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b0630d1845
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Nathan Chancellor b0630d1845 kbuild: Disable -Wdefault-const-init-unsafe 
commit d0afcfeb9e upstream.

A new on by default warning in clang [1] aims to flags instances where
const variables without static or thread local storage or const members
in aggregate types are not initialized because it can lead to an
indeterminate value. This is quite noisy for the kernel due to
instances originating from header files such as:

  drivers/gpu/drm/i915/gt/intel_ring.h:62:2: error: default initialization of an object of type 'typeof (ring->size)' (aka 'const unsigned int') leaves the object uninitialized [-Werror,-Wdefault-const-init-var-unsafe]
     62 |         typecheck(typeof(ring->size), next);
        |         ^
  include/linux/typecheck.h:10:9: note: expanded from macro 'typecheck'
     10 | ({      type __dummy; \
        |              ^

  include/net/ip.h:478:14: error: default initialization of an object of type 'typeof (rt->dst.expires)' (aka 'const unsigned long') leaves the object uninitialized [-Werror,-Wdefault-const-init-var-unsafe]
    478 |                 if (mtu && time_before(jiffies, rt->dst.expires))
        |                            ^
  include/linux/jiffies.h:138:26: note: expanded from macro 'time_before'
    138 | #define time_before(a,b)        time_after(b,a)
        |                                 ^
  include/linux/jiffies.h:128:3: note: expanded from macro 'time_after'
    128 |         (typecheck(unsigned long, a) && \
        |          ^
  include/linux/typecheck.h:11:12: note: expanded from macro 'typecheck'
     11 |         typeof(x) __dummy2; \
        |                   ^

  include/linux/list.h:409:27: warning: default initialization of an object of type 'union (unnamed union at include/linux/list.h:409:27)' with const member leaves the object uninitialized [-Wdefault-const-init-field-unsafe]
    409 |         struct list_head *next = smp_load_acquire(&head->next);
        |                                  ^
  include/asm-generic/barrier.h:176:29: note: expanded from macro 'smp_load_acquire'
    176 | #define smp_load_acquire(p) __smp_load_acquire(p)
        |                             ^
  arch/arm64/include/asm/barrier.h:164:59: note: expanded from macro '__smp_load_acquire'
    164 |         union { __unqual_scalar_typeof(*p) __val; char __c[1]; } __u;   \
        |                                                                  ^
  include/linux/list.h:409:27: note: member '__val' declared 'const' here

  crypto/scatterwalk.c:66:22: error: default initialization of an object of type 'struct scatter_walk' with const member leaves the object uninitialized [-Werror,-Wdefault-const-init-field-unsafe]
     66 |         struct scatter_walk walk;
        |                             ^
  include/crypto/algapi.h:112:15: note: member 'addr' declared 'const' here
    112 |                 void *const addr;
        |                             ^

  fs/hugetlbfs/inode.c:733:24: error: default initialization of an object of type 'struct vm_area_struct' with const member leaves the object uninitialized [-Werror,-Wdefault-const-init-field-unsafe]
    733 |         struct vm_area_struct pseudo_vma;
        |                               ^
  include/linux/mm_types.h:803:20: note: member 'vm_flags' declared 'const' here
    803 |                 const vm_flags_t vm_flags;
        |                                  ^

Silencing the instances from typecheck.h is difficult because '= {}' is
not available in older but supported compilers and '= {0}' would cause
warnings about a literal 0 being treated as NULL. While it might be
possible to come up with a local hack to silence the warning for
clang-21+, it may not be worth it since -Wuninitialized will still
trigger if an uninitialized const variable is actually used.

In all audited cases of the "field" variant of the warning, the members
are either not used in the particular call path, modified through other
means such as memset() / memcpy() because the containing object is not
const, or are within a union with other non-const members.

Since this warning does not appear to have a high signal to noise ratio,
just disable it.

Cc: stable@vger.kernel.org
Link: 576161cb60 [1]
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Closes: https://lore.kernel.org/CA+G9fYuNjKcxFKS_MKPRuga32XbndkLGcY-PVuoSwzv6VWbY=w@mail.gmail.com/
Reported-by: Marcus Seyfarth <m.seyfarth@gmail.com>
Closes: https://github.com/ClangBuiltLinux/linux/issues/2088
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2025-06-19 15:28:45 +02:00
arch powerpc/vas: Return -EINVAL if the offset is non-zero in mmap() 2025-06-19 15:28:40 +02:00
block scsi: sd_zbc: block: Respect bio vector limits for REPORT ZONES buffer 2025-05-22 14:12:22 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2025-04-25 10:45:58 +02:00
crypto crypto: xts - Only add ecb if it is not already there 2025-06-19 15:28:03 +02:00
Documentation dt-bindings: vendor-prefixes: Add Liontron name 2025-06-19 15:28:24 +02:00
drivers HID: usbhid: Eliminate recurrent out-of-bounds bug in usbhid_parse() 2025-06-19 15:28:44 +02:00
fs fs/filesystems: Fix potential unsigned integer underflow in fs_name() 2025-06-19 15:28:43 +02:00
include io_uring: add io_file_can_poll() helper 2025-06-19 15:28:44 +02:00
init sched/isolation: Make CONFIG_CPU_ISOLATION depend on CONFIG_SMP 2025-05-02 07:50:57 +02:00
io_uring Revert "io_uring: ensure deferred completions are posted for multishot" 2025-06-19 15:28:45 +02:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-09 10:32:54 +01:00
kernel posix-cpu-timers: fix race between handle_posix_cpu_timers() and posix_cpu_timer_del() 2025-06-19 15:28:45 +02:00
lib kunit: Fix wrong parameter to kunit_deactivate_static_stub() 2025-06-19 15:28:04 +02:00
LICENSES
mm kasan: use unchecked __memset internally 2025-06-19 15:28:36 +02:00
net net_sched: ets: fix a race in ets_qdisc_change() 2025-06-19 15:28:43 +02:00
rust rust: lockdep: Remove support for dynamically allocated LockClassKeys 2025-03-22 12:50:50 -07:00
samples samples/bpf: Fix compilation failure for samples/bpf on LoongArch Fedora 2025-06-04 14:41:53 +02:00
scripts kbuild: Disable -Wdefault-const-init-unsafe 2025-06-19 15:28:45 +02:00
security smack: Revert "smackfs: Added check catlen" 2025-06-04 14:42:09 +02:00
sound ALSA: usb-audio: Add implicit feedback quirk for RODE AI-1 2025-06-19 15:28:44 +02:00
tools tools/resolve_btfids: Fix build when cross compiling kernel with clang. 2025-06-19 15:28:44 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 12:58:38 +01:00
virt KVM: Use dedicated mutex to protect kvm_usage_count to avoid deadlock 2024-10-04 16:29:47 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore Remove *.orig pattern from .gitignore 2024-10-04 16:29:44 +02:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.rustfmt.toml
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS sign-file,extract-cert: move common SSL helper functions to a header 2025-04-25 10:45:57 +02:00
Makefile Linux 6.6.93 2025-06-04 14:42:26 +02:00
README

README

Linux kernel

There are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. Please read Documentation/admin-guide/README.rst first.

In order to build the documentation, use make htmldocs or make pdfdocs. The formatted documentation can also be read online at:

https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.