Re: [PATCH v2 1/3] Makefile: Compute libraries for libqemuutil.a and libvhost-user.a

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Fri, Jun 26, 2020 at 06:27:04PM +0200, Christophe de Dinechin wrote:
> In util/Makefile.objs, there is a setting for dbus.o-libs.
> Trying to copy-paste that to add a library for module.o that was was
> not otherwise linked yields link errors on a number of binaries,
> e.g. qemu-ga, with unsatisfied symbols in libqemuutil.a(module.o).
> The reason is that library dependencies are not propagated to the .a
> files automatically.
> 
> Adding a call to extract-libs to get the libraries for the two .a
> files that are used elsewhere.
> 
> Signed-off-by: Christophe de Dinechin <dinechin@redhat.com>
> ---
>  Makefile | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/Makefile b/Makefile
> index a0092153af..b29b0eeefa 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -589,6 +589,8 @@ Makefile: $(version-obj-y)
>  ######################################################################
>  # Build libraries
>  
> +libqemuutil.a-libs += $(call extract-libs, $(util-obj-y) $(trace-obj-y) $(stub-obj-y))
> +libvhost-user.a-libs += $(call extract-libs, $(libvhost-user-obj-y) $(util-obj-y) $(stub-obj-y))
>  libqemuutil.a: $(util-obj-y) $(trace-obj-y) $(stub-obj-y)
>  libvhost-user.a: $(libvhost-user-obj-y) $(util-obj-y) $(stub-obj-y)

Please see https://patchwork.kernel.org/patch/11608247/#23440227.

If this change causes all libraries from .a object files to be linked
then this patch is incomplete. The purpose of the .a file is to link
only the subset of .o files required by the program. Unused .o files in
the .a file are not linked into the program. The libraries must also be
linked as needed but this patch seems to extract them unconditionally.

Stefan

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