https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69179
--- Comment #3 from Iain Sandoe <iains at gcc dot gnu.org> --- (In reply to sandra from comment #0) > config/darwin.c defines attributes "apple_kext_compatibility" and > "weak_import" which have no documentation in the GCC manual. > > "apple_kext_compatibility" seems related to the also-undocumented > -fapple-kext command-line option (see PR 62273). Reading the code, I'm > wondering if a feature intended to provide backwards compatibility with GCC > 2.95 is even relevant to modern versions of Darwin, or whether this might be > a candidate for deletion as obsolete. The purpose of the attribute is to allow the VTABLE for c++ (in kernel modules) to be altered to be compatible with GCC2.95 layouts for use with Darwin <= 8. There is an outside possibility it might be relevant to m32 Darwin9 (this needs checking). This option is recognised but not implemented - it looks like the APPLE_LOCAL changes in 4.2.1 were never upstreamed (or never accepted, or subsequently removed). I think, documentation-wise, we could (now) note the facts (i.e. that it's recognised in sources but unimplemented). For the future; 1. I doubt that there's any serious appetite for introducing intrusive changes to c++ to support an EOL platform (if we do it at all I'd say save it for a "Vendor Branch"). ISTM that folks who need to support such kernel modules are not looking for up-to-date c++11 features and could just use apple g++-4.2. 2. We should introduce at least a warning in the current source that the option is not enacted. 3. Unless anyone disagrees with (1) and has the time/enthusiasm to implement and push the implementation though, I think we should note that this attribute is deprecated 4. It's likely that we should review whether the -fapple-kext stuff has any function/meaning [to the ppc port] as things stand.
