Linker problems with system vs bundled libraries (RPATH vs RUNPATH) / LTO / gold

[Дилян Палаузов]

Hello,

my initial understanding of the case “Linker problems with system vs bundled libraries (RPATH vs RUNPATH) ” is, that
ld.bfd and ld.gold behave differently, which is exposed by invoking --enable-linker=

How do ld.bfd and ld.gold differ, that triggered the problem?

Based on what does ./configure --help print behind --enable-lto: best used with “gold”.  Are there any known problems
with ld.bfd?

The "gold as linker" in configure.in/configure.ac comes from commit fc41132306 back in 2011 and ld.bfd can handle linker
plugins at least since 2015.

The AS_HELP_STRING for --enable-lto says "both gold and lld linkers generally use less memory and link faster". 
Compared to what?  It shoud say "compared to ld.bfd".

--enable-lto switches AR, NM and RANLIB to be gcc-ar, gcc-nm and gcc-ranlib, but… on some systems the binary is called
gcc-ar-4, for clang you have to use llvm-ar, which on some systems is called llvm-ar-5.0.  I am not aware of a single
autoconf project that manages this right; new versions of CMake do.

I propose removing all the LTO extras from LibreOffice.  Competent users are supposed to install the linker plugin
liblto_plugin.so and LLVMgold.so in $libdir/bfd-plugins and insert -flto into CFLAGS and CXXFLAGS, respectively -flto=6
in LDFLAGS.  Incompetent users don’t have a problem without LTO, as they do not know LTO exists.

Regards
  Дилян

On Fri, 2019-02-01 at 21:32 +0100, Michael Stahl wrote:
> On 01.02.19 20:12, Luboš Luňák wrote:
> > On Monday 28 of January 2019, Michael Stahl wrote:
> > > hope this will help:
> > > 
> > > https://gerrit.libreoffice.org/#/c/67012/
> > > 
> > > the idea is we use different symbol version for everything so LO libs
> > > call into bundled library, system libs call into system library.
> > > 
> > > haven't tested it though, just make check runs fine here...
> > 
> >   Yes, that works. But before you do, could you please e.g. add URL of this
> > discussion to the commit message? "unintended hilarity" is a rather poor
> > problem description.
> 
> ... unfortunately it's too late to add anything to the commit message as 
> the patch somehow reviewed and pushed itself.
> 
> well, anybody who knows what a gloriously misguided idea the ELF global 
> namespace is can think of any number of problems that would be fixed by 
> the patch :)
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