[Buildroot] [PATCH 1/1] package/libabseil-cpp: add patch to fix build with gcc <= 12

[Romain Naour]

Hello Julien,

Le 27/04/2026 à 22:16, Julien Olivain via buildroot a écrit :
> libabseil-cpp headers can break some packages build, like protobuf,
> when compiled with gcc 12. See [1] [2]. The issue has been reported
> in protobuf upstream, in [3].
> 
> The issue is due to gcc <= 12 not supporting the mix of standard
> C++ attributes with GNU attributes. See [4].
> 
> Gcc 12 has been removed from Buildroot internal toolchains in
> commit [5], but gcc 12 can still be present in external toolchains
> or on the host. This is currently the case of the Buildroot Docker
> reference image, based on Debian 12 (Bookworm).
> 
> This commit fixes the issue by adding a package patch.
> 
> Fixes:
> - [1] [2] and many more.
> 
> [1] https://gitlab.com/buildroot.org/buildroot/-/jobs/13904066346
> [2] https://autobuild.buildroot.org/results/33f6cfd37cb48c15a53b3e7123d5ce8388a0f2ab
> [3] https://github.com/protocolbuffers/protobuf/issues/26383
> [4] https://gcc.gnu.org/PR69585
> [5] https://gitlab.com/buildroot.org/buildroot/-/commit/58cf7c51da3ae4804332f68ee934e153d695d047
> [6] https://github.com/abseil/abseil-cpp/pull/2044

Following the reply from Dowan:
https://lore.kernel.org/buildroot/29057165-7222-444f-87b5-731fd99e94d2@smile.fr/

Applied to master. Thanks.

Best regards,
Romain

> 
> Signed-off-by: Julien Olivain <ju.o at free.fr>
> ---
>  ...SL_ATTRIBUTE_WARN_UNUSED-with-gcc-12.patch | 55 +++++++++++++++++++
>  1 file changed, 55 insertions(+)
>  create mode 100644 package/libabseil-cpp/0002-base-fix-ABSL_ATTRIBUTE_WARN_UNUSED-with-gcc-12.patch
> 
> diff --git a/package/libabseil-cpp/0002-base-fix-ABSL_ATTRIBUTE_WARN_UNUSED-with-gcc-12.patch b/package/libabseil-cpp/0002-base-fix-ABSL_ATTRIBUTE_WARN_UNUSED-with-gcc-12.patch
> new file mode 100644
> index 0000000000..8f5e255795
> --- /dev/null
> +++ b/package/libabseil-cpp/0002-base-fix-ABSL_ATTRIBUTE_WARN_UNUSED-with-gcc-12.patch
> @@ -0,0 +1,55 @@
> +From 77326826119439c06e341c9d090633ecd9b520d6 Mon Sep 17 00:00:00 2001
> +From: Julien Olivain <ju.o at free.fr>
> +Date: Mon, 27 Apr 2026 19:38:19 +0200
> +Subject: [PATCH] base: fix ABSL_ATTRIBUTE_WARN_UNUSED with gcc <= 12
> +
> +Gcc <= 12 does not support mixing standard C++ attributes with
> +GNU attributes. See [1].
> +
> +This can lead to build failures such as [2] [3] and [4]. In those
> +situations, the compilation fails with error such as:
> +
> +    /usr/include/absl/base/attributes.h:1076:36: error: expected identifier before '[' token
> +
> +Gcc maintainers mentioned in [1] comment 9 that this bugfix will
> +not be backported in Gcc 12. Gcc 12 is still used in LTS
> +distributions. For example, it is included in Debian 12 (Bookworm),
> +which is still supported until 2028. See [5].
> +
> +This commit adds a workaround for gcc <= 12 which uses
> +__attribute__ in that case, which fixes the compilation failure.
> +
> +[1] https://gcc.gnu.org/PR69585
> +[2] https://github.com/protocolbuffers/protobuf/issues/26383
> +[3] https://autobuild.buildroot.org/results/33f6cfd37cb48c15a53b3e7123d5ce8388a0f2ab/build-end.log
> +[4] https://gitlab.com/buildroot.org/buildroot/-/jobs/13904066346
> +[5] https://www.debian.org/releases/bookworm/
> +
> +Upstream: https://github.com/abseil/abseil-cpp/pull/2044
> +Signed-off-by: Julien Olivain <ju.o at free.fr>
> +---
> + absl/base/attributes.h | 7 +++++++
> + 1 file changed, 7 insertions(+)
> +
> +diff --git a/absl/base/attributes.h b/absl/base/attributes.h
> +index 5887fcaf..a26143e1 100644
> +--- a/absl/base/attributes.h
> ++++ b/absl/base/attributes.h
> +@@ -1092,7 +1092,14 @@ struct AbslInternal_YouForgotToExplicitlyInitializeAField {
> + // See https://clang.llvm.org/docs/AttributeReference.html#warn-unused and
> + // https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Attributes.html#index-warn_005funused-type-attribute
> + #if ABSL_HAVE_CPP_ATTRIBUTE(gnu::warn_unused)
> ++// Only GCC >= 13 allows mixing standard and gnu attributes.
> ++// In case of gcc < 13, fallback on using __attribute__.
> ++// https://gcc.gnu.org/PR69585
> ++#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 13
> ++#define ABSL_ATTRIBUTE_WARN_UNUSED __attribute__((warn_unused))
> ++#else
> + #define ABSL_ATTRIBUTE_WARN_UNUSED [[gnu::warn_unused]]
> ++#endif
> + #else
> + #define ABSL_ATTRIBUTE_WARN_UNUSED
> + #endif
> +-- 
> +2.54.0
> +