Grand Central Dispatch (GCD)
GCD is a concurrent programming framework first shipped with Mac OS X Snow
Leopard. This package is an open source bundling of libdispatch, the core
user space library implementing GCD. At the time of writing, support for
the BSD kqueue API, and specifically extensions introduced in Mac OS X Snow
Leopard and FreeBSD 9-CURRENT, are required to use libdispatch. Support
for Linux is a work in progress (see Linux notes below). Other systems are
currently unsupported.
Configuring and installing libdispatch
GCD is built using autoconf, automake, and libtool, and has a number of
compile-time configuration options that should be reviewed before starting.
An uncustomized install requires:
sh autogen.sh
./configure
make
make install
The following configure options may be of general interest:
--with-apple-libpthread-source
Specify the path to Apple's libpthread package, so that appropriate headers
can be found and used.
--with-apple-libplatform-source
Specify the path to Apple's libplatform package, so that appropriate headers
can be found and used.
--with-apple-libclosure-source
Specify the path to Apple's Libclosure package, so that appropriate headers
can be found and used.
--with-apple-xnu-source
Specify the path to Apple's XNU package, so that appropriate headers can be
found and used.
--with-blocks-runtime
On systems where -fblocks is supported, specify an additional library path
in which libBlocksRuntime can be found. This is not required on OS X,
where the Blocks runtime is included in libSystem, but is required on
FreeBSD.
The following options are likely to only be useful when building libdispatch on
OS X as a replacement for /usr/lib/system/libdispatch.dylib:
--with-apple-objc4-source
Specify the path to Apple's objc4 package, so that appropriate headers can
be found and used.
--disable-libdispatch-init-constructor
Do not tag libdispatch's init routine as __constructor, in which case it
must be run manually before libdispatch routines can be called. This is the
default when building on OS X. For /usr/lib/system/libdispatch.dylib
the init routine is called automatically during process start.
--enable-apple-tsd-optimizations
Use a non-portable allocation scheme for pthread per-thread data (TSD) keys
when building libdispatch for /usr/lib/system on OS X. This should not
be used on other OS's, or on OS X when building a stand-alone library.
Typical configuration commands
The following command lines create the configuration required to build
libdispatch for /usr/lib/system on OS X El Capitan:
clangpath=$(dirname `xcrun --find clang`)
sudo mkdir -p "$clangpath/../local/lib/clang/enable_objc_gc"
LIBTOOLIZE=glibtoolize sh autogen.sh
cflags='-arch x86_64 -arch i386 -g -Os'
./configure CFLAGS="$cflags" OBJCFLAGS="$cflags" CXXFLAGS="$cflags" \
--prefix=/usr --libdir=/usr/lib/system --disable-static \
--enable-apple-tsd-optimizations \
--with-apple-libpthread-source=/path/to/10.11.0/libpthread-137.1.1 \
--with-apple-libplatform-source=/path/to/10.11.0/libplatform-73.1.1 \
--with-apple-libclosure-source=/path/to/10.11.0/libclosure-65 \
--with-apple-xnu-source=/path/to/10.11.0/xnu-3247.1.106 \
--with-apple-objc4-source=/path/to/10.11.0/objc4-680
make check
Typical configuration line for FreeBSD 8.x and 9.x to build libdispatch with
clang and blocks support:
sh autogen.sh
./configure CC=clang --with-blocks-runtime=/usr/local/lib
make check
Instructions for building on Linux. Initial focus is on ubuntu 15.04.
Prepare your system
1. Install compiler, autotools
sudo apt-get install clang
sudo apt-get install autoconf libtool pkg-config
2. Install dtrace (to generate provider.h)
sudo apt-get install systemtap-sdt-dev
3. Install libdispatch pre-reqs
sudo apt-get install libblocksruntime-dev libkqueue-dev libbsd-dev
Initialize git submodules:
We are using git submodules to incorporate a specific revision of the
upstream pthread_workqueue library into the build.
git submodule init
git submodule update
Build:
sh autogen.sh
./configure
make
Note: the build currently fails building tests, but libdispatch.so should
build successfully.