[Interest] QMetaMethod::invoke / Q_ARG with a temporary

[Giuseppe D'Angelo]

Il 07/05/2018 20:24, Christian Ehrlicher ha scritto:
> I did not found a hint int the documentation about this behavior.
> Therefore my question - should this work for a queued connection or not?
> At least msvc2017 and gcc 4.8 don't like it when compiling with -O2...

The documentation doesn't talk about QArgument, but about Q_ARG and 
Q_RETURN_ARG, which is what you should use.

(Under the hood, the problem is that QArgument simply stores a pointer 
to your variable. If that variable is a temporary, that pointer becomes 
immediately dangling. For this reason, do not store what Q_ARG builds, 
e.g. in an variable declared auto!)

HTH,
-- 
Giuseppe D'Angelo | giuseppe.dangelo at kdab.com | Senior Software Engineer
KDAB (France) S.A.S., a KDAB Group company
Tel. France +33 (0)4 90 84 08 53, http://www.kdab.com
KDAB - The Qt, C++ and OpenGL Experts

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