Question

Using autoconf in configure.ac I need to append to an output variable.

Specifically I want to append to the LIBS variable differently for each of my programs (myprogram1 and myprogram2 in the Makefile.am). Lets imagine myprogram1 requires a -lboost_python and myprogram2 requires -losg.

Essentially some programs require certain libs while others do not. Here is an example of what I am doing. Of course AC_SUBST does an assignment (= vs +=) from what I understand so that doesn’t work.

AC_CHECK_LIB([boost_python], [main], [AC_SUBST([myprogram1_LIBS], ["-lboost_python"])                      
  AC_DEFINE([HAVE_LIBBOOST_PYTHON], [1], [Define if you have libboost_python])],                  
  [AC_MSG_FAILURE([boost_python library not found])])  
AC_CHECK_LIB([osg], [main], [AC_SUBST([myprogram2_LIBS], ["-losg"])                      
  AC_DEFINE([HAVE_LIBOSG], [1], [Define if you have libosg])],                  
  [AC_MSG_FAILURE([osg library not found])])  

What I need is for the myprogram1_SOURCES to be built with the first lib and the myprogram2_SOURCES to be built with the second lib.

Is there an AC_APPEND_SUBST type macro I can use? And/or is there a better way for me to do what I need to do to build different programs with different libraries being linked?

Answer 1

I assume that your AC_CHECK_LIB calls and such do the right thing (if they don’t, have you tried using the macros from the autoconf archive (specifically AX_BOOST_PYTHON))? I can’t believe that both boost python and osg provide main.

Anyway, to answer the question as asked, you don’t have to provide the contents of an AC_SUBST‘d variable all at once, so you can do stuff like this:

myprogram1_LIBS=""
AX_BOOST_PYTHON
myprogram1_LIBS="$myprogram1_LIBS $BOOST_PYTHON_LIB"
# ...
AC_SUBST([myprogram1_LIBS])

P.S. the variable to add libraries to a program is LDADD or myprogram1_LDADD.