Bug#1110453: geary: FTBFS on arm64 with GCC-15 due to GCS warning

[Jeremy Bícha]

On Tue, Aug 5, 2025 at 3:13 PM Emanuele Rocca <ema at debian.org> wrote:
> geary fails to build from source on arm64 if built with GCC-15, currently in
> experimental.
>
> GCC-15 includes support for an arm64 security feature called Guarded Control
> Stack (GCS). To help with GCS adoption, the linker warns about shared libraries
> built without GCS. For example:
>
>  /usr/lib/gcc/aarch64-linux-gnu/15/../../../aarch64-linux-gnu/libncursesw.so.6: warning: GCS is required by -z gcs, but this shared library lacks the necessary property note. The dynamic loader might not enable GCS or refuse to load the program unless all the shared library dependencies have the GCS marking.
>
> The warning is harmless, and can be ignored. However, geary is built with
> --fatal-warnings, and for this reason will fail to build on arm64 once GCC-15
> becomes the default compiler in Debian.
>
> Luckily, it is possible to switch the warning off by passing the argument
> gcs-report-dynamic=none to the linker. Please consider adding the following to
> your debian/rules:
>
> ifeq ($(DEB_TARGET_ARCH),arm64)
> DEB_LDFLAGS_MAINT_APPEND=-Wl,-z,gcs-report-dynamic=none
> endif
>
> This can be done even before GCC-15 becomes the default compiler, to avoid
> build failures when it does.

gcc 15 is now the default in unstable and in Ubuntu questing.

I did a test build in a questing PPA and the build succeeded on arm64
with no changes:
https://launchpad.net/~jbicha/+archive/ubuntu/arch/+build/31132402

Thank you,
Jeremy Bícha