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Subject: | Re: Updated: gcc-5.2.0-1 (Test x86/x86_64) |
To: | cygwin AT cygwin DOT com |
References: | <560BC46D DOT 3060500 AT gmail DOT com> <560C0863 DOT 70505 AT tiscali DOT co DOT uk> <560C6369 DOT 7060602 AT gmail DOT com> <560C71FB DOT 4030005 AT tiscali DOT co DOT uk> <560D2F6D DOT 90608 AT gmail DOT com> <5613F632 DOT 1080205 AT t-online DOT de> <56140A2F DOT 3000004 AT cornell DOT edu> |
From: | David Stacey <drstacey AT tiscali DOT co DOT uk> |
Message-ID: | <56144739.7040602@tiscali.co.uk> |
Date: | Tue, 6 Oct 2015 23:12:09 +0100 |
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On 06/10/15 18:51, Ken Brown wrote: > On 10/6/2015 12:26 PM, Christian Franke wrote: >> cyg Simple wrote: >>> On 9/30/2015 7:36 PM, David Stacey wrote: >>>> On 30/09/15 23:34, JonY wrote: >>>>> On 10/1/2015 00:05, David Stacey wrote: >>>>>> On 30/09/15 12:15, JonY wrote: >>>>>>> gcc-5.2.0-1 has been uploaded for 32bit and 64bit Cygwin. >>>>>>> >>>>>>> This is the first series of the 5.x releases, and should be >>>>>>> considered >>>>>>> as experimental as such. >>>>>> Have you managed to work around the ABI change in gcc-5 [1], or will >>>>>> this require a mass rebuild at the point gcc-5 becomes 'current'? >>>>>> >>>>>> [1] >>>>>> -http://developerblog.redhat.com/2015/02/05/gcc5-and-the-c11-abi/ >>>>> As far as I know, every gcc release will break C++ ABI, so it would >>>>> mean >>>>> rebuilding everything C++. >>>> According to the Red Hat blog above, the last time g++ caused an ABI >>>> change was back in the 3.x days, so it hasn't happened for a while. Ah >>>> well, we have maintainers for most packages in Cygwin, so we'll >>>> have to >>>> co-ordinate a rebuild. >>> Regardless, JonY is correct. Every C++ release, regardless of the >>> vendor, causes an ABI break with shared libraries and the naming of the >>> object elements (mangled names). >> >> Probably not in this 4.X -> 5.X case. Otherwise the new cygstdc++-6.dll >> should IMO be renamed to -6.1, -7 or similar. >> >> A diff of exported symbols of cygstdc++-6.dll 4.9.3-1 and 5.2.0 shows >> that the new version only adds new symbols. >> >> >> Results of a quick build check with smartmontools package: >> >> - Existing package which was built with g++ 4.9.2 runs with 5.2.0 >> cygstdc++-6.dll and cyggcc_s-1.dll. >> >> - A rebuild with g++ 5.2.0 does not run with 4.9.3 cygstdc++-6.dll due >> to missing symbols. This is as expected because 5.X adds a new C++11 >> conforming std::string which is used by default >> (https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dual_abi.html). >> >> - A rebuild with g++ 5.2.0 and CXXFLAGS=-D_GLIBCXX_USE_CXX11_ABI=0 runs >> with old 4.9.3 cygstdc++-6.dll and cyggcc_s.dll. >> >> So there is probably no need to rebuild existing C++ packages. > > What about the following scenario: Package P links against library L. > Library L is rebuilt to use the new ABI. Isn't it possible that > package P will then have to be rebuilt as well? My understanding is that if 'L' is built with -D_GLIBCXX_USE_CXX11_ABI=0 then P wouldn't need to be rebuilt (I haven't tested that, though). However, this compiler switch loses some C++11 features of the STL, so it isn't a magic cure. Dave. -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
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