[CLN-list] Linking against cln fails when built with link-time-optimization

[Atri Bhattacharya]

On Sun, 2020-09-20 at 13:11 +0200, Atri Bhattacharya wrote:
> Hello,
> When the shared library for CLN is built with link-time optimization
> [1] (LTO) enabled, linking against libcln.so fails (for example GiNaC
> fails to build). Turning off link-time optimization fixes the linking
> issue, but I wonder if this is a bug in CLN that needs fixing or a
> compiler issue and if we can build and use LTO enabled CLN in the
> future.
> 
> This issue was first reported [2] against openSUSE Tumbleweed which
> builds its packages with LTO flags by default; we are currently in
> the
> process of working around this by disabling the LTO flags
> specifically
> for CLN [3].
> 
> Thanks in advance for any suggestion as to how to fix TLO-enabled CLN
> builds or if indeed disabling LTO is the only way to go (at least for
> now). I maintain openSUSE's CLN and GiNaC packages.

To follow up on this, we found that the problem was us building the cln
library with "-fvisibility-inlines-hidden" in combination with LTO.
Turning off the "-fvisibility-inlines-hidden" flag has fixed this issue
(even with LTO enabled). Please see the original bug report for a
discussion:
<https://bugzilla.opensuse.org/show_bug.cgi?id=1176710>
if interested.

Thanks in particular to Alexei for testing and commenting on my initial
post.

Cheers,
--
Atri Bhattacharya