Re: [Getfem-users] C++11 in Getfem

[Konstantinos Poulios]

Dear all,

I had interpreted Andriy's question, as if getfem++ should use C++11 by default or not. I now see that the actual question is if it is ok for getfem++ to depend on C++11. My opinion is that at some point soon or later getfem++ (like also many other software projects) will depend on C++11 anyway. So the actual question is when.

A dependence on C++11 will not affect me personally and packaging for future Linux distribution is not a problem either because most of them come with gcc 4.8 anyway. One problem that I see is with people that may need to compile getfem++ on e.g. university clusters with older linux distributions like Ubuntu 12.04 and CentOS. I think it is common for university clusters to run on outdated --some call it stable-- linux distributions with older compiler versions. So making C++11 a hard dependence may affect some people for the next 1-2 years or so.

I think a realistic approach is to release the next version (soon) without depending on C++11 and merge all C++11 specific features just after the release. In any case I would recommend to give it a more technical thought before doing the switch, in the sense that Yves mentioned in his email.

Btw. some code clean up would also be very welcome but I think this also fits better after the next stable release.

Best regards

Kostas

On Wed, Mar 19, 2014 at 1:13 PM, Yves Renard <address@hidden> wrote:

Dear All,

What made me hesitate to definitely switch to C++11 is the fact that the version of gcc on the stable release of Ubuntu (2012) is gcc 4.6.4. that does not support C++11. Consequently, caution rather led me to wait a little longer (namely 2017 the next stable version of Ubuntu). In addition, I did not personally need the new features of C++11 for the moment (of course, I would not have developed the library gmm in the same way with the features of C++11 if it had been available in the early 2000s!).
But of course, I understand Andriy who sees the interest to use these new features. Three years is a little bit long. I am not against the switch but it will force us to use at least gcc 4.8  and force the update of a few things in the code (such as obsolescence of auto_ptr).

In conclusion, has anybody some further arguments against the switch ?

If not, I think I will check carrefully the compatibility of Getfem sources to gcc 4.8 and  enforce C++11 ...

Yves.



Le 19/03/2014 12:08, Andriy Andreykiv a écrit :

Dear Kostas and Getfem users,

At our company we build Getfem on Windows with Intel C++ as well as MSVS 2012 C++

and on Linux with GCC 4.81. As far as I know Clang supports 11th standard too. 

These are major C++ compilers (correct me if I"m wrong) and all of them 

happily support major C++11 features.

What you, Kostas, are proposing, about conditional compilation of 11th features, sure possible, but 

is really a big burden to maintain, at least for our side. Imagine if I use Lambda's and auto's and then 

I have to conditionally provide code for the case C++11 is not enabled, then I have to sometimes 

re-design several functions. If I have to do that, then I have no reasons to use 11th features at all.

I do use conditional compilation now and then, during implementation of multithreaded assembly. 

It, sure, makes sense for performance reasons, but C++11 is always available and not such a reason. 

Given the above I would propose to Getfem community to have 11th standard enforced by default,

and allow code that compiles only with C++11 on. Please tell me what you think about this.

Best regards,

                      Andriy

On 19 March 2014 11:17, Konstantinos Poulios <address@hidden> wrote:

Dear Andriy,

actually the intention of my change was getfem to support C++11 by default if the compiler supports it by default.

Are you using msvc or gcc? I thought that my change would affect only compiling with gcc which officially does not support c++11 by default.

Even with gcc one can still enable c++11 by adding the appropriate CXXFLAGS at running the configure script.

Within getfem we just need to use
#if __cplusplus > 199711L

#endif

conditionals for features that depend on C++11.

Is there any practical issue that I am forgetting here?

Best regards

Kostas

On Wed, Mar 19, 2014 at 10:26 AM, Andriy Andreykiv <address@hidden> wrote:

Dear Getfem users,

Currently, Getfem is configured by default not to support C++11 (revision 4536).

May I ask why?  I would really want to have it supported. I like to use lambda's auto's and the new for loop syntax in my code, but,

more importantly, C++11 includes libraries that otherwise have to be included through Boost (I'm using at least <thread> and <atomic>)

Best regards,

                        Andriy

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  Yves Renard (address@hidden)       tel : (33) 04.72.43.87.08
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