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** This file is adapted from libcurl and not yet fully rewritten for c-ares! **
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How To Compile
Installing Binary Packages
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.
Building from git
If you get your code off a git repository, see the GIT-INFO file in the
root directory for specific instructions on how to proceed.
A normal unix installation is made in three or four steps (after you've
unpacked the source archive):
make ahost adig acountry (optional)
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
install in your own home directory:
./configure --prefix=$HOME
make install
To force configure to use the standard cc compiler if both cc and gcc are
present, run configure like
CC=cc ./configure
env CC=cc ./configure
To force a static library compile, disable the shared library creation
by running configure like:
./configure --disable-shared
If you're a c-ares developer and use gcc, you might want to enable more
debug options with the --enable-debug option.
Some versions of uClibc require configuring with CPPFLAGS=-D_GNU_SOURCE=1
to get correct large file support.
The Open Watcom C compiler on Linux requires configuring with the variables:
./configure CC=owcc AR="$WATCOM/binl/wlib" AR_FLAGS=-q \
RANLIB=/bin/true STRIP="$WATCOM/binl/wstrip" CFLAGS=-Wextra
Building Windows DLLs and C run-time (CRT) linkage issues
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 Microsoft Knowledge Base articles
KB94248 and KB140584 is a must for any Windows developer. Especially
important is full understanding if you are not going to follow the
advice given above.
KB94248 - How To Use the C Run-Time
KB140584 - How to link with the correct C Run-Time (CRT) library
KB190799 - Potential Errors Passing CRT Objects Across DLL Boundaries
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.
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.
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'
See the separate INSTALL.devcpp file for details.
MSVC 6 caveats
If you use MSVC 6 it is required that you use the February 2003 edition PSDK:
MSVC from command line
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
Details in README.msvc
Important static c-ares usage note
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.
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
(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
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
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:
- recent Novell LibC SDK available from:
- or recent Novell CLib SDK available from:
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;
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:
which creates a usual cross-compile toolchain. Lets 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]
- 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
and config.guess which can be obtained here:;a=tree
you need to replace your system-own versions which usually can be
found in your automake folder:
find /usr -name config.sub
(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.
(begin script)
#! /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 \
(end script)
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
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!
- Alpha Tru64 v5.0 5.1
- ARM Android 1.5, 2.1, 2.3
- MIPS IRIX 6.2, 6.5
- Power AIX 3.2.5, 4.2, 4.3.1, 4.3.2, 5.1, 5.2
- i386 Linux 1.3, 2.0, 2.2, 2.3, 2.4, 2.6
- i386 Novell NetWare
- i386 Windows 95, 98, ME, NT, 2000, XP, 2003
- x86_64 Linux
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