CODEWITHSUNDEEP
c++visual-studio-2013
BRabbit27
BRabbit27

Reputation: 6633

Variadic macro in VS2013 not valid

I am trying to compile the example from QtSocketIO called EchoClient.

However when I try to compile using MSVC2013, I get the following error in the echoclient.cpp

1> echoclient.cpp

1>echoclient.cpp(7): error C2010: '.' : unexpected in macro formal parameter list

The code looks like this where I have put as comments the errors in each line

#include "echoclient.h"
#include "qsocketioclient.h"
#include <QtCore/QJsonObject>
#include <QtCore/QJsonArray>
#include <QtCore/QDebug>
    
#define function(args...) [=](args)   // Error expected a ')'

void EchoClient::connected(QString endpoint)
{
    qDebug() << "Connected to endpoint" << endpoint;
    m_client.emitMessage("event with 2 arguments", 
                         QVariantList() << 1 << QStringLiteral("Hello socket.io"),
                         function(QJsonArray returnValue) {  // Error expected an expression
        qDebug() << "Got reply from event with 2 arguments:" << returnValue;
    });
    m_client.emitMessage("event with a json object",
                         QVariantMap({ {"number", 1}, { QStringLiteral("message"), 
                         QStringLiteral("Hello socket.io")}}),
                         function(QJsonArray returnValue) { // Error expected an expression
        qDebug() << "Got reply from event with a json object:" << returnValue;
    });
    m_client.on("event from server", function(QJsonArray data) { // Error expected an expression
        qDebug() << "Got event from server with data" << data;
    });
}

Can someone explain to me what does that macro is doing? Is there a way to solve the error?

Upvotes: 0

Views: 323

Answers (1)

Weak to Enuma Elish
Weak to Enuma Elish

Reputation: 4637

The macro is making a lambda look sort of like an ordinary function declaration. The reason it doesn't work is because, as mentioned in the comments, #define function(args...) [=](args) isn't correct. Changing it to #define function(...) [=](__VA_ARGS__) will work.

Upvotes: 1

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