Re: [PATCH] configure: add support for psuedo-"in source tree" builds

[Peter Maydell]

On Thu, 20 Aug 2020 at 17:56, Daniel P. Berrangé <berrange@redhat.com> wrote:
>
> Meson requires the build dir to be separate from the source tree. Many
> people are used to just running "./configure && make" though and the
> meson conversion breaks that.
>
> This introduces some backcompat support to make it appear as if an
> "in source tree" build is being done, but with the the results in the
> "build/" directory. This allows "./configure && make" to work as it
> did historically, albeit with the output binaries staying under build/.
>
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>
> This is a simple integration of Eric's proposal from
>
>   https://lists.gnu.org/archive/html/qemu-devel/2020-03/msg07290.html
>
> with a bit of configure magic. It is enough to enable
>
>    ./configure
>    make
>    make check
>
> I've not tested it beyond that. Note it blows away the "build/"
> dir each time ./configure is run so it is pristine each time.
>
> We could optionally symlink binaries from build/ into $PWD
> if poeople think that is important, eg by changing GNUmakefile
> to have:
>
> recurse: all
>         for bin in `find build -maxdepth 1 -type f -executable | grep -v -E 
> '(ninjatool|config.status)'`; \
>         do \
>           ln -f -s $$bin . ; \
>         done
>
> and some cleanup logic to purge the symlinks for "make clean"
>
> This goes on top of Paolo's most recent meson port v175 posting,
> or whatever number it is upto now :-)
>
>  .gitignore |  2 ++
>  configure  | 40 ++++++++++++++++++++++++++++++++--------
>  2 files changed, 34 insertions(+), 8 deletions(-)
>
> diff --git a/.gitignore b/.gitignore
> index 92311284ef..4ccb9ed975 100644
> --- a/.gitignore
> +++ b/.gitignore
> @@ -1,3 +1,5 @@
> +/GNUmakefile
> +/build/
>  /.doctrees
>  /config-devices.*
>  /config-all-devices.*
> diff --git a/configure b/configure
> index cc5f58f31a..a5c88ad1ac 100755
> --- a/configure
> +++ b/configure
> @@ -11,6 +11,38 @@ unset CLICOLOR_FORCE GREP_OPTIONS
>  # Don't allow CCACHE, if present, to use cached results of compile tests!
>  export CCACHE_RECACHE=yes
>
> +source_path=$(cd "$(dirname -- "$0")"; pwd)
> +
> +if printf %s\\n "$source_path" "$PWD" | grep -q "[[:space:]:]";
> +then
> +  error_exit "main directory cannot contain spaces nor colons"
> +fi
> +
> +if test "$PWD" == "$source_path"
> +then
> +    echo "Using './build' as the directory for build output"
> +    rm -rf build
> +    mkdir -p build
> +    cat > GNUmakefile <<EOF
> +

Since this created file ends up in the source directory it would
be useful to have it start with a brief comment saying
(a) that it's autogenerated by configure (b) what it's for.

thanks
-- PMM