From: Jonathan Wakely <jwakely@redhat.com>
To: Iain Sandoe <iain@sandoe.co.uk>
Cc: libstdc++ <libstdc++@gcc.gnu.org>, GCC-patches <gcc-patches@gcc.gnu.org>
Subject: Re: [Darwin] Fix build warnings for libstdc++ [NFC]
Date: Mon, 03 Dec 2018 14:25:00 -0000 [thread overview]
Message-ID: <20181203142555.GA809@redhat.com> (raw)
In-Reply-To: <33F6DDD7-3914-4A04-9F43-0411A46A206E@sandoe.co.uk>
On 03/12/18 00:37 +0000, Iain Sandoe wrote:
>Hi,
>
>GCC does not export construction vtable symbols from shared libraries**.
>
>The symbols are marked hidden in the objects; for Darwin that makes them also external (âprivate_externâ is Darwinâs hidden) which means that they show up in the list of possible symbols for export from libstdc++, and there are sufficiently relaxed match conditions that they reach the exports list. When Darwinâs static linker encounters them it generates a warning that they cannot be exported. This patch prunes them from the list of symbols to be considered, thus eliminating the warnings.
>
>OK for trunk?
Yes, OK.
>Iain
>
>** This seems a design decision, rather than an ABI mandate - note that, on Darwin at least, these symbols *are* visible in libc++.
>
>libstdc++-v3/
>
> * scripts/make_exports.pl (check names): Donât try to export construction
> vtable symbols.
>
>
>diff --git a/libstdc++-v3/scripts/make_exports.pl b/libstdc++-v3/scripts/make_exports.pl
>index 7c9e4e31d4..93100e17dd 100644
>--- a/libstdc++-v3/scripts/make_exports.pl
>+++ b/libstdc++-v3/scripts/make_exports.pl
>@@ -103,6 +103,14 @@ NAME: while (<NM>) {
> # Ignore undefined and local symbols.
> next if (/^([^ ]+) [Ua-z] /);
>
>+ # GCC does not export construction vtables from shared libraries.
>+ # However the symbols are marked hidden, for Darwin that makes them
>+ # also external "private_extern", which means that they show up in
>+ # this list. When ld64 encounters them it generates a warning that
>+ # they cannot be exported, so trim them from the set now.
>+ next if (/^construction vtable.*$/);
>+ next if (/^__ZTC.*$/);
>+
>
prev parent reply other threads:[~2018-12-03 14:25 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-03 0:37 Iain Sandoe
2018-12-03 14:25 ` Jonathan Wakely [this message]
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