[PATCH] Makefile: use override directive on engine CFLAGS

[PATCH] Makefile: use override directive on engine CFLAGS

[Stefan Hajnoczi]

The GNU Make documentation says the following about the override
keyword:

  Subsequent assignments or appends to this variable which are not
  marked override will be ignored.

  https://www.gnu.org/software/make/manual/html_node/Override-Directive.html

When the override CFLAGS line was moved in commit
f4bd2c3d80bc35f76892205a7e50426711e3def3 it broke the engine template,
which does not use the override directive. Since the engine template is
now evaluated afterwards, the engine CFLAGS are ignored.

Add the override keyword to the engine template so that engine CFLAGS
are honored again.

Note that the CONFIG_DYNAMIC_ENGINES case doesn't need the override
directive. It seems that GNU Make assigns CFLAGS even without the
override directive in this case:

  $$($(1)_OBJS): CFLAGS := -fPIC $$($(1)_CFLAGS) $(CFLAGS)

Fixes: f4bd2c3d80bc35f76892205a7e50426711e3def3 ("fix dynamic engine build")
Cc: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index f57569d5..510e07fc 100644
--- a/Makefile
+++ b/Makefile
@@ -293,7 +293,7 @@ else # !CONFIG_DYNAMIC_ENGINES
 define engine_template =
 SOURCE += $$($(1)_SRCS)
 LIBS += $$($(1)_LIBS)
-CFLAGS += $$($(1)_CFLAGS)
+override CFLAGS += $$($(1)_CFLAGS)
 endef
 endif
 
-- 
2.31.1

Re: [PATCH] Makefile: use override directive on engine CFLAGS

[Jens Axboe]

On 7/6/21 11:27 AM, Stefan Hajnoczi wrote:
> The GNU Make documentation says the following about the override
> keyword:
> 
>   Subsequent assignments or appends to this variable which are not
>   marked override will be ignored.
> 
>   https://www.gnu.org/software/make/manual/html_node/Override-Directive.html
> 
> When the override CFLAGS line was moved in commit
> f4bd2c3d80bc35f76892205a7e50426711e3def3 it broke the engine template,
> which does not use the override directive. Since the engine template is
> now evaluated afterwards, the engine CFLAGS are ignored.
> 
> Add the override keyword to the engine template so that engine CFLAGS
> are honored again.
> 
> Note that the CONFIG_DYNAMIC_ENGINES case doesn't need the override
> directive. It seems that GNU Make assigns CFLAGS even without the
> override directive in this case:
> 
>   $$($(1)_OBJS): CFLAGS := -fPIC $$($(1)_CFLAGS) $(CFLAGS)

Applied, thanks.

-- 
Jens Axboe