Darling is a

free and open-source Free and open-source software (FOSS) is software available under a Software license, license that grants users the right to use, modify, and distribute the software modified or not to everyone free of charge. FOSS is an inclusive umbrella term ...

macOS

compatibility layer In software engineering, a compatibility layer is an interface that allows binaries for a legacy or foreign system to run on a host system. This translates system calls for the foreign system into native system calls for the host system. With s ...

for Linux. It duplicates functions of

macOS macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. With ...

by providing alternative implementations of the libraries and frameworks that macOS programs call. This method of duplication differs from other methods that might also be considered emulation, where macOS programs run in a

virtual machine In computing, a virtual machine (VM) is the virtualization or emulator, emulation of a computer system. Virtual machines are based on computer architectures and provide the functionality of a physical computer. Their implementations may involve ...

. Darling has been called the counterpart to

WINE Wine is an alcoholic drink made from Fermentation in winemaking, fermented fruit. Yeast in winemaking, Yeast consumes the sugar in the fruit and converts it to ethanol and carbon dioxide, releasing heat in the process. Wine is most often made f ...

for running macOS apps. The project started in the summer of 2012 and builds on a previous project, named maloader, which was discontinued due to a lack of time. The layer has been shown to work with many console apps, such as Midnight Commander, The Unarchiver, Python, etc. on the layer, but it also has basic support for graphical applications based on the Cocoa framework. Darling has the ability to extract Apple Disk Images. The project aims to support

iOS Ios, Io or Nio (, ; ; locally Nios, Νιός) is a Greek island in the Cyclades group in the Aegean Sea. Ios is a hilly island with cliffs down to the sea on most sides. It is situated halfway between Naxos and Santorini. It is about long an ...

applications in the future.

Architecture

At the entry of the Darling system is a loader for Mach-O binaries, the executable format for Apple's

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

s. Darling's predecessor, maloader, presented a maximalist approach to the problem by trying to replicate everything that Apple's dynamic library loader dyld does. This proved to be hard, and since a 2017 "Mach-O transition" Darling has been using a lightweight loader just enough to launch the open-source Apple dyld instead. To provide the macOS binaries with a kernel, Darling uses a modified XNU kernel (with an APSL license) wrapped into a Linux kernel module with a GPL license. It is not the same as including GPL code in APSL software, and the APSL license allows for linking from code with a different license (in this case GPL). The module handles the typical job of a Mach kernel, mainly Ports IPC handling. Some licensing issues exist in the darling-mach module, as the team are adding GNU GPL modifications to the APSL kernel. Higher than the kernel is the root environment. Darling, like WINE, supports

chroot chroot is a shell (computer), shell command (computing), command and a system call on Unix and Unix-like operating systems that changes the apparent root directory for the current running process and its Child process, children. A program that i ...

prefixes, implemented using the Linux overlayfs (as opposed to path translation in WINE). PID, IPC, and UTS namespaces are used to create a

container A container is any receptacle or enclosure for holding a product used in storage, packaging, and transportation, including shipping. Things kept inside of a container are protected on several sides by being inside of its structure. The term ...

for the Darwin system inside. The frameworks and system libraries in Darling are, to the best possible extent, based on

source code In computing, source code, or simply code or source, is a plain text computer program written in a programming language. A programmer writes the human readable source code to control the behavior of a computer. Since a computer, at base, only ...

released by Apple. The Mach-O transition allows these frameworks to be built more easily, because they are now built as the Mach-O format they were intended for. To fill in the gaps for many higher-level frameworks like Cocoa, Darling uses code from Cocotron, ApportableFoundation, and

GNUstep GNUstep is a free software implementation of the Cocoa (formerly OpenStep) Objective-C frameworks, widget toolkit, and application development tools for Unix-like operating systems and Microsoft Windows. It is part of the GNU Project. GNUst ...

License

The larger Darling system is based on many external components which use various licenses, all of which are open-source. The primary license is

GPLv3 The GNU General Public Licenses (GNU GPL or simply GPL) are a series of widely used free software licenses, or ''copyleft'' licenses, that guarantee end users the freedom to run, study, share, or modify the software. The GPL was the first ...

External links

* https://www.darlinghq.org/ * https://github.com/darlinghq/darling

References

{{reflist, 30em 2013 software Compatibility layers Free software programmed in C Free system software Linux emulation software Software using the GNU General Public License