From: Thomas Huth <thuth@redhat.com>
To: Markus Armbruster <armbru@redhat.com>,
qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>
Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>,
"Philippe Mathieu-Daudé" <philmd@redhat.com>
Subject: Re: libqemuutil
Date: Tue, 16 Mar 2021 10:24:21 +0100 [thread overview]
Message-ID: <0c90e3ce-6be7-291f-3121-b6d7d725bcdf@redhat.com> (raw)
In-Reply-To: <87zgz38o0v.fsf@dusky.pond.sub.org>
On 16/03/2021 10.07, Markus Armbruster wrote:
> I rebased my "[PATCH v6 00/10] Configurable policy for handling
> deprecated interfaces" to master, and it surprisingly fails to link
> several utility programs. Here's the first error:
>
> gcc -o tests/bench/benchmark-crypto-hmac tests/bench/benchmark-crypto-hmac.p/benchmark-crypto-hmac.c.o -Wl,--as-needed -Wl,--no-undefined -pie -Wl,--whole-archive libcrypto.fa libauthz.fa libqom.fa -Wl,--no-whole-archive -Wl,--warn-common -Wl,-z,relro -Wl,-z,now -m64 -fstack-protector-strong -Wl,--start-group libqemuutil.a subprojects/libvhost-user/libvhost-user-glib.a subprojects/libvhost-user/libvhost-user.a libcrypto.fa libauthz.fa libqom.fa -pthread -lgthread-2.0 -lglib-2.0 -lgio-2.0 -lgobject-2.0 -lglib-2.0 -lgio-2.0 -lgobject-2.0 -lglib-2.0 -lgnutls -lutil -lm -lgthread-2.0 -lglib-2.0 -lnettle -lgnutls -lpam -Wl,--end-group
> /usr/bin/ld: libqemuutil.a(util_main-loop.c.o): in function `qemu_set_fd_handler':
> /work/armbru/qemu/bld-x86/../util/main-loop.c:581: multiple definition of `qemu_set_fd_handler'; libqemuutil.a(stubs_set-fd-handler.c.o):/work/armbru/qemu/bld-x86/../stubs/set-fd-handler.c:8: first defined here
> collect2: error: ld returned 1 exit status
>
> Both master and PATCH 01 still link fine, PATCH 02 doesn't. PATCH 02
> doesn't go anywhere near qemu_set_fd_handler().
>
> Turns out libqemuutil.a contains two definitions of
> qemu_set_fd_handler(). In master:
>
> $ nm --defined-only libqemuutil.a | awk '/:$/ { f=$0 } / qemu_set_fd_handler/ { if (f) { print f; f="" } print $0 }'
> util_main-loop.c.o:
> 00000000000007fe T qemu_set_fd_handler
> stubs_set-fd-handler.c.o:
> 0000000000000000 T qemu_set_fd_handler
>
> This is obviously unhealthy.
>
> I suspect the linker happens to pick the one that makes things work,
> until something in my patch makes it pick the other one.
>
> Is qemu_set_fd_handler() the only one? Nope:
>
> $ nm --defined-only bld-x86/libqemuutil.a | awk '/ T / { print $NF }' | sort | uniq -c | grep -v '^ *1 '
> 2 qemu_set_fd_handler
> 2 yank_generic_iochannel
> 2 yank_register_function
> 2 yank_register_instance
> 2 yank_unregister_function
> 2 yank_unregister_instance
>
> I didn't run into this issue when I posted my series last Friday. The
> issue now blocks its merge, and today is the soft freeze. Help!
A very, very quick-n-dirty band-aid is likely to mark the function in stubs
as weak:
diff --git a/stubs/set-fd-handler.c b/stubs/set-fd-handler.c
--- a/stubs/set-fd-handler.c
+++ b/stubs/set-fd-handler.c
@@ -1,6 +1,7 @@
#include "qemu/osdep.h"
#include "qemu/main-loop.h"
+__attribute__((weak))
void qemu_set_fd_handler(int fd,
IOHandler *fd_read,
IOHandler *fd_write,
... should IMHO be good enough for the soft freeze. In the long run, you
might want to analyze the problem more thoroughly, of course. I had similar
problems in the past already, and solved them by moving the stubs around. See:
b0476d6602adbf818132dc896b585e01f47eaf96
stubs: Move qemu_timer_notify_cb() and remove
qemu_notify_event() stub
8c2787629eee73ca8ce4f100cff4f4946583b4e8
stubs: Move qemu_fd_register stub to util/main-loop.c
HTH,
Thomas
next prev parent reply other threads:[~2021-03-16 9:25 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-16 9:07 libqemuutil Markus Armbruster
2021-03-16 9:24 ` Thomas Huth [this message]
2021-03-16 9:41 ` libqemuutil Paolo Bonzini
2021-03-16 9:28 ` libqemuutil Paolo Bonzini
2021-03-16 10:09 ` libqemuutil Markus Armbruster
2021-03-16 10:15 ` libqemuutil Paolo Bonzini
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