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How To Compile
Lots of people download binary distributions of c-ares. This document does not describe how to install c-ares using such a binary package. This document describes how to compile, build and install c-ares from source code.
If you get your code off a Git repository rather than an official release tarball, see the GIT-INFO file in the root directory for specific instructions on how to proceed.
In particular, if not using CMake you will need to run ./buildconf
(Unix) or
buildconf.bat
(Windows) to generate build files, and for the former
you will need a local installation of Autotools. If using CMake the steps are
the same for both Git and official release tarballs.
A normal Unix installation is made in three or four steps (after you've unpacked the source archive):
./configure
make
make install
You probably need to be root when doing the last command.
If you have checked out the sources from the git repository, read the GIT-INFO on how to proceed.
Get a full listing of all available configure options by invoking it like:
./configure --help
If you want to install c-ares in a different file hierarchy than /usr/local, you need to specify that already when running configure:
./configure --prefix=/path/to/c-ares/tree
If you happen to have write permission in that directory, you can do make install
without being root. An example of this would be to make a local
installation in your own home directory:
./configure --prefix=$HOME
make
make install
To force configure to use the standard cc compiler if both cc and gcc are present, run configure like
CC=cc ./configure
# or
env CC=cc ./configure
To force a static library compile, disable the shared library creation by running configure like:
./configure --disable-shared
If you're a c-ares developer and use gcc, you might want to enable more
debug options with the --enable-debug
option.
Some versions of uClibc require configuring with CPPFLAGS=-D_GNU_SOURCE=1
to get correct large file support.
The Open Watcom C compiler on Linux requires configuring with the variables:
./configure CC=owcc AR="$WATCOM/binl/wlib" AR_FLAGS=-q \
RANLIB=/bin/true STRIP="$WATCOM/binl/wstrip" CFLAGS=-Wextra
(This section was graciously brought to us by Jim Duey, with additions by Dan Fandrich)
Download and unpack the c-ares package.
cd
to the new directory. (e.g. cd c-ares-1.7.6
)
Set environment variables to point to the cross-compile toolchain and call
configure with any options you need. Be sure and specify the --host
and
--build
parameters at configuration time. The following script is an
example of cross-compiling for the IBM 405GP PowerPC processor using the
toolchain from MonteVista for Hardhat Linux.
#! /bin/sh
export PATH=$PATH:/opt/hardhat/devkit/ppc/405/bin
export CPPFLAGS="-I/opt/hardhat/devkit/ppc/405/target/usr/include"
export AR=ppc_405-ar
export AS=ppc_405-as
export LD=ppc_405-ld
export RANLIB=ppc_405-ranlib
export CC=ppc_405-gcc
export NM=ppc_405-nm
./configure --target=powerpc-hardhat-linux \
--host=powerpc-hardhat-linux \
--build=i586-pc-linux-gnu \
--prefix=/opt/hardhat/devkit/ppc/405/target/usr/local \
--exec-prefix=/usr/local
You may also need to provide a parameter like --with-random=/dev/urandom
to configure as it cannot detect the presence of a random number
generating device for a target system. The --prefix
parameter
specifies where c-ares will be installed. If configure
completes
successfully, do make
and make install
as usual.
In some cases, you may be able to simplify the above commands to as little as:
./configure --host=ARCH-OS
Almost identical to the unix installation. Run the configure script in the
c-ares root with sh configure
. Make sure you have the sh executable in
/bin/
or you'll see the configure fail toward the end.
Run make
(This section was graciously brought to us by David Bentham)
As QNX is targeted for resource constrained environments, the QNX headers
set conservative limits. This includes the FD_SETSIZE
macro, set by default
to 32. Socket descriptors returned within the c-ares library may exceed this,
resulting in memory faults/SIGSEGV crashes when passed into select(..)
calls using fd_set
macros.
A good all-round solution to this is to override the default when building
c-ares, by overriding CFLAGS
during configure, example:
# configure CFLAGS='-DFD_SETSIZE=64 -g -O2'
The library can be cross-compiled using gccsdk as follows:
CC=riscos-gcc AR=riscos-ar RANLIB='riscos-ar -s' ./configure \
--host=arm-riscos-aof --without-random --disable-shared
make
where riscos-gcc
and riscos-ar
are links to the gccsdk tools.
You can then link your program with c-ares/lib/.libs/libcares.a
.
Method using a configure cross-compile (tested with Android NDK r7b):
-
prepare the toolchain of the Android NDK for standalone use; this can be done by invoking the script:
./tools/make-standalone-toolchain.sh
which creates a usual cross-compile toolchain. Let's assume that you put this toolchain below
/opt
then invoke configure with something like:export PATH=/opt/arm-linux-androideabi-4.4.3/bin:$PATH ./configure --host=arm-linux-androideabi [more configure options] make
-
if you want to compile directly from our GIT repo you might run into this issue with older automake stuff:
checking host system type... Invalid configuration `arm-linux-androideabi': system `androideabi' not recognized configure: error: /bin/sh ./config.sub arm-linux-androideabi failed
this issue can be fixed with using more recent versions of
config.sub
andconfig.guess
which can be obtained here: http://git.savannah.gnu.org/gitweb/?p=config.git;a=tree you need to replace your system-own versions which usually can be found in your automake folder:find /usr -name config.sub
Current releases of c-ares introduce a CMake v3+ build system that has been tested on most platforms including Windows, Linux, FreeBSD, macOS, AIX and Solaris.
In the most basic form, building with CMake might look like:
cd /path/to/cmake/source
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr/local/cares ..
make
sudo make install
Options to CMake are passed on the command line using "-D${OPTION}=${VALUE}". The values defined are all boolean and take values like On, Off, True, False.
Option Name | Description | Default Value |
---|---|---|
CARES_STATIC | Build the static library | Off |
CARES_SHARED | Build the shared library | On |
CARES_INSTALL | Hook in installation, useful to disable if chain building | On |
CARES_STATIC_PIC | Build the static library as position-independent | Off |
CARES_BUILD_TESTS | Build and run tests | Off |
CARES_BUILD_CONTAINER_TESTS | Build and run container tests (implies CARES_BUILD_TESTS, Linux only) | Off |
CARES_BUILD_TOOLS | Build tools | On |
CARES_SYMBOL_HIDING | Hide private symbols in shared libraries | Off |
CARES_THREADS | Build with thread-safety support | On |
Ninja is the next-generation build system meant for generators like CMake that heavily parallelize builds. Its use is very similar to the normal build:
cd /path/to/cmake/source
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr/local/cares -G "Ninja" ..
ninja
sudo ninja install
cd \path\to\cmake\source
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=C:\cares -G "NMake Makefiles" ..
nmake
nmake install
cd \path\to\cmake\source
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=C:\cares -G "MSYS Makefiles" ..
make
make install
As a general rule, building a DLL with static CRT linkage is highly discouraged, and intermixing CRTs in the same app is something to avoid at any cost.
Reading and comprehension of the following Microsoft Learn article is a must for any Windows developer. Especially important is full understanding if you are not going to follow the advice given above.
If your app is misbehaving in some strange way, or it is suffering from memory corruption, before asking for further help, please try first to rebuild every single library your app uses as well as your app using the debug multithreaded dynamic C runtime.
Building is supported for native windows via both AutoTools and CMake. When
building with autotools, you can only build either a shared version or a static
version (use --disable-shared
or --disable-static
). CMake can build both
simultaneously.
All of the MSYS environments are supported: MINGW32
, MINGW64
, UCRT64
,
CLANG32
, CLANG64
, CLANGARM64
.
Make sure that MinGW32's bin dir is in the search path, for example:
set PATH=c:\mingw32\bin;%PATH%
then run 'make -f Makefile.m32' in the root dir.
If you use MSVC 6 it is required that you use the February 2003 edition PSDK: http://www.microsoft.com/msdownload/platformsdk/sdkupdate/psdk-full.htm
Run the vcvars32.bat
file to get a proper environment. The
vcvars32.bat
file is part of the Microsoft development environment and
you may find it in C:\Program Files\Microsoft Visual Studio\vc98\bin
provided that you installed Visual C/C++ 6 in the default directory.
Further details in README.msvc
When building an application that uses the static c-ares library, you must
add -DCARES_STATICLIB
to your CFLAGS
. Otherwise the linker will look for
dynamic import symbols.
c-ares supports building as a 32bit protected mode application via DJGPP. It is recommended to use a DJGPP cross compiler from Andrew Wu as building directly in a DOS environment can be difficult.
It is required to also have Watt-32 available
built using the same compiler. It is recommended to build the latest master
branch from GitHub.
Finally, the DJ_PREFIX
and WATT_ROOT
environment variables must be set
appropriately before calling make Makefile.dj
to build c-ares.
Please refer to our CI GitHub Actions Workflow for a full build example, including building the latest Watt-32 release.
Building under OS/2 is not much different from building under unix. You need:
- emx 0.9d
- GNU make
- GNU patch
- ksh
- GNU bison
- GNU file utilities
- GNU sed
- autoconf 2.13
If during the linking you get an error about _errno
being an undefined
symbol referenced from the text segment, you need to add -D__ST_MT_ERRNO__
in your definitions.
If you're getting huge binaries, probably your makefiles have the -g
in
CFLAGS
.
To compile libcares.a
/ libcares.lib
you need:
- either any gcc / nlmconv, or CodeWarrior 7 PDK 4 or later.
- gnu make and awk running on the platform you compile on; native Win32 versions can be downloaded from: http://www.gknw.net/development/prgtools/
- recent Novell LibC SDK available from: http://developer.novell.com/ndk/libc.htm
- or recent Novell CLib SDK available from: http://developer.novell.com/ndk/clib.htm
Set a search path to your compiler, linker and tools; on Linux make
sure that the var OSTYPE
contains the string 'linux'; set the var
NDKBASE
to point to the base of your Novell NDK; and then type
make -f Makefile.netware
from the top source directory;
You can build and install c-ares using vcpkg dependency manager:
git clone https://github.com/Microsoft/vcpkg.git
cd vcpkg
./bootstrap-vcpkg.sh
./vcpkg integrate install
./vcpkg install c-ares
The c-ares port in vcpkg is kept up to date by Microsoft team members and community contributors. If the version is out of date, please create an issue or pull request on the vcpkg repository.
To build c-ares with OpenWatcom, you need to have at least version 1.9 of OpenWatcom. You can get the latest version from http://openwatcom.org/ftp/install/. Install the version that corresponds to your current host platform.
After installing OpenWatcom, open a new command prompt and execute the following commands:
cd \path\to\cmake\source
buildconf.bat
wmake -u -f Makefile.Watcom
After running wmake, you should get adig.exe, ahost.exe, and the static and dynamic versions of libcares.
This is a probably incomplete list of known hardware and operating systems that c-ares has been compiled for. If you know a system c-ares compiles and runs on, that isn't listed, please let us know!
- Linux (i686, x86_64, AARCH64, and more)
- MacOS 10.4+
- iOS
- Windows 8+ (i686, x86_64)
- Android (ARM, AARCH64, x86_64)
- FreeBSD
- NetBSD
- OpenBSD
- Solaris (SPARC, x86_64)
- AIX (POWER)
- Tru64 (Alpha)
- IRIX (MIPS)
- Novell NetWare (i386)
- c-ares: https://c-ares.org/
- MinGW-w64: http://mingw-w64.sourceforge.net/
- MSYS2: https://msys2.org
- OpenWatcom: http://www.openwatcom.org/