Re: Non-standard link paths

[Bob Friesenhahn]

On Thu, 29 Jan 2004, Bill Moseley wrote:

> We are always struggling with linking with (run-time) libraries
> installed in non-standard locations.
>
> Is it true now that with autoconf the way to do this is:
>
>    ./configure \
>        CPPFLAGS=-I/path/to/headers \
>        LDFLAGS='-R/path/to/lib -L/path-to/lib'
>
> and that avoids the need for LD_RUN_PATH?  I get confused because I
> install some packages using old versions of autoconf and need to use
> LD_RUN_PATH before building/linking.

The -R/path/to/lib does the same thing as LD_RUN_PATH.  These options
are passed directly to the compiler and linker.

For old Autoconf, doing

  CPPFLAGS=-I/path/to/headers \
  LDFLAGS='-R/path/to/lib -L/path-to/lib'  \
  ./configure

accomplishes the same thing except that modern Autoconf will remember
these options for reconfigures while old Autoconf will not.

> How portable is the above?  Does autoconf also deal with platforms where
> LD_RUN_PATH is not supported?  I believe IRIX doesn't support
> LD_RUN_PATH.

Autoconf is not doing anything other than to validate that the
provided options successfully build working software.  The
user-provided *FLAGS options are compiler/platform/site specific.

> And to clear up something else, is it correct that using
>
>    --with-foo=/path/to/foo
>
> is not recommended -- rather the recommended way is simply --with-foo
> and use CPPFLAGS and LDFLAGS.

Using --with-foo=/path/to/foo is not Autoconf standard.  It is a
popular scheme added by many packages since it seems more
user-friendly.  However, the portability of this depends on how
sophisticated the implementation is.  It may work on just a few
operating systems or with a few compilers.

Bob
======================================
Bob Friesenhahn
address@hidden
http://www.simplesystems.org/users/bfriesen