[Development] clang and auto-setting of QT_NO_EXCEPTIONS

[Thiago Macieira]

On Thursday, 25 May 2017 12:14:09 PDT René J. V. Bertin wrote:
> Thiago Macieira wrote:
> > It's a bug in your testing, because it sets QT_NO_EXCEPTIONS here with
> > Clang.
> No it's not, ditto for testing by others. In fact, your test is wrong
> because it misses a detail: this concerns ObjC++.

You never mentioned ObjC++.

However:
$ clang -std=c++14 -fno-exceptions -I. -include QtCore/qglobal.h -fPIC 
-xobjective-c++ -c -o /dev/null - <<<'
#ifndef QT_NO_EXCEPTIONS
# error Was not defined
#endif'
[nothing]

So it still works.

I also tested four different Clang versions: 3.8, 3.9, 4.0 and trunk (5.0). 
What's more, this used to work when Clang 3.6 was current. It even used to 
work when 2.8 was current, because this has never needed updates.

> See
> http://releases.llvm.org/3.6.0/tools/clang/docs/ReleaseNotes.html#the-excep
> tions-macro :
> 
> It explains rather unambiguously that clang 3.6 and later set _EXCEPTIONS
> `if C++ or ObjC exceptions are enabled` and that `To reliably test if C++
> exceptions are enabled, use _EXCEPTIONS && __has_feature(cxx_exceptions),
> else things won’t work in all versions of Clang in Objective-C++ files.`

We're testing __EXCEPTIONS, like we should.

Please describe the environment in which:
 a) -fno-exceptions is active
 b) __EXCEPTIONS is defined

Provide the full command-line and the compiler version.

I still advise you to look into what's wrong with your testing, because I 
can't reproduce it.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center