Re: [PATCH v2] kbuild: add GCC stability warning

[Nicolas Schier <nsc@kernel.org>]

Hi Samuel,

On Sun, Mar 29, 2026 at 01:21:39PM -0600, Samuel Rowberry wrote:
> Newer GCC versions are not fully compatible with the code.
> Adding a warning lets users know without getting in the way
> of setups where it is okay to use GCC 15 (or is needed.)

can you please elaborate, _why_ you state that gcc 15 is incompatible in
some ways?

> 
> Signed-off-by: Samuel Rowberry <sprowdev@gmail.com>
> ---
> v2:
>  - Fixed line wrapping in commit desc
> 
>  Makefile | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/Makefile b/Makefile
> index 02902bcae..361b5a509 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -720,6 +720,19 @@ endif
>  
>  export KBUILD_MODULES KBUILD_BUILTIN
>  
> +# Version check on demand because configs can get stale

kbuild already warns on compiler changes between kernel and out-of-tree
module builds, cp. Makefile target 'prepare'.

> +# This check is GCC-only because that is standard
> +# and if someone is using a custom setup, then it is
> +# assumed that their setup works.
> +ifeq ($(KBUILD_BUILTIN)$(KBUILD_MODULES),11)
> +ifneq ($(findstring GCC,$(CC_VERSION_TEXT)),)

What about CONFIG_CC_IS_GCC ?  Or ...

> +CURRENT_CC_VERSION := $(shell $(CC) -dumpversion | cut -d. -f1)

CONFIG_GCC_VERSION ?

> +ifeq ($(shell expr $(CURRENT_CC_VERSION) \>= 15),1)

ifeq ($(call gcc-min-version, $(CONFIG_GCC_VERSION)),y)   ?

> +$(warning "GCC $(CURRENT_CC_VERSION) detected. Please use GCC 11, 12, or 13 for stability.")

Why do you leave out gcc-14 here?

Kind regards

-- 
Nicolas