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GCC 7 Getting Closer To Release, But Running Behind On Regressions

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  • #21
    Originally posted by carewolf View Post

    No it doesn't. The ABI change was in libstdc++ not in gcc, and libstdc++ can do both ABIs and will also use the new definition in code compiled with --std=c++98. There is another flag for switching std::string definition.
    yeah you are right

    Although the changes were made for C++11 conformance, the choice of ABI to use is independent of the -std option used to compile your code, i.e. for a given GCC build the default value of the _GLIBCXX_USE_CXX11_ABI macro is the same for all dialects. This ensures that the -std does not change the ABI, so that it is straightforward to link C++03 and C++11 code together.
    EDIT: not sure if this breaks between -std=C++98 and C++1x/z though. I think it does.
    Last edited by cj.wijtmans; 10 January 2017, 08:41 AM.

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    • #22
      Originally posted by atomsymbol

      Although, in my opinion, the following would be a better solution: If a package is known to fail to compile with gcc 6.x Gentoo should choose an older C/C++ compiler automatically (and print an elog warning message about it).
      I am not sure if any package depends on any GCC version.

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      • #23
        Originally posted by atomsymbol

        In Gentoo it is possible to customize the compiler on a per-package basis:



        Setting CC and CXX to (for example) gcc-4.9.4 and g++-4.9.4 might work for www-client/chromium.
        To be honest gentoo should do it like clearlinux and set the best flags for best performance. Or perhaps a new flag set to pick between debugging, performance and generic.

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        • #24
          Originally posted by atomsymbol

          In the Gentoo context, switching GCC from 5.x to 6.x is questionable because 6.3 compiles slower. GCC 7.0 will compile faster than 6.x.
          GCC 6.x should optimize better and more importantly, works better with LTO.

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          • #25
            Originally posted by cj.wijtmans View Post

            To be honest gentoo should do it like clearlinux and set the best flags for best performance. Or perhaps a new flag set to pick between debugging, performance and generic.
            I like their per package approach. I have a couple of templates in /etc/portage/env and whenevery I need it, I just make new directory, copy best template there and tweak it accrodingly. I just wish I could version those env-files so that I could use for example, one fo package-x.y.z <=A, another for package in general ( if nothing else matches) or perhaps compund them ( like CSS).

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            • #26
              Originally posted by cj.wijtmans View Post
              Better to stay on GCC5.
              better stay away from keyboard

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              • #27
                Originally posted by atomsymbol
                I flagged/reported your post as harassment.
                thanks for quoting me

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