Re: preparing for 1.5.24

[Ralf Wildenhues]

Hello Charles, 

Charles Wilson writes:
> > - It would help me greatly if someone could look into the Cygwin and
> >   MinGW mdemo* failures; and documentation updates if needed.

> Solution in this case is to turn auto-export back on

Or to mark all symbols as to be exported, no?
(Or to mark all other symbols explicitly.  But let's not go that way.) 

> It'd be nice to be able to say "whenever libltdl is used as a convenience 
> library to build a DLL, on windows libtool should automatically turn on 
> --export-all-symbols".  But that isn't true: if the target DLL is already 
> doing explicit declspec(dllexport), then (1) the target library would 
> work, today, without any changes, and (2) we don't want to override that 
> target DLL's explicit export settings by saying, "no, I'm going to export 
> everything".

ACK. 

> So, I'm not sure how to solve this, in a way that is platform-agnostic. 

I think the patch below should work, and be platform-agnostic.  WDYT?
OK for branch-1-5 and HEAD alike?  It fixes the similar failure there.
Do you think we should add some documentation bits a la "if you have the
same problem, consider this solution as well"? 

(FWIW, on HEAD there are other mdemo test failures which I haven't looked
at yet.) 

> FWIW, it doesn't appear that libtool's -export-dynamic will do the right 
> thing here.  I thought about setting export_dynamic_flag_spec to 
> '${wl}--export-all-symbols' for mingw/cygwin (currently, they inherit the 
> generic '${wl}--export-dynamic' setting [3]), and then using 
> '-export-dynamic' in libmlib_la_LDFLAGS for all platforms.

I don't think -export-dynamic is intended to have the semantics of
--export-all-symbols. 

> But I'm nervous about changing the definition of export_dynamic_flag_spec 
> -- because that would have wide-ranging effects.  Esepcially in a release 
> candidate, and especially especially in the RC for the last-ever 1.5.x 
> libtool.

I guess I should have written "the last 1.5.x release, unless serious
issues show up".  When writing, the intention was more of a "after this,
we work towards 2.0" then anything else. 

> [1] mdemo README:
>     Note that on Windows, for the purposes of illustrating ltdl, the
>     libraries *are* built as dll's, but do not have the __declspec
>     machinery to make them suitable for loading at link time.  This is
>     only for clarity inside this example, look at the example in ../demo
>     to see how the __declspec macros should be set up. 
>
> [2] BTW, ../demo does not set up any __declspec macros. I believe the 
> readme snippet above is really old, and pre-dates auto-export/auto-import 
> functionality.  At best, this snippet is now specific only to non-gcc on 
> Windows, which is at present only barely supported in libtool-1.5.x 
> anyway.  Notwithstanding my reference to this snippet in the context of 
> libltdl-as-convenience-lib, I think this snippet should be deleted 
> entirely.

Indeed.  I guess for branch-1-5 it should be removed.  For HEAD and
eventual MSVC support, those would need to be added again. 

> [3] I'm not sure, but it looks like cygwin's ld simply ignores 
> --export-dynamic.  From a brief look at the bfd/ld source code, this ld 
> option seems to be ELF-specific.

I guess.  I don't know what its effect on Cygwin should be though.
Not --export-all-symbols, that's not the right thing. 

Cheers, and thank you,
Ralf 

      * mdemo/Makefile.am (libmlib_la_LDFLAGS): Add -export-symbols-regex
      ".*" because the convenience libltdl uses export markers and thus
      turns off autoexport on w32.  Fixes test failures for Cygwin and
      MinGW.  Bug analysis by Charles Wilson. 


Index: mdemo/Makefile.am
===================================================================
RCS file: /sources/libtool/libtool/mdemo/Attic/Makefile.am,v
retrieving revision 1.46.2.2
diff -u -r1.46.2.2 Makefile.am
--- mdemo/Makefile.am   3 Feb 2006 09:37:34 -0000       1.46.2.2
+++ mdemo/Makefile.am   18 Feb 2007 12:07:21 -0000
@@ -19,9 +19,12 @@
 libsub_la_SOURCES = sub.c
 libsub_la_LDFLAGS = -no-undefined
 
+## Use -export-symbols-regex here explicitly because libltdl marks
+## its exported symbols, and we use libltdl as a convenience archive.
+## Thus, on w32, auto-exporting is turned off.
 libmlib_la_SOURCES = mlib.c
 libmlib_la_LIBADD = @LIBLTDL@ "-dlopen" foo1.la "-dlopen" libfoo2.la
-libmlib_la_LDFLAGS = -no-undefined
+libmlib_la_LDFLAGS = -no-undefined -export-symbols-regex ".*"
 libmlib_la_DEPENDENCIES = @LIBLTDL@ libsub.la foo1.la libfoo2.la
 
 noinst_HEADERS = foo.h