宏在C ++中的含義

Question

我碰巧在c ++代碼（ https://github.com/LairdCP/UwTerminalX ）中遇到了如下所示的宏定義。

 #define SpeedModeInactive                 0b00
 #define SpeedModeRecv                     0b01
 #define SpeedModeSend                     0b10
 #define SpeedModeSendRecv                 0b11

當我嘗試使用Visual Studio 2010進行編譯時，出現以下錯誤。

Error   14  error C2059: syntax error : ')' 

這個宏的含義是什么？ 宏的用法如下所示。

if ((gchSpeedTestMode == SpeedModeSendRecv || gchSpeedTestMode == SpeedModeRecv) && (gintSpeedBytesReceived10s > 0 || ui->edit_SpeedBytesRec10s->text().toInt() > 0))
{
    //Data has been received in the past 10 seconds: start a timer before stopping to catch the extra data packets
    gchSpeedTestMode = SpeedModeRecv;
    gtmrSpeedTestDelayTimer = new QTimer();
    gtmrSpeedTestDelayTimer->setSingleShot(true);
    connect(gtmrSpeedTestDelayTimer, SIGNAL(timeout()), this, SLOT(SpeedTestStopTimer()));
    gtmrSpeedTestDelayTimer->start(5000);

    //Show message that test will end soon
    ui->statusBar->showMessage("Waiting 5 seconds for packets to be received... Click cancel again to stop instantly.");
}

Answer 1

這是因為Visual Studio無法識別二進制值（以0bXXX開頭），但是您可以像這樣簡單地將其定義為十六進制值：

#define SpeedModeInactive                 0x0
#define SpeedModeRecv                    0x1
#define SpeedModeSend                    0x2
#define SpeedModeSendRecv                0x3

二進制文字的使用最早是在C ++ 14中引入的，VS2010不支持該二進制文字， https： //en.wikipedia.org/wiki/C%2B%2B14#Binary_literals