On Mon, Sep 11 2023, Jonathan Schleifer <js-openbsd-po...@nil.im> wrote: > Am 11.09.23 um 13:01 schrieb Jeremie Courreges-Anglas: > >> This diff and the previous one were likely mangled by your MUA. There >> are hints available: >> https://www.kernel.org/doc/html/latest/process/email-clients.html >> Or you may just send diffs as attachments (inline is still preferred). > > Ah, sorry about that. I'll double check next time. > >> Using /usr/src/lib/check_sym I can spot: >> /usr/local/lib/libobjfwtls.so.0.0 --> >> /usr/obj/pobj/objfw-1.0.2/fake-amd64/usr/local/lib/libobjfwtls.so.0.0 >> Dynamic export changes: >> added: >> .objc_sel_nameof_isWaitingForDelimiter >> Applying blindly our rules for shared libraries, this would warrant >> a minor bump because of the additional interface. But maybe the initial >> '.' in the name means it's a local, private symbol? nm -g tells me it's >> a weak symbol so with public visibility. Insights welcome. > > Nope, this shouldn't be a bump. libobjfwtls.so.0.0 subclasses > OFTLSStream from libobjfw.so.0.0 as OFOpenSSLTLSStream. What's new is > that it overrides the private method of_isWaitingForDelimiter. It > shouldn't override a private method, yes, but for now, that is the fix > without changing the API/ABI and can be done since I control both libs. > This works due to the dynamic dispatch. The > .objc_sel_nameof_isWaitingForDelimiter is merely a new symbol that > provides the string for the selector that gets registered with the > runtime so it can be overridden. It's references by the > .objc_method_list that is in turn referenced by the class structure that > is in turn referenced by the ObjC module that is passed to __objc_exec > via a constructor to register all classes, categories and selectors in > the module with the runtime. > > libobjfwtls in turn sets the global variable OFTLSStreamImplementation > in libobjfw via the +load method of OFOpenSSLTLSStream, which in turn > gets called by the runtime via this chain started by __objc_exec, at > which point libobjfw knows to use OFOpenSSLTLSStream when an OFTLSStream > is requested. The only way someone interfaces with libobjfwtls is by > linking it in and not referencing any symbols from it. > > Hope that explains :). All these structures are emitted by the compiler > automatically. You can find a declaration of those structs emitted by > the compiler here: > https://objfw.nil.im/file?name=src/runtime/private.h&ci=trunk > > Or, tl;dr: A method that existed before was overridden in a subclass. > Because ObjC uses dynamic dispatch, this symbol is never referenced, as > all method calls are dispatched via the runtime. But the metadata > changes so the runtime knows this method is now overridden - without > accessing that symbol.
Thanks for the long explanation, I'll take your word about this. Update committed, thanks! -- jca | PGP : 0x1524E7EE / 5135 92C1 AD36 5293 2BDF DDCC 0DFA 74AE 1524 E7EE
