[PATCH v2 1/9] Compiler Attributes: Add __must_init macro
From: Ian Rogers
Date: Tue Oct 27 2026 - 18:41:36 EST
Clang supports the 'require_explicit_initialization' attribute on struct
fields to indicate that a field must be initialized explicitly by the
user when the object is constructed. When an aggregate initializer or
uninitialized variable omits an annotated field, Clang emits a
-Wuninitialized-explicit-init warning (enabled by default).
Add the __must_init macro to include/linux/compiler_attributes.h (which
is included by include/linux/compiler_types.h and
include/linux/compiler.h) so kernel structs with error-prone
initialization (such as mandatory callbacks or cleanup handlers) can
enforce explicit initialization at compile time, as discussed at the
Linux Plumbers Conference. The shorter __must_init spelling, rather than
the attribute's full name, keeps annotated struct members readable and
was suggested by Greg Kroah-Hartman.
Note that Clang does not yet diagnose file-scope objects declared
without any initializer (initializers at file scope that omit the field
are diagnosed), see https://github.com/llvm/llvm-project/issues/232483.
Also teach Sphinx (Documentation/conf.py), kernel-doc
(tools/lib/python/kdoc/xforms_lists.py), and checkpatch.pl about the new
attribute macro.
Link: https://lpc.events/event/20/contributions/2392/
Link: https://lore.kernel.org/lkml/2026101532-fantastic-deafness-e04c@gregkh/
Acked-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
Documentation/conf.py | 1 +
include/linux/compiler_attributes.h | 12 ++++++++++++
scripts/checkpatch.pl | 1 +
tools/lib/python/kdoc/xforms_lists.py | 1 +
4 files changed, 15 insertions(+)
diff --git a/Documentation/conf.py b/Documentation/conf.py
index 5ab26ce89daf..baaa4035258c 100644
--- a/Documentation/conf.py
+++ b/Documentation/conf.py
@@ -203,6 +203,7 @@ c_id_attributes = [
"__noreturn",
"__packed",
"__pure",
+ "__must_init",
"__section",
"__always_unused",
"__maybe_unused",
diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
index 476c4c560d17..b9c0b56dd22e 100644
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -322,6 +322,18 @@
*/
#define __pure __attribute__((__pure__))
+/*
+ * Optional: not supported by gcc
+ * Optional: only supported since clang >= 20.0
+ *
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#require-explicit-initialization
+ */
+#if __has_attribute(__require_explicit_initialization__)
+# define __must_init __attribute__((__require_explicit_initialization__))
+#else
+# define __must_init
+#endif
+
/*
* gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
* gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index c9840f5219c2..5232f66d2b80 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6860,6 +6860,7 @@ sub process {
"noreturn" => "__noreturn",
"packed" => "__packed",
"pure" => "__pure",
+ "require_explicit_initialization" => "__must_init",
"section" => "__section",
"used" => "__used",
"weak" => "__weak"
diff --git a/tools/lib/python/kdoc/xforms_lists.py b/tools/lib/python/kdoc/xforms_lists.py
index 320f977c5bac..3c744cbd2f34 100644
--- a/tools/lib/python/kdoc/xforms_lists.py
+++ b/tools/lib/python/kdoc/xforms_lists.py
@@ -36,6 +36,7 @@ class CTransforms:
(CMatch("CRYPTO_MINALIGN_ATTR"), ""),
(CMatch("__private"), ""),
(CMatch("__rcu"), ""),
+ (CMatch("__must_init"), ""),
(CMatch("____cacheline_aligned_in_smp"), ""),
(CMatch("____cacheline_aligned"), ""),
(CMatch("__cacheline_group_(?:begin|end)"), ""),
--
2.56.0.313.g2479322e68-goog