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From: Peter Maydell <peter.maydell@linaro.org>
Date: Fri, 2 Oct 2015 23:49:01 +0100
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Subject: Re: [Qemu-devel] [PATCH] libtasn1: check if static library is
	present
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To: Laurent Vivier <laurent@vivier.eu>
Cc: Paolo Bonzini <pbonzini@redhat.com>, QEMU Developers <qemu-devel@nongnu.org>

On 2 October 2015 at 22:46, Laurent Vivier <laurent@vivier.eu> wrote:
> Some distros [1] don't ship systematically static libraries,
> and pkg-config doesn't give us the information.
>
> This is the case for libtasn1, so add a check in configure
> to see if linker is able to find the library.
>
> [1] https://fedoraproject.org/wiki/Archive:PackagingDrafts/StaticLibraryPolicy
>
> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
> ---
>  configure | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/configure b/configure
> index f14454e..99d4269 100755
> --- a/configure
> +++ b/configure
> @@ -2284,9 +2284,20 @@ fi
>  tasn1=yes
>  if $pkg_config --exists "libtasn1"; then
>      tasn1_cflags=`$pkg_config --cflags libtasn1`
> -    tasn1_libs=`$pkg_config --libs libtasn1`
> -    test_cflags="$test_cflags $tasn1_cflags"
> -    test_libs="$test_libs $tasn1_libs"
> +    if test "$static" = "yes" ; then
> +        # some distros (fedora) don't ship all static libraries
> +        tasn1_libs=`$pkg_config --static --libs libtasn1`
> +        if compile_prog "$tasn1_cflags" "$tasn1_libs" ; then
> +            test_cflags="$test_cflags $tasn1_cflags"
> +            test_libs="$test_libs $tasn1_libs"
> +        else
> +            tasn1=no
> +        fi
> +    else
> +        tasn1_libs=`$pkg_config --libs libtasn1`
> +        test_cflags="$test_cflags $tasn1_cflags"
> +        test_libs="$test_libs $tasn1_libs"
> +    fi
>  else
>      tasn1=no
>  fi

If $static is 'yes' then calling $pkg_config already
passes the --static flag (see $QEMU_PKG_CONFIG_FLAGS).
You probably just want to always do the compile_prog,
rather than special-casing $static=yes.

See also the gnutls_works function which is doing a
similar "ask pkg_config, but sanity check that it compiles"
job.

(We could maybe abstract the idea out into a
'pkg_exists_and_works thing' function, but I'd be
happy to wait til we have 3 uses before doing that.)

PS: this is a bug in Fedora, which is shipping bogus
pkg-config info for the static case.

thanks
-- PMM