Re: ld: error: duplicate symbol:

On Mon, 17 Aug 2020 21:49:52 +0200
Dimitry Andric <dim_at_FreeBSD.org> wrote:

> On 17 Aug 2020, at 15:42, O. Hartmann <ohartmann_at_walstatt.org> wrote:
> > 
> > On CURRENT 9not necessarily most recent with LLVM11, but since noon
> > of today it is FreeBSD 13.0-CURRENT #15 r364297: Mon Aug 17
> > 14:39:06 CEST 2020 amd64) I'm faced with some very sticky and nasty
> > micompilations in several essential ports, for instance
> > 
> > ports-mgmt/pkg
> > devel/libunwind
> > devel/binutils
> > 
> > In most cases somewhere in the (parallel) build the process fails
> > with the error
> > 
> > ld: error: duplicate symbol: xxxxxxxx  
> 
> This is because clang 11 (and gcc 10) now default to -fno-common. The
> rationale is explained pretty well in
> <https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=6271dd984d7f920d4fb17ad37af6a1f8e6b796dc>:
> 
> "GCC currently defaults to -fcommon.  As discussed in the PR, this is
> an ancient C feature which is not conforming with the latest C
> standards.  On many targets this means global variable accesses have
> a codesize and performance penalty. This applies to C code only, C++
> code is not affected by -fcommon.  It is about time to change the
> default."
> 
> A quick fix is to add CFLAGS+=-fcommon to your make.conf, but that is
> rather a big hammer. It is better to add it to just the ports that
> show problems due to duplicated symbols. And ideally, those duplicated
> symbols should be patched out of the ports.
> 
> For example, ports-mgmt/pkg already has such a patch:
> https://github.com/freebsd/pkg/commit/7fbde60c4af4a1a07db7c5c36efbb2a495f7b1a4
> but I have no idea why it is not yet in the ports tree.
> 
> -Dimitry
> 

Thank you for the fast response and thorough explanation.

oh