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From: Peter Maydell <peter.maydell@linaro.org>
Date: Tue, 25 Apr 2017 10:04:54 +0100
Message-ID: <CAFEAcA9S+q8FiZ2chaLoUWmQJ3uForGaDVGqwrBHnxmpH4sy_Q@mail.gmail.com>
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Subject: Re: [Qemu-devel] [PATCH RFC] configure: fix clang failure for
 libatomic
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To: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
Cc: "qemu-ppc@nongnu.org" <qemu-ppc@nongnu.org>, QEMU Developers <qemu-devel@nongnu.org>, David Gibson <david@gibson.dropbear.id.au>, Richard Henderson <rth@twiddle.net>, =?UTF-8?B?QWxleCBCZW5uw6ll?= <alex.bennee@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>

On 25 April 2017 at 09:58, Nikunj A Dadhania <nikunj@linux.vnet.ibm.com> wrote:
> I was trying out the program in the configure script with clang and I do
> get errors without libatomic:
>
>     $ clang /tmp/atomic.c
>     /tmp/atomic.c:6:7: warning: implicit declaration of function '__atomic_load_8' is invalid in C99 [-Wimplicit-function-declaration]
>       y = __atomic_load_8(&x, 0);
>           ^
>     /tmp/atomic.c:7:3: warning: implicit declaration of function '__atomic_store_8' is invalid in C99 [-Wimplicit-function-declaration]
>       __atomic_store_8(&x, y, 0);
>       ^
>     /tmp/atomic.c:8:3: warning: implicit declaration of function '__atomic_compare_exchange_8' is invalid in C99 [-Wimplicit-function-declaration]
>       __atomic_compare_exchange_8(&x, &y, x, 0, 0, 0);
>       ^
>     /tmp/atomic.c:9:3: warning: implicit declaration of function '__atomic_exchange_8' is invalid in C99 [-Wimplicit-function-declaration]
>       __atomic_exchange_8(&x, y, 0);
>       ^
>     /tmp/atomic.c:10:3: warning: implicit declaration of function '__atomic_fetch_add_8' is invalid in C99 [-Wimplicit-function-declaration]
>       __atomic_fetch_add_8(&x, y, 0);
>       ^
>     5 warnings generated.
>     /tmp/atomic-1660e0.o: In function `main':
>     /tmp/atomic.c:(.text+0x28): undefined reference to `__atomic_load_8'
>     /tmp/atomic.c:(.text+0x40): undefined reference to `__atomic_store_8'
>     /tmp/atomic.c:(.text+0x69): undefined reference to `__atomic_compare_exchange_8'
>     /tmp/atomic.c:(.text+0x7d): undefined reference to `__atomic_exchange_8'
>     /tmp/atomic.c:(.text+0x91): undefined reference to `__atomic_fetch_add_8'
>     clang-3.9: error: linker command failed with exit code 1 (use -v to see invocation)
>
> With -latomic, the linker succeeds in getting the binary.

What host is this on ?

thanks
-- PMM