Fix HEAD build on amd64

[Daniel Jacobowitz <drow at false dot org>]

The unconditional provision of __EH_FRAME_BEGIN__ caused a problem on amd64,
because amd64 also always generates unwind tables.  soinit.os had both
a manually generated .eh_frame entry and a compiler-generated one; one
of the two was writable and the other not.  In GCC 4.0 this causes an
ICE and in GCC HEAD (4.2) a polite error.

I also noticed that the symbol was unused; if it's to make it to the
output file, it had better be marked used.  There's a chance
that some future version of GCC will not put __EH_FRAME_BEGIN__
before the unwind data for __libc_fini, but that won't be a tragedy,
just a little bit odd - __FRAME_END__ is the important one.

__FRAME_END__ updated likewise for consistency.

-- 
Daniel Jacobowitz
CodeSourcery

2006-02-24  Daniel Jacobowitz  <dan@codesourcery.com>

	* config.h.in (HAVE_EH_FRAME_READONLY): New template.
	* configure.in: Check for read-only .eh_frame.
	* elf/sofini.c (__FRAME_END__): Mark const if
	HAVE_EH_FRAME_READONLY.
	* elf/soinit.c (__EH_FRAME_BEGIN__): Likewise.  Also mark used.

Index: config.h.in
===================================================================
RCS file: /big/fsf/rsync/glibc/libc/config.h.in,v
retrieving revision 1.78
diff -u -p -r1.78 config.h.in
--- config.h.in	22 Feb 2006 02:09:03 -0000	1.78
+++ config.h.in	24 Feb 2006 16:08:56 -0000
@@ -105,6 +105,9 @@
 /* Define if the compiler supports __attribute__((tls_model(""))).  */
 #undef HAVE_TLS_MODEL_ATTRIBUTE
 
+/* Define if .eh_frame additions should be const.  */
+#undef HAVE_EH_FRAME_READONLY
+
 /* Define if the regparm attribute shall be used for local functions
    (gcc on ix86 only).  */
 #undef	USE_REGPARMS
Index: configure.in
===================================================================
RCS file: /big/fsf/rsync/glibc/libc/configure.in,v
retrieving revision 1.455
diff -u -p -r1.455 configure.in
--- configure.in	22 Feb 2006 02:09:03 -0000	1.455
+++ configure.in	24 Feb 2006 16:08:57 -0000
@@ -1823,6 +1823,25 @@ EOF
   fi
 fi
 
+dnl Check whether manual additions to .eh_frame should be const.  If not,
+dnl this will either error or ICE depending on the GCC version.
+AC_CACHE_CHECK([for read-only .eh_frame], libc_cv_gcc_eh_frame_readonly, [dnl
+cat > conftest.c <<\EOF
+const char baz[] __attribute__ ((section (".eh_frame"))) = { 0 };
+void zab (void)
+{ }
+EOF
+if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS -S -fexceptions conftest.c >&AS_MESSAGE_LOG_FD]); then
+  libc_cv_gcc_eh_frame_readonly=yes
+else
+  libc_cv_gcc_eh_frame_readonly=no
+fi
+rm -f conftest*])
+if test "$libc_cv_gcc_eh_frame_readonly" = yes; then
+  AC_DEFINE(HAVE_EH_FRAME_READONLY)
+fi
+  
+
 dnl Check whether we have the gd library available.
 AC_MSG_CHECKING(for libgd)
 if test "$with_gd" != "no"; then
Index: elf/sofini.c
===================================================================
RCS file: /big/fsf/rsync/glibc/libc/elf/sofini.c,v
retrieving revision 1.5
diff -u -p -r1.5 sofini.c
--- elf/sofini.c	22 Feb 2006 02:09:03 -0000	1.5
+++ elf/sofini.c	24 Feb 2006 16:08:57 -0000
@@ -12,6 +12,9 @@ static void (*const __DTOR_END__[1]) (vo
    this would be the 'length' field in a real FDE.  */
 
 typedef unsigned int ui32 __attribute__ ((mode (SI)));
-static ui32 __FRAME_END__[1]
-     __attribute__ ((used, section (".eh_frame")))
+static ui32
+#ifdef HAVE_EH_FRAME_READONLY
+     const
+#endif
+     __FRAME_END__[1] __attribute__ ((used, section (".eh_frame")))
      = { 0 };
Index: elf/soinit.c
===================================================================
RCS file: /big/fsf/rsync/glibc/libc/elf/soinit.c,v
retrieving revision 1.13
diff -u -p -r1.13 soinit.c
--- elf/soinit.c	22 Feb 2006 02:09:03 -0000	1.13
+++ elf/soinit.c	24 Feb 2006 16:08:57 -0000
@@ -20,8 +20,11 @@ run_hooks (void (*const list[]) (void))
     (**list) ();
 }
 
-static char __EH_FRAME_BEGIN__[]
-     __attribute__ ((section (".eh_frame")))
+static char
+#ifdef HAVE_EH_FRAME_READONLY
+     const
+#endif
+     __EH_FRAME_BEGIN__[] __attribute__ ((used, section (".eh_frame")))
      = { };
 
 /* This function will be called from _init in init-first.c.  */