Re: [Qemu-devel] [PATCH] configure: Detect when glibc implements makecontext() to always fail

["Andreas Färber" <afaerber@suse.de>]

Am 12.10.2011 18:21, schrieb Peter Maydell:
> Improve the configure test for presence of ucontext functions by
> making linker warnings fatal; this allows us to detect when we are
> linked with a glibc which implements makecontext() to always return
> ENOSYS.
>
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>

Tested-by: Andreas Färber <afaerber@suse.de>

> ---
> Compiling on an Ubuntu Natty ARM host will hit this.

Works on Ubuntu Maverick ARM host as well.

> (Anybody think we should clean up our configure tests so we can
> enable -Werror and -Wl,--fatal-warnings on all of them?)

In theory that would be nice. I noticed for example that a missing 
glib2-devel package is not caught by configure, on openSUSE.

As a start for cleaning up...

>   configure |    7 +++++--
>   1 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/configure b/configure
> index 9b4fe34..4d9d9e0 100755
> --- a/configure
> +++ b/configure
> @@ -2549,9 +2549,12 @@ ucontext_coroutine=no
>   if test "$darwin" != "yes"; then
>     cat>  $TMPC<<  EOF
>   #include<ucontext.h>
> -int main(void) { makecontext(0, 0, 0); }
> +int main(void) { makecontext(0, 0, 0); return 0; }

...we could give a good example by adopting regular multi-line Coding 
Style, like accept4() and others.

Andreas

>   EOF
> -  if compile_prog "" "" ; then
> +  # Note that we enable fatal linker warnings to catch the
> +  # glibc "makecontext is not implemented and will always fail"
> +  # linker warning.
> +  if compile_prog "-Wl,--fatal-warnings" "" ; then
>         ucontext_coroutine=yes
>     fi
>   fi


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