Re: [PATCH v2] configure: warn if not using a separate build directory

[Eric Blake <eblake@redhat.com>]

On 3/31/20 10:51 AM, Daniel P. Berrangé wrote:
> Running configure directly from the source directory is a build
> configuration that will go away in future. It is also not currently
> covered by any automated testing. Display a deprecation warning if
> the user attempts to use an in-srcdir build setup, so that they are
> aware that they're building QEMU in an undesirable manner.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
> 
> Changed in v2:
> 
>   - Use existing $source_path variable (Eric)

Phillipe, actually - but this line isn't permanent.

>   - Remove bash-ism in comparison (Eric)
>   - Safe quoting of directory paths (Eric)
>   - Rename variables to reflect that we're applying canonicalization (Eric)
> 
>   configure | 27 +++++++++++++++++++++++++++
>   1 file changed, 27 insertions(+)
> 
> diff --git a/configure b/configure
> index e225a1e3ff..5991e0e6e5 100755
> --- a/configure
> +++ b/configure
> @@ -285,6 +285,16 @@ then
>     error_exit "main directory cannot contain spaces nor colons"
>   fi
>   
> +canon_build_path=$(realpath -- "$PWD")
> +canon_source_path=$(realpath -- "$source_path")
> +
> +in_srcdir=no
> +if [ "$canon_build_path" = "$canon_source_path" ]
> +then
> +    in_srcdir=yes
> +fi

This part is good.

> +
> +
>   # default parameters
>   cpu=""
>   iasl="iasl"
> @@ -6799,6 +6809,23 @@ if test "$supported_os" = "no"; then
>       echo "us upstream at qemu-devel@nongnu.org."
>   fi
>   
> +if test "$in_srcdir" = "yes"; then
> +    echo
> +    echo "WARNING: SUPPORT FOR IN SOURCE DIR BUILDS IS DEPRECATED"
> +    echo
> +    echo "Support for running the 'configure' script directly from the"
> +    echo "source directory is deprecated and will go away in a future"
> +    echo "release. In source dir builds are not covered by automated"
> +    echo "testing and are liable to break without warning. Users are"
> +    echo "strongly recommended to switch to a separate build directory:"

Per Kevin's response, we may want to tweak this wording slightly; maybe:

Support for running the 'configure' script directly from the source 
directory is deprecated.  In-tree builds are not covered by automated 
testing and are liable to break without warning.  Future releases may 
change the default location of built executables for an in-tree build, 
or drop in-tree build support altogether.  Users are strongly 
recommended to switch to a separate build directory:

> +    echo
> +    echo "  $ mkdir build"
> +    echo "  $ cd build"
> +    echo "  $ ../configure"
> +    echo "  $ make"
> +    echo
> +fi
> +
>   config_host_mak="config-host.mak"
>   
>   echo "# Automatically generated by configure - do not modify" >config-all-disas.mak
> 

Whether we keep your wording or switch to somthing based on mine,
Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org