Porting shared library ELF projects in autoconf to OS X

Question

How do I use autoconf macros to conditionally change values in a configure-script or Makefile it ouputs through AC_OUTPUT.

The goal is to use AC_CANONICAL_TARGET, or some other way, to identify that I'm on OS X and then allow my Makefiles to adapt the LDFLAGS by removing -shared and replacing -soname with -dylib_install_name.

So I basically need to learn how to modify the AC_SUBST values or the local variables in the configure.ac file using a conditional statement that checks the target host.

I must add that I've been trying to use AC_COMPILE_IFELSE with AC_LANG_PROGRAM to compile this code.

#include <unistd.h>
#ifndef __APPLE__
error: This is not apple Darwin
#endif

While I don't get any errors, I can't really confirm that it works. There is no output related to it when I run the new script on FreeBSD or Darwin. Also I always use autoconf -Wall.

Second and third arguments to AC_COMPILE_IFELSE is [is_darwin=yes], [is_darwin=no] but how do I access these values?

Thanks very much in advance for any help.

Answer 1

Well just to get the question off of stack I'll answer it by saying that those variables in the second and third arguments of AC_COMPILE_IFELSE are available as SHELL variables throughout the configure.ac script. In fact I solved this by placing multiple variable definitions in these two arguments as they accept multiple lines of Shell code and not just one variable definition.