http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53673
--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-06-15 17:46:51 UTC --- (In reply to comment #6) > Technically, you could add it to the top of <stddef.h> or whatever is a > guaranteed included library header: libstdc++'s <bits/c++config.h> would be the right place and as part of the std lib the symbol should probably be named __glibcxx_blah I think you'd also need an actual definition or nothing will be emitted for the declaration alone: #if __GXX_WEAK__ #if __cplusplus == 201103L extern "C" void __glibcxx_std_cxx11() __attribute__((weak)); extern "C" void __glibcxx_std_cxx11() { } #else if __cplusplus == 199711L extern "C" void __glibcxx_std_cxx98() __attribute__((weak)); extern "C" void __glibcxx_std_cxx98() { } #else #warning Unknown C++ standard version #endif #endif > No, it's fair enough, I only know that from watching the discussions on ISO > and > I have no idea if it's actually written in the final published standard. It is > however written in Nicolai Josuttis' updated C++11 "The C++ standard library" > in the chapter on C++11 core language changes. And if you think it through, > there has to be in practice ABI breakage in 03 ABIs because no one could have > anticipated during their design of what 11 would require [1]. > > [1]: This may not apply to GCC as it revised its ABI quite recently, and I'm > sure its designers took into account likely future 11 requirements. The current G++ ABI is eight years old and (modulo bugs) the same for c++98 and c++11, see Bug 53646 comment 17 Again, the incompatibilities are in the library not the core language. Whether that's generally true for other compilers is irrelevant here.