C++ 运算符 & 与枚举的计算结果为 false

Question

以下代码输出 reportAllDataRanges = 0。

BOOLEAN updateDataRanges = IsFirstUpdate || (m_uiDataRangeMode & IAdapterCommon::UpdatePinDataRanges);
BOOLEAN updateConstrainedDataRanges = m_uiDataRangeMode & IAdapterCommon::UpdatePinConstrainedDataRanges;
BOOLEAN reportAllDataRanges = m_uiDataRangeMode & IAdapterCommon::ReportAllDataRanges;

DPF_ENTER(("[CAdapterCommon::UpdatePinDescriptor(%p, %lu)] - m_uiDataRangeMode = %lu, updateDataRanges = %lu, updateConstrainedDataRanges = %lu, reportAllDataRanges = %lu, a & b = %lu, b = %lu", PinDescriptor, IsFirstUpdate, m_uiDataRangeMode, updateDataRanges, updateConstrainedDataRanges, reportAllDataRanges, m_uiDataRangeMode & IAdapterCommon::ReportAllDataRanges, IAdapterCommon::ReportAllDataRanges));

---

[CAdapterCommon::UpdatePinDescriptor(FFFFF8064CCE42F0, 1)] - m_uiDataRangeMode = 3070, updateDataRanges = 1, updateConstrainedDataRanges = 64, reportAllDataRanges = 0, a & b = 512, b = 512

---

typedef enum : UINT32
{
    None = 0,
    UseDataRanges = 1 << 0,
    UseDiscreteDataRanges = 1 << 1,
    RaiseUpdateEvent = 1 << 2,
    RaiseUpdatePinDescriptor = 1 << 3,
    DoNotUpdateOriginalDescriptor = 1 << 4,
    UpdatePinDataRanges = 1 << 5,
    UpdatePinConstrainedDataRanges = 1 << 6,
    UseDataRangeIntersection = 1 << 7,
    UseProposedDataFormat = 1 << 8,
    ReportAllDataRanges = 1 << 9,
    DataRangeIntersectionAcceptAllRanges = 1 << 10,
    SupportedDataRangesFirst = 1 << 11,
} DataRangeModeEnum;

---

不应该

BOOLEAN value = 3070 & 512;

评估为 TRUE？ (大于零)？

Answer 1

我认为您使用的是 <Windows.h> 中的 BOOLEAN 类型header 是 BYTE 类型的 typedef，它是 unsinged char 类型的 typedef，它可以保存 0 - 255 的值，而不是 3070 & 512 到的 512。表达式求值。存在导致值 0 的溢出，相当于 FALSE .