Compile error in qjsonrpcservice.cpp (gcc 4.6.3-1ubuntu5 and Qt 4.8.2)

[Ricardo Costa]

I get the following error when compiling on Ubuntu 12.04 with GCC 4.6.3 and Qt 4.8.2:

../../src/qjsonrpcservice.cpp: In function ‘QVariant convertArgument(const QJsonValue&, const QJsonRpcServicePrivate::ParameterInfo&)’:
../../src/qjsonrpcservice.cpp:211:40: error: call of overloaded ‘QVariant(const int&, NULL)’ is ambiguous
../../src/qjsonrpcservice.cpp:211:40: note: candidates are:
/usr/include/qt4/QtCore/qvariant.h:436:12: note: QVariant::QVariant(bool, int)
/usr/include/qt4/QtCore/qvariant.h:170:5: note: QVariant::QVariant(int, const void*)
../../src/qjsonrpcservice.cpp: In member function ‘bool QJsonRpcService::dispatch(const QJsonRpcMessage&)’:
../../src/qjsonrpcservice.cpp:328:67: error: call of overloaded ‘QVariant(QMetaType::Type&, NULL)’ is ambiguous
../../src/qjsonrpcservice.cpp:328:67: note: candidates are:
/usr/include/qt4/QtCore/qvariant.h:436:12: note: QVariant::QVariant(bool, int)
/usr/include/qt4/QtCore/qvariant.h:170:5: note: QVariant::QVariant(int, const void*)

Replacing NULL by C++11's nullptr keyword on both call sites solves the problem.

[Matt Broadstone]

hmm, we can't use nullptr since we can't assume c++11 support until qt5. Unfortunately I also don't have access to such an old version of Qt, could you propose a portable alternative? Perhaps one that we can include just as an ifdef for Qt < 4.8.6

[Ricardo Costa]

Hm yes, we can explicitly cast NULL to const char* to avoid the ambiguity, as follows:

Line 211: return QVariant(info.type, (const char*)NULL);

Line 328: QVariant() : QVariant(returnType, (const char*)NULL);

[Matt Broadstone]

Can you please try building the "issue-14" branch and let me know if it compiles fine on your version of Qt? I suspect this change made it in from another submitted PR, as I generally don't use the NULL keyword (simply using 0 might have worked as well).

[Matt Broadstone]

@ricardoglc ping. can you try compiling this branch to see if the patch fixes your issue?

[Ricardo Costa]

Yes, tested it today and it works fine. Thanks.

[Matt Broadstone]

thanks, merged in with c7b7bff