Hi Julian, On 07/08/17 11:33, Julian Andres Klode wrote: > On Mon, Aug 07, 2017 at 03:47:15PM +0100, jcowgill@debian.org wrote: >> Package: libapt-pkg5.0 >> Version: 1.5~beta1 >> Severity: serious >> Tags: sid buster >> User: debian-gcc@lists.debian.org >> Usertags: gcc-7-op-mangling >> >> Hi, >> >> It appears that your package provides an external symbol that is >> affected by the recent name mangling changes in GCC 7. See: >> https://gcc.gnu.org/gcc-7/porting_to.html#conversion-op-mangling >> >> In GCC 7, the name mangling for C++ conversion operators which return a >> type using the abi_tag attribute (most commonly std::string) has >> changed. When your library is compiled with GCC 7, it will now emit two >> symbols for the conversion operator using the new and old naming. >> Executables compiled with GCC 7 will always use the new symbol, while >> old executables compiled using <= GCC 6 will use the old symbol. For new >> executables to build without undefined references, your library will >> need rebuilding with GCC 7. > > I'd say that's a bug in GCC, and it should link to the old name until > GCC 8 is out (and build both) to have a transition period. I don't think that will help much - it just moves the time when we have to do the rebuilds by a year. The symbols/shlibs changes would still be required to fix the dependencies. >> To ensure that new executables will pull in the newer version of the >> library built with GCC 7: >> - Your library package should Build-Depend on g++ (>= 4:7). > > It's complicated. We also want the package to work in Ubuntu, and that > does not have that yet. For Debian, not doing that works entirely fine, > for Ubuntu it's getting weird down the line and that needs a rebuild > then. > > We could just binNMU that, but the next upload is happening any minute > now anyway. I think Ubuntu does have GCC 7 as the default in artful-proposed (though I can't remember what cases that gets pulled in). I'm not sure when the buildds get uploaded, but yesterday a lot of them still had GCC 6, so build-depending on GCC 7 is required to ensure it's used on every architecture. >> - If your package provides a symbols file, ensure that the new >> conversion operator symbols have a version matching the version this >> bug is fixed in (including the Debian revision and tilde if >> necessary). >> >> Using apt as an example (debian/libapt-pkg5.0.symbols): >> (c++)"URI::operator std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >[abi:cxx11]()@APTPKG_5.0" 0.8.0 >> + (c++)"URI::operator std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >()@APTPKG_5.0" 1.5~beta2~ >> >> Where "1.5~beta2" is the version this bug was fixed in. > > Sure, we can do that. The symbol file is not up to date > anyway, but missing symbols do not really hurt - they > just mean "latest". Which is better for now. > > The next upload will obviously be built with gcc 7, we > can do the extra stuff later on (that's wishlist then > I'd say). So I won't close the bug in the upload and > keep it open until we have the annotations. Assuming it is actually built using GCC 7 (which may not be the case), this is probably OK because as you say dpkg-gensymbols will add the extra symbol using the latest version from the changelog. Thanks, James
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