Re: libtool can't build shared library unless -no-undefined specified

[Brian Inglis <Brian.Inglis@SystematicSw.ab.ca>]

On 2024-05-21 07:18, Jon Turney via Cygwin-apps wrote:
> On 17/05/2024 05:50, Brian Inglis via Cygwin-apps wrote:
>> On 2024-05-16 15:45, Ken Brown via Cygwin-apps wrote:
>>> On 5/16/2024 4:24 PM, Brian Inglis via Cygwin-apps wrote:
>>>> Trying to update dateutils, autotools build fails with:
>>>> libtool: error: can't build x86_64-pc-cygwin shared library unless 
>>>> -no-undefined is specified
>>>> Suggestions for overrides or fixes?
>>>> Tried:
>>>> LDFLAGS="$LDFLAGS -Wl,--no-allow-shlib-undefined -Wl,--no-undefined"
>>>> CYGCONF_ARGS="
>>>>       --enable-contrib
>>>>       --enable-tzmap-fetch
>>>>       lt_no_undefined_flag=--no-undefined
>>>>       no_undefined_flag=--no-undefined
>>> You and I discussed this a few years ago in connection with curl.  The 
>>> solution there, and in most similar cases, is to add -no-undefined to the 
>>> appropriate lib*_la_LDFLAGS variable(s) in Makefile.am.  See

Had to patch into lib AM_LDFLAGS variable, then found out that library was not 
for use in open source packages, but only required to link with a (missing) 
proprietary MatLab module, so dropped the config --enable-contrib option!

> Yeah, building stuff for Cygwin often requires adding this flag in the 
> appropriate places, to say "yes, I really do want a shared library".
> https://www.gnu.org/software/libtool/manual/html_node/Link-mode.html#Link-mode
>> -no-undefined
>> Declare that output-file does not depend on any libraries other than
>> the ones listed on the command line, i.e., after linking, it will not
>> have unresolved symbols. Some platforms require all symbols in shared
>> libraries to be resolved at library creation (see Inter-library
>> dependencies), and using this parameter allows libtool to assume that
>> this will not happen.
> Note that because this flag doesn't do anything for non-PE targets, it's (a) 
> always safe to upstream, and (b) doesn't actually prevent development from 
> unwittingly introducing unresolved symbols.

In that case, could we ask Bruno to add into gnulib somewhere appropriate?

> This should probably be mentioned in the FAQ item on PE linkage peculiarities.

In libtool info?

-- 
Take care. Thanks, Brian Inglis              Calgary, Alberta, Canada

La perfection est atteinte                   Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter  not when there is no more to add
mais lorsqu'il n'y a plus rien à retirer     but when there is no more to cut
                                 -- Antoine de Saint-Exupéry