"Joseph S. Myers" <jos...@codesourcery.com> writes:
> On Mon, 28 Sep 2009, Diego Novillo wrote:
>
>> - libiberty
>> I need help with this one. When the linker plugin is
>> enabled (if GCC is configured to use gold), LTO can
>> detect LTO objects inside archives via the callbacks it
>> gets from the linker. Since the linker plugin is a
>> shared object, and it uses libiberty functions, it needs
>> to use a shared libiberty.
>>
>> Currently, we just force --enable-shared on libiberty,
>> but I would only want to do that if gold and lto are
>> enabled. We detect gold and lto support in the top
>> configure script, but how do I send that down to
>> libiberty's configure?
>
> Shared libiberty seems like a bad idea as you then need to deal with
> soname allocation and changing the soname whenever an ABI-incompatible
> change is made. What you actually need is a PIC libiberty to link into
> the plugin (and avoiding using any global data in libiberty that needs a
> single copy in any program; hopefully it doesn't have any), not a shared
> one.
Yes. Fortunately there is no such thing as a shared libiberty. If
you configure libiberty with --enable-shared, what you get is a PIC
libiberty (libiberty/pic/libiberty.a) alongside the non-PIC one
(libiberty/libiberty.a).
So all Diego needs to do is pass --enable-shared down to libiberty
when --enable-lto/--enable-gold. The way to do that is something like
the appended.
Ian
Index: configure.ac
===================================================================
--- configure.ac (revision 152253)
+++ configure.ac (working copy)
@@ -2495,6 +2495,11 @@ case $enable_bootstrap in
;;
esac
+extra_host_libiberty_configure_flags=
+if test "$enable_gold" = "yes" -a "$enable_lto" = "yes"; then
+ extra_host_libiberty_configure_flags=--enable-shared
+fi
+
AC_MSG_CHECKING(for default BUILD_CONFIG)
AC_ARG_WITH([build-config],
Index: Makefile.def
===================================================================
--- Makefile.def (revision 152253)
+++ Makefile.def (working copy)
@@ -97,7 +97,8 @@ host_modules= { module= ld; bootstrap=tr
host_modules= { module= libcpp; bootstrap=true; };
host_modules= { module= libdecnumber; bootstrap=true; };
host_modules= { module= libgui; };
-host_modules= { module= libiberty; bootstrap=true; };
+host_modules= { module= libiberty; bootstrap=true;
+ extra_configure_flags='@extra_host_libiberty_configure_flags@'};
// We abuse missing to avoid installing anything for libiconv.
host_modules= { module= libiconv;
extra_configure_flags='--disable-shared';
