[Development] Clang (trunk) no longer builds Qt applications

[Tobias Hunger]

Hello,

I just noticed that clang from trunk is no longer able to build Qt 
applications. This is due to a change which makes clang consider "break" 
statements outside of a loop body or switch statement illegal.

Unfortunately this triggers on each Q_FOREACH/foreach used by Qt 
applications!


The following code:

QList<QObject *> m_components << obj1 << obj2;
foreach (QObject *component, m_components) {
     ...
}

will get expanded to:


for (QForeachContainer<__typeof__(m_components)> 
_container_(m_components); !_container_.brk && _container_.i != 
_container_.e; __extension__ ({ ++_container_.brk; ++_container_.i; })) 
for (QObject *component = *_container_.i;; __extension__ 
({--_container_.brk; break;})) {
     ...
}

which Clang now considers an error and will produce the following message


.... error: 'break' statement not in loop or switch statement body


stopping the build.



Apparently that is exactly what the C++ standard requires. Based on my 
limited understanding of the details of the standard the condition in 
the for statement is not part of the loop body. Is there somebody with a 
deeper knowledge of the standard that can provide some insights here?



http://llvm.org/viewvc/llvm-project?view=revision&revision=193073 is the 
relevant change that introduced this diagnosis into clang.

http://llvm.org/bugs/show_bug.cgi?id=17650 is the bug I just filed with 
Clang, making them aware that they broke the build of basically all Qt 
applications out there. The commit massage states that gcc rejects the 
code -- which is wrong as I can build QtC fine using gcc.

I hope the clang project will consider to disable this patch (or at 
least have a switch to turn it off again).

But IMHO we need to address this in Qt, too.

Best Regards,
Tobias

-- 
Tobias Hunger, Senior Software Engineer - Digia, Qt
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