Re: [Qemu-devel] [PATCH 4/7] libvhost-user: convert to Meson

[Markus Armbruster <armbru@redhat.com>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> Because libqemuutil.a is not converted yet, selected files have to be
> compiled twice, once with Meson and once with Makefile.objs.  Apart
> from this the conversion is straightforward.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  Makefile                            | 10 ++++------
>  Makefile.objs                       |  1 -
>  contrib/libvhost-user/Makefile.objs |  1 -
>  contrib/libvhost-user/meson.build   |  7 +++++++
>  meson.build                         |  2 ++
>  5 files changed, 13 insertions(+), 8 deletions(-)
>  delete mode 100644 contrib/libvhost-user/Makefile.objs
>  create mode 100644 contrib/libvhost-user/meson.build
>
> diff --git a/Makefile b/Makefile
> index b8f802c..6a3461e 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -426,7 +426,6 @@ dummy := $(call unnest-vars,, \
>                  ivshmem-client-obj-y \
>                  ivshmem-server-obj-y \
>                  rdmacm-mux-obj-y \
> -                libvhost-user-obj-y \
>                  vhost-user-scsi-obj-y \
>                  vhost-user-blk-obj-y \
>                  vhost-user-input-obj-y \
> @@ -529,7 +528,6 @@ Makefile: $(version-obj-y)
>  # Build libraries
>  
>  libqemuutil.a: $(util-obj-y) $(trace-obj-y) $(stub-obj-y)
> -libvhost-user.a: $(libvhost-user-obj-y) $(util-obj-y) $(stub-obj-y)
>  
>  ######################################################################
>  
> @@ -632,21 +630,21 @@ ivshmem-client$(EXESUF): $(ivshmem-client-obj-y) $(COMMON_LDADDS)
>  ivshmem-server$(EXESUF): $(ivshmem-server-obj-y) $(COMMON_LDADDS)
>  	$(call LINK, $^)
>  endif
> -vhost-user-scsi$(EXESUF): $(vhost-user-scsi-obj-y) libvhost-user.a
> +vhost-user-scsi$(EXESUF): $(vhost-user-scsi-obj-y) contrib/libvhost-user/libvhost-user.a
>  	$(call LINK, $^)
> -vhost-user-blk$(EXESUF): $(vhost-user-blk-obj-y) libvhost-user.a
> +vhost-user-blk$(EXESUF): $(vhost-user-blk-obj-y) contrib/libvhost-user/libvhost-user.a
>  	$(call LINK, $^)
>  
>  rdmacm-mux$(EXESUF): LIBS += "-libumad"
>  rdmacm-mux$(EXESUF): $(rdmacm-mux-obj-y) $(COMMON_LDADDS)
>  	$(call LINK, $^)
>  
> -vhost-user-gpu$(EXESUF): $(vhost-user-gpu-obj-y) $(libvhost-user-obj-y) libqemuutil.a libqemustub.a
> +vhost-user-gpu$(EXESUF): $(vhost-user-gpu-obj-y) contrib/libvhost-user/libvhost-user.a
>  	$(call LINK, $^)
>  
>  ifdef CONFIG_VHOST_USER_INPUT
>  ifdef CONFIG_LINUX
> -vhost-user-input$(EXESUF): $(vhost-user-input-obj-y) libvhost-user.a libqemuutil.a
> +vhost-user-input$(EXESUF): $(vhost-user-input-obj-y) contrib/libvhost-user/libvhost-user.a $(COMMON_LDADDS)
>  	$(call LINK, $^)
>  
>  # build by default, do not install

This hunk is only due to the move of libvhost-user.a from the root of
the build tree to contrib/libvhost-user/.  I'm not counting it as "meson
churn".

> diff --git a/Makefile.objs b/Makefile.objs
> index c8337fa..4f2fa6a 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -116,7 +116,6 @@ qga-vss-dll-obj-y = qga/
>  elf2dmp-obj-y = contrib/elf2dmp/
>  ivshmem-client-obj-$(CONFIG_IVSHMEM) = contrib/ivshmem-client/
>  ivshmem-server-obj-$(CONFIG_IVSHMEM) = contrib/ivshmem-server/
> -libvhost-user-obj-y = contrib/libvhost-user/
>  vhost-user-scsi.o-cflags := $(LIBISCSI_CFLAGS)
>  vhost-user-scsi.o-libs := $(LIBISCSI_LIBS)
>  vhost-user-scsi-obj-y = contrib/vhost-user-scsi/
> diff --git a/contrib/libvhost-user/Makefile.objs b/contrib/libvhost-user/Makefile.objs
> deleted file mode 100644
> index ef3778e..0000000
> --- a/contrib/libvhost-user/Makefile.objs
> +++ /dev/null
> @@ -1 +0,0 @@
> -libvhost-user-obj-y += libvhost-user.o libvhost-user-glib.o
> diff --git a/contrib/libvhost-user/meson.build b/contrib/libvhost-user/meson.build
> new file mode 100644
> index 0000000..7ef610a
> --- /dev/null
> +++ b/contrib/libvhost-user/meson.build
> @@ -0,0 +1,7 @@
> +libvhost_user = static_library('vhost-user',
> +               [files('libvhost-user.c', 'libvhost-user-glib.c'),

These are the "selected files [that] have to be compiled twice, once
with Meson and once with Makefile.objs":

> +                meson.source_root() / 'stubs/error-printf.c',
> +                meson.source_root() / 'stubs/monitor.c',
> +                meson.source_root() / 'util/error.c',
> +                meson.source_root() / 'util/qemu-error.c',
> +                meson.source_root() / 'util/memfd.c'])

Quite okay for a PoC.

> diff --git a/meson.build b/meson.build
> index b683d70..a6748f9 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -7,3 +7,5 @@ add_project_arguments(config_host['QEMU_CFLAGS'].split(),
>                        language: 'c')
>  add_project_arguments(config_host['QEMU_INCLUDES'].split(),
>                        language: 'c')
> +
> +subdir('contrib/libvhost-user')

In your cover letter, you wrote "it's a simple example of how the
current build system causes clutter in the toplevel Makefiles and how
interrelated the Makefile, Makefile.objs and contrib/*/Makefile.objs
file are even for such simple executables."  True.  Before this patch,
the logic for building libvhost-user.a is split over Makefile (two
lines), Makefile.obj (one) and contrib/libvhost-user/Makefile.objs
(one).  Afterwards, its all in one place.