Re: AM_LDFLAGS += -no-undefined

[Bob Friesenhahn]

On Tue, 8 Apr 2014, Akim Demaille wrote:

> Hi all,
>
> My project builds many libraries and some modules.  I've just started
> using ltdl in it, with a non-recursive build.  As a result,
> I have inherited the following line in my single Makefile:
>
> AM_LDFLAGS             += -no-undefined
>
> so my libraries now fail to link.  Is this on purpose?
> Shouldn't this flag be for libltdl only?  I have not seen
> information about this in the documentation, but I might
> have not looked correctly (I looked at occurrences of
> -no-undefined and LDFLAGS).

This option is necessary in order to build DLLs under Windows (and 
likely shared libraries under AIX).  It expects a commitment to supply 
all dependency libraries at library/module link time.  You could edit 
the copy of libltd/Makefile.inc in your project if it causes an issue 
for you but there may be consequences for platforms which need it.

GraphicsMagick uses a non-recursive build and used to build libltdl as 
part of the build (for at least 8 years).  Even though ltdl added 
-no-undefined it was not a problem since GraphicsMagick was 
intentionally using this option.

Since then, I realized that building libltdl as part of the project 
was prohibitive, costly, and dangerous.  It was better to rely on 
libltdl to be a formally installed dependency on the system.  Now 
GraphicsMagick treats libltdl just like any other external library and 
life is much improved.  I would encourage any other package to not 
bundle libltdl and to simply document that it must already be 
installed on the system.

Perhaps it would be wise for libltdl to be unbundled from libtool 
itself and libltdl become a separate project.  They would still have a 
relationship but then it would be easier to install libltdl.

Bob
--
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/