Re: Making shared libraries (DLLs) on Windows: -no-undefined

[Ralf Wildenhues]

* Christian Biesinger wrote on Mon, Apr 30, 2007 at 10:40:40PM CEST:
> Brian Dessent wrote:
> >So yes, you need to either use -no-undefined unconditionally, or
> >conditionalized on PE targets.
> 
> What's the point of doing this only on PE targets? Surely the library 
> will either have undefined symbols or not, independent of target... (and 
> note that Windows is not the only platform that needs -no-undefined for 
> shared libraries)

There are/were systems where libtool would use (the equivalent of)
  -Wl,-z -Wl,defs

but where this would hit issues with system libraries.  Compare for
example this comment about some SCO systems, from libtool.m4, which
indicates such a situation (before Libtool changed not to use -z defs
there):

      # Note: We can NOT use -z defs as we might desire, because we do not
      # link with -lc, and that would cause any symbols used from libc to
      # always be unresolved, which means just about no library would
      # ever link correctly.  If we're not using GNU ld we use -z text
      # though, which does catch some bad symbols but isn't as heavy-handed
      # as -z defs.

Generally I think you should be able to just use it everywhere.  The
Libtool testsuite uses it throughout and I cannot remember a test
failure due to it.  I'm however not sure whether there was an issue with
C++ code some time ago (so this data point may be FUD; sorry for not
investigating now).

Hope that helps.

Cheers,
Ralf