policy on c++11 in source code

henry7638@gmail.com hank at millerfarm.com
Fri Oct 21 08:35:21 UTC 2011

Milian Wolff <mail at milianw.de> wrote:

>Four years is a bit much. Maybe if we'd use all of C++11 but imo noone 
>suggests that. Rather it's about cherry-picking nice features that are 
>available already and work well and improve productivity. >
>Anyhow, I also think that a year will at least be required. Or well,
>have to wait until the BSD guys have ditched the outdated GCC in favor
>of a 
>current CLang ;-)

If we intend to wait until all the world is ready for C++11, then 4 years is optimistic. Not only does Clang need to become ready, but also we need to wait for the current releases to become non-supported. BSD supports current ports running a couple versions back.

However we do not have to wait. FreeBSD has support for installing latter versions of gcc. Default is /usr/bin/gcc. We can use /usr/local/bin/gcc47, it just needs to explicate that we need this. If we find a subset of C++11 that is already supported (something the gcc 4.5, clang 2.9, visual studio 2010, etc), documenting the minimum required compiler is the minimum required.

Ideally someone would write a cmake macro to require some minimum compiler based on features, that would modify the current macro to keep looking if the default compiler isn't enough. Then add some analysis tools (krazy?) To give warnings if someone introduces code that isn't in the allowed subset. 

The above would help all C++ projects, so feel free to suggest the idea to someone outside kdevelop who might better know how to pull it off. 

I think the above is the right focus for efforts to get C++11 used for now. I don't know how to find the right subset. Compilers may have something checked off as working, but they missed some obscure case. Compilers are known to have released support before the standard, only to have the standard be different. Both situations to watch for.

( what follows are BSD related, and not really related to the important part of the discussion. Feel free to stop reading here)

As for clang, FreeBSD already boots when compiled with it, and 15000 ports compile as well, but that leaves several thousand that don't: some assume gcc, some hit clang bugs. Unknown if there are random breakages in any of the ports that compile. These are being worked on. 

I don't know what the other BSDs are doing. OpenBSD is looking at pcc as their compiler, and then all C++ would come from a user installed compiler not the base system. NetBSD needs support for targets that are not in LLVM. Both of the above have seen some effort into using Clang though,and might switch directions. 

Clang will probably take the longest to get full C++11 support since they have more serious known bugs to fix before adding more features. However the supported parts are useful.
Sent from my Android phone with K-9 Mail. Please excuse my brevity.
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