[Clang] Implement diagnostics for why std::is_standard_layout is false
#144161
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zwuis
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Rebased and testing the again. The Windows build failure seems largely unrelated to my changes. |
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@llvm/pr-subscribers-clang Author: Samarth Narang (snarang181) ChangesAs part of the effort in #141911 Full diff: https://github.com/llvm/llvm-project/pull/144161.diff 4 Files Affected:
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 8fe7ad6138aa0..8660ba6231998 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1767,7 +1767,8 @@ def note_unsatisfied_trait
: Note<"%0 is not %enum_select<TraitName>{"
"%TriviallyRelocatable{trivially relocatable}|"
"%Replaceable{replaceable}|"
- "%TriviallyCopyable{trivially copyable}"
+ "%TriviallyCopyable{trivially copyable}|"
+ "%StandardLayout{standard-layout}"
"}1">;
def note_unsatisfied_trait_reason
@@ -1787,6 +1788,12 @@ 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}|"
+ "%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 1738ab4466001..08682cc09f350 100644
--- a/clang/lib/Sema/SemaTypeTraits.cpp
+++ b/clang/lib/Sema/SemaTypeTraits.cpp
@@ -1947,6 +1947,7 @@ static std::optional<TypeTrait> StdNameToTypeTrait(StringRef Name) {
TypeTrait::UTT_IsCppTriviallyRelocatable)
.Case("is_replaceable", TypeTrait::UTT_IsReplaceable)
.Case("is_trivially_copyable", TypeTrait::UTT_IsTriviallyCopyable)
+ .Case("is_standard_layout", TypeTrait::UTT_IsStandardLayout)
.Default(std::nullopt);
}
@@ -2276,6 +2277,119 @@ 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();
+ }
+ }
+ // find any indirect base classes that have fields
+ if (D->hasDirectFields()) {
+ const CXXRecordDecl *Indirect = nullptr;
+ D->forallBases([&](const CXXRecordDecl *BaseDef) {
+ if (BaseDef->hasDirectFields()) {
+ Indirect = BaseDef;
+ return false; // stop traversal
+ }
+ return true; // continue to the next base
+ });
+ if (Indirect) {
+ SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+ << diag::TraitNotSatisfiedReason::IndirectBaseWithFields << Indirect
+ << Indirect->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())
@@ -2296,6 +2410,9 @@ void Sema::DiagnoseTypeTraitDetails(const Expr *E) {
case UTT_IsTriviallyCopyable:
DiagnoseNonTriviallyCopyableReason(*this, E->getBeginLoc(), Args[0]);
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 329b611110c1d..59f3d95a4d215 100644
--- a/clang/test/SemaCXX/type-traits-unsatisfied-diags-std.cpp
+++ b/clang/test/SemaCXX/type-traits-unsatisfied-diags-std.cpp
@@ -20,6 +20,13 @@ struct is_trivially_copyable {
template <typename T>
constexpr bool is_trivially_copyable_v = __is_trivially_copyable(T);
+
+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
@@ -44,6 +51,17 @@ using is_trivially_copyable = __details_is_trivially_copyable<T>;
template <typename T>
constexpr bool is_trivially_copyable_v = __is_trivially_copyable(T);
+
+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
@@ -73,6 +91,13 @@ using is_trivially_copyable = __details_is_trivially_copyable<T>;
template <typename T>
constexpr bool is_trivially_copyable_v = is_trivially_copyable<T>::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
}
@@ -100,6 +125,21 @@ 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}}
+
+
namespace test_namespace {
using namespace std;
static_assert(is_trivially_relocatable<int&>::value);
@@ -119,6 +159,16 @@ namespace test_namespace {
// expected-error@-1 {{static assertion failed due to requirement 'is_trivially_copyable_v<int &>'}} \
// expected-note@-1 {{'int &' is not trivially copyable}} \
// expected-note@-1 {{because it is a reference 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}}
}
diff --git a/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp b/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
index a8c78f6304ca9..404f6e914b3f6 100644
--- a/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
+++ b/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
@@ -488,3 +488,83 @@ static_assert(__is_trivially_copyable(S12));
// expected-note@-1 {{'S12' is not trivially copyable}} \
// expected-note@#tc-S12 {{'S12' defined here}}
}
+
+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@-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
+struct BaseX {}; // #sl-BaseX
+struct BaseY {}; // #sl-BaseY
+struct MultiBase : BaseX, BaseY {}; // #sl-MultiBase
+static_assert(__is_standard_layout(MultiBase));
+
+ }
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Looks like all tests pass now. Requesting review now. |
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Thank you for working on this! I had some nits and some questions about whether we could improve the diagnostics further or not. (If my suggestions turn out to be hard, we can always move forward with what you've already got here as this is still a good set of changes by themselves.)
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std::is_standard_layout is falsestd::is_standard_layout is false
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clang/lib/Sema/SemaTypeTraits.cpp
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| << B.getSourceRange(); | ||
| } | ||
| } | ||
| if (hasMixedAccessSpecifier(D)) { |
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Rather than do this walk twice, it may make sense to have the lambda calculate the fields with mixed access so you don't need to have the same logic in two places.
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Thank you for reviewing @AaronBallman. Addressed your suggestions. |
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Can probably rebase and test again but the Windows failure seems to be unrelated. |
to diagnose virtual function failures
Diagnose fields which have different access
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I'm happy with that (modulo nits) once @AaronBallman is happy
Revert note in ReleaseNotes Remove no_unique_address test
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Needs some manual intervention after the merge. Conflicting redundance in the tablegen descriptions of |
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Precommit CI found relevant failures: |
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@AaronBallman, as per the comment I left below: it is because of the conflicting definitions of the TableGen description of
(This creeped in because of the |
Oops! I thought you were talking about merge conflicts. :-) |
to deconflict it and make it coherent with existing tablegen diagnostics.
I think the |
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As part of the effort in #141911