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Date: Fri, 24 Feb 2012 13:47:39 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH] configure: Check whether makecontext() is
 a glibc stub function
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-devel@nongnu.org, patches@linaro.org

On 02/23/2012 10:20 AM, Peter Maydell wrote:
> On some systems (notably ARM Linux) glibc provides implementations
> of makecontext(), getcontext() and friends which are stubs which
> always return failure. Make the configure test for makecontext()
> also check for the presence of the __stub_makecontext macro which
> indicates the presence of these stubs, so we can avoid trying to use
> them and fall back to a different coroutine implementation instead.
>
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
> ---
> I think this fixes the last of the bugs which meant we had to declare
> ARM hosts as officially unsupported in QEMU 1.0...

Applied.  Thanks.

And happy to see ARM host support restored.  I guess it's now time to try 
running Windows under QEMU on my beaglebone :-)

Regards,

Anthony Liguori

>
>   configure |    4 ++++
>   1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/configure b/configure
> index 037f7f7..9fbf88a 100755
> --- a/configure
> +++ b/configure
> @@ -2712,11 +2712,15 @@ fi
>
>   ##########################################
>   # check if we have makecontext
> +# (and that it's not a glibc stub which always returns -1)
>
>   ucontext_coroutine=no
>   if test "$darwin" != "yes"; then
>     cat>  $TMPC<<  EOF
>   #include<ucontext.h>
> +#ifdef __stub_makecontext
> +#error Ignoring glibc stub makecontext which will always fail
> +#endif
>   int main(void) { makecontext(0, 0, 0); return 0; }
>   EOF
>     if compile_prog "" "" ; then