[gentoo-dev] moving gcc-5.2 to unstable

[gentoo-dev] moving gcc-5.2 to unstable

[Mike Frysinger]

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what do people want to have in place before we move gcc-5.2 into ~arch ?

the general list looks pretty good:
	https://bugs.gentoo.org/536984

the only glaring issue is the C++11 ABI breakage:
	https://bugs.gentoo.org/542482

we already posted a news item when the breakage started in gcc-4.7:
	https://archives.gentoo.org/gentoo-dev/message/4fa0c84858b4df49668da20302fc5b6f

but since gcc-5.x makes this the new default standard, more people are going to
run into it, so we probably want a reminder.  do we want any sort of automation
otherwise here ?
-mike

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Re: [gentoo-dev] moving gcc-5.2 to unstable

[Alexandre Rostovtsev]

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On Thu, 2015-10-01 at 09:49 -0400, Mike Frysinger wrote:
> what do people want to have in place before we move gcc-5.2 into ~arch ?

For one thing, the fix for runtime failure in 64-bit wine:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66838
https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=225935

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Re: [gentoo-dev] moving gcc-5.2 to unstable

[Mike Frysinger]

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On 01 Oct 2015 10:11, Alexandre Rostovtsev wrote:
> On Thu, 2015-10-01 at 09:49 -0400, Mike Frysinger wrote:
> > what do people want to have in place before we move gcc-5.2 into ~arch ?
> 
> For one thing, the fix for runtime failure in 64-bit wine:
> 
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66838
> https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=225935

did you file a bug for toolchain@ ?  i'm not seeing one.
changes don't go in w/out a bug on our side.
-mike

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Re: [gentoo-dev] moving gcc-5.2 to unstable

[Georg Rudoy]

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2015-10-01 16:49 GMT+03:00 Mike Frysinger <vapier@gentoo.org>:

> what do people want to have in place before we move gcc-5.2 into ~arch ?
>

Just letting know that gcc 5 isn't compatible with clang due to
https://llvm.org/bugs/show_bug.cgi?id=23529

Setting gcc as a primary compiler will effectively make programs
non-buildable with clang (and perhaps icc, not sure about its status).

-- 
  Georg Rudoy

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Re: [gentoo-dev] moving gcc-5.2 to unstable

[Alexandre Rostovtsev]

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On Thu, 2015-10-01 at 10:24 -0400, Mike Frysinger wrote:
> On 01 Oct 2015 10:11, Alexandre Rostovtsev wrote:
> > On Thu, 2015-10-01 at 09:49 -0400, Mike Frysinger wrote:
> > > what do people want to have in place before we move gcc-5.2 into
> > > ~arch ?
> > 
> > For one thing, the fix for runtime failure in 64-bit wine:
> > 
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66838
> > https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=225935
> 
> did you file a bug for toolchain@ ?  i'm not seeing one.
> changes don't go in w/out a bug on our side.
> -mike

https://bugs.gentoo.org/show_bug.cgi?id=549768 - now reassigned from
wine to toolchain :)

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Re: [gentoo-dev] moving gcc-5.2 to unstable

[Anthony G. Basile]

On 10/1/15 9:49 AM, Mike Frysinger wrote:
> what do people want to have in place before we move gcc-5.2 into ~arch ?
>
> the general list looks pretty good:
> 	https://bugs.gentoo.org/536984
>
> the only glaring issue is the C++11 ABI breakage:
> 	https://bugs.gentoo.org/542482
>
> we already posted a news item when the breakage started in gcc-4.7:
> 	https://archives.gentoo.org/gentoo-dev/message/4fa0c84858b4df49668da20302fc5b6f
>
> but since gcc-5.x makes this the new default standard, more people are going to
> run into it, so we probably want a reminder.  do we want any sort of automation
> otherwise here ?
> -mike

A reminder message with suggestions about how to upgrade safely would be 
good.

-- 
Anthony G. Basile, Ph.D.
Gentoo Linux Developer [Hardened]
E-Mail    : blueness@gentoo.org
GnuPG FP  : 1FED FAD9 D82C 52A5 3BAB  DC79 9384 FA6E F52D 4BBA
GnuPG ID  : F52D4BBA

[gentoo-dev] Re: moving gcc-5.2 to unstable

[Ryan Hill]

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On Thu, 1 Oct 2015 09:49:47 -0400
Mike Frysinger <vapier@gentoo.org> wrote:

> what do people want to have in place before we move gcc-5.2 into ~arch ?
> 
> the general list looks pretty good:
> 	https://bugs.gentoo.org/536984

IMO these should be fixed before we unmask:

   546742: x11-apps/sessreg-1.1.0 fail to build with gcc5
   547626: dev-lang/python-3.3 / 3.4 test_faulthandler hangs with GCC 5.1
   547950: app-shells/zsh-5.0.7-r2 builds but has runtime errors with GCC 5
   555866: media-libs/phonon-4.8.3-r1[qt5] fails to build with gcc-5

Just because they're common packages that lots of people will have installed.
Also they all have patches.

> the only glaring issue is the C++11 ABI breakage:
> 	https://bugs.gentoo.org/542482
> 
> we already posted a news item when the breakage started in gcc-4.7:
> 	https://archives.gentoo.org/gentoo-dev/message/4fa0c84858b4df49668da20302fc5b6f
> 
> but since gcc-5.x makes this the new default standard, more people are going
> to run into it, so we probably want a reminder.  do we want any sort of
> automation otherwise here ?

I think we need a news item to remind people they really do have to emerge -e
@world after this one or they could have a bad time.

FWIW I updated one system from 4.9 to 5.2 by rebuilding ~700 packages in random
order just to see how bad the ABI breakage would be and only ran into it once.
I may have just gotten lucky though.


-- 
Ryan Hill                        psn: dirtyepic_sk
   gcc-porting/toolchain/wxwidgets @ gentoo.org

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Re: [gentoo-dev] Re: moving gcc-5.2 to unstable

[Mike Frysinger]

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On 02 Oct 2015 02:21, Ryan Hill wrote:
> IMO these should be fixed before we unmask:
> 
>    546742: x11-apps/sessreg-1.1.0 fail to build with gcc5
>    547626: dev-lang/python-3.3 / 3.4 test_faulthandler hangs with GCC 5.1
>    547950: app-shells/zsh-5.0.7-r2 builds but has runtime errors with GCC 5

done

>    555866: media-libs/phonon-4.8.3-r1[qt5] fails to build with gcc-5

it already has a patch that's been merged upstream, so just waiting on the kde
guys to actually merge it.  i don't think we need to block gcc-5 unmasking on it
if it's not going to get merged any time soon.

also it relies on USE=qt5 (my qt4 builds are fine).  not sure the distribution
of those flags in practice.

> > the only glaring issue is the C++11 ABI breakage:
> > 	https://bugs.gentoo.org/542482
> > 
> > we already posted a news item when the breakage started in gcc-4.7:
> > 	https://archives.gentoo.org/gentoo-dev/message/4fa0c84858b4df49668da20302fc5b6f
> > 
> > but since gcc-5.x makes this the new default standard, more people are going
> > to run into it, so we probably want a reminder.  do we want any sort of
> > automation otherwise here ?
> 
> I think we need a news item to remind people they really do have to emerge -e
> @world after this one or they could have a bad time.

feel like writing it ? ;)

> FWIW I updated one system from 4.9 to 5.2 by rebuilding ~700 packages in random
> order just to see how bad the ABI breakage would be and only ran into it once.
> I may have just gotten lucky though.

i upgraded gradually and it wasn't that much of a hassle, but it helps to know
how to read the failing logs/symbols.  so an empty world would be OK.
-mike

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Re: [gentoo-dev] Re: moving gcc-5.2 to unstable

[Mike Gilbert]

On Fri, Oct 2, 2015 at 4:21 AM, Ryan Hill <rhill@gentoo.org> wrote:
> On Thu, 1 Oct 2015 09:49:47 -0400
> Mike Frysinger <vapier@gentoo.org> wrote:
>
>> what do people want to have in place before we move gcc-5.2 into ~arch ?
>>
>> the general list looks pretty good:
>>       https://bugs.gentoo.org/536984
>
> IMO these should be fixed before we unmask:
>
>    546742: x11-apps/sessreg-1.1.0 fail to build with gcc5
>    547626: dev-lang/python-3.3 / 3.4 test_faulthandler hangs with GCC 5.1
>    547950: app-shells/zsh-5.0.7-r2 builds but has runtime errors with GCC 5
>    555866: media-libs/phonon-4.8.3-r1[qt5] fails to build with gcc-5
>
> Just because they're common packages that lots of people will have installed.
> Also they all have patches.
>
>> the only glaring issue is the C++11 ABI breakage:
>>       https://bugs.gentoo.org/542482
>>
>> we already posted a news item when the breakage started in gcc-4.7:
>>       https://archives.gentoo.org/gentoo-dev/message/4fa0c84858b4df49668da20302fc5b6f
>>
>> but since gcc-5.x makes this the new default standard, more people are going
>> to run into it, so we probably want a reminder.  do we want any sort of
>> automation otherwise here ?
>
> I think we need a news item to remind people they really do have to emerge -e
> @world after this one or they could have a bad time.

I was able to get by with a targeted revdep-rebuild run.

revdep-rebuild --library 'libstdc\+\+\.so\.6'

The backslashes are significant since revdep-rebuild passes the
expression to grep -E.

Is there any reason to rebuild programs that do not link with the C++
standard library?

Re: [gentoo-dev] Re: moving gcc-5.2 to unstable

[Brian Evans]

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On 10/2/2015 10:27 AM, Mike Gilbert wrote:
> On Fri, Oct 2, 2015 at 4:21 AM, Ryan Hill <rhill@gentoo.org>
> wrote:
>> On Thu, 1 Oct 2015 09:49:47 -0400 Mike Frysinger
>> <vapier@gentoo.org> wrote: I think we need a news item to remind
>> people they really do have to emerge -e @world after this one or
>> they could have a bad time.
> 
> I was able to get by with a targeted revdep-rebuild run.
> 
> revdep-rebuild --library 'libstdc\+\+\.so\.6'
> 
> The backslashes are significant since revdep-rebuild passes the 
> expression to grep -E.
> 
> Is there any reason to rebuild programs that do not link with the
> C++ standard library?
> 

I would propose:
revdep-rebuild --library 'libstdc\+\+\.so\.6' -- --exclude sys-devel/gcc

I don't think we really need to have gcc rebuild itself for the ABI
change.

Brian
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[gentoo-dev] gcc-5 news item wrt C++ ABI

[Mike Frysinger]

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Title: GCC 5 Defaults to the New C++11 ABI 
Author: Mike Frysinger <vapier@gentoo.org>
Content-Type: text/plain
Posted: 2015-10-02
Revision: 1
News-Item-Format: 1.0
Display-If-Installed: >=sys-devel/gcc-5

GCC 5 uses the new C++ ABI by default.  When building new code, you might run
into link time errors like:
...: undefined reference to '_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17'
Or you might see linkage failures with "std::__cxx11::string" in the output.

These are signs that you need to rebuild packages using the new C++ ABI.
You can quickly do so by using revdep-rebuild like so:
# revdep-rebuild --library 'libstdc\+\+\.so\.6'

For more details, feel free to peruse:
https://developerblog.redhat.com/2015/02/05/gcc5-and-the-c11-abi/
https://blogs.gentoo.org/blueness/2015/03/10/the-c11-abi-incompatibility-problem-in-gentoo/

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[gentoo-dev] Re: gcc-5 news item wrt C++ ABI

[Ryan Hill]

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On Fri, 2 Oct 2015 22:13:09 -0400
Mike Frysinger <vapier@gentoo.org> wrote:

> Title: GCC 5 Defaults to the New C++11 ABI 
> Author: Mike Frysinger <vapier@gentoo.org>
> Content-Type: text/plain
> Posted: 2015-10-02
> Revision: 1
> News-Item-Format: 1.0
> Display-If-Installed: >=sys-devel/gcc-5
> 
> GCC 5 uses the new C++ ABI by default.  When building new code, you might run
> into link time errors like:
> ...: undefined reference to '_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17'
> Or you might see linkage failures with "std::__cxx11::string" in the output.
> 
> These are signs that you need to rebuild packages using the new C++ ABI.
> You can quickly do so by using revdep-rebuild like so:
> # revdep-rebuild --library 'libstdc\+\+\.so\.6'
> 
> For more details, feel free to peruse:
> https://developerblog.redhat.com/2015/02/05/gcc5-and-the-c11-abi/
> https://blogs.gentoo.org/blueness/2015/03/10/the-c11-abi-incompatibility-problem-in-gentoo/
> 

LGTM.

-- 
Ryan Hill                        psn: dirtyepic_sk
   gcc-porting/toolchain/wxwidgets @ gentoo.org

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Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Jason Zaman]

On Fri, Oct 02, 2015 at 10:13:09PM -0400, Mike Frysinger wrote:
> Title: GCC 5 Defaults to the New C++11 ABI 
> Author: Mike Frysinger <vapier@gentoo.org>
> Content-Type: text/plain
> Posted: 2015-10-02
> Revision: 1
> News-Item-Format: 1.0
> Display-If-Installed: >=sys-devel/gcc-5
> 
> GCC 5 uses the new C++ ABI by default.  When building new code, you might run
> into link time errors like:
> ...: undefined reference to '_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17'

Exactly what part of this line is the important part? I take it its the
@GLIBCXX_3.4.17? or is it the lack of the __cxx11::? I have a feeling
that posted like this and users will think anytime it says undefined
reference then its a C++ issue which is likely not the case.

> Or you might see linkage failures with "std::__cxx11::string" in the output.
> 
> These are signs that you need to rebuild packages using the new C++ ABI.
> You can quickly do so by using revdep-rebuild like so:
> # revdep-rebuild --library 'libstdc\+\+\.so\.6'
> 
> For more details, feel free to peruse:
> https://developerblog.redhat.com/2015/02/05/gcc5-and-the-c11-abi/
> https://blogs.gentoo.org/blueness/2015/03/10/the-c11-abi-incompatibility-problem-in-gentoo/


-- Jason

[gentoo-dev] Re: gcc-5 news item wrt C++ ABI

[Ryan Hill]

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On Sat, 3 Oct 2015 13:04:08 +0800
Jason Zaman <perfinion@gentoo.org> wrote:

> On Fri, Oct 02, 2015 at 10:13:09PM -0400, Mike Frysinger wrote:

> > GCC 5 uses the new C++ ABI by default.  When building new code, you might
> > run into link time errors like:
> > ...: undefined reference to
> > '_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17'
> 
> Exactly what part of this line is the important part? I take it its the
> @GLIBCXX_3.4.17? or is it the lack of the __cxx11::? I have a feeling
> that posted like this and users will think anytime it says undefined
> reference then its a C++ issue which is likely not the case.

If it's got a GLIBCXX symbol version and a mangled name and it broke when you
switched compilers and revdep-rebuild fixes it then you know it's a C++ ABI
issue. :)

The __cxx11 errors look a little different:

cmGlobalGenerator.cxx:(.text+0x12c04): undefined reference to
`Json::Value::Value(std::__cxx11::basic_string<char, std::char_traits<char>,
std::allocator<char> > const&)'

kfilemetainfo.cpp:(.text+0xfb5): undefined reference to
`Strigi::AnalysisResult::AnalysisResult(std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> > const&, long,
Strigi::IndexWriter&, Strigi::StreamAnalyzer&, std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> > const&)'

Either way CXX is right there in the error message.  Compare it to something
that fails due to C99 inline:

../../src/tcs/libtcs.a(libtcs_a-tcsps.o): In function `psfile_get_parent_uuid_by_uuid':
tcsps.c:(.text+0x3e8): undefined reference to `read_data'

bwm-ng.o: In function `main':
bwm-ng.c:(.text.startup+0x1d3): undefined reference to `get_iface_stats'

Rebuilding won't help with these of course.


-- 
Ryan Hill                        psn: dirtyepic_sk
   gcc-porting/toolchain/wxwidgets @ gentoo.org

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Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Ciaran McCreesh]

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On Fri, 2 Oct 2015 22:13:09 -0400
Mike Frysinger <vapier@gentoo.org> wrote:
> Display-If-Installed: >=sys-devel/gcc-5

This means that two years from now, when stages are built using GCC 5,
every new user will get this news item shown to them.

-- 
Ciaran McCreesh

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Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Mike Frysinger]

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On 03 Oct 2015 13:38, Ciaran McCreesh wrote:
> On Fri, 2 Oct 2015 22:13:09 -0400 Mike Frysinger wrote:
> > Display-If-Installed: >=sys-devel/gcc-5
> 
> This means that two years from now, when stages are built using GCC 5,
> every new user will get this news item shown to them.

multiple news items already use this syntax
-mike

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Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Ciaran McCreesh]

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On Sat, 3 Oct 2015 13:24:11 -0400
Mike Frysinger <vapier@gentoo.org> wrote:
> On 03 Oct 2015 13:38, Ciaran McCreesh wrote:
> > On Fri, 2 Oct 2015 22:13:09 -0400 Mike Frysinger wrote:
> > > Display-If-Installed: >=sys-devel/gcc-5
> > 
> > This means that two years from now, when stages are built using GCC
> > 5, every new user will get this news item shown to them.
> 
> multiple news items already use this syntax

Yes, and they cause problems. Do you want to cause another problem, or
do you want to think more carefully about who should see the news item?

-- 
Ciaran McCreesh

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Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[hasufell]

On 10/03/2015 04:13 AM, Mike Frysinger wrote:
> Title: GCC 5 Defaults to the New C++11 ABI 
> Author: Mike Frysinger <vapier@gentoo.org>
> Content-Type: text/plain
> Posted: 2015-10-02
> Revision: 1
> News-Item-Format: 1.0
> Display-If-Installed: >=sys-devel/gcc-5
> 
> GCC 5 uses the new C++ ABI by default.  When building new code, you might run
> into link time errors like:
> ...: undefined reference to '_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17'
> Or you might see linkage failures with "std::__cxx11::string" in the output.
> 
> These are signs that you need to rebuild packages using the new C++ ABI.
> You can quickly do so by using revdep-rebuild like so:
> # revdep-rebuild --library 'libstdc\+\+\.so\.6'
> 

We shouldn't assume a particular PM/toolset in news items, IMO. Just
saying that people might have to rebuild packages linked against
libstdc++.so.6 should be enough.

They can read the docs if they don't know how.

Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Anthony G. Basile]

On 10/3/15 7:16 PM, hasufell wrote:
> On 10/03/2015 04:13 AM, Mike Frysinger wrote:
>> Title: GCC 5 Defaults to the New C++11 ABI
>> Author: Mike Frysinger <vapier@gentoo.org>
>> Content-Type: text/plain
>> Posted: 2015-10-02
>> Revision: 1
>> News-Item-Format: 1.0
>> Display-If-Installed: >=sys-devel/gcc-5
>>
>> GCC 5 uses the new C++ ABI by default.  When building new code, you might run
>> into link time errors like:
>> ...: undefined reference to '_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17'
>> Or you might see linkage failures with "std::__cxx11::string" in the output.
>>
>> These are signs that you need to rebuild packages using the new C++ ABI.
>> You can quickly do so by using revdep-rebuild like so:
>> # revdep-rebuild --library 'libstdc\+\+\.so\.6'
>>
> We shouldn't assume a particular PM/toolset in news items, IMO. Just
> saying that people might have to rebuild packages linked against
> libstdc++.so.6 should be enough.
>
> They can read the docs if they don't know how.
>
Nothing precludes adding "see .... if you use paludis or clang." 
However, I'd like to see the above in there.

-- 
Anthony G. Basile, Ph.D.
Gentoo Linux Developer [Hardened]
E-Mail    : blueness@gentoo.org
GnuPG FP  : 1FED FAD9 D82C 52A5 3BAB  DC79 9384 FA6E F52D 4BBA
GnuPG ID  : F52D4BBA

[gentoo-dev] Re: gcc-5 news item wrt C++ ABI

[Duncan]

Anthony G. Basile posted on Sat, 03 Oct 2015 19:53:14 -0400 as excerpted:

> On 10/3/15 7:16 PM, hasufell wrote:
>> On 10/03/2015 04:13 AM, Mike Frysinger wrote:
>>> Title: GCC 5 Defaults to the New C++11 ABI Author: Mike Frysinger
>>> <vapier@gentoo.org>
>>> Content-Type: text/plain Posted: 2015-10-02 Revision: 1
>>> News-Item-Format: 1.0 Display-If-Installed: >=sys-devel/gcc-5
>>>
>>> GCC 5 uses the new C++ ABI by default.  When building new code, you
>>> might run into link time errors like:
>>> ...: undefined reference to
>>> '_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17'
>>> Or you might see linkage failures with "std::__cxx11::string" in the
>>> output.
>>>
>>> These are signs that you need to rebuild packages using the new C++
>>> ABI.
>>> You can quickly do so by using revdep-rebuild like so:
>>> # revdep-rebuild --library 'libstdc\+\+\.so\.6'
>>>
>> We shouldn't assume a particular PM/toolset in news items, IMO. Just
>> saying that people might have to rebuild packages linked against
>> libstdc++.so.6 should be enough.
>>
>> They can read the docs if they don't know how.
>>
> Nothing precludes adding "see .... if you use paludis or clang."
> However, I'd like to see the above in there.

... Or simply...

 "If you have gentoolkit installed, you can quickly do so by using revdep-
rebuild like so:"...

I've seen that wording used before, and it seems reasonable enough to me, 
not assuming anything about whether it's installed, but giving at least 
some guidance to the folks who need it.

(If they don't have gentoolkit installed and don't know why, that it 
doesn't work with their PM or so, they probably simply followed the basic 
handbook install and are thus using portage.  In which case, that's a 
hint to install gentoolkit...  If they're using a PM other than portage, 
an assumption that they can read between the lines and make their own 
decisions on the merits is reasonable, given that they already did so in 
ordered to have that PM in the first place.)

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Paweł Hajdan, Jr.]

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On 10/3/15 7:30 PM, Ciaran McCreesh wrote:
> On Sat, 3 Oct 2015 13:24:11 -0400
> Mike Frysinger <vapier@gentoo.org> wrote:
>> On 03 Oct 2015 13:38, Ciaran McCreesh wrote:
>>> On Fri, 2 Oct 2015 22:13:09 -0400 Mike Frysinger wrote:
>>>> Display-If-Installed: >=sys-devel/gcc-5
>>>
>>> This means that two years from now, when stages are built using GCC
>>> 5, every new user will get this news item shown to them.
>>
>> multiple news items already use this syntax
> 
> Yes, and they cause problems. Do you want to cause another problem, or
> do you want to think more carefully about who should see the news item?

Hey Ciaran - I see you can point technical deficiencies in a lot of cases.

Could you just suggest an alternative solution?

Paweł


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Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Paweł Hajdan, Jr.]

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On 10/3/15 4:13 AM, Mike Frysinger wrote:
> Title: GCC 5 Defaults to the New C++11 ABI 
> Author: Mike Frysinger <vapier@gentoo.org>
> Content-Type: text/plain
> Posted: 2015-10-02
> Revision: 1
> News-Item-Format: 1.0
> Display-If-Installed: >=sys-devel/gcc-5
> 
> GCC 5 uses the new C++ ABI by default.  When building new code, you might run
> into link time errors like:
> ...: undefined reference to '_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17'
> Or you might see linkage failures with "std::__cxx11::string" in the output.
> 
> These are signs that you need to rebuild packages using the new C++ ABI.
> You can quickly do so by using revdep-rebuild like so:
> # revdep-rebuild --library 'libstdc\+\+\.so\.6'
> 
> For more details, feel free to peruse:
> https://developerblog.redhat.com/2015/02/05/gcc5-and-the-c11-abi/
> https://blogs.gentoo.org/blueness/2015/03/10/the-c11-abi-incompatibility-problem-in-gentoo/

Curious, can one reasonably easy downgrade from GCC 5 back to GCC 4?

Are there any instructions for that? Is it sufficient to do a similar
revdep-rebuild command?

In case the downgrade would horribly break systems or be otherwise
highly nontrivial, I'd recommend some note for that.

Paweł



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Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Jason A. Donenfeld]

On Mon, Oct 5, 2015 at 8:45 PM, Paweł Hajdan, Jr. <phajdan.jr@gentoo.org> wrote:
> Curious, can one reasonably easy downgrade from GCC 5 back to GCC 4?
>

I've gone 4->5, urg I don't want 5, 5->4, okay it works, hey wait I
want 5, 4->5. Things went fine.

Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Mike Frysinger]

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On 03 Oct 2015 18:30, Ciaran McCreesh wrote:
> On Sat, 3 Oct 2015 13:24:11 -0400 Mike Frysinger wrote:
> > On 03 Oct 2015 13:38, Ciaran McCreesh wrote:
> > > On Fri, 2 Oct 2015 22:13:09 -0400 Mike Frysinger wrote:
> > > > Display-If-Installed: >=sys-devel/gcc-5
> > > 
> > > This means that two years from now, when stages are built using GCC
> > > 5, every new user will get this news item shown to them.
> > 
> > multiple news items already use this syntax
> 
> Yes, and they cause problems. Do you want to cause another problem, or
> do you want to think more carefully about who should see the news item?

i see no reason to hold things up when the issue won't show up for over a
year, can be retroactively fixed, and really makes no difference to the
status quo.  so if you had actual thoughts on improving things (rather
than pointless rhetorical questions), feel free to post them.
-mike

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Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Mike Frysinger]

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On 05 Oct 2015 20:45, Paweł Hajdan, Jr. wrote:
> On 10/3/15 4:13 AM, Mike Frysinger wrote:
> > Title: GCC 5 Defaults to the New C++11 ABI 
> > Author: Mike Frysinger <vapier@gentoo.org>
> > Content-Type: text/plain
> > Posted: 2015-10-02
> > Revision: 1
> > News-Item-Format: 1.0
> > Display-If-Installed: >=sys-devel/gcc-5
> > 
> > GCC 5 uses the new C++ ABI by default.  When building new code, you might run
> > into link time errors like:
> > ...: undefined reference to '_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17'
> > Or you might see linkage failures with "std::__cxx11::string" in the output.
> > 
> > These are signs that you need to rebuild packages using the new C++ ABI.
> > You can quickly do so by using revdep-rebuild like so:
> > # revdep-rebuild --library 'libstdc\+\+\.so\.6'
> > 
> > For more details, feel free to peruse:
> > https://developerblog.redhat.com/2015/02/05/gcc5-and-the-c11-abi/
> > https://blogs.gentoo.org/blueness/2015/03/10/the-c11-abi-incompatibility-problem-in-gentoo/
> 
> Curious, can one reasonably easy downgrade from GCC 5 back to GCC 4?
> 
> Are there any instructions for that? Is it sufficient to do a similar
> revdep-rebuild command?
> 
> In case the downgrade would horribly break systems or be otherwise
> highly nontrivial, I'd recommend some note for that.

it's like any other attempt to downgrade an ABI: you're on your own.
in Gentoo, we guarantee backwards compatibility, not forward -- this
is not specific to GCC.

in practice, as long as you don't unmerge gcc-5, you can switch the
active compiler to gcc-4.9 and use it, but the runtime libs will be
taken from the latest one you have installed (gcc-5).
-mike

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Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Mike Frysinger]

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On 04 Oct 2015 01:16, hasufell wrote:
> On 10/03/2015 04:13 AM, Mike Frysinger wrote:
> > Title: GCC 5 Defaults to the New C++11 ABI 
> > Author: Mike Frysinger <vapier@gentoo.org>
> > Content-Type: text/plain
> > Posted: 2015-10-02
> > Revision: 1
> > News-Item-Format: 1.0
> > Display-If-Installed: >=sys-devel/gcc-5
> > 
> > GCC 5 uses the new C++ ABI by default.  When building new code, you might run
> > into link time errors like:
> > ...: undefined reference to '_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17'
> > Or you might see linkage failures with "std::__cxx11::string" in the output.
> > 
> > These are signs that you need to rebuild packages using the new C++ ABI.
> > You can quickly do so by using revdep-rebuild like so:
> > # revdep-rebuild --library 'libstdc\+\+\.so\.6'
> 
> We shouldn't assume a particular PM/toolset in news items, IMO. Just
> saying that people might have to rebuild packages linked against
> libstdc++.so.6 should be enough.

there's no requirement for you to use revdep-rebuild.  including quick
insns for the common case is a no brainer really.

> They can read the docs if they don't know how.

and they can if the common case doesn't work for them.
-mike

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Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Michał Górny]

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Hash: SHA512



Dnia 4 października 2015 01:16:51 CEST, hasufell <hasufell@gentoo.org> napisał(a):
>On 10/03/2015 04:13 AM, Mike Frysinger wrote:
>> Title: GCC 5 Defaults to the New C++11 ABI
>> Author: Mike Frysinger <vapier@gentoo.org>
>> Content-Type: text/plain
>> Posted: 2015-10-02
>> Revision: 1
>> News-Item-Format: 1.0
>> Display-If-Installed: >=sys-devel/gcc-5
>>
>> GCC 5 uses the new C++ ABI by default.  When building new code, you
>might run
>> into link time errors like:
>> ...: undefined reference to
>'_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17'
>> Or you might see linkage failures with "std::__cxx11::string" in the
>output.
>>
>> These are signs that you need to rebuild packages using the new C++
>ABI.
>> You can quickly do so by using revdep-rebuild like so:
>> # revdep-rebuild --library 'libstdc\+\+\.so\.6'
>>
>
>We shouldn't assume a particular PM/toolset in news items, IMO. Just
>saying that people might have to rebuild packages linked against
>libstdc++.so.6 should be enough.

Wrong. We should provide examples for the common case. Examples are often easier to comprehend than elaborate attempts of explaining what needs to be done.

>
>They can read the docs if they don't know how.

- --
Best regards,
Michał Górny
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Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Anthony G. Basile]

On 10/2/15 10:13 PM, Mike Frysinger wrote:
> Title: GCC 5 Defaults to the New C++11 ABI
> Author: Mike Frysinger <vapier@gentoo.org>
> Content-Type: text/plain
> Posted: 2015-10-02
> Revision: 1
> News-Item-Format: 1.0
> Display-If-Installed: >=sys-devel/gcc-5
>
> GCC 5 uses the new C++ ABI by default.  When building new code, you might run
> into link time errors like:
> ...: undefined reference to '_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17'
> Or you might see linkage failures with "std::__cxx11::string" in the output.
>
> These are signs that you need to rebuild packages using the new C++ ABI.
> You can quickly do so by using revdep-rebuild like so:
> # revdep-rebuild --library 'libstdc\+\+\.so\.6'
>
> For more details, feel free to peruse:
> https://developerblog.redhat.com/2015/02/05/gcc5-and-the-c11-abi/
> https://blogs.gentoo.org/blueness/2015/03/10/the-c11-abi-incompatibility-problem-in-gentoo/

i know there's no rush, but let's not loose sight of this.

-- 
Anthony G. Basile, Ph.D.
Gentoo Linux Developer [Hardened]
E-Mail    : blueness@gentoo.org
GnuPG FP  : 1FED FAD9 D82C 52A5 3BAB  DC79 9384 FA6E F52D 4BBA
GnuPG ID  : F52D4BBA

Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Mike Frysinger]

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On 03 Oct 2015 19:53, Anthony G. Basile wrote:
> On 10/3/15 7:16 PM, hasufell wrote:
> > On 10/03/2015 04:13 AM, Mike Frysinger wrote:
> >> Title: GCC 5 Defaults to the New C++11 ABI
> >> Author: Mike Frysinger <vapier@gentoo.org>
> >> Content-Type: text/plain
> >> Posted: 2015-10-02
> >> Revision: 1
> >> News-Item-Format: 1.0
> >> Display-If-Installed: >=sys-devel/gcc-5
> >>
> >> GCC 5 uses the new C++ ABI by default.  When building new code, you might run
> >> into link time errors like:
> >> ...: undefined reference to '_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17'
> >> Or you might see linkage failures with "std::__cxx11::string" in the output.
> >>
> >> These are signs that you need to rebuild packages using the new C++ ABI.
> >> You can quickly do so by using revdep-rebuild like so:
> >> # revdep-rebuild --library 'libstdc\+\+\.so\.6'
> >>
> > We shouldn't assume a particular PM/toolset in news items, IMO. Just
> > saying that people might have to rebuild packages linked against
> > libstdc++.so.6 should be enough.
> >
> > They can read the docs if they don't know how.
> 
> Nothing precludes adding "see .... if you use paludis or clang." 
> However, I'd like to see the above in there.

what is the alternative suggestion for paludis ?

wrt clang, i thought we were using gcc's libstdc++ and not the libc++ project.
if people are using libc++ & clang, then this news entry does not change ...
you'd still need to rebuild anything using libstdc++.  that said, i'm not sure
libc++ & clang builds are common enough to warrant mentioning here.
-mike

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Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Mike Frysinger]

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i've pushed the news item now since there hasn't been any actionable
feedback since.  it can always be refined based on user feedback.
-mike

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Re: [gentoo-dev] moving gcc-5.2 to unstable

[Mike Frysinger]

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On 01 Oct 2015 09:49, Mike Frysinger wrote:
> what do people want to have in place before we move gcc-5.2 into ~arch ?

i want to fix these two bugs (or at least get a better handle on them).
they're related to graphite/ISL, so they don't impact most people.
	https://bugs.gentoo.org/555684
	https://bugs.gentoo.org/560904
hopefully i should get to them in the next week

any other 11th hour reports ?
-mike

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[gentoo-dev] moving gcc-5.3 to unstable

[Mike Frysinger]

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all the blocking issues raised have been addressed w/gcc-5.3,
so i'll be moving it into ~arch this weekend
-mike

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Re: [gentoo-dev] gcc-5 news item wrt C++ ABI

[Mike Gilbert]

On Fri, Oct 2, 2015 at 10:13 PM, Mike Frysinger <vapier@gentoo.org> wrote:
> Title: GCC 5 Defaults to the New C++11 ABI
> Author: Mike Frysinger <vapier@gentoo.org>
> Content-Type: text/plain
> Posted: 2015-10-02
> Revision: 1
> News-Item-Format: 1.0
> Display-If-Installed: >=sys-devel/gcc-5
>
> GCC 5 uses the new C++ ABI by default.  When building new code, you might run
> into link time errors like:
> ...: undefined reference to '_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17'
> Or you might see linkage failures with "std::__cxx11::string" in the output.
>
> These are signs that you need to rebuild packages using the new C++ ABI.
> You can quickly do so by using revdep-rebuild like so:
> # revdep-rebuild --library 'libstdc\+\+\.so\.6'
>
> For more details, feel free to peruse:
> https://developerblog.redhat.com/2015/02/05/gcc5-and-the-c11-abi/
> https://blogs.gentoo.org/blueness/2015/03/10/the-c11-abi-incompatibility-problem-in-gentoo/

Just a heads-up: the python-based revdep-rebuild which is included
with gentoolkit-0.3.1 requires slightly different syntax:

# revdep-rebuild --library 'libstdc++.so.6'

I pushed a revision to the news item with updated instructions.