kbuild: Never respect CONFIG_WERROR / W=e to fixdep

[PATCH] kbuild: Never respect CONFIG_WERROR / W=e to fixdep

Posted by Thomas Weißschuh 1 month, 3 weeks ago

The fixdep hostprog may be built multiple times during a single build.
Once during the configuration phase and later during the regular phase.
As only the regular build phase respects CONFIG_WERROR / W=e, the
compiler flags might change between the phases, leading to rebuilds.

Example, the rebuilds will happen twice on each invocation of the build:

  $ make allyesconfig prepare
  make[1]: Entering directory '/tmp/deleteme'
    HOSTCC  scripts/basic/fixdep
  #
  # No change to .config
  #
    HOSTCC  scripts/basic/fixdep
    DESCEND objtool
    INSTALL libsubcmd_headers
  make[1]: Leaving directory '/tmp/deleteme'

Fix the compilation flags used for scripts/basic/ before
scripts/Makefile.warn is evaluated to stop CONFIG_WERROR / W=e
influencing the fixdep build to avoid the spurious rebuilds.

Fixes: 7ded7d37e5f5 ("scripts/Makefile.extrawarn: Respect CONFIG_WERROR / W=e for hostprogs")
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Makefile b/Makefile
index 54e1ae602000..6c8a1b2e7c8a 100644
--- a/Makefile
+++ b/Makefile
@@ -657,6 +657,8 @@ export RCS_FIND_IGNORE := \( -name SCCS -o -name BitKeeper -o -name .svn -o    \
 
 # Basic helpers built in scripts/basic/
 PHONY += scripts_basic
+scripts_basic: KBUILD_HOSTCFLAGS := $(KBUILD_HOSTCFLAGS)
+scripts_basic: KBUILD_HOSTLDFLAGS := $(KBUILD_HOSTLDFLAGS)
 scripts_basic:
 	$(Q)$(MAKE) $(build)=scripts/basic
 

---
base-commit: 6596a02b207886e9e00bb0161c7fd59fea53c081
change-id: 20260422-kbuild-scripts-basic-werror-f8f7bfc39cfc

Best regards,
--  
Thomas Weißschuh <linux@weissschuh.net>

Re: [PATCH] kbuild: Never respect CONFIG_WERROR / W=e to fixdep

Posted by Nathan Chancellor 1 month, 3 weeks ago

On Wed, Apr 22, 2026 at 05:10:27PM +0200, Thomas Weißschuh wrote:
> The fixdep hostprog may be built multiple times during a single build.
> Once during the configuration phase and later during the regular phase.
> As only the regular build phase respects CONFIG_WERROR / W=e, the
> compiler flags might change between the phases, leading to rebuilds.
> 
> Example, the rebuilds will happen twice on each invocation of the build:
> 
>   $ make allyesconfig prepare
>   make[1]: Entering directory '/tmp/deleteme'
>     HOSTCC  scripts/basic/fixdep
>   #
>   # No change to .config
>   #
>     HOSTCC  scripts/basic/fixdep
>     DESCEND objtool
>     INSTALL libsubcmd_headers
>   make[1]: Leaving directory '/tmp/deleteme'
> 
> Fix the compilation flags used for scripts/basic/ before
> scripts/Makefile.warn is evaluated to stop CONFIG_WERROR / W=e
> influencing the fixdep build to avoid the spurious rebuilds.
> 
> Fixes: 7ded7d37e5f5 ("scripts/Makefile.extrawarn: Respect CONFIG_WERROR / W=e for hostprogs")
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

> ---
>  Makefile | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/Makefile b/Makefile
> index 54e1ae602000..6c8a1b2e7c8a 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -657,6 +657,8 @@ export RCS_FIND_IGNORE := \( -name SCCS -o -name BitKeeper -o -name .svn -o    \
>  
>  # Basic helpers built in scripts/basic/
>  PHONY += scripts_basic
> +scripts_basic: KBUILD_HOSTCFLAGS := $(KBUILD_HOSTCFLAGS)
> +scripts_basic: KBUILD_HOSTLDFLAGS := $(KBUILD_HOSTLDFLAGS)
>  scripts_basic:
>  	$(Q)$(MAKE) $(build)=scripts/basic
>  
> 
> ---
> base-commit: 6596a02b207886e9e00bb0161c7fd59fea53c081
> change-id: 20260422-kbuild-scripts-basic-werror-f8f7bfc39cfc
> 
> Best regards,
> --  
> Thomas Weißschuh <linux@weissschuh.net>
>