ObjFW  Documentation

There are three ways you are probably reading this right now:

  • On ObjFW's homepage, via Fossil
  • On GitHub
  • Via an editor or pager, by opening README.md from a checkout or tarball

ObjFW is developed using Fossil, so if you are reading this on GitHub or any other place, you are most likely using a mirror.

Table of Contents

What is ObjFW?

ObjFW is a portable, lightweight framework for the Objective-C language. It enables you to write an application in Objective-C that will run on any platform supported by ObjFW without having to worry about differences between operating systems or various frameworks you would otherwise need if you want to be portable.

It supports all modern Objective-C features when using Clang, but is also compatible with GCC ≥ 4.6 to allow maximum portability.

ObjFW is intentionally incompatible with Foundation. This has two reasons:

  • GNUstep already provides a reimplementation of Foundation, which is only compatible to a certain degree. This means that a developer still needs to care about differences between frameworks if they want to be portable. The idea behind ObjFW is that a developer does not need to concern themselves with portablility and making sure their code works with multiple frameworks: Instead, if it works it ObjFW on one platform, they can reasonably expect it to also work with ObjFW on another platform. ObjFW behaving differently on different operating systems (unless inevitable because it is a platform-specific part, like the Windows Registry) is considered a bug and will be fixed.
  • Foundation predates a lot of modern Objective-C concepts. The most prominent one is exceptions, which are only used in Foundation as a replacement for abort(). This results in cumbersome error handling, especially in initializers, which in Foundation only return nil on error with no indication of what went wrong. It also means that the return of every init call needs to be checked against nil. But in the wild, nobody actually checks each and every return from init against nil, leading to bugs. ObjFW fixes this by making exceptions a first class citizen.

ObjFW also comes with its own lightweight and extremely fast Objective-C runtime, which in real world use cases was found to be significantly faster than both GNU's and Apple's runtime.


ObjFW is released under three licenses:

The QPL allows you to use ObjFW in any open source project. Because the GPL does not allow using code under any other license, ObjFW is also available under the GPLv2 and GPLv3 to allow GPL-licensed projects to use ObjFW.

You can pick under which of those three licenses you want to use ObjFW. If none of them work for you, contact me and we can find a solution.


Releases of ObjFW, as well as changelogs and the accompanying documentation can be found here.

Cloning the repository

ObjFW is developed in a Fossil repository, with automatic incremental exports to Git. This means you can either clone the Fossil repository or the Git repository - it does not make a huge difference. The main advantage of cloning the Fossil repository over cloning the Git repository is that you also get all the tickets, wiki pages, etc.


Clone the Fossil repository like this:

$ fossil clone https://objfw.nil.im objfw.fossil
$ mkdir objfw && cd objfw
$ fossil open ../objfw.fossil

You can then use Fossil's web interface to browse the timeline, tickets, wiki pages, etc.:

$ fossil ui

It's also possible to open the same local repository multiple times, so that you have multiple working directories all backed by the same local repository.


To clone the Git repository, use the following:

$ git clone https://github.com/ObjFW/ObjFW


To install ObjFW, just run the following commands:

$ ./configure
$ make
$ make install

In case you checked out ObjFW from the Fossil or Git repository, you need to run the following command first:

$ ./autogen.sh

macOS and iOS

Building as a framework

When building for macOS or iOS, everything is built as a .framework by default if --disable-shared has not been specified to configure.

To build for iOS, use something like this:

$ clang="clang -isysroot $(xcrun --sdk iphoneos --show-sdk-path)"
$ export OBJC="$clang -arch armv7 -arch arm64"
$ export OBJCPP="$clang -arch armv7 -E"
$ ./configure --prefix=/usr/local/ios --host=arm-apple-darwin

To build for the iOS simulator, use something like this:

$ clang="clang -isysroot $(xcrun --sdk iphonesimulator --show-sdk-path)"
$ export OBJC="$clang -arch i386 -arch x86_64"
$ export OBJCPP="$clang -arch i386 -E"
$ ./configure --prefix=/usr/local/iossim --host=i386-apple-darwin

Using the macOS or iOS framework in Xcode

To use the macOS framework in Xcode, you need to add the .frameworks to your project and add the following flags to Other C Flags:

-fconstant-string-class=OFConstantString -fno-constant-cfstrings

Broken Xcode versions

Some versions of Xcode shipped with a version of Clang that ignores -fconstant-string-class=OFConstantString. This will manifest in an error like this:

OFAllocFailedException.m:94:10: error: cannot find interface declaration for
        return @"Allocating an object failed!";
1 error generated.

Unfortunately, there is no workaround for this other than to upgrade/downgrade Xcode or to build upstream Clang yourself.

In particular, Xcode 11 Beta 1 to Beta 3 are known to be affected. While Xcode 11 Beta 4 to Xcode 11.3 work, the bug was unfortunately reintroduced in Xcode 11.4.1 and a fix is not expected before Xcode 11.6.

You can get older versions of Xcode here by clicking on "More" in the top-right corner.


Windows is only officially supported when following these instructions, as there are many MinGW versions that behave slightly differently and often cause problems.

Getting MSYS2

The first thing to install is MSYS2 to provide a basic UNIX-like environment for Windows. Unfortunately, the binaries are not signed and there is no way to verify their integrity, so only download this from a trusted connection. Everything else you will download using MSYS2 later will be cryptographically signed.

Updating MSYS2

The first thing to do is updating MSYS2. It is important to update things in a certain order, as pacman (the package manager MSYS2 uses, which comes from Arch Linux) does not know about a few things that are special on Windows.

First, update the mirror list:

$ pacman -Sy pacman-mirrors

Then proceed to update the msys2-runtime itself, bash and pacman:

$ pacman -S msys2-runtime bash pacman mintty

Now close the current window and restart MSYS2, as the current window is now defunct. In a new MSYS2 window, update the rest of MSYS2:

$ pacman -Su

Now you have a fully updated MSYS2. Whenever you want to update MSYS2, proceed in this order. Notice that the first pacman invocation includes -y to actually fetch a new list of packages.

Installing MinGW-w64 using MSYS2

Now it's time to install MinGW-w64. If you want to build 32 bit binaries:

$ pacman -S mingw-w64-i686-clang mingw-w64-i686-gcc-objc

For 64 bit binaries:

$ pacman -S mingw-w64-x86_64-clang mingw-w64-x86_64-gcc-objc

There is nothing wrong with installing them both, as MSYS2 has created two entries in your start menu: MinGW-w64 Win32 Shell and MinGW-w64 Win64 Shell. So if you want to build for 32 or 64 bit, you just start the correct shell.

Finally, install a few more things needed to build ObjFW:

$ pacman -S autoconf automake fossil make

Getting, building and installing ObjFW

Start the MinGW-w64 Win32 or Win64 Shell (depening on what version you want to build - do not use the MSYS2 Shell shortcut, but use the MinGW-w64 Win32 or Win64 Shell shortcut instead!) and check out ObjFW:

$ fossil clone https://objfw.nil.im objfw.fossil
$ mkdir objfw && cd objfw
$ fossil open ../objfw.fossil

You can also download a release tarball if you want. Now go to the newly checked out repository and build and install it:

$ ./autogen.sh && ./configure && make -j16 install

If everything was successfully, you can now build projects using ObjFW for Windows using the normal objfw-compile and friends.

Nintendo DS, Nintendo 3DS and Wii

Download and install devkitPro.

Nintendo DS

Follow the normal process, but instead of ./configure run:

$ ./configure --host=arm-none-eabi --with-nds

Nintendo 3DS

Follow the normal process, but instead of ./configure run:

$ ./configure --host=arm-none-eabi --with-3ds


Follow the normal process, but instead of ./configure run:

$ ./configure --host=powerpc-eabi --with-wii


Install amiga-gcc. Then follow the normal process, but instead of ./configure run:

$ ./configure --host=m68k-amigaos

Writing your first application with ObjFW

To create your first, empty application, you can use objfw-new:

$ objfw-new app MyFirstApp

This creates a file MyFirstApp.m. The -[applicationDidFinishLaunching] method is called as soon as ObjFW finished all initialization. Use this as the entry point to your own code. For example, you could add the following line there to create a "Hello World":

[of_stdout writeLine: @"Hello World!"];

You can compile your new app using objfw-compile:

$ objfw-compile -o MyFirstApp MyFirstApp.m

objfw-compile is a tool that allows building applications and libraries using ObjFW without needing a full-blown build system. If you want to use your own build system, you can get the necessary flags from objfw-config.


You can find the documentation for released versions of ObjFW here.

In order to build the documentation yourself (necessary to have documentation for trunk / master), you need to have Doxygen installed. Once installed, you can build the documentation from the root directory of the repository:

$ doxygen >/dev/null

Bugs and feature requests

If you find any bugs or have feature requests, please file a new bug in the bug tracker.

Alternatively, feel free to send a mail to js@nil.im!

Support and community

If you have any questions about ObjFW or would like to talk to other ObjFW users, the following venues are available:

Please don't hesitate to join any or all of those!

Commercial use

If for whatever reason neither the terms of the QPL nor those of the GPL work for you, a proprietary license for ObjFW including support is available upon request. Just write a mail to js@nil.im and we can find a reasonable solution for both parties.