<![CDATA[Macro inside macro: Q_DECLARE_METATYPE]]>Hi,

I noticed that the Q_DECLARE_METATYPE macro contains another macro in this line:

@static QBasicAtomicInt metatype_id = Q_BASIC_ATOMIC_INITIALIZER(0); @

How is Q_BASIC_ATOMIC_INITIALIZER expanded inside this macro? I thought you couldn't use a macro inside another macro.

I'm asking because I register types in my program using my own macro, and it'd be helpful if I could register the type to Qt at the same time. Right now, I call both MY_TYPE_REGISTER_MACRO(MyClass) and Q_DECLARE_METATYPE(MyClass) in my program.

]]>https://forum.qt.io/topic/35667/macro-inside-macro-q_declare_metatypeRSS for NodeTue, 22 Sep 2026 15:37:55 GMTThu, 19 Dec 2013 03:33:04 GMT60<![CDATA[Reply to Macro inside macro: Q_DECLARE_METATYPE on Thu, 19 Dec 2013 11:38:46 GMT]]>Hmm... You're right, I must have done something wrong when I tried to include Q_DECLARE_METATYPE in my macro.

It's funny (well, not really :)) how you can program for years and still miss basic stuff like this. It even says in one of the docs you linked to (thanks for that!) " Recall that all macro definitions are rescanned for more macros to replace". For some reason I took for granted that the preprocessor only runs a single scan.

Thanks again, if I cant get my modified macro to work I may drop another message. :)

]]>https://forum.qt.io/post/207944https://forum.qt.io/post/207944Thu, 19 Dec 2013 11:38:46 GMT<![CDATA[Reply to Macro inside macro: Q_DECLARE_METATYPE on Thu, 19 Dec 2013 07:43:49 GMT]]>macros can be nested. Of course there are some "pitfalls":http://gcc.gnu.org/onlinedocs/cpp/Macro-Pitfalls.html#Macro-Pitfalls.
Do you receive an error?

]]>https://forum.qt.io/post/207906https://forum.qt.io/post/207906Thu, 19 Dec 2013 07:43:49 GMT