Hi!
On 04/22/11 11:17, David Timms wrote:
> I'm having trouble with building dvbcut [1] for Fedora 15. It occurs on
> both an F15 beta machine and in mock from F14, on both i386 and x86_64.
>
> The error is:
> =====
> dvbcut.cpp: In member function 'virtual void
> dvbcut::eventlistcontextmenu(QListBoxItem*, const QPoint&)':
>
> dvbcut.cpp:1328:60: error: invalid initialization of reference of type
> 'EventListItem&' from expression of type 'const EventListItem'
Honestly, I don't understand why the code is casting something non-const
to something const, dereferencing it, and then passing that to a
non-const reference. That's one of these ugly pieces of C++ hackery I
really abhor.
The `const' is definitely wrong because the EventListItem& must refer to
a mutable object. Besides that, I don't know why Sven decided to use a
reference at that point.
Try removing the `const' keyword in line 1328 and recompiling. And don't
forget to let me know if that helps. I can't compile dvbcut with gcc
4.6.0 at all because g++ complains about ptrdiff_t not being a type in
several Qt header files the code includes. I suppose that's something
that should be fixed in the Qt3 source code, though, not in dvbcut.
New compilers suck, and new C++ compilers in particular.
> dvbcut.cpp: In member function 'void
> dvbcut::open(std::list<std::basic_string<char> >, std::string,
> std::string)':
>
> dvbcut.cpp:1863:57: warning: ignoring return value of 'int chdir(const
> char*)', declared with attribute warn_unused_result [-Wunused-result]
> make[1]: *** [dvbcut.o] Error 1
If `chdir("/");' doesn't work, you're probably running a really strange
operating system.
> make[1]: Leaving directory `/builddir/build/BUILD/dvbcut-svn170/src'
> make: *** [all] Error 2
> =====
> The source [2] hasn't changed, so I guess gcc has gained the ability to
> check for this sort of problem, and exits.
>
> Is that code dodgy/risky ?
In principle, using static_cast is unsafe because there's no type check.
You could use a dynamic_cast instead, but then you would have to check
if the result is != 0, and return otherwise. On the other hand, all list
members are supposed to be of type EventListItem, so you can as well
avoid the overhead of a run-time type check and use static_cast. Just
without the `const'.
--
Michael "Tired" Riepe <mich...@mr511.de>
X-Tired: Each morning I get up I die a little
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