Library resolution with autoconf

autoconf

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…

Best Answer

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.

Related Solutions

Autoconf — including a static library (newbie)

You can set the location in configure.ac:

LOCATION=/home/john/mystuff
AC_SUBST(LOCATION)

AC_SUBST defines the variable $LOCATION in all your Makefile.ams and also replaces all occurrences of @LOCATION@ with the contents of $LOCATION. So then in your Makefile.am you can do

myprog_CPPFLAGS="-I$LOCATION"
myprog_LDADD="$LOCATION/helper.a"

PS. The reason why you need to reference the library directly is because -l looks for a properly-named library (e.g. libhelper.a) in the system library directories. However, since there's not all that much difference between a static library and an object file, there's no need to magically reference it using -l; you can just compile it into your program like you are doing now.

Why doesn’t autoconf pass the AC_CHECK_HEADER test when the .h is file clearly available

I found what the issue was. The library that I am working with is a C library, but the "inky" library that I am linking against is a C++ library. So, the language (AC_LANG) was set to C early in the configure.ac script. While performing checks for "inky", I needed to change the language to C++ so that Autoconf used the C++ compiler instead of the C compiler. This was done rather easily by using:

AC_LANG_PUSH([C++])
dnl # Do the checks for inky
AC_LANG_POP([C++])

This solved both the problem that I asked about in this thread, and on that I hand't posted yet wherein I couldn't get the AC_CHECK_LIB macro to work.

Thank you everyone for your input.

Best Answer

Related Solutions

Autoconf — including a static library (newbie)

Why doesn’t autoconf pass the AC_CHECK_HEADER test when the .h is file clearly available

Related Topic