Since binutils 2.27 I can not compile dmd with the `gold` linker any more. On my Gentoo Linux amd64 host, when linking the 32-bit version of druntime the following error is repeatedly output for all kinds of symbols:

  libdruntime.so.a(libdruntime.so.o):
  relocation R_386_GOTOFF against preemptible symbol <some
  mangled name> cannot be used when making a shared object

Now starting with binutils 2.28 - in addition to the above - dynamically linked Dlang executables error out in druntime with an error message of this type:

  Fatal Error while loading '/usr/lib64/libphobos2.so.0.74':
  The module '<some module>' is already defined in '<executable>'.

Does anyone have solutions to one or both of these issues at
hand? For Gentoo packages I made shared linking the default
and unless my configuration is a unique snowflake this is
right now affecting all DMD users there.
From reading `checkModuleCollisions()`
[https://github.com/dlang/druntime/blob/master/src/rt/sections_elf_shared.d#L891]
it would seem that changes in copy-relocations have something
to do with the second issue it.

-- 
Marco

Marco Leise wrote:

> Since binutils 2.27 I can not compile dmd with the `gold`
> linker any more. On my Gentoo Linux amd64 host, when linking
> the 32-bit version of druntime the following error is
> repeatedly output for all kinds of symbols:
>
>   libdruntime.so.a(libdruntime.so.o):
>   relocation R_386_GOTOFF against preemptible symbol <some
>   mangled name> cannot be used when making a shared object
>
> Now starting with binutils 2.28 - in addition to the above -
> dynamically linked Dlang executables error out in druntime
> with an error message of this type:
>
>   Fatal Error while loading '/usr/lib64/libphobos2.so.0.74':
>   The module '<some module>' is already defined in '<executable>'.
>
> Does anyone have solutions to one or both of these issues at
> hand? For Gentoo packages I made shared linking the default
> and unless my configuration is a unique snowflake this is
> right now affecting all DMD users there.
> From reading `checkModuleCollisions()`
> [https://github.com/dlang/druntime/blob/master/src/rt/sections_elf_shared.d#L891]
> it would seem that changes in copy-relocations have something
> to do with the second issue it.

1. patch your compiler to use old ELF_COMDAT hack in elfobj.c:
	#define ELF_COMDAT      TARGET_LINUX
	+#undef ELF_COMDAT
	+#define ELF_COMDAT  0

2. downgrade to old binutils, new binutils are not working with dmd .so's.

step "2" is essential. alas.

Am Wed, 5 Jul 2017 22:14:47 +0300
schrieb ketmar <ketmar@ketmar.no-ip.org>:

> Marco Leise wrote:
> 
> > Since binutils 2.27 I can not compile dmd with the `gold` linker any more. On my Gentoo Linux amd64 host, when linking the 32-bit version of druntime the following error is repeatedly output for all kinds of symbols:
> >
> >   libdruntime.so.a(libdruntime.so.o):
> >   relocation R_386_GOTOFF against preemptible symbol <some
> >   mangled name> cannot be used when making a shared object
> >
> > Now starting with binutils 2.28 - in addition to the above - dynamically linked Dlang executables error out in druntime with an error message of this type:
> >
> >   Fatal Error while loading '/usr/lib64/libphobos2.so.0.74':
> >   The module '<some module>' is already defined in '<executable>'.
> >
> > Does anyone have solutions to one or both of these issues at
> > hand? For Gentoo packages I made shared linking the default
> > and unless my configuration is a unique snowflake this is
> > right now affecting all DMD users there.
> > From reading `checkModuleCollisions()`
> > [https://github.com/dlang/druntime/blob/master/src/rt/sections_elf_shared.d#L891]
> > it would seem that changes in copy-relocations have something
> > to do with the second issue it.
> 
> 1. patch your compiler to use old ELF_COMDAT hack in elfobj.c:
> 	#define ELF_COMDAT      TARGET_LINUX
> 	+#undef ELF_COMDAT
> 	+#define ELF_COMDAT  0
> 
> 2. downgrade to old binutils, new binutils are not working with dmd .so's.
> 
> step "2" is essential. alas.

That information is gold, ketmar!

-- 
Marco

Marco Leise wrote:

> That information is gold, ketmar!

sorry for not helping much, tho. i hit this issue some time ago, and the only way i found (which solves *all* problems) is downgrading binutils. without that, COMDAT trick won't help (but it helps with other cases, like duplicate identifiers -- this case is partially patched in new dmd, tho).

This is the bug report for binutils 2.28 and the "module is already defined in" error:

https://issues.dlang.org/show_bug.cgi?id=17375

Basically you need to add -fPIC to the command line for the executable when linking against shared objects. One way to do so is to add that switch to dmd.conf. Now that x86 32-bit is dying I feel that's acceptable in most situations.

-- 
Marco