https://github.com/higher-performance created
https://github.com/llvm/llvm-project/pull/102040
This is a new Clang-specific attribute to ensure that field initializations are
performed explicitly.
For example, if we have
```
struct B {
[[clang::explicit]] int f1;
};
>From e141508349c193f41b15c69a26f3096dd2ee1520 Mon Sep 17 00:00:00 2001
From: higher-performance <higher.performance.git...@gmail.com>
Date: Mon, 5 Aug 2024 15:04:19 -0400
Subject: [PATCH] Add Clang attribute to ensure that fields are initialized
explicitly
---
.../clang/AST/CXXRecordDeclDefinitionBits.def | 8 +++++++
clang/include/clang/AST/DeclCXX.h | 5 +++++
clang/include/clang/Basic/Attr.td | 8 +++++++
clang/include/clang/Basic/AttrDocs.td | 22 +++++++++++++++++++
clang/include/clang/Basic/DiagnosticGroups.td | 1 +
.../clang/Basic/DiagnosticSemaKinds.td | 3 +++
clang/lib/AST/DeclCXX.cpp | 9 ++++++++
clang/lib/Sema/SemaDeclAttr.cpp | 7 ++++++
clang/lib/Sema/SemaInit.cpp | 11 ++++++++++
clang/test/SemaCXX/uninitialized.cpp | 22 +++++++++++++++++++
10 files changed, 96 insertions(+)
diff --git a/clang/include/clang/AST/CXXRecordDeclDefinitionBits.def
b/clang/include/clang/AST/CXXRecordDeclDefinitionBits.def
index cdf0804680ad0..a782026462566 100644
--- a/clang/include/clang/AST/CXXRecordDeclDefinitionBits.def
+++ b/clang/include/clang/AST/CXXRecordDeclDefinitionBits.def
@@ -119,6 +119,14 @@ FIELD(HasInitMethod, 1, NO_MERGE)
/// within anonymous unions or structs.
FIELD(HasInClassInitializer, 1, NO_MERGE)
+/// Custom attribute that is True if any field is marked as explicit in a type
+/// without a user-provided default constructor, or if this is the case for any
+/// base classes and/or member variables whose types are aggregates.
+///
+/// In this case, default-construction is diagnosed, as it would not explicitly
+/// initialize the field.
+FIELD(HasUninitializedExplicitFields, 1, NO_MERGE)
+
/// True if any field is of reference type, and does not have an
/// in-class initializer.
///
diff --git a/clang/include/clang/AST/DeclCXX.h
b/clang/include/clang/AST/DeclCXX.h
index bf6a5ce92d438..8228595d84b0f 100644
--- a/clang/include/clang/AST/DeclCXX.h
+++ b/clang/include/clang/AST/DeclCXX.h
@@ -1151,6 +1151,11 @@ class CXXRecordDecl : public RecordDecl {
/// structs).
bool hasInClassInitializer() const { return data().HasInClassInitializer; }
+ bool hasUninitializedExplicitFields() const {
+ return !isUnion() && !hasUserProvidedDefaultConstructor() &&
+ data().HasUninitializedExplicitFields;
+ }
+
/// Whether this class or any of its subobjects has any members of
/// reference type which would make value-initialization ill-formed.
///
diff --git a/clang/include/clang/Basic/Attr.td
b/clang/include/clang/Basic/Attr.td
index 8ac2079099c85..409a7cd9177e8 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -1823,6 +1823,14 @@ def Leaf : InheritableAttr {
let SimpleHandler = 1;
}
+def Explicit : InheritableAttr {
+ let Spellings = [Clang<"explicit", 0>];
+ let Subjects = SubjectList<[Field], ErrorDiag>;
+ let Documentation = [ExplicitDocs];
+ let LangOpts = [CPlusPlus];
+ let SimpleHandler = 1;
+}
+
def LifetimeBound : DeclOrTypeAttr {
let Spellings = [Clang<"lifetimebound", 0>];
let Subjects = SubjectList<[ParmVar, ImplicitObjectParameter], ErrorDiag>;
diff --git a/clang/include/clang/Basic/AttrDocs.td
b/clang/include/clang/Basic/AttrDocs.td
index 94c284fc73158..66d0044aa979d 100644
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/clang/include/clang/Basic/AttrDocs.td
@@ -1419,6 +1419,28 @@ is not specified.
}];
}
+def ExplicitDocs : Documentation {
+ let Category = DocCatField;
+ let Content = [{
+The ``clang::explicit`` attribute indicates that the field must be initialized
+explicitly by the caller when the class is constructed.
+
+Example usage:
+
+.. code-block:: c++
+
+ struct some_aggregate {
+ int x;
+ int y [[clang::explicit]];
+ };
+
+ some_aggregate create() {
+ return {.x = 1}; // error: y is not initialized explicitly
+ }
+
+ }];
+}
+
def NoUniqueAddressDocs : Documentation {
let Category = DocCatField;
let Content = [{
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td
b/clang/include/clang/Basic/DiagnosticGroups.td
index 19c3f1e043349..52af3d3a7af39 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -787,6 +787,7 @@ def Trigraphs : DiagGroup<"trigraphs">;
def UndefinedReinterpretCast : DiagGroup<"undefined-reinterpret-cast">;
def ReinterpretBaseClass : DiagGroup<"reinterpret-base-class">;
def Unicode : DiagGroup<"unicode">;
+def UninitializedExplicit : DiagGroup<"uninitialized-explicit">;
def UninitializedMaybe : DiagGroup<"conditional-uninitialized">;
def UninitializedSometimes : DiagGroup<"sometimes-uninitialized">;
def UninitializedStaticSelfInit : DiagGroup<"static-self-init">;
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 581434d33c5c9..fb493e3c4f7f0 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2325,6 +2325,9 @@ def err_init_reference_member_uninitialized : Error<
"reference member of type %0 uninitialized">;
def note_uninit_reference_member : Note<
"uninitialized reference member is here">;
+def warn_field_requires_init : Warning<
+ "field %0 is left uninitialized, but was marked as requiring
initialization">,
+ InGroup<UninitializedExplicit>;
def warn_field_is_uninit : Warning<"field %0 is uninitialized when used here">,
InGroup<Uninitialized>;
def warn_base_class_is_uninit : Warning<
diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
index 9a3ede426e914..732117ae263c2 100644
--- a/clang/lib/AST/DeclCXX.cpp
+++ b/clang/lib/AST/DeclCXX.cpp
@@ -81,6 +81,7 @@ CXXRecordDecl::DefinitionData::DefinitionData(CXXRecordDecl
*D)
HasPrivateFields(false), HasProtectedFields(false),
HasPublicFields(false), HasMutableFields(false),
HasVariantMembers(false),
HasOnlyCMembers(true), HasInitMethod(false),
HasInClassInitializer(false),
+ HasUninitializedExplicitFields(false),
HasUninitializedReferenceMember(false), HasUninitializedFields(false),
HasInheritedConstructor(false), HasInheritedDefaultConstructor(false),
HasInheritedAssignment(false),
@@ -1108,6 +1109,10 @@ void CXXRecordDecl::addedMember(Decl *D) {
} else if (!T.isCXX98PODType(Context))
data().PlainOldData = false;
+ if (Field->hasAttr<ExplicitAttr>() && !Field->hasInClassInitializer()) {
+ data().HasUninitializedExplicitFields = true;
+ }
+
if (T->isReferenceType()) {
if (!Field->hasInClassInitializer())
data().HasUninitializedReferenceMember = true;
@@ -1359,6 +1364,10 @@ void CXXRecordDecl::addedMember(Decl *D) {
if (!FieldRec->hasCopyAssignmentWithConstParam())
data().ImplicitCopyAssignmentHasConstParam = false;
+ if (FieldRec->hasUninitializedExplicitFields() &&
+ FieldRec->isAggregate() && !Field->hasInClassInitializer())
+ data().HasUninitializedExplicitFields = true;
+
if (FieldRec->hasUninitializedReferenceMember() &&
!Field->hasInClassInitializer())
data().HasUninitializedReferenceMember = true;
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 9011fa547638e..b55c845b74528 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -5943,6 +5943,10 @@ static void handleNoMergeAttr(Sema &S, Decl *D, const
ParsedAttr &AL) {
D->addAttr(NoMergeAttr::Create(S.Context, AL));
}
+static void handleExplicitAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+ D->addAttr(ExplicitAttr::Create(S.Context, AL));
+}
+
static void handleNoUniqueAddressAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
D->addAttr(NoUniqueAddressAttr::Create(S.Context, AL));
}
@@ -6848,6 +6852,9 @@ ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
const ParsedAttr &AL,
case ParsedAttr::AT_NoMerge:
handleNoMergeAttr(S, D, AL);
break;
+ case ParsedAttr::AT_Explicit:
+ handleExplicitAttr(S, D, AL);
+ break;
case ParsedAttr::AT_NoUniqueAddress:
handleNoUniqueAddressAttr(S, D, AL);
break;
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 90fd6df782f09..47b5c4bd388eb 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -743,6 +743,11 @@ void InitListChecker::FillInEmptyInitForField(unsigned
Init, FieldDecl *Field,
ILE->updateInit(SemaRef.Context, Init, Filler);
return;
}
+
+ if (Field->hasAttr<ExplicitAttr>()) {
+ SemaRef.Diag(ILE->getExprLoc(), diag::warn_field_requires_init) << Field;
+ }
+
// C++1y [dcl.init.aggr]p7:
// If there are fewer initializer-clauses in the list than there are
// members in the aggregate, then each member not explicitly initialized
@@ -4475,6 +4480,12 @@ static void TryConstructorInitialization(Sema &S,
CXXConstructorDecl *CtorDecl = cast<CXXConstructorDecl>(Best->Function);
if (Result != OR_Deleted) {
+ if (!IsListInit && Kind.getKind() == InitializationKind::IK_Default &&
+ DestRecordDecl != nullptr && DestRecordDecl->isAggregate() &&
+ DestRecordDecl->hasUninitializedExplicitFields()) {
+ S.Diag(Kind.getLocation(), diag::warn_field_requires_init) << "in class";
+ }
+
// C++11 [dcl.init]p6:
// If a program calls for the default initialization of an object
// of a const-qualified type T, T shall be a class type with a
diff --git a/clang/test/SemaCXX/uninitialized.cpp
b/clang/test/SemaCXX/uninitialized.cpp
index 8a640c9691b32..3a339b4f9c9c4 100644
--- a/clang/test/SemaCXX/uninitialized.cpp
+++ b/clang/test/SemaCXX/uninitialized.cpp
@@ -1472,3 +1472,25 @@ template<typename T> struct Outer {
};
};
Outer<int>::Inner outerinner;
+
+void aggregate() {
+ struct B {
+ [[clang::explicit]] int f1;
+ };
+
+ struct S : B { // expected-warning {{uninitialized}}
+ int f2;
+ int f3 [[clang::explicit]];
+ };
+
+#if __cplusplus >= 202002L
+ S a({}, 0); // expected-warning {{'f1' is left uninitialized}}
expected-warning {{'f3' is left uninitialized}}
+#endif
+ S b{.f3 = 1}; // expected-warning {{'f1' is left uninitialized}}
+ S c{.f2 = 5}; // expected-warning {{'f1' is left uninitialized}}
expected-warning {{'f3' is left uninitialized}} expected-warning {{'f3' is left
uninitialized}}
+ c = {{}, 0}; // expected-warning {{'f1' is left uninitialized}}
expected-warning {{'f3' is left uninitialized}}
+ S d; // expected-warning {{uninitialized}} expected-note {{constructor}}
+ (void)b;
+ (void)c;
+ (void)d;
+}
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