Re: [Audacity-devel] Can we upgrade our required gcc version? Travis is using a five year old version.

[Paul L. <pau...@gm...>]

I'd like to get us using C++11 language and library features but I am not
the Unix and gcc expert here.

Let's see:  when did gcc deprecate the "std=c++0x" option and start calling
it "std=c++11" ?  I Googled online documentation for some versions.

4.6.4 (last 4.6) says:

"The ISO C++ committee is working on a new ISO C++ standard, dubbed C++0x,
that is intended to be published by 2009. C++0x contains several changes to
the C++ language, some of which have been implemented in an experimental
C++0x mode in GCC."

4.7.0 says:

"A fourth version of the C standard, known as C11, was published in 2011 as
ISO/IEC 9899:2011. GCC has limited incomplete support for parts of this
standard, enabled with -std=c11 or -std=iso9899:2011. (While in
development, drafts of this standard version were referred to as C1X.)"

4.8.0 says the same.

4.9.0 says:

"A fourth version of the C standard, known as C11, was published in 2011 as
ISO/IEC 9899:2011. GCC has substantially complete support for this
standard, enabled with -std=c11 or -std=iso9899:2011. (While in
development, drafts of this standard version were referred to as C1X.) "

4.9.3 says the same.

So it seems 4.7 was the earliest that was good enough to call it -std=c++11
despite some incompletenesses.  Is that the conservative choice then?

PRL



On Sun, Feb 7, 2016 at 12:18 PM, Richard Ash <ri...@au...>
wrote:

> On Fri, 5 Feb 2016 13:01:42 -0800 (PST)
> Bill Unruh <un...@ph...> wrote:
> > > Debian Stable, which tends to be slow to update, has gcc 4.9.2,
> > > which gives it 'experimental' C++11 support.
> > > https://gcc.gnu.org/projects/cxx0x.html
> >
> > Mageia 5 which is the latest version of a distro which tends to be
> > toward the "bleeding edge" has gcc 4.9.2.
> 4.8.x seems to be a good minimum version:
> * Ubuntu 14.04 (latest Long Term support release) comes with gcc 4.8.2,
>   so Mint inherits the same
> * OpenSUSE Leap (as opposed to Tumbleweed) is at GCC 4.8.
> * Fedora 19 shipped GCC 4.8 - this was the base for Centos 7 - and
>   Fedora are now on version 23.
> * Gentoo has 4.9 stable on all architectures except Sparc (which is
>   pretty niche these days)
>
> I suspect GCC 5 will take a while to be widespread, because it breaks
> C++ ABI (meaning rebuilding ever C++ package on the system), and is
> reported to cause problems compiling quite a few packages still.
>
> The other question is Mac OS. Someone with a Mac development system
> will have to say what GCC version we get there, because it probably
> won't be trivial to upgrade that. The latest Xcode switches from GCC to
> Clang, but I don't think we are using that yet.
>
> > Mageia 3 which is now about
> > 2 years old is 4.7.2.
> > Redhat which has a 7 year support -- the opensource version, CentOS
> > 6.7 has gcc 4.4.7.
> > So I guess it depends on how much you want to support older, but
> > widely used versions.
> I don't think support for either of these is particularly relevant.
> RedHat / CentOS exists on a "time-warp" basis - whatever was current
> when the warp was frozen, is what continues for the whole support life.
> So the same should apply to Audacity, users who opt into the time warp
> get to keep whatever old version of Audacity was current at that time.
> The maintenance impact of not doing so is high, because the time warp
> will also mean old versions of all the libraries we use, which causes
> complexity we can't support.
>
> One final thing - we should have a configure test for whatever compiler
> features we use, so that if someone tries to compile with too old a
> compiler, they will get an error at that stage. This can then test the
> various possible compiler flags to find out which one a given compiler
> needs to build our code.
>
> Richard
>
>
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