https://github.com/snarang181 updated
https://github.com/llvm/llvm-project/pull/143722
>From e96c9c940bbfaf9da752c3537ea8bd023b8b15aa Mon Sep 17 00:00:00 2001
From: Samarth Narang <snar...@umass.edu>
Date: Mon, 2 Jun 2025 19:30:39 -0400
Subject: [PATCH 1/2] Add std layout diagnostics Add diagnostic test cases
---
.../clang/Basic/DiagnosticSemaKinds.td | 8 +-
clang/lib/Sema/SemaTypeTraits.cpp | 100 ++++++++++++++++++
.../type-traits-unsatisfied-diags-std.cpp | 54 ++++++++++
.../SemaCXX/type-traits-unsatisfied-diags.cpp | 80 ++++++++++++++
4 files changed, 241 insertions(+), 1 deletion(-)
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 95d24e9f1e6b5..dfe68991afb8a 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1768,7 +1768,8 @@ def note_unsatisfied_trait
"%TriviallyRelocatable{trivially relocatable}|"
"%Replaceable{replaceable}|"
"%TriviallyCopyable{trivially copyable}|"
- "%Constructible{constructible with provided types}"
+ "%Constructible{constructible with provided types}|"
+ "%StandardLayout{standard-layout}"
"}1">;
def note_unsatisfied_trait_reason
@@ -1788,6 +1789,11 @@ def note_unsatisfied_trait_reason
"%NonReplaceableField{has a non-replaceable member %1 of type %2}|"
"%NTCBase{has a non-trivially-copyable base %1}|"
"%NTCField{has a non-trivially-copyable member %1 of type %2}|"
+ "%NonStdLayoutBase{has a non-standard-layout base %1}|"
+ "%MixedAccess{has mixed access specifiers}|"
+ "%MultipleDataBase{has multiple base classes with data members}|"
+ "%VirtualFunction{has virtual functions}|"
+ "%NonStdLayoutMember{has a non-standard-layout member %1 of type
%2}|"
"%DeletedDtr{has a %select{deleted|user-provided}1 destructor}|"
"%UserProvidedCtr{has a user provided %select{copy|move}1 "
"constructor}|"
diff --git a/clang/lib/Sema/SemaTypeTraits.cpp
b/clang/lib/Sema/SemaTypeTraits.cpp
index 22c690bedc1ed..3134487f7e76d 100644
--- a/clang/lib/Sema/SemaTypeTraits.cpp
+++ b/clang/lib/Sema/SemaTypeTraits.cpp
@@ -1949,6 +1949,7 @@ static std::optional<TypeTrait>
StdNameToTypeTrait(StringRef Name) {
.Case("is_replaceable", TypeTrait::UTT_IsReplaceable)
.Case("is_trivially_copyable", TypeTrait::UTT_IsTriviallyCopyable)
.Case("is_constructible", TypeTrait::TT_IsConstructible)
+ .Case("is_standard_layout", TypeTrait::UTT_IsStandardLayout)
.Default(std::nullopt);
}
@@ -2340,6 +2341,102 @@ static void DiagnoseNonTriviallyCopyableReason(Sema
&SemaRef,
SemaRef.Diag(D->getLocation(), diag::note_defined_here) << D;
}
+static bool hasMixedAccessSpecifier(const CXXRecordDecl *D) {
+ AccessSpecifier FirstAccess = AS_none;
+ for (const FieldDecl *Field : D->fields()) {
+ if (Field->isUnnamedBitField())
+ continue;
+ AccessSpecifier FieldAccess = Field->getAccess();
+ if (FirstAccess == AS_none) {
+ FirstAccess = FieldAccess;
+ } else if (FieldAccess != FirstAccess) {
+ return true;
+ }
+ }
+ return false;
+}
+
+static bool hasMultipleDataBaseClassesWithFields(const CXXRecordDecl *D) {
+ int NumBasesWithFields = 0;
+ for (const CXXBaseSpecifier &Base : D->bases()) {
+ const CXXRecordDecl *BaseRD = Base.getType()->getAsCXXRecordDecl();
+ if (!BaseRD || BaseRD->isInvalidDecl())
+ continue;
+
+ for (const FieldDecl *Field : BaseRD->fields()) {
+ if (!Field->isUnnamedBitField()) {
+ ++NumBasesWithFields;
+ break; // Only count the base once.
+ }
+ }
+ }
+ return NumBasesWithFields > 1;
+}
+
+static void DiagnoseNonStandardLayoutReason(Sema &SemaRef, SourceLocation Loc,
+ const CXXRecordDecl *D) {
+ for (const CXXBaseSpecifier &B : D->bases()) {
+ assert(B.getType()->getAsCXXRecordDecl() && "invalid base?");
+ if (B.isVirtual()) {
+ SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+ << diag::TraitNotSatisfiedReason::VBase << B.getType()
+ << B.getSourceRange();
+ }
+ if (!B.getType()->isStandardLayoutType()) {
+ SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+ << diag::TraitNotSatisfiedReason::NonStdLayoutBase << B.getType()
+ << B.getSourceRange();
+ }
+ }
+ if (hasMixedAccessSpecifier(D)) {
+ SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+ << diag::TraitNotSatisfiedReason::MixedAccess;
+ }
+ if (hasMultipleDataBaseClassesWithFields(D)) {
+ SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+ << diag::TraitNotSatisfiedReason::MultipleDataBase;
+ }
+ if (D->isPolymorphic()) {
+ SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+ << diag::TraitNotSatisfiedReason::VirtualFunction;
+ }
+ for (const FieldDecl *Field : D->fields()) {
+ if (!Field->getType()->isStandardLayoutType()) {
+ SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+ << diag::TraitNotSatisfiedReason::NonStdLayoutMember << Field
+ << Field->getType() << Field->getSourceRange();
+ }
+ }
+}
+
+static void DiagnoseNonStandardLayoutReason(Sema &SemaRef, SourceLocation Loc,
+ QualType T) {
+ SemaRef.Diag(Loc, diag::note_unsatisfied_trait)
+ << T << diag::TraitName::StandardLayout;
+
+ // Check type-level exclusion first
+ if (T->isVariablyModifiedType()) {
+ SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+ << diag::TraitNotSatisfiedReason::VLA;
+ return;
+ }
+
+ if (T->isReferenceType()) {
+ SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+ << diag::TraitNotSatisfiedReason::Ref;
+ return;
+ }
+ T = T.getNonReferenceType();
+ const CXXRecordDecl *D = T->getAsCXXRecordDecl();
+ if (!D || D->isInvalidDecl())
+ return;
+
+ if (D->hasDefinition())
+ DiagnoseNonStandardLayoutReason(SemaRef, Loc, D);
+
+ SemaRef.Diag(D->getLocation(), diag::note_defined_here) << D;
+}
+
void Sema::DiagnoseTypeTraitDetails(const Expr *E) {
E = E->IgnoreParenImpCasts();
if (E->containsErrors())
@@ -2363,6 +2460,9 @@ void Sema::DiagnoseTypeTraitDetails(const Expr *E) {
case TT_IsConstructible:
DiagnoseNonConstructibleReason(*this, E->getBeginLoc(), Args);
break;
+ case UTT_IsStandardLayout:
+ DiagnoseNonStandardLayoutReason(*this, E->getBeginLoc(), Args[0]);
+ break;
default:
break;
}
diff --git a/clang/test/SemaCXX/type-traits-unsatisfied-diags-std.cpp
b/clang/test/SemaCXX/type-traits-unsatisfied-diags-std.cpp
index a403a0450607a..0aec240672d1c 100644
--- a/clang/test/SemaCXX/type-traits-unsatisfied-diags-std.cpp
+++ b/clang/test/SemaCXX/type-traits-unsatisfied-diags-std.cpp
@@ -28,6 +28,13 @@ struct is_constructible {
template <typename... Args>
constexpr bool is_constructible_v = __is_constructible(Args...);
+
+template <typename T>
+struct is_standard_layout {
+ static constexpr bool value = __is_standard_layout(T);
+};
+template <typename T>
+constexpr bool is_standard_layout_v = __is_standard_layout(T);
#endif
#ifdef STD2
@@ -63,6 +70,15 @@ using is_constructible =
__details_is_constructible<Args...>;
template <typename... Args>
constexpr bool is_constructible_v = __is_constructible(Args...);
+
+template <typename T>
+struct __details_is_standard_layout {
+ static constexpr bool value = __is_standard_layout(T);
+};
+template <typename T>
+using is_standard_layout = __details_is_standard_layout<T>;
+template <typename T>
+constexpr bool is_standard_layout_v = __is_standard_layout(T);
#endif
@@ -101,6 +117,15 @@ using is_constructible =
__details_is_constructible<Args...>;
template <typename... Args>
constexpr bool is_constructible_v = is_constructible<Args...>::value;
+
+
+template <typename T>
+struct __details_is_standard_layout : bool_constant<__is_standard_layout(T)>
{};
+template <typename T>
+using is_standard_layout = __details_is_standard_layout<T>;
+template <typename T>
+constexpr bool is_standard_layout_v = is_standard_layout<T>::value;
+
#endif
}
@@ -128,6 +153,21 @@ static_assert(std::is_trivially_copyable_v<int&>);
// expected-note@-1 {{because it is a reference type}}
+// Direct tests
+static_assert(std::is_standard_layout<int>::value);
+static_assert(std::is_standard_layout_v<int>);
+
+static_assert(std::is_standard_layout<int&>::value);
+// expected-error-re@-1 {{static assertion failed due to requirement
'std::{{.*}}is_standard_layout<int &>::value'}} \
+// expected-note@-1 {{'int &' is not standard-layout}} \
+// expected-note@-1 {{because it is a reference type}}
+
+static_assert(std::is_standard_layout_v<int&>);
+// expected-error@-1 {{static assertion failed due to requirement
'std::is_standard_layout_v<int &>'}} \
+// expected-note@-1 {{'int &' is not standard-layout}} \
+// expected-note@-1 {{because it is a reference type}}
+
+
static_assert(std::is_constructible<int, int>::value);
static_assert(std::is_constructible<void>::value);
@@ -163,9 +203,21 @@ namespace test_namespace {
static_assert(is_constructible_v<void>);
// expected-error@-1 {{static assertion failed due to requirement
'is_constructible_v<void>'}} \
// expected-note@-1 {{because it is a cv void type}}
+
+ static_assert(is_standard_layout<int&>::value);
+ // expected-error-re@-1 {{static assertion failed due to requirement
'{{.*}}is_standard_layout<int &>::value'}} \
+ // expected-note@-1 {{'int &' is not standard-layout}} \
+ // expected-note@-1 {{because it is a reference type}}
+
+ static_assert(is_standard_layout_v<int&>);
+ // expected-error@-1 {{static assertion failed due to requirement
'is_standard_layout_v<int &>'}} \
+ // expected-note@-1 {{'int &' is not standard-layout}} \
+ // expected-note@-1 {{because it is a reference type}}
+
}
+
namespace concepts {
template <typename T>
requires std::is_trivially_relocatable<T>::value void f(); // #cand1
@@ -258,3 +310,5 @@ static_assert(std::is_replaceable_v<int&>);
// expected-error@-1 {{static assertion failed due to requirement
'std::is_replaceable_v<int &>'}} \
// expected-note@-1 {{'int &' is not replaceable}} \
// expected-note@-1 {{because it is a reference type}}
+
+
diff --git a/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
b/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
index d0b3f294fbcab..d3f9b64fa2bfc 100644
--- a/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
+++ b/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
@@ -550,3 +550,83 @@ static_assert(__is_constructible(void (int, float)));
// expected-error@-1 {{static assertion failed due to requirement
'__is_constructible(void (int, float))'}} \
// expected-note@-1 {{because it is a function type}}
}
+
+namespace standard_layout_tests {
+ struct WithVirtual { // #sl-Virtual
+ virtual void foo();
+};
+static_assert(__is_standard_layout(WithVirtual));
+// expected-error@-1 {{static assertion failed due to requirement
'__is_standard_layout(standard_layout_tests::WithVirtual)'}} \
+// expected-note@-1 {{'WithVirtual' is not standard-layout}} \
+// expected-note@-1 {{because it has virtual functions}} \
+// expected-note@#sl-Virtual {{'WithVirtual' defined here}}
+
+struct MixedAccess { // #sl-Mixed
+public:
+ int a;
+private:
+ int b;
+};
+static_assert(__is_standard_layout(MixedAccess));
+// expected-error@-1 {{static assertion failed due to requirement
'__is_standard_layout(standard_layout_tests::MixedAccess)'}} \
+// expected-note@-1 {{'MixedAccess' is not standard-layout}} \
+// expected-note@-1 {{because it has mixed access specifiers}} \
+// expected-note@#sl-Mixed {{'MixedAccess' defined here}}
+
+struct VirtualBase { virtual ~VirtualBase(); }; //
#sl-VirtualBase
+struct VB : virtual VirtualBase {}; // #sl-VB
+static_assert(__is_standard_layout(VB));
+// expected-error@-1 {{static assertion failed due to requirement
'__is_standard_layout(standard_layout_tests::VB)'}} \
+// expected-note@-1 {{'VB' is not standard-layout}} \
+// expected-note@-1 {{because it has a virtual base 'VirtualBase'}} \
+// expected-note@-1 {{because it has a non-standard-layout base
'VirtualBase'}} \
+// expected-note@-1 {{because it has virtual functions}}
+// expected-note@#sl-VB {{'VB' defined here}}
+
+union U { // #sl-U
+public:
+ int x;
+private:
+ int y;
+};
+static_assert(__is_standard_layout(U));
+// expected-error@-1 {{static assertion failed due to requirement
'__is_standard_layout(standard_layout_tests::U)'}} \
+// expected-note@-1 {{'U' is not standard-layout}} \
+// expected-note@-1 {{because it has mixed access specifiers}}
+// expected-note@#sl-U {{'U' defined here}}
+
+// Single base class is OK
+struct BaseClass{ int a; }; // #sl-BaseClass
+struct DerivedOK : BaseClass {}; //
#sl-DerivedOK
+static_assert(__is_standard_layout(DerivedOK));
+
+// Primitive types should be standard layout
+static_assert(__is_standard_layout(int)); // #sl-Int
+static_assert(__is_standard_layout(float)); // #sl-Float
+
+// Multi-level inheritance: Non-standard layout
+struct Base1 { int a; }; // #sl-Base1
+struct Base2 { int b; }; // #sl-Base2
+struct DerivedClass : Base1, Base2 {}; //
#sl-DerivedClass
+static_assert(__is_standard_layout(DerivedClass));
+// expected-error@-1 {{static assertion failed due to requirement
'__is_standard_layout(standard_layout_tests::DerivedClass)'}} \
+// expected-note@-1 {{'DerivedClass' is not standard-layout}} \
+// expected-note@-1 {{because it has multiple base classes with data members}}
\
+// expected-note@#sl-DerivedClass {{'DerivedClass' defined here}}
+
+// Inheritance hierarchy with multiple classes having data members
+struct BaseA { int a; }; // #sl-BaseA
+struct BaseB : BaseA {}; // inherits
BaseA, has no new members
+struct BaseC: BaseB { int c; }; // #sl-BaseC
+static_assert(__is_standard_layout(BaseC));
+// expected-error@-1 {{static assertion failed due to requirement
'__is_standard_layout(standard_layout_tests::BaseC)'}} \
+// expected-note@-1 {{'BaseC' is not standard-layout}} \
+// expected-note@#sl-BaseC {{'BaseC' defined here}} \
+
+// Multiple direct base classes with no data members --> standard layout
+struct BaseX {}; // #sl-BaseX
+struct BaseY {}; // #sl-BaseY
+struct MultiBase : BaseX, BaseY {}; // #sl-MultiBase
+static_assert(__is_standard_layout(MultiBase));
+
+}
>From 0754b80e3c20eb6e5c550bb805c541ab7fdef936 Mon Sep 17 00:00:00 2001
From: Samarth Narang <snar...@umass.edu>
Date: Thu, 12 Jun 2025 22:48:48 -0400
Subject: [PATCH 2/2] Add more descriptive messages for indirect base class
inheritance
---
.../clang/Basic/DiagnosticSemaKinds.td | 1 +
clang/lib/Sema/SemaTypeTraits.cpp | 31 +++++++++++++++++++
.../SemaCXX/type-traits-unsatisfied-diags.cpp | 1 +
3 files changed, 33 insertions(+)
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index dfe68991afb8a..9d4695763b832 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1794,6 +1794,7 @@ def note_unsatisfied_trait_reason
"%MultipleDataBase{has multiple base classes with data members}|"
"%VirtualFunction{has virtual functions}|"
"%NonStdLayoutMember{has a non-standard-layout member %1 of type
%2}|"
+ "%IndirectBaseWithFields{has an indirect base %1 with data
members}|"
"%DeletedDtr{has a %select{deleted|user-provided}1 destructor}|"
"%UserProvidedCtr{has a user provided %select{copy|move}1 "
"constructor}|"
diff --git a/clang/lib/Sema/SemaTypeTraits.cpp
b/clang/lib/Sema/SemaTypeTraits.cpp
index 3134487f7e76d..9b5c7e0f91dd6 100644
--- a/clang/lib/Sema/SemaTypeTraits.cpp
+++ b/clang/lib/Sema/SemaTypeTraits.cpp
@@ -2407,6 +2407,37 @@ static void DiagnoseNonStandardLayoutReason(Sema
&SemaRef, SourceLocation Loc,
<< Field->getType() << Field->getSourceRange();
}
}
+
+ // if this class and an indirect base
+ // both have non-static data members, grab the first such base.
+ if (D->hasDirectFields()) {
+ SmallVector<const CXXRecordDecl *, 4> Records;
+
+ // Recursive lambda to collect all bases that declare fields
+ std::function<void(const CXXRecordDecl *)> collect =
+ [&](const CXXRecordDecl *R) {
+ for (const CXXBaseSpecifier &B : R->bases()) {
+ const auto *BR = B.getType()->getAsCXXRecordDecl();
+ if (!BR || !BR->hasDefinition())
+ continue;
+ if (BR->hasDirectFields())
+ Records.push_back(BR);
+ // Recurse into the base class.
+ collect(BR);
+ }
+ };
+
+ // Collect all bases that declare fields.
+ collect(D);
+
+ // If more than one record has fields, then the layout is non-standard.
+ if (!Records.empty()) {
+ const CXXRecordDecl *Indirect = Records.front();
+ SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+ << diag::TraitNotSatisfiedReason::IndirectBaseWithFields << Indirect
+ << Indirect->getSourceRange();
+ }
+ }
}
static void DiagnoseNonStandardLayoutReason(Sema &SemaRef, SourceLocation Loc,
diff --git a/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
b/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
index d3f9b64fa2bfc..9a934187a13ee 100644
--- a/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
+++ b/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
@@ -621,6 +621,7 @@ struct BaseC: BaseB { int c; };
// #sl-BaseC
static_assert(__is_standard_layout(BaseC));
// expected-error@-1 {{static assertion failed due to requirement
'__is_standard_layout(standard_layout_tests::BaseC)'}} \
// expected-note@-1 {{'BaseC' is not standard-layout}} \
+// expected-note@-1 {{because it has an indirect base 'BaseA' with data
members}} \
// expected-note@#sl-BaseC {{'BaseC' defined here}} \
// Multiple direct base classes with no data members --> standard layout
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