![]() ![]() ASLR (Address Space Layout Randomization), which means that every time you loaded any library, they may be at a different address.More platforms support: iOS, tvOS, watchOS.More architectures support: x86, x86_64, arm, arm64.if you've ever seen the phrase optimizing system performance appear in your software update, that was added to the installer to be displayed during the time the system was updating prebinding (nowadays the message is used for all sort of optimizations).only edited the system library addresses.It had security issues for speed's sake (Apple went back and fix some of those).Full native dlopen()/ dlsym() semantics (deprecated legacy proprietary APIs).Correct C++ initializer semantics (extended the mach-o format and updated dyld so that we could get efficient C++ library support).cons: prebinding was editing your binaries on every launch.technology where macOS would try to find fixed addresses for every dylib in the system and for your application, and the dynamic loader would try to load everything at those addresses and if it succeeded, it would edit all of those binaries to have those precalculated addresses in it, and then the next time when it put them in the same addresses, it didn't have to do any additional work.Prebinding added in macOS Cheetah (10.0).large C++ code bases cause the dynamic linker to have to do a lot of work and it was quite slow.did not work with good performance in a dynamic environment.C++ has a number of features, such as how its initializer ordering works.Released before most systems used large C++ dynamic libraries.NeXTStep had different proprietary extensions.dlopen already existed on some Unix systems, but were proprietary extensions.Originally dyld did not have version numbers, but Apple is retroactively giving them. works across multiple dylibs, including system dylibs that may be taking a long time because of inputs you've given them, such as complicated nibs.provides precise timing for each static initializer. ![]() initializers are code that have to run before main to set up objects for your app.Use the Static Initializer tracer in instruments to profile your startup time: Swift does not allow certain types of misaligned data structures that cost us time in launch.Swift avoids a lot of pitfalls that C, C++ and Objective-C allow you to do.Launch Closure: all of the information necessary to launch an application (e.g., what dylibs the app uses, what the offsets in them are for various symbols, where their code signatures are).Startup time (for the scope of this talk): time spent before the app main() is executed.Find out how improved tooling makes it easier to optimize your app's launch time, and see how new changes coming in dyld will bring even further launch time improvements. Description: Learn about the dyld dynamic linker used on Apple platforms, how it's changed over the years, and where it's headed next. ![]()
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