https://github.com/JustinStitt updated https://github.com/llvm/llvm-project/pull/203392
>From 02bf80112c24147e57918cf814be2098e57dca8f Mon Sep 17 00:00:00 2001 From: Justin Stitt <[email protected]> Date: Thu, 11 Jun 2026 13:35:00 -0700 Subject: [PATCH 1/3] [Clang] Add AttrDocs entry for OverflowBehavior These docs were previously missing. Basically just add what was in the formal docs here. Fixes: https://github.com/llvm/llvm-project/issues/203322 Signed-off-by: Justin Stitt <[email protected]> --- clang/include/clang/Basic/Attr.td | 2 +- clang/include/clang/Basic/AttrDocs.td | 45 +++++++++++++++++++++++++++ 2 files changed, 46 insertions(+), 1 deletion(-) diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td index 7f7e9489782a7..b5c50a0d16e51 100644 --- a/clang/include/clang/Basic/Attr.td +++ b/clang/include/clang/Basic/Attr.td @@ -5477,7 +5477,7 @@ def OverflowBehavior : TypeAttr { let Args = [IdentifierArgument<"BehaviorKind">]; let Subjects = SubjectList<[Var, TypedefName, Field], WarnDiag, "variables, typedefs, and data members">; - let Documentation = [Undocumented]; + let Documentation = [OverflowBehaviorDocs]; } def Personality : InheritableAttr { diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td index dab778d4047aa..280b75957c971 100644 --- a/clang/include/clang/Basic/AttrDocs.td +++ b/clang/include/clang/Basic/AttrDocs.td @@ -10051,6 +10051,51 @@ The following aspects are currently supported: }]; } +def OverflowBehaviorDocs : Documentation { + let Category = DocCatType; + let Content = [{ +The ``overflow_behavior`` attribute provides fine-grained, type-level control +over how arithmetic operations on an integer type behave on overflow. It may be +applied to a ``typedef``, to a variable or data member, or to an integer type +directly, and accepts one of two behaviors as its argument: + +* ``wrap``: arithmetic on the attributed type wraps on overflow, using two's + complement semantics. This is equivalent to ``-fwrapv`` but scoped to the + attributed type, and works for both signed and unsigned types. UBSan's + ``signed-integer-overflow``, ``unsigned-integer-overflow``, + ``implicit-signed-integer-truncation``, and + ``implicit-unsigned-integer-truncation`` checks are suppressed for the type. + +* ``trap``: arithmetic on the attributed type is checked for overflow, enabling + overflow checks for the type even when ``-fwrapv`` is in effect globally. + +.. code-block:: c++ + + typedef unsigned int __attribute__((overflow_behavior(trap))) non_wrapping_uint; + + non_wrapping_uint add_one(non_wrapping_uint a) { + return a + 1; // Overflow is checked for this operation. + } + + int mul_alot(int n) { + int __attribute__((overflow_behavior(wrap))) a = n; + return a * 1337; // Overflow is not checked and is well-defined. + } + +The keyword spellings ``__ob_wrap`` and ``__ob_trap`` are equivalent to +``overflow_behavior(wrap)`` and ``overflow_behavior(trap)`` respectively. + +The attribute wholly overrides global flags (``-ftrapv``, ``-fwrapv``, +sanitizers, and Sanitizer Special Case Lists) for the attributed type. It can +only be applied to integer types. + +This feature is experimental and must be enabled with the ``-cc1`` option +``-fexperimental-overflow-behavior-types``. For full details on promotion and +conversion rules, pointer semantics, diagnostics, and interaction with +sanitizers, see :doc:`OverflowBehaviorTypes`. + }]; +} + def MSStructDocs : Documentation { let Category = DocCatDecl; let Content = [{ >From ab67efe26d799cfb5c0ad95340a90393edb6b148 Mon Sep 17 00:00:00 2001 From: Justin Stitt <[email protected]> Date: Thu, 11 Jun 2026 16:07:57 -0700 Subject: [PATCH 2/3] remove from undocumented-attrs.cpp Signed-off-by: Justin Stitt <[email protected]> --- clang/test/AST/undocumented-attrs.cpp | 1 - 1 file changed, 1 deletion(-) diff --git a/clang/test/AST/undocumented-attrs.cpp b/clang/test/AST/undocumented-attrs.cpp index c7a2c74631ea2..da00c90e70ffb 100644 --- a/clang/test/AST/undocumented-attrs.cpp +++ b/clang/test/AST/undocumented-attrs.cpp @@ -69,7 +69,6 @@ CHECK-NEXT: ObjCPreciseLifetime CHECK-NEXT: ObjCRequiresPropertyDefs CHECK-NEXT: ObjCReturnsInnerPointer CHECK-NEXT: ObjCRootClass -CHECK-NEXT: OverflowBehavior CHECK-NEXT: Packed CHECK-NEXT: Pascal CHECK-NEXT: PointerFieldProtection >From 068cb2291ce227d301dd83d0d29448999cb4c94a Mon Sep 17 00:00:00 2001 From: Justin Stitt <[email protected]> Date: Fri, 12 Jun 2026 08:02:38 -0700 Subject: [PATCH 3/3] further fix tests Signed-off-by: Justin Stitt <[email protected]> --- clang/test/AST/undocumented-attrs.cpp | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/clang/test/AST/undocumented-attrs.cpp b/clang/test/AST/undocumented-attrs.cpp index da00c90e70ffb..eeebd7f938644 100644 --- a/clang/test/AST/undocumented-attrs.cpp +++ b/clang/test/AST/undocumented-attrs.cpp @@ -90,4 +90,4 @@ CHECK-NEXT: Visibility CHECK-NEXT: WeakImport CHECK-NEXT: WeakRef CHECK-NEXT: WorkGroupSizeHint -CHECK-NEXT: Total: 85 +CHECK-NEXT: Total: 84 _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
