Consider `-Wzero-init-padding-bits` for C and C++ Compiler Hardening

[thomasnyman]

Via @thesamesam in comment to #919

GCC 16 is expected to add a warning diagnostic, -Wzero-init-padding-bits=, which is intended to help programmers to find code that might now need to be rewritten or recompiled with-fzero-init-padding-bits=unions or -fzero-init-padding-bits=all in order to replicate the behaviour that it had when compiled by older versions of GCC (see #857 and #933). It can also be used to find struct padding that was never previously guaranteed to be zero initialized and still isn't unless GCC is invoked with -fzero-init-padding-bits=all option.

Resources:

• https://inbox.sourceware.org/gcc-patches/20250521151302.32847-1-chris.bazley@arm.com/