> Joerg Sonnenberger <jo...@bec.de> hat am 28. September 2017 um 15:10 > geschrieben: > > > Hello everyone, > during the developer summit, I was made aware that we got the fancy dual > ABI for libstdc++ with the GCC 5 import. I thought that $#%#$% was > disabled from the start, but alas, it isn't. > > What does dual ABI mean? Long story. std::string in libstdc++ had > a performance "feature" for ages where it avoided string copying by > using reference counting. This has a number of implications, one of them > is that in-place modifications will invalidate iterators. Since this > makes the behavior highly unpredictable especially in multithreaded > programs, C++11 forbids it. Since changing central parts of std::string > requires an ABI change, GCC decided to provide both old and new > interface in the same code and introduce a fancy hack in the name > mangler. Inline namespaces as used by libc++ wouldn't allow both ABIs to > coexist, since functions using std::string only in the return type > wouldn't be mangled different as that case is not allowed in C++. > > Why is this bad? It means that if libfoo is compiled with -std=c++11 and > foobar is compiled with -std=c++03, they can't be linked together and > vice versa. While many libraries are starting to adopt C++11 features, > not everyone does. The dual ABI makes interaction between the standards > *worse*, just to avoid a major bump. > > What should we do? I want to take the time before the 8.0 release and > switch GCC over to always use the new ABI. This means recompiling all > C++ code, but I consider it the lesser evil of having to deal with the > fallout in pkgsrc for years to come. > > Joerg
Yes, please. This dual ABI is annoying and I've got hit by it (under Linux) Lars
