Re: LT_* equivalent to AC_CHECK_LIB?

[Bob Friesenhahn]

> > support it.
>
> > For example, specifying just -lpng might not cause the linker to
> > implicitly add -lz.
>
> Note that the linker that needs to figure this out is actually the dynamic
> linker as such dependencies should be resolved at run-time, *not* at link
> time.  A linker that does such resolution at link time actually re-adds
> most of the problems that libtool currently causes.

Right.  The linker needs to record that libpng.so is dependent on 
libz.so.X.X.X when libpng.so is built.  When a library or application 
links using -lpng, a system with full dependency support does not 
require (or want) -lz to be specified.  On the other hand, when using 
static libraries, or on systems lacking the dependency support, all 
the libraries involved need to be specified.  Usually the configure 
script has no reliable way to know if a library is static or shared.

Under Microsoft Windows (and versions of AIX) it is definitely 
necessary for all libraries to be specified.

libpng is an interesting case because some users of libpng will use 
libz functions directly (e.g. to compute a PNG chunk CRC).  In such 
cases, libz is also a direct dependency.

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