See http://sources.redhat.com/ml/libc-hacker/2005-03/msg00008.html

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Date: Sat, 5 Mar 2005 10:20:49 +0100

From: Jakub Jelinek <jakub at redhat dot com>

To: Ulrich Drepper <drepper at redhat dot com>, Roland McGrath <roland at redhat dot com>

Cc: Glibc hackers <libc-hacker at sources dot redhat dot com>

Subject: [PATCH] Fix build with GCC 4

Message-ID: <20050305092049.GJ4777@sunsite.mff.cuni.cz>

Reply-To: Jakub Jelinek <jakub at redhat dot com>

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Hi!

The thread_offsetof change just mirrors what Alan Modra did to NPTL

tcb-offsets.sym.  Apparently for GCC 4 an offsetof like expression,

but not really offsetof, is no longer constant folded and therefore

not suitable for "i" constraint.

The ELF_MACHINE_NO_RELA change is needed to avoid

rtld.c: In function '_dl_start':

dynamic-link.h:50: error: nested function 'elf_machine_rela_relative' declared but never defined

dynamic-link.h:47: error: nested function 'elf_machine_rela' declared but never defined

This is what happens.

rtld.c first includes dl-machine.h without RESOLVE_MAP

and without RTLD_BOOTSTRAP defined.  This means that ELF_MACHINE_NO_RELA

is not defined on i386/arm.  Later on it defines RESOLVE_MAP

and RTLD_BOOTSTRAP and includes dynamic-link.h which has:

# if ! ELF_MACHINE_NO_RELA

auto void __attribute__((always_inline))

elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,

                  const ElfW(Sym) *sym, const struct r_found_version *version,

                  void *const reloc_addr);

auto void __attribute__((always_inline))

elf_machine_rela_relative (ElfW(Addr) l_addr, const ElfW(Rela) *reloc,

                           void *const reloc_addr);

# endif

and later on includes dl-machine.h which sees RTLD_BOOTSTRAP is

defined and defines ELF_MACHINE_NO_RELA and doesn't define

elf_machine_rela* nested functions.

But the prototypes were already defined and GCC 4 doesn't like this.

ELF_MACHINE_NO_RELA is only ever used in preprocessing conditionals

and never in defined ELF_MACHINE_NO_RELA, so the trick below

already defines ELF_MACHINE_NO_RELA to 1/0 depending on whether

RTLD_BOOTSTRAP is defined and thus the prototypes in dynamic-link.h

that are not desirable are gone.

2005-03-05  Jakub Jelinek  <jakub@redhat.com>

	* sysdeps/i386/dl-machine.h (ELF_MACHINE_NO_RELA): Define

	unconditionally to (defined RTLD_BOOTSTRAP).

	* sysdeps/arm/dl-machine.h (ELF_MACHINE_NO_RELA): Likewise.

linuxthreads/

	* sysdeps/powerpc/tcb-offsets.sym (thread_offsetof): Rework for GCC 4.

--- libc/linuxthreads/sysdeps/powerpc/tcb-offsets.sym.jj	2005-03-04 14:21:29.000000000 -0500

+++ libc/linuxthreads/sysdeps/powerpc/tcb-offsets.sym	2005-03-04 14:26:29.000000000 -0500

@@ -8,7 +8,7 @@

 -- Abuse tls.h macros to derive offsets relative to the thread register.

 #  undef __thread_register

 #  define __thread_register	((void *) 0)

-#  define thread_offsetof(mem)	((void *) &THREAD_SELF->p_##mem - (void *) 0)

+#  define thread_offsetof(mem)	((ptrdiff_t) THREAD_SELF + offsetof (struct _pthread_descr_struct, p_##mem))

 # else