[llvm-branch-commits] [clang] 89b0972 - [Sema] Fix deleted function problem in implicitly movable test

Yang Fan via llvm-branch-commits llvm-branch-commits at lists.llvm.org
Thu Dec 31 23:52:28 PST 2020


Author: Yang Fan
Date: 2021-01-01T15:47:49+08:00
New Revision: 89b0972aa2f58f927633c63570b36550a17f4e63

URL: https://github.com/llvm/llvm-project/commit/89b0972aa2f58f927633c63570b36550a17f4e63
DIFF: https://github.com/llvm/llvm-project/commit/89b0972aa2f58f927633c63570b36550a17f4e63.diff

LOG: [Sema] Fix deleted function problem in implicitly movable test

In implicitly movable test, a two-stage overload resolution is performed.
If the first overload resolution selects a deleted function, Clang directly
performs the second overload resolution, without checking whether the
deleted function matches the additional criteria.

This patch fixes the above problem.

Reviewed By: Quuxplusone

Differential Revision: https://reviews.llvm.org/D92936

Added: 
    clang/test/CXX/class/class.init/class.copy.elision/p3.cpp

Modified: 
    clang/lib/Sema/SemaInit.cpp
    clang/lib/Sema/SemaStmt.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 6d2e6094e79c..4a965c60c74e 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -4119,7 +4119,9 @@ static void TryConstructorInitialization(Sema &S,
                       InitializationSequence::FK_ListConstructorOverloadFailed :
                       InitializationSequence::FK_ConstructorOverloadFailed,
                                 Result);
-    return;
+
+    if (Result != OR_Deleted)
+      return;
   }
 
   bool HadMultipleCandidates = (CandidateSet.size() > 1);
@@ -4140,31 +4142,45 @@ static void TryConstructorInitialization(Sema &S,
     return;
   }
 
-  // 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
-  //   user-provided default constructor.
-  // C++ core issue 253 proposal:
-  //   If the implicit default constructor initializes all subobjects, no
-  //   initializer should be required.
-  // The 253 proposal is for example needed to process libstdc++ headers in 5.x.
   CXXConstructorDecl *CtorDecl = cast<CXXConstructorDecl>(Best->Function);
-  if (Kind.getKind() == InitializationKind::IK_Default &&
-      Entity.getType().isConstQualified()) {
-    if (!CtorDecl->getParent()->allowConstDefaultInit()) {
-      if (!maybeRecoverWithZeroInitialization(S, Sequence, Entity))
-        Sequence.SetFailed(InitializationSequence::FK_DefaultInitOfConst);
+  if (Result != OR_Deleted) { // TODO: Support for more than one failure.
+    // 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
+    //   user-provided default constructor.
+    // C++ core issue 253 proposal:
+    //   If the implicit default constructor initializes all subobjects, no
+    //   initializer should be required.
+    // The 253 proposal is for example needed to process libstdc++ headers
+    // in 5.x.
+    if (Kind.getKind() == InitializationKind::IK_Default &&
+        Entity.getType().isConstQualified()) {
+      if (!CtorDecl->getParent()->allowConstDefaultInit()) {
+        if (!maybeRecoverWithZeroInitialization(S, Sequence, Entity))
+          Sequence.SetFailed(InitializationSequence::FK_DefaultInitOfConst);
+        return;
+      }
+    }
+
+    // C++11 [over.match.list]p1:
+    //   In copy-list-initialization, if an explicit constructor is chosen, the
+    //   initializer is ill-formed.
+    if (IsListInit && !Kind.AllowExplicit() && CtorDecl->isExplicit()) {
+      Sequence.SetFailed(InitializationSequence::FK_ExplicitConstructor);
       return;
     }
   }
 
-  // C++11 [over.match.list]p1:
-  //   In copy-list-initialization, if an explicit constructor is chosen, the
-  //   initializer is ill-formed.
-  if (IsListInit && !Kind.AllowExplicit() && CtorDecl->isExplicit()) {
-    Sequence.SetFailed(InitializationSequence::FK_ExplicitConstructor);
+  // [class.copy.elision]p3:
+  // In some copy-initialization contexts, a two-stage overload resolution
+  // is performed.
+  // If the first overload resolution selects a deleted function, we also
+  // need the initialization sequence to decide whether to perform the second
+  // overload resolution.
+  // For deleted functions in other contexts, there is no need to get the
+  // initialization sequence.
+  if (Result == OR_Deleted && Kind.getKind() != InitializationKind::IK_Copy)
     return;
-  }
 
   // Add the constructor initialization step. Any cv-qualification conversion is
   // subsumed by the initialization.
@@ -5260,7 +5276,16 @@ static void TryUserDefinedConversion(Sema &S,
     Sequence.SetOverloadFailure(
                         InitializationSequence::FK_UserConversionOverloadFailed,
                                 Result);
-    return;
+
+    // [class.copy.elision]p3:
+    // In some copy-initialization contexts, a two-stage overload resolution
+    // is performed.
+    // If the first overload resolution selects a deleted function, we also
+    // need the initialization sequence to decide whether to perform the second
+    // overload resolution.
+    if (!(Result == OR_Deleted &&
+          Kind.getKind() == InitializationKind::IK_Copy))
+      return;
   }
 
   FunctionDecl *Function = Best->Function;

diff  --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index 8d0ebe7e2409..3318fda07175 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -3118,11 +3118,14 @@ bool Sema::isCopyElisionCandidate(QualType ReturnType, const VarDecl *VD,
 /// If move-initialization is not possible, such that we must fall back to
 /// treating the operand as an lvalue, we will leave Res in its original
 /// invalid state.
-static void TryMoveInitialization(Sema& S,
-                                  const InitializedEntity &Entity,
+///
+/// \returns Whether we need to do the second overload resolution. If the first
+/// overload resolution fails, or if the first overload resolution succeeds but
+/// the selected constructor/operator doesn't match the additional criteria, we
+/// need to do the second overload resolution.
+static bool TryMoveInitialization(Sema &S, const InitializedEntity &Entity,
                                   const VarDecl *NRVOCandidate,
-                                  QualType ResultType,
-                                  Expr *&Value,
+                                  QualType ResultType, Expr *&Value,
                                   bool ConvertingConstructorsOnly,
                                   ExprResult &Res) {
   ImplicitCastExpr AsRvalue(ImplicitCastExpr::OnStack, Value->getType(),
@@ -3135,8 +3138,10 @@ static void TryMoveInitialization(Sema& S,
 
   InitializationSequence Seq(S, Entity, Kind, InitExpr);
 
-  if (!Seq)
-    return;
+  bool NeedSecondOverloadResolution = true;
+  if (!Seq && Seq.getFailedOverloadResult() != OR_Deleted) {
+    return NeedSecondOverloadResolution;
+  }
 
   for (const InitializationSequence::Step &Step : Seq.steps()) {
     if (Step.Kind != InitializationSequence::SK_ConstructorInitialization &&
@@ -3179,6 +3184,7 @@ static void TryMoveInitialization(Sema& S,
       }
     }
 
+    NeedSecondOverloadResolution = false;
     // Promote "AsRvalue" to the heap, since we now need this
     // expression node to persist.
     Value =
@@ -3189,6 +3195,8 @@ static void TryMoveInitialization(Sema& S,
     // using the constructor we found.
     Res = Seq.Perform(S, Entity, Kind, Value);
   }
+
+  return NeedSecondOverloadResolution;
 }
 
 /// Perform the initialization of a potentially-movable value, which
@@ -3213,6 +3221,7 @@ Sema::PerformMoveOrCopyInitialization(const InitializedEntity &Entity,
   // select the constructor for the copy is first performed as if the object
   // were designated by an rvalue.
   ExprResult Res = ExprError();
+  bool NeedSecondOverloadResolution = true;
 
   if (AllowNRVO) {
     bool AffectedByCWG1579 = false;
@@ -3229,11 +3238,11 @@ Sema::PerformMoveOrCopyInitialization(const InitializedEntity &Entity,
     }
 
     if (NRVOCandidate) {
-      TryMoveInitialization(*this, Entity, NRVOCandidate, ResultType, Value,
-                            true, Res);
+      NeedSecondOverloadResolution = TryMoveInitialization(
+          *this, Entity, NRVOCandidate, ResultType, Value, true, Res);
     }
 
-    if (!Res.isInvalid() && AffectedByCWG1579) {
+    if (!NeedSecondOverloadResolution && AffectedByCWG1579) {
       QualType QT = NRVOCandidate->getType();
       if (QT.getNonReferenceType()
                      .getUnqualifiedType()
@@ -3256,7 +3265,7 @@ Sema::PerformMoveOrCopyInitialization(const InitializedEntity &Entity,
         Diag(Value->getExprLoc(), diag::note_add_std_move_in_cxx11)
             << FixItHint::CreateReplacement(Value->getSourceRange(), Str);
       }
-    } else if (Res.isInvalid() &&
+    } else if (NeedSecondOverloadResolution &&
                !getDiagnostics().isIgnored(diag::warn_return_std_move,
                                            Value->getExprLoc())) {
       const VarDecl *FakeNRVOCandidate =
@@ -3297,7 +3306,7 @@ Sema::PerformMoveOrCopyInitialization(const InitializedEntity &Entity,
   // Either we didn't meet the criteria for treating an lvalue as an rvalue,
   // above, or overload resolution failed. Either way, we need to try
   // (again) now with the return value expression as written.
-  if (Res.isInvalid())
+  if (NeedSecondOverloadResolution)
     Res = PerformCopyInitialization(Entity, SourceLocation(), Value);
 
   return Res;

diff  --git a/clang/test/CXX/class/class.init/class.copy.elision/p3.cpp b/clang/test/CXX/class/class.init/class.copy.elision/p3.cpp
new file mode 100644
index 000000000000..b3427243bd61
--- /dev/null
+++ b/clang/test/CXX/class/class.init/class.copy.elision/p3.cpp
@@ -0,0 +1,50 @@
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -fcxx-exceptions -verify=expected %s
+// RUN: %clang_cc1 -std=c++17 -fsyntax-only -fcxx-exceptions -verify=expected %s
+// RUN: %clang_cc1 -std=c++14 -fsyntax-only -fcxx-exceptions -verify=expected %s
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -fcxx-exceptions -verify=expected %s
+
+namespace test_delete_function {
+struct A1 {
+  A1();
+  A1(const A1 &);
+  A1(A1 &&) = delete; // expected-note {{'A1' has been explicitly marked deleted here}}
+};
+A1 test1() {
+  A1 a;
+  return a; // expected-error {{call to deleted constructor of 'test_delete_function::A1'}}
+}
+
+struct A2 {
+  A2();
+  A2(const A2 &);
+
+private:
+  A2(A2 &&); // expected-note {{declared private here}}
+};
+A2 test2() {
+  A2 a;
+  return a; // expected-error {{calling a private constructor of class 'test_delete_function::A2'}}
+}
+
+struct C {};
+
+struct B1 {
+  B1(C &);
+  B1(C &&) = delete; // expected-note {{'B1' has been explicitly marked deleted here}}
+};
+B1 test3() {
+  C c;
+  return c; // expected-error {{conversion function from 'test_delete_function::C' to 'test_delete_function::B1' invokes a deleted function}}
+}
+
+struct B2 {
+  B2(C &);
+
+private:
+  B2(C &&); // expected-note {{declared private here}}
+};
+B2 test4() {
+  C c;
+  return c; // expected-error {{calling a private constructor of class 'test_delete_function::B2'}}
+}
+} // namespace test_delete_function


        


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