[Buildroot] [git commit] package/m4: fix build failure with host-gcc 15

[Luca Ceresoli]

Hello Julian, All,

On Sun, 4 May 2025 19:36:21 +0200
Julien Olivain <ju.o at free.fr> wrote:

> commit: https://git.buildroot.net/buildroot/commit/?id=7a07a9d155b8f601d68f07ee0ed1dc8d48907644
> branch: https://git.buildroot.net/buildroot/commit/?id=refs/heads/master
> 
> When compiling host-m4 1.4.19 with a host gcc 15 (which is the version
> included in Fedora 42, released on 2025-04-15), compilation fails with
> error:

[...]

> +ifeq ($(BR2_HOST_GCC_AT_LEAST_15),y)
> +HOST_M4_CONF_ENV = CFLAGS="$(HOST_CFLAGS) -std=gnu17"
> +endif

While this patch fixes builds with gcc 15 on the master branch, there
is currently no fix on the 2025.02.x LTS branch.

This patch does not fix 2025.02.x however, because
BR2_HOST_GCC_AT_LEAST_15 does not exist on that branch, thus the ifeq
never triggers.

I tested this patch on 2025.02.1 as it was originally submitted [1],
unconditionally applying -std=gnu17, and it fixes the host-m4 build on
Fedora 42 (gcc 15.1.1). However I suspect it would not break host-m4 on
hosts with an older gcc version.

I instead tried cherry-picking these two patches on 2025.02.1:

  cca8d68461e6 ("Config.in: introduce BR2_HOST_GCC_AT_LEAST_{12..15}")
  7a07a9d155b8 ("package/m4: fix build failure with host-gcc 15") <this commit>

With those, host-m4 built successfully.

Would it be OK to apply both of these on 2025.02.x?

[1] https://lore.kernel.org/buildroot/20250503135217.490404-2-zik@jambula.net/

Luca

-- 
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com