Re: [Qemu-devel] [PATCH] configure: preserve various environment variables in config.status

[Eric Blake <eblake@redhat.com>]

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On 11/17/2015 10:59 AM, Daniel P. Berrange wrote:
> Suggested in
> 
>   https://lists.gnu.org/archive/html/qemu-devel/2015-11/msg03298.html
> 
> The config.status script is auto-generated by configure upon
> completion. The intention is that config.status can be later
> invoked by the developer to re-detect the same environment
> that configure originally used. The current config.status
> script, however, only contains a record of the command line
> arguments to configure. Various environment variables have
> an effect on what configure will find. In particular the
> PKG_CONFIG_LIBDIR & PKG_CONFIG_PATH vars will affect what
> libraries pkg-config finds. The PATH var will affect what
> toolchain binaries and XXXX-config scripts are found. The
> LD_LIBRARY_PATH var will affect what libraries are found.
> All these key env variables should be recorded in the
> config.status script.
> 
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---
> 
> Open question: are there more env vars we should preserve ?

Yes - anything that autoconf would mark as precious.  See below.

> +++ b/configure
> @@ -5925,6 +5925,24 @@ cat <<EOD >config.status
>  # Compiler output produced by configure, useful for debugging
>  # configure, is in config.log if it exists.
>  EOD
> +
> +preserve_env() {
> +    envname=$1
> +
> +    if test -n "${!envname}"

Bashism, but configure is /bin/sh.  This won't work on dash :(

I think you'll have to use eval, and we'll just have to audit that
preserve_env can never be called with suspicious text where eval would
open a security hole.

> +    then
> +	echo "$envname=\"${!envname}\"" >> config.status

Another use of the bashism.

> +	echo "export $envname" >> config.status
> +    fi
> +}
> +
> +# Preserve various env variables that influence what
> +# features/build target configure will detect
> +preserve_env PATH
> +preserve_env LD_LIBRARY_PATH
> +preserve_env PKG_CONFIG_LIBDIR
> +preserve_env PKG_CONFIG_PATH
> +

Autoconf preserves CC, CFLAGS, LDFLAGS, LIBS, CPPFLAGS, and CPP by
default.  Also, PKG_CONFIG is typically preserved.  If you run libvirt's
'./configure --help', you'll also notice a bunch of *_CFLAGS and *_LIBS
in the precious list starting under the label "Some influential
environment variables".

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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