Library resolution with autoconf? - autoconf

Question

I'm building my first autoconf managed package.
However I can't find any simple examples anywhere of how to specify a required library, and find that library where it might be in various different places.
I've currently got:
AC_CHECK_LIB(['event'], ['event_init'])
but:
It doesn't find the version installed in /opt/local/lib
It doesn't complain if the library isn't actually found
I need to set the include path to /opt/local/include too
any help, or links to decent tutorials much appreciated...

Answer 1

autoconf script cannot guess the "optional" library locations, which may vary from one platform to another. So you can say
CPPFLAGS="-I/opt/local/include" LDFLAGS="-L/opt/local/lib" ./configure
For AC_CHECK_LIB() you need to specify the fail condition explicitly in "action-if-false" argument:
dnl This is simply print "no" and continue:
AC_CHECK_LIB([m], [sqrt123])
dnl This will stop:
AC_CHECK_LIB([m], [sqrt123], [], [AC_MSG_ERROR([sqrt123 was not found in libm])])
Output:
checking for sqrt123 in -lm... no
checking for sqrt123 in -lm... no
configure: error: sqrt123 was not found in libm
AC_CHECK_LIB() does not fail by default on obvious reasons: one may check for several different libraries that provide similar functionality and choose one of them :)
Also have a look at this post for similar topic.

Answer 2

You need to manually set CFLAGS, CXXFLAGS and LDFLAGS if you want gcc/g++ to look in non-standard locations.
So, before calling AC_CHECK_LIB(), do something like
CFLAGS="$CFLAGS -I/opt/local/include"
CXXFLAGS="$CXXFLAGS -I/opt/local/include"
LDFLAGS="$LDFLAGS -L/opt/local/lib"
You don't need CXXFLAGS if you're only using gcc throughout your configure script.

Answer 3

If the library ships a .pc file, consider using the PKG_CHECK_MODULES() macro which does the things you want. If it's your own library, just ship a .pc file into /usr/lib/pkgconfig, it'll make it much easier for other developers to depend/use it.

Answer 4

I know this is an old thread now, but I guess this may help some people out. This is how I find some stuff.
hdff="no"
hdffprefix="ERROR"
AC_ARG_WITH(hdf,[ --with-hdf Compile with hdf library, for output.],[hdffprefix=$withval hdff="yes"],[])
# if there is no value given, it appears tha hdffprefix is set to "yes"
if test $hdffprefix = "yes" -a $hdff = "yes"
then
echo "HDF: Attempting to find HDF"
hdffprefix="ERROR"
# check if hdffprefix is set, if it is not, it sets it to "ERROR" and the
# 'if' comparison evaluates to true
if [[ "$hdffprefix" == "ERROR" ]]
then
echo "HDF: hdffprefix not set, searching PATH"
for i in `echo $PATH | tr ':' '\n'`
do
if [[ $i == *hdf* ]]
then
if [[ $i == *bin/* ]]
then
hdffprefix=${i%bin/}
# if it doesn't exist, re-set to ERROR
if [[ ! -f ${hdffprefix}include/hdf.h ]]
then
hdffprefix="ERROR"
fi
elif [[ $i == *bin* ]]
then
hdffprefix=${i%bin}
# if it doesn't exist, re-set to ERROR
if [[ ! -f ${hdffprefix}include/hdf.h ]]
then
hdffprefix="ERROR"
fi
fi
fi
done
if [[ "$hdffprefix" == "ERROR" ]]
then
echo "HDF: hdffprefix not found in PATH, trying 'which'"
WHICH_TEST_HDF=`which hdf2gif`
if [[ WHICH_TEST_HDF != "" ]]
then
hdffprefix=${WHICH_TEST_HDF%bin/hdf2gif}
else
echo "HDF: Warning - hdf not found"
fi
fi
fi
if [[ "$hdffprefix" != "ERROR" ]]
then
hdff="yes"
echo "HDF found: $hdffprefix"
fi
fi
if test $hdff = 'yes'; then
hdfincs=" -DUSE_HDF -I"${hdffprefix}"include"
scriptotherlibsinc=${scriptotherlibsinc}" -L"${hdffprefix}"/lib"
scriptotherlibs=${scriptotherlibs}" -lmfhdf -ldf -ljpeg -lz"
AC_CHECK_HEADERS([${hdffprefix}/include/hdf.h],,[AC_MSG_ERROR([Cannot find hdf.h])])
AC_CHECK_HEADERS([${hdffprefix}/include/mfhdf.h],,[AC_MSG_ERROR([Cannot find mfhdf.h])])
fi

Answer 5

Here's how to do it:
# We need the math library for some tests.
AC_CHECK_LIB([m], [floor], [],
[AC_MSG_ERROR([Can't find or link to the math library.])])
Note that it does not automatically error out when the library is not found, you must called AC_MSG_ERROR() as in the code above.

Answer 6

So you want to setup autoconf to find these directories automatically and codelogic gives the answer; but suppose you don't want to search there on all system, only on a mac. You can add the following
AC_CANONICAL_HOST
case $host_os in
darwin* )
CFLAGS="$CFLAGS -I/opt/local/include"
CXXFLAGS="$CXXFLAGS -I/opt/local/include"
LDFLAGS="$LDFLAGS -L/opt/local/lib"
;;
esac
Note that I added it as a case tree so that you can add things for a variety of operating systems later (such as linux* and BSD).

Answer 7

If you are happen to be using GCC or CLANG, the standard way is having the environment variable CPLUS_INCLUDE_PATH with the path of the non-official includes files and LIBRARY_PATH for the libraries. Remind that you do not have to change anything in the configure.ac. So you can just call the configure in this way:
$ export CPLUS_INCLUDE_PATH=/opt/local/include
$ export LIBRARY_PATH=/opt/local/lib
$ ./configure
The facto standard variables
Variable | lang | Usage
-------------------|------|---------
C_INCLUDE_PATH | C | colon separated list of include directory paths
CPLUS_INCLUDE_PATH | C++ | colon separated list of include directory paths
LIBRARY_PATH | C/C++| colon separated compiling time static linking dirs
LD_RUN_PATH | C/C++| colon separated compiling time dynamic linking dirs
LD_LIBRARY_PATH | C/C++| colon separated run-time dynamic linking dirs
CPPFLAGS | C/C++| prepocessor flags
CFLAGS | C | Compiling flags
CXXFLAGS | C++ | Compiling flags
LDFLAGS | C++ | Linking flags
NOTE You can use CPPFLAGS or LDFLAGS, however, CPLUS_INCLUDE_PATH /LIBRARY_PATH exactly fits your requirement. CPPFLAGS/LDFLAGS are for flags which can be many things but *_PATH are for PATHs
Portability Note: While this will work on many modern compilers, not all compilers will respect these variables. Some cross-compilers will outright ignore or overwrite them, which forces one to resort to CFLAGS and LDFLAGS modifications as mentioned in other answers.
SOURCE Might the downvotes here be because of the lack of sources in my answer. Here is for CPLUS_INCLUDE_PATH in GCC: https://gcc.gnu.org/onlinedocs/cpp/Environment-Variables.html