llvm dev - Oct 2016 - unable to compile llvm with gcc 4.7.4

Why is it more important to be backward compatible with ancient versions of GCC
than relatively more recent versions of Visual Studio?  We are removing support
for VS2013 because of defects in that product, yet GCC v4.7.x is more ancient
than VS2013, so why should the answer be any different?

Devil's Advocate,

	MartinO

-----Original Message-----
From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Renato
Golin via llvm-dev
Sent: 11 October 2016 18:01
To: Sylvain Bertrand <sylvain.bertrand at gmail.com>
Cc: llvm-dev <llvm-dev at lists.llvm.org>; Peter Collingbourne <pcc at
google.com>
Subject: Re: [llvm-dev] unable to compile llvm with gcc 4.7.4

On 11 October 2016 at 17:35,  <sylvain.bertrand at gmail.com>
wrote:
> Those bots should have been the first to be set up. Hope you can fix this
soon.
We had 4.7 bots for a long time, but migrations happen, and we probably
(separately) didn't expect to be the last 4.7 ones. This was a coordination
problem.

Now, there are talks to upgrade the GCC version from 4.7, but we can't do
4.9 because many stable distributions still 4.8, but we can do 4.8, which has
enough buildbots (and will for the long term).

I'm not saying this is a "fix" for your problem, but your problem
would happen any time soon when we move the GCC version up anyway.

Can you upgrade to 4.8?

cheers,
--renato
_______________________________________________
LLVM Developers mailing list
llvm-dev at lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

To the best of my understanding - because we want to be able to bootstrap
clang with the system compiler that ships with various linux and BSD
distributions.
Windows has no equivalent concept.

(This is probably not a good enough reason to keep GCC 4.7 support, but it
apparently is for GCC 4.8).

Michael

On Tue, Oct 11, 2016 at 10:28 AM, Martin J. O'Riordan via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Why is it more important to be backward compatible with ancient versions
> of GCC than relatively more recent versions of Visual Studio?  We are
> removing support for VS2013 because of defects in that product, yet GCC
> v4.7.x is more ancient than VS2013, so why should the answer be any
> different?
>
> Devil's Advocate,
>
>         MartinO
>
> -----Original Message-----
> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of
> Renato Golin via llvm-dev
> Sent: 11 October 2016 18:01
> To: Sylvain Bertrand <sylvain.bertrand at gmail.com>
> Cc: llvm-dev <llvm-dev at lists.llvm.org>; Peter Collingbourne <
> pcc at google.com>
> Subject: Re: [llvm-dev] unable to compile llvm with gcc 4.7.4
>
> On 11 October 2016 at 17:35,  <sylvain.bertrand at gmail.com> wrote:
> > Those bots should have been the first to be set up. Hope you can fix
> this soon.
>
> We had 4.7 bots for a long time, but migrations happen, and we probably
> (separately) didn't expect to be the last 4.7 ones. This was a
coordination
> problem.
>
> Now, there are talks to upgrade the GCC version from 4.7, but we can't
do
> 4.9 because many stable distributions still 4.8, but we can do 4.8, which
> has enough buildbots (and will for the long term).
>
> I'm not saying this is a "fix" for your problem, but your
problem would
> happen any time soon when we move the GCC version up anyway.
>
> Can you upgrade to 4.8?
>
> cheers,
> --renato
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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+1 for calling 4.8 the minimum version. It appears that the last time 4.7
(at least, the one in ubuntu, "gcc-4.7 (Ubuntu/Linaro 4.7.3-12ubuntu1)
4.7.3") could actually compile clang was July 8th -- about 3 months ago.

Besides this reported error, it also doesn't like "<::", which
have been
introduced in various places, it has some issue with the lambda in
clang/lib/StaticAnalyzer/Checkers/MallocOverflowSecurityChecker.cpp (even
after the commit which says it fixes it), and possibly more issues besides
(I didn't attempt to comprehensively catalog the errors).

On Tue, Oct 11, 2016 at 1:28 PM, Martin J. O'Riordan via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Why is it more important to be backward compatible with ancient versions
> of GCC than relatively more recent versions of Visual Studio?  We are
> removing support for VS2013 because of defects in that product, yet GCC
> v4.7.x is more ancient than VS2013, so why should the answer be any
> different?
>
> Devil's Advocate,
>
>         MartinO
>
> -----Original Message-----
> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of
> Renato Golin via llvm-dev
> Sent: 11 October 2016 18:01
> To: Sylvain Bertrand <sylvain.bertrand at gmail.com>
> Cc: llvm-dev <llvm-dev at lists.llvm.org>; Peter Collingbourne <
> pcc at google.com>
> Subject: Re: [llvm-dev] unable to compile llvm with gcc 4.7.4
>
> On 11 October 2016 at 17:35,  <sylvain.bertrand at gmail.com> wrote:
> > Those bots should have been the first to be set up. Hope you can fix
> this soon.
>
> We had 4.7 bots for a long time, but migrations happen, and we probably
> (separately) didn't expect to be the last 4.7 ones. This was a
coordination
> problem.
>
> Now, there are talks to upgrade the GCC version from 4.7, but we can't
do
> 4.9 because many stable distributions still 4.8, but we can do 4.8, which
> has enough buildbots (and will for the long term).
>
> I'm not saying this is a "fix" for your problem, but your
problem would
> happen any time soon when we move the GCC version up anyway.
>
> Can you upgrade to 4.8?
>
> cheers,
> --renato
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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On 11 October 2016 at 21:46, Michael Kuperstein <mkuper at google.com>
wrote:
> (This is probably not a good enough reason to keep GCC 4.7 support, but it
> apparently is for GCC 4.8).
4.8 is the oldest shipped version on many stable LTS Linux and BSD
releases. Simple as that. :)

Upgrading to 4.9 or later will not be possible any time soon, due to
multiple bugs we're finding and fixing on newer versions of libstdc++,
glibc, binutils that is bundled with them.

So I am, and will be relying on 4.8 for the next year or so, and so
will many other people in the community (some more than a year).

cheers,
--renato

On 11 October 2016 at 16:46, Michael Kuperstein via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> To the best of my understanding - because we want to be able to bootstrap
> clang with the system compiler that ships with various linux and BSD
> distributions.
> Windows has no equivalent concept.
>
> (This is probably not a good enough reason to keep GCC 4.7 support, but it
> apparently is for GCC 4.8).
Also, as of January 1 2017 FreeBSD will have Clang 3.4.1 or newer as
the system compiler on all supported tier-1 architectures. I'm not
sure what other open source operating systems or distributions are
using Clang as their system compiler, but I suspect the same argument
for GCC 4.8 can be made for Clang 3.4 as a minimum.

For your information:

gcc 4.7.4 is the last C boostrapable c++98-ish compiler/runtime.

We are going towards a world where only a modern c++ compiler will be able to
compile a modern c++ compiler.

Once critical system components/applications are hard dependent on modern c++,
that will phase out C only compilers for any standard usage.

Coding a C only compiler alternative is a child play compared to coding a modern
c++
compiler alternative (even a non-optimizing, naive one).

As a consequence, it will kill in the egg many temptations to write
alternative compilers for standard usage.

my 2c,

-- 
Sylvain

On Tue, 11 Oct 2016 13:46:35 -0700
Michael Kuperstein via llvm-dev <llvm-dev at lists.llvm.org>
wrote:
> To the best of my understanding - because we want to be able to bootstrap
> clang with the system compiler that ships with various linux and BSD
> distributions.
> Windows has no equivalent concept.
To elaborate on this: if you want to produce binaries compatible with
old Linux systems, it is pretty much necessary to build on such an old
Linux system, because otherwise you'll get bitten by glibc ABI issues
(not to mention libstdc++, but at least you can link libstdc++
statically).

Windows has no such problem: you can redistribute a recent MSVCRT DLL
on an old Windows system.

Regards

Antoine.

> On Oct 11, 2016, at 1:46 PM, Michael Kuperstein via llvm-dev <llvm-dev
at lists.llvm.org> wrote:
> 
> To the best of my understanding - because we want to be able to bootstrap
clang with the system compiler that ships with various linux and BSD
distributions.
> Windows has no equivalent concept.
I mean no offense to linux/BSD developers, but should we have a discussion (in
another thread perhaps) about whether its reasonable to treat them specially in
this regard?

Both macOS and Windows developers need to download compilers separately to be
LLVM developers.  Why shouldn’t linux/BSD developers?

Given that we ship prebuilt binaries for many distros, it seems like its easy to
get a new enough compiler.  This way we won’t be faced with the problem of old
GCCs holding us back in future.

Pete
> 
> (This is probably not a good enough reason to keep GCC 4.7 support, but it
apparently is for GCC 4.8).
> 
> Michael
> 
> On Tue, Oct 11, 2016 at 10:28 AM, Martin J. O'Riordan via llvm-dev
<llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>>
wrote:
> Why is it more important to be backward compatible with ancient versions of
GCC than relatively more recent versions of Visual Studio?  We are removing
support for VS2013 because of defects in that product, yet GCC v4.7.x is more
ancient than VS2013, so why should the answer be any different?
> 
> Devil's Advocate,
> 
>         MartinO
> 
> -----Original Message-----
> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org
<mailto:llvm-dev-bounces at lists.llvm.org>] On Behalf Of Renato Golin via
llvm-dev
> Sent: 11 October 2016 18:01
> To: Sylvain Bertrand <sylvain.bertrand at gmail.com
<mailto:sylvain.bertrand at gmail.com>>
> Cc: llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at
lists.llvm.org>>; Peter Collingbourne <pcc at google.com <mailto:pcc
at google.com>>
> Subject: Re: [llvm-dev] unable to compile llvm with gcc 4.7.4
> 
> On 11 October 2016 at 17:35,  <sylvain.bertrand at gmail.com
<mailto:sylvain.bertrand at gmail.com>> wrote:
> > Those bots should have been the first to be set up. Hope you can fix
this soon.
> 
> We had 4.7 bots for a long time, but migrations happen, and we probably
(separately) didn't expect to be the last 4.7 ones. This was a coordination
problem.
> 
> Now, there are talks to upgrade the GCC version from 4.7, but we can't
do 4.9 because many stable distributions still 4.8, but we can do 4.8, which has
enough buildbots (and will for the long term).
> 
> I'm not saying this is a "fix" for your problem, but your
problem would happen any time soon when we move the GCC version up anyway.
> 
> Can you upgrade to 4.8?
> 
> cheers,
> --renato
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
> 
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
> 
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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