https://github.com/ahatanak created https://github.com/llvm/llvm-project/pull/157778
This addresses an issue introduced by 0a9c08c59ba61e727e9dee6d71883d9106963442, which implemented P2280R4. This fixes the issue reported in https://github.com/llvm/llvm-project/pull/95474#issuecomment-3025887023. rdar://149897839 >From 9399a0cda1a55a18e33d68be331284c654ea7c6b Mon Sep 17 00:00:00 2001 From: Akira Hatanaka <ahata...@gmail.com> Date: Tue, 9 Sep 2025 10:50:27 -0700 Subject: [PATCH] Fix __builtin_object_size calculation for references of unknown origin in C++23 This addresses an issue introduced by 0a9c08c59ba61e727e9dee6d71883d9106963442, which implemented P2280R4. This fixes the issue reported in https://github.com/llvm/llvm-project/pull/95474#issuecomment-3025887023. rdar://149897839 --- clang/lib/AST/ExprConstant.cpp | 16 ++++++++- clang/test/Sema/builtin-object-size.cpp | 48 +++++++++++++++++++++++++ 2 files changed, 63 insertions(+), 1 deletion(-) create mode 100644 clang/test/Sema/builtin-object-size.cpp diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp index 2376e482a19f5..229211c4f2cb7 100644 --- a/clang/lib/AST/ExprConstant.cpp +++ b/clang/lib/AST/ExprConstant.cpp @@ -13279,6 +13279,9 @@ static bool refersToCompleteObject(const LValue &LVal) { if (LVal.Designator.Invalid) return false; + if (LVal.AllowConstexprUnknown) + return false; + if (!LVal.Designator.Entries.empty()) return LVal.Designator.isMostDerivedAnUnsizedArray(); @@ -13328,7 +13331,7 @@ static bool isUserWritingOffTheEnd(const ASTContext &Ctx, const LValue &LVal) { return false; }; - return LVal.InvalidBase && + return (LVal.InvalidBase || LVal.AllowConstexprUnknown) && Designator.Entries.size() == Designator.MostDerivedPathLength && Designator.MostDerivedIsArrayElement && isFlexibleArrayMember() && isDesignatorAtObjectEnd(Ctx, LVal); @@ -13396,6 +13399,17 @@ static bool determineEndOffset(EvalInfo &Info, SourceLocation ExprLoc, if (LVal.InvalidBase) return false; + // We cannot deterimine the end offset of the enitre object if this is an + // unknown reference. + if (Type == 0 && LVal.AllowConstexprUnknown) + return false; + + // We cannot deterimine the end offset of the subobject if this is an + // unknown reference and the subobject designator is invalid (e.g., unsized + // array designator). + if (Type == 1 && LVal.Designator.Invalid && LVal.AllowConstexprUnknown) + return false; + QualType BaseTy = getObjectType(LVal.getLValueBase()); const bool Ret = CheckedHandleSizeof(BaseTy, EndOffset); addFlexibleArrayMemberInitSize(Info, BaseTy, LVal, EndOffset); diff --git a/clang/test/Sema/builtin-object-size.cpp b/clang/test/Sema/builtin-object-size.cpp new file mode 100644 index 0000000000000..3995e1880ec81 --- /dev/null +++ b/clang/test/Sema/builtin-object-size.cpp @@ -0,0 +1,48 @@ +// RUN: %clang_cc1 -triple x86_64-apple-darwin -fsyntax-only -fstrict-flex-arrays=0 -DSTRICT0 -std=c++23 -verify %s +// RUN: %clang_cc1 -triple x86_64-apple-darwin -fsyntax-only -fstrict-flex-arrays=1 -DSTRICT1 -std=c++23 -verify %s +// RUN: %clang_cc1 -triple x86_64-apple-darwin -fsyntax-only -fstrict-flex-arrays=2 -DSTRICT2 -std=c++23 -verify %s +// RUN: %clang_cc1 -triple x86_64-apple-darwin -fsyntax-only -fstrict-flex-arrays=3 -DSTRICT3 -std=c++23 -verify %s + +struct EmptyS { + int i; + char a[]; +}; + +template <unsigned N> +struct S { + int i; + char a[N]; +}; + +extern S<2> &s2; +static_assert(__builtin_object_size(s2.a, 0)); // expected-error {{static assertion expression is not an integral constant expression}} +static_assert(__builtin_object_size(s2.a, 1) == 2); +#if defined(STRICT0) +// expected-error@-2 {{static assertion expression is not an integral constant expression}} +#endif +static_assert(__builtin_object_size(s2.a, 2) == 4); +static_assert(__builtin_object_size(s2.a, 3) == 2); + +extern S<1> &s1; +static_assert(__builtin_object_size(s1.a, 0)); // expected-error {{static assertion expression is not an integral constant expression}} +static_assert(__builtin_object_size(s1.a, 1) == 1); +#if defined(STRICT0) || defined(STRICT1) +// expected-error@-2 {{static assertion expression is not an integral constant expression}} +#endif +static_assert(__builtin_object_size(s1.a, 2) == 4); +static_assert(__builtin_object_size(s1.a, 3) == 1); + +extern S<0> &s0; +static_assert(__builtin_object_size(s0.a, 0)); // expected-error {{static assertion expression is not an integral constant expression}} +static_assert(__builtin_object_size(s0.a, 1) == 0); +#if defined(STRICT0) || defined(STRICT1) || defined(STRICT2) +// expected-error@-2 {{static assertion expression is not an integral constant expression}} +#endif +static_assert(__builtin_object_size(s0.a, 2) == 0); +static_assert(__builtin_object_size(s0.a, 3) == 0); + +extern EmptyS ∅ +static_assert(__builtin_object_size(empty.a, 0)); // expected-error {{static assertion expression is not an integral constant expression}} +static_assert(__builtin_object_size(empty.a, 1)); // expected-error {{static assertion expression is not an integral constant expression}} +static_assert(__builtin_object_size(empty.a, 2) == 0); +static_assert(__builtin_object_size(empty.a, 3)); // expected-error {{static assertion expression is not an integral constant expression}} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
