Re: [PATCH 7/6] Makefile: Make Makefile depend on generated qga files, too

[Eric Blake <eblake@redhat.com>]

On 11/29/19 3:59 AM, Markus Armbruster wrote:
> Generated .h need to be generated before compiling any .c using them.
> To know which .h a .c uses, we need to compile it.
> 
> Since commit 4115852bb0 "build: do not sprinkle around
> GENERATED_HEADERS dependencies", we break this circular dependency the
> simple & stupid way: the generated headers are a prerequisite of
> Makefile, which causes Make to generate them first, then start over.

which is a pain when using 'make --dry-run' to see what would get built 
(a dependency of Makefile _is_ rebuilt if Makefile itself has to be 
updated), but not the fault of this patch.

> 
> Except for qga we still use the older method of making all its .o
> summarily depend on all its generated .h (commit 016c77ad62 "Makefile:
> add missing deps on $(GENERATED_HEADERS)").
> 
> Add qga's generated files to generated-files-y to get rid of this
> exception.
> 
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---
>   Makefile | 21 +++++++++++----------
>   1 file changed, 11 insertions(+), 10 deletions(-)

Reviewed-by: Eric Blake <eblake@redhat.com>


> +++ b/Makefile
> @@ -130,6 +130,15 @@ GENERATED_QAPI_FILES += qapi/qapi-doc.texi
>   
>   generated-files-y += $(GENERATED_QAPI_FILES)
>   
> +GENERATED_QGA_FILES := qga-qapi-types.c qga-qapi-types.h
> +GENERATED_QGA_FILES += qga-qapi-visit.c qga-qapi-visit.h
> +GENERATED_QGA_FILES += qga-qapi-commands.h qga-qapi-commands.c
> +GENERATED_QGA_FILES += qga-qapi-init-commands.h qga-qapi-init-commands.c
> +GENERATED_QGA_FILES += qga-qapi-doc.texi
> +GENERATED_QGA_FILES := $(addprefix qga/qapi-generated/, $(GENERATED_QGA_FILES))

Would it be worth using two separate variable names (maybe 
GENERATED_QGA_BASEFILES for the first list) rather than exploiting the 
arcane knowledge that consecutive use of := causes GNU make to rewrite 
an existing variable with new contents?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
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