One of the strategies for speeding up ObjC dispatch was for the runtime to include a vtable that did direct dispatch for some very common methods (e.g. -[NSArray count]). Since method dispatch is dynamic, we always have to figure out the implementation for a given selector, so we had to be able to detect & decode these vtables. That strategy is no longer used in recent versions of the ObjC runtime. It's been a couple of years now, so it's about time to declare that we no longer support older versions of OS X that still have the feature, and take it out. Why do you ask?
Jim > On May 18, 2017, at 7:57 AM, Nat! via lldb-dev <lldb-dev@lists.llvm.org> > wrote: > > > At first I thought it might have something to do with C++. But then I looked > a little closer and then it looked like it is building up information about > information contained in a linked list called "gdb_objc_trampolines". > > A google search yields: > https://opensource.apple.com/source/objc4/objc4-437/runtime/objc-gdb.h > > But in the actual runtime, ojc4-709, I find only a reference to it in > `libobjc.order`. > > ``` > libobjc.order > 32:_gdb_objc_trampolines_changed > ``` > > So I'd like to know if AppleObjCVTables is just used for these apparently > obsolete objc_trampoline_header structures, or if there is more to it. > > Ciao > Nat! > > > > > > _______________________________________________ > lldb-dev mailing list > lldb-dev@lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev _______________________________________________ lldb-dev mailing list lldb-dev@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
