
        if (*lpsz != '%' || *(lpsz = CharNext(lpsz)) == '%')
        {
            nMaxLen += (int)_tclen(lpsz);
            continue;
        }

        int nItemLen = 0;

        // handle '%' character with format
        int nWidth = 0;
        for (; *lpsz != '\0'; lpsz = CharNext(lpsz))
        {
            // check for valid flags
            if (*lpsz == '#')
                nMaxLen += 2;   // for '0x'
            else if (*lpsz == '*')
                nWidth = va_arg(argList, int);
            else if (*lpsz == '-' || *lpsz == '+' || *lpsz == '0' ||
                *lpsz == ' ')
                ;
            else // hit non-flag character
                break;
        }
        // get width and skip it
        if (nWidth == 0)
        {
            // width indicated by
            nWidth = _ttoi(lpsz);
            for (; *lpsz != '\0' && _istdigit(*lpsz); lpsz = CharNext(lpsz))
                ;
        }

        int nPrecision = 0;
        if (*lpsz == '.')
        {
            // skip past '.' separator (width.precision)
            lpsz = CharNext(lpsz);

            // get precision and skip it
            if (*lpsz == '*')
            {
                nPrecision = va_arg(argList, int);
                lpsz = CharNext(lpsz);
            }
            else
            {
                nPrecision = _ttoi(lpsz);
                for (; *lpsz != '\0' && _istdigit(*lpsz); lpsz = CharNext(lpsz))
                    ;
            }
        }

        // should be on type modifier or specifier
        int nModifier = 0;
        switch (*lpsz)
        {
        // modifiers that affect size
        case 'h':
            nModifier = _atltmpFORCE_ANSI;
            lpsz = CharNext(lpsz);
            break;
        case 'l':
            nModifier = _atltmpFORCE_UNICODE;
            lpsz = CharNext(lpsz);
            break;

        // modifiers that do not affect size
        case 'F':
        case 'N':
        case 'L':
            lpsz = CharNext(lpsz);
            break;
        }

        // now should be on specifier
        switch (*lpsz | nModifier)
        {
        // single characters
        case 'c':
        case 'C':
            nItemLen = 2;
            va_arg(argList, TCHAR_ARG);
            break;
        case 'c'|_atltmpFORCE_ANSI:
        case 'C'|_atltmpFORCE_ANSI:
            nItemLen = 2;
            va_arg(argList, CHAR_ARG);
            break;
        case 'c'|_atltmpFORCE_UNICODE:
        case 'C'|_atltmpFORCE_UNICODE:
            nItemLen = 2;
            va_arg(argList, WCHAR_ARG);
            break;

        // strings
        case 's':
        {
            LPCTSTR pstrNextArg = va_arg(argList, LPCTSTR);
            if (pstrNextArg == NULL)
               nItemLen = 6;  // "(null)"
            else
            {
               nItemLen = lstrlen(pstrNextArg);
               nItemLen = max(1, nItemLen);
            }
            break;
        }

        case 'S':
        {
#ifndef _UNICODE
            LPWSTR pstrNextArg = va_arg(argList, LPWSTR);
            if (pstrNextArg == NULL)
               nItemLen = 6;  // "(null)"
            else
            {
               nItemLen = (int)wcslen(pstrNextArg);
               nItemLen = max(1, nItemLen);
            }
#else
            LPCSTR pstrNextArg = va_arg(argList, LPCSTR);
            if (pstrNextArg == NULL)
               nItemLen = 6; // "(null)"
            else
            {
               nItemLen = lstrlenA(pstrNextArg);
               nItemLen = max(1, nItemLen);
            }
#endif
            break;
        }

        case 's'|_atltmpFORCE_ANSI:
        case 'S'|_atltmpFORCE_ANSI:
        {
            LPCSTR pstrNextArg = va_arg(argList, LPCSTR);
            if (pstrNextArg == NULL)
               nItemLen = 6; // "(null)"
            else
            {
               nItemLen = lstrlenA(pstrNextArg);
               nItemLen = max(1, nItemLen);
            }
            break;
        }

        case 's'|_atltmpFORCE_UNICODE:
        case 'S'|_atltmpFORCE_UNICODE:
        {
            LPWSTR pstrNextArg = va_arg(argList, LPWSTR);
            if (pstrNextArg == NULL)
               nItemLen = 6; // "(null)"
            else
            {
               nItemLen = (int)wcslen(pstrNextArg);
               nItemLen = max(1, nItemLen);
            }
            break;
        }
        }

        // adjust nItemLen for strings
        if (nItemLen != 0)
        {
            nItemLen = max(nItemLen, nWidth);
            if (nPrecision != 0)
                nItemLen = min(nItemLen, nPrecision);
        }
        else
        {
            switch (*lpsz)
            {
            // integers
            case 'd':
            case 'i':
            case 'u':
            case 'x':
            case 'X':
            case 'o':
                va_arg(argList, int);
                nItemLen = 32;
                nItemLen = max(nItemLen, nWidth+nPrecision);
                break;

            case 'e':
            case 'f':
            case 'g':
            case 'G':
#ifndef _DEBUG
                ::OutputDebugString(_T("Floating point (%%e, %%f, %%g, and %%G) is not supported by the WTL::CXString class."));
                ::DebugBreak();
#endif //!_DEBUG
                break;

            case 'p':
                va_arg(argList, void*);
                nItemLen = 32;
                nItemLen = max(nItemLen, nWidth+nPrecision);
                break;

            // no output
            case 'n':
                va_arg(argList, int*);
                break;

            default:
                break;
            };
        }

        // adjust nMaxLen for output nItemLen
        nMaxLen += nItemLen;
    }

    GetBuffer(nMaxLen);
    int nRet = _vstprintf_s(m_pchData, GetAllocLength(), lpszFormat, argListSave);
    nRet;   // ref
    ReleaseBuffer();

    va_end(argListSave);
}

Answer 1

编译器可能会因为您不使用返回值而感到困惑。你尝试过吗：

TCHAR_ARG arg1 = va_arg(argList, TCHAR_ARG);
int* arg2 = va_arg(argList, int*);