diff options
| author | Marc Mutz <marc.mutz@kdab.com> | 2012-03-02 11:51:52 +0100 |
|---|---|---|
| committer | Qt by Nokia <qt-info@nokia.com> | 2012-03-08 23:58:08 +0100 |
| commit | 73a5ce5195bc27acf02d787787a69ec493c037c2 (patch) | |
| tree | 23319a94f7a34f0440decd5e68cfdc7219d1d06b /src/corelib/global | |
| parent | dbab994b2cdc5469cf53e3f6c5d09bc2d7b39ce9 (diff) | |
QVariant: fix HasIsNullMethod for final classes
HasIsNullMethod uses the accepted C++98 idiom to
check for members that might be inherited from
baseclasses.
The technique, however, requires inheriting from
the type-under-test, which fails for C++11 final
classes.
Fortunately, under C++11 we have much better
support for static type introspection: sfinae
for expressions. We use this here (see decltype()
use in qvariant_p.h) to write a C++11 version of
HasIsNullMethod that works with final classes, too.
However, since this technique required decltype()
support in the compiler, Q_DECL_FINAL can no longer
be used for both method and class markup. So we
declare a new Q_DECL_FINAL_CLASS which is only
set iff the compiler supports decltype(), too.
MSVC 2005 and 2008 support a non-standard, but
sufficiently compatible, version of override/final,
but no decltype(). A later patch will use MSVC
'override/'sealed' to implement Q_DECL_{OVERRIDE,FINAL}
for these compilers, but I currently don't see a
version of HasIsNullMethod that could support these
two, so the split off of Q_DECL_FINAL_CLASS is in
anticipation of that commit. If someone _does_ find
an implementation of HasIsNullMethod that works on
MSVC2005 and 2008 sealed classes, then it's a simple
matter of s/Q_DECL_FINAL_CLASS/Q_DECL_FINAL/g.
This code has been tested on GCC 4.7 (prerelease)
and GCC 4.8 (prerelease).
Change-Id: I8700c8307d79a74d45fef0aec1c6027b4a922a43
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@nokia.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Diffstat (limited to 'src/corelib/global')
| -rw-r--r-- | src/corelib/global/qglobal.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/src/corelib/global/qglobal.h b/src/corelib/global/qglobal.h index 99328d52ac..d0d6e851ad 100644 --- a/src/corelib/global/qglobal.h +++ b/src/corelib/global/qglobal.h @@ -415,9 +415,15 @@ QT_END_INCLUDE_NAMESPACE #ifdef Q_COMPILER_EXPLICIT_OVERRIDES # define Q_DECL_OVERRIDE override # define Q_DECL_FINAL final +# ifdef Q_COMPILER_DECLTYPE // required for class-level final to compile in qvariant_p.h +# define Q_DECL_FINAL_CLASS final +# else +# define Q_DECL_FINAL_CLASS +# endif #else # define Q_DECL_OVERRIDE # define Q_DECL_FINAL +# define Q_DECL_FINAL_CLASS #endif //defines the type for the WNDPROC on windows |