Linking a Shared Library Autotools

Question

I'm an autotools beginner, and I can't seem to figure out how to use an external library correctly with autotools.

Here is my directory hierarchy.

.
├── configure.ac
├── Makefile.am
├── README
└── src
    (source files)
    └── Makefile.am

The library's name is acml_mp and is, by default, installed in /opt/acml5.3.1/gfortran64/lib. There is also a directory called /opt/acml5.3.1/gfortran64/include to include. When I compile without autotools, including the usual compiler flags works fine:

g++ ... -L/opt/acml5.3.1/gfortran64_mp/lib -I/opt/acml5.3.1/gfortran64_mp/include -lacml_mp ...

In configure.ac, I put the command AC_LIB_LINKFLAGS([acml_mp]) which I think only deals with the -lacml_mp flag.

Basically, the end goal is to have autoconf search for this library, and have the makefile generated by automake include the correct link/include paths when compiling. Finally, when compiling by hand, I always need to modify the environment variable LD_LIBRARY_PATH using the command

Export LD_LIBRARY_PATH=/opt/acml5.3.1/gfortran64_mp/lib:$LD_LIBRARY_PATH

which, ideally, I would like to avoid having the user do. Apologies if this information exists already, I looked through SO and Google for a few hours to no avail.

Brett Hale Brett Hale · Accepted Answer · 2013-08-13T18:58:31

The problem with searching is that /opt/acml5.3.1/gfortran is never going to be a standard (search) location for libraries (and headers) like /usr/lib, /usr/local/lib etc. Probably the best bet is to supply this location explicitly via --with-acml to configure.

The AC_ARG_WITH macro is described here. Assuming test "x$with_acml" != xno, you can try linking a program with AC_LINK_IFELSE.

AC_LANG_PUSH([C]) # or [Fortran]

ac_save_acml_CPPFLAGS="$CPPFLAGS" # or FCFLAGS instead of CPPFLAGS.
ac_save_acml_LIBS="$LIBS"

ac_acml_CPPFLAGS="-I${with_acml}/include"
ac_acml_LIBS="-L${with_acml}/libs -lacml_mp"

CPPFLAGS+="$ac_acml_CPPFLAGS"
LIBS+="$ac_acml_LIBS"

AC_LINK_IFELSE([AC_LANG_PROGRAM( ... some C or Fortran program ... )],,
               AC_MSG_FAILURE([couldn't link with acml]))

AC_LANG_POP

# we *could* stop here... but we might need the original values later.

CPPFLAGS="$ac_save_acml_CPPFLAGS"
LIBS="$ac_save_acml_LIBS"

AC_SUBST(ACML_CPPFLAGS, $ac_acml_CPPFLAGS)
AC_SUBST(ACML_LIBFLAGS, $ac_acml_LIBS)

Assuming you've initialized libtool support with LT_INIT, you can add the acml library with $(ACML_LIBFLAGS) to your own libraries in src/Makefile.am via the LIBADD variable, or to executables with the LDADD variable. or <lib>_la_LIBADD, <prog>_LDADD respectively.

To compile sources with the $(ACML_CPPFLAGS) include path, add it to the AM_CPPFLAGS variable. Or the <prog>_CPPFLAGS variable.

It's difficult to be specific without knowing how your Makefile.am is already set up. I know it looks complicated - but it's better to get the infrastructure right the first time. I'll add to the answer if you have further questions.

Linking a Shared Library Autotools

1 Answers