+ compiler-clangh-require-llvm-1910-or-higher-for-__typeof_unqual__.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: compiler-clang.h: Require LLVM 19.1.0 or higher for __typeof_unqual__
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     compiler-clangh-require-llvm-1910-or-higher-for-__typeof_unqual__.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/compiler-clangh-require-llvm-1910-or-higher-for-__typeof_unqual__.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Nathan Chancellor <nathan@kernel.org>
Subject: compiler-clang.h: Require LLVM 19.1.0 or higher for __typeof_unqual__
Date: Fri, 16 Jan 2026 16:26:27 -0700

When building the kernel using a version of LLVM between llvmorg-19-init
(the first commit of the LLVM 19 development cycle) and the change in
LLVM that actually added __typeof_unqual__ for all C modes [1], which
might happen during a bisect of LLVM, there is a build failure:

  In file included from arch/x86/kernel/asm-offsets.c:9:
  In file included from include/linux/crypto.h:15:
  In file included from include/linux/completion.h:12:
  In file included from include/linux/swait.h:7:
  In file included from include/linux/spinlock.h:56:
  In file included from include/linux/preempt.h:79:
  arch/x86/include/asm/preempt.h:61:2: error: call to undeclared function '__typeof_unqual__'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     61 |         raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED);
        |         ^
  arch/x86/include/asm/percpu.h:478:36: note: expanded from macro 'raw_cpu_and_4'
    478 | #define raw_cpu_and_4(pcp, val)                         percpu_binary_op(4, , "and", (pcp), val)
        |                                                         ^
  arch/x86/include/asm/percpu.h:210:3: note: expanded from macro 'percpu_binary_op'
    210 |                 TYPEOF_UNQUAL(_var) pto_tmp__;                          \
        |                 ^
  include/linux/compiler.h:248:29: note: expanded from macro 'TYPEOF_UNQUAL'
    248 | # define TYPEOF_UNQUAL(exp) __typeof_unqual__(exp)
        |                             ^

The current logic of CC_HAS_TYPEOF_UNQUAL just checks for a major
version of 19 but half of the 19 development cycle did not have support
for __typeof_unqual__.

Harden the logic of CC_HAS_TYPEOF_UNQUAL to avoid this error by only
using __typeof_unqual__ with a released version of LLVM 19, which is
greater than or equal to 19.1.0 with LLVM's versioning scheme that
matches GCC's [2].

Link: https://github.com/llvm/llvm-project/commit/cc308f60d41744b5920ec2e2e5b25e1273c8704b [1]
Link: https://github.com/llvm/llvm-project/commit/4532617ae420056bf32f6403dde07fb99d276a49 [2]
Link: https://lkml.kernel.org/r/20260116-require-llvm-19-1-for-typeof_unqual-v1-1-3b9a4a4b212b@kernel.org
Fixes: ac053946f5c4 ("compiler.h: introduce TYPEOF_UNQUAL() macro")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Cc: Bill Wendling <morbo@google.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Uros Bizjak <ubizjak@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/compiler-clang.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/compiler-clang.h~compiler-clangh-require-llvm-1910-or-higher-for-__typeof_unqual__
+++ a/include/linux/compiler-clang.h
@@ -153,4 +153,4 @@
  * Bindgen uses LLVM even if our C compiler is GCC, so we cannot
  * rely on the auto-detected CONFIG_CC_HAS_TYPEOF_UNQUAL.
  */
-#define CC_HAS_TYPEOF_UNQUAL (__clang_major__ >= 19)
+#define CC_HAS_TYPEOF_UNQUAL (__clang_major__ > 19 || (__clang_major__ == 19 && __clang_minor__ > 0))
_

Patches currently in -mm which might be from nathan@kernel.org are

compiler-clangh-require-llvm-1910-or-higher-for-__typeof_unqual__.patch