1 files changed, 111 insertions, 82 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 15564918b37..eddc4207dfc 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -8929,35 +8929,21 @@ static bool convertPointersToCompositeType(Sema &S, SourceLocation Loc,
   // C++ [expr.eq]p1 uses the same notion for (in)equality
   // comparisons of pointers.
 
-  // C++ [expr.eq]p2:
-  //   In addition, pointers to members can be compared, or a pointer to
-  //   member and a null pointer constant. Pointer to member conversions
-  //   (4.11) and qualification conversions (4.4) are performed to bring
-  //   them to a common type. If one operand is a null pointer constant,
-  //   the common type is the type of the other operand. Otherwise, the
-  //   common type is a pointer to member type similar (4.4) to the type
-  //   of one of the operands, with a cv-qualification signature (4.4)
-  //   that is the union of the cv-qualification signatures of the operand
-  //   types.
-
   QualType LHSType = LHS.get()->getType();
   QualType RHSType = RHS.get()->getType();
-  assert((LHSType->isPointerType() && RHSType->isPointerType()) ||
-         (LHSType->isMemberPointerType() && RHSType->isMemberPointerType()));
+  assert(LHSType->isPointerType() || RHSType->isPointerType() ||
+         LHSType->isMemberPointerType() || RHSType->isMemberPointerType());
 
-  bool NonStandardCompositeType = false;
-  bool *BoolPtr = S.isSFINAEContext() ? nullptr : &NonStandardCompositeType;
-  QualType T = S.FindCompositePointerType(Loc, LHS, RHS, BoolPtr);
+  QualType T = S.FindCompositePointerType(Loc, LHS, RHS);
   if (T.isNull()) {
-    diagnoseDistinctPointerComparison(S, Loc, LHS, RHS, /*isError*/true);
+    if ((LHSType->isPointerType() || LHSType->isMemberPointerType()) &&
+        (RHSType->isPointerType() || RHSType->isMemberPointerType()))
+      diagnoseDistinctPointerComparison(S, Loc, LHS, RHS, /*isError*/true);
+    else
+      S.InvalidOperands(Loc, LHS, RHS);
     return true;
   }
 
-  if (NonStandardCompositeType)
-    S.Diag(Loc, diag::ext_typecheck_comparison_of_distinct_pointers_nonstandard)
-      << LHSType << RHSType << T << LHS.get()->getSourceRange()
-      << RHS.get()->getSourceRange();
-
   LHS = S.ImpCastExprToType(LHS.get(), T, CK_BitCast);
   RHS = S.ImpCastExprToType(RHS.get(), T, CK_BitCast);
   return false;
@@ -9314,41 +9300,53 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
                                    LHS.get()->getSourceRange());
   }
 
-  // All of the following pointer-related warnings are GCC extensions, except
-  // when handling null pointer constants. 
-  if (LHSType->isPointerType() && RHSType->isPointerType()) { // C99 6.5.8p2
-    QualType LCanPointeeTy =
-      LHSType->castAs<PointerType>()->getPointeeType().getCanonicalType();
-    QualType RCanPointeeTy =
-      RHSType->castAs<PointerType>()->getPointeeType().getCanonicalType();
-
-    if (getLangOpts().CPlusPlus) {
-      if (LCanPointeeTy == RCanPointeeTy)
-        return ResultTy;
-      if (!IsRelational &&
-          (LCanPointeeTy->isVoidType() || RCanPointeeTy->isVoidType())) {
-        // Valid unless comparison between non-null pointer and function pointer
-        // This is a gcc extension compatibility comparison.
-        // In a SFINAE context, we treat this as a hard error to maintain
-        // conformance with the C++ standard.
-        if ((LCanPointeeTy->isFunctionType() || RCanPointeeTy->isFunctionType())
-            && !LHSIsNull && !RHSIsNull) {
-          diagnoseFunctionPointerToVoidComparison(
-              *this, Loc, LHS, RHS, /*isError*/ (bool)isSFINAEContext());
-          
-          if (isSFINAEContext())
-            return QualType();
-          
-          RHS = ImpCastExprToType(RHS.get(), LHSType, CK_BitCast);
-          return ResultTy;
-        }
-      }
+  if ((LHSType->isIntegerType() && !LHSIsNull) ||
+      (RHSType->isIntegerType() && !RHSIsNull)) {
+    // Skip normal pointer conversion checks in this case; we have better
+    // diagnostics for this below.
+  } else if (getLangOpts().CPlusPlus) {
+    // Equality comparison of a function pointer to a void pointer is invalid,
+    // but we allow it as an extension.
+    // FIXME: If we really want to allow this, should it be part of composite
+    // pointer type computation so it works in conditionals too?
+    if (!IsRelational &&
+        ((LHSType->isFunctionPointerType() && RHSType->isVoidPointerType()) ||
+         (RHSType->isFunctionPointerType() && LHSType->isVoidPointerType()))) {
+      // This is a gcc extension compatibility comparison.
+      // In a SFINAE context, we treat this as a hard error to maintain
+      // conformance with the C++ standard.
+      diagnoseFunctionPointerToVoidComparison(
+          *this, Loc, LHS, RHS, /*isError*/ (bool)isSFINAEContext());
+      
+      if (isSFINAEContext())
+        return QualType();
+      
+      RHS = ImpCastExprToType(RHS.get(), LHSType, CK_BitCast);
+      return ResultTy;
+    }
 
+    // C++ [expr.eq]p2:
+    //   If at least one operand is a pointer [...] bring them to their
+    //   composite pointer type.
+    // C++ [expr.rel]p2:
+    //   If both operands are pointers, [...] bring them to their composite
+    //   pointer type.
+    if ((int)LHSType->isPointerType() + (int)RHSType->isPointerType() >=
+        (IsRelational ? 2 : 1)) {
       if (convertPointersToCompositeType(*this, Loc, LHS, RHS))
         return QualType();
       else
         return ResultTy;
     }
+  } else if (LHSType->isPointerType() &&
+             RHSType->isPointerType()) { // C99 6.5.8p2
+    // All of the following pointer-related warnings are GCC extensions, except
+    // when handling null pointer constants.
+    QualType LCanPointeeTy =
+      LHSType->castAs<PointerType>()->getPointeeType().getCanonicalType();
+    QualType RCanPointeeTy =
+      RHSType->castAs<PointerType>()->getPointeeType().getCanonicalType();
+
     // C99 6.5.9p2 and C99 6.5.8p2
     if (Context.typesAreCompatible(LCanPointeeTy.getUnqualifiedType(),
                                    RCanPointeeTy.getUnqualifiedType())) {
@@ -9393,36 +9391,63 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
   }
 
   if (getLangOpts().CPlusPlus) {
-    // Comparison of nullptr_t with itself.
-    if (LHSType->isNullPtrType() && RHSType->isNullPtrType())
-      return ResultTy;
-    
-    // Comparison of pointers with null pointer constants and equality
-    // comparisons of member pointers to null pointer constants.
-    if (RHSIsNull &&
-        ((LHSType->isAnyPointerType() || LHSType->isNullPtrType()) ||
-         (!IsRelational && 
-          (LHSType->isMemberPointerType() || LHSType->isBlockPointerType())))) {
-      RHS = ImpCastExprToType(RHS.get(), LHSType, 
-                        LHSType->isMemberPointerType()
-                          ? CK_NullToMemberPointer
-                          : CK_NullToPointer);
+    // C++ [expr.eq]p4:
+    //   Two operands of type std::nullptr_t or one operand of type
+    //   std::nullptr_t and the other a null pointer constant compare equal.
+    if (!IsRelational && LHSIsNull && RHSIsNull) {
+      if (LHSType->isNullPtrType()) {
+        RHS = ImpCastExprToType(RHS.get(), LHSType, CK_NullToPointer);
+        return ResultTy;
+      }
+      if (RHSType->isNullPtrType()) {
+        LHS = ImpCastExprToType(LHS.get(), RHSType, CK_NullToPointer);
+        return ResultTy;
+      }
+    }
+
+    // Comparison of Objective-C pointers and block pointers against nullptr_t.
+    // These aren't covered by the composite pointer type rules.
+    if (!IsRelational && RHSType->isNullPtrType() &&
+        (LHSType->isObjCObjectPointerType() || LHSType->isBlockPointerType())) {
+      RHS = ImpCastExprToType(RHS.get(), LHSType, CK_NullToPointer);
       return ResultTy;
     }
-    if (LHSIsNull &&
-        ((RHSType->isAnyPointerType() || RHSType->isNullPtrType()) ||
-         (!IsRelational && 
-          (RHSType->isMemberPointerType() || RHSType->isBlockPointerType())))) {
-      LHS = ImpCastExprToType(LHS.get(), RHSType, 
-                        RHSType->isMemberPointerType()
-                          ? CK_NullToMemberPointer
-                          : CK_NullToPointer);
+    if (!IsRelational && LHSType->isNullPtrType() &&
+        (RHSType->isObjCObjectPointerType() || RHSType->isBlockPointerType())) {
+      LHS = ImpCastExprToType(LHS.get(), RHSType, CK_NullToPointer);
       return ResultTy;
     }
 
-    // Comparison of member pointers.
+    if (IsRelational &&
+        ((LHSType->isNullPtrType() && RHSType->isPointerType()) ||
+         (RHSType->isNullPtrType() && LHSType->isPointerType()))) {
+      // HACK: Relational comparison of nullptr_t against a pointer type is
+      // invalid per DR583, but we allow it within std::less<> and friends,
+      // since otherwise common uses of it break.
+      // FIXME: Consider removing this hack once LWG fixes std::less<> and
+      // friends to have std::nullptr_t overload candidates.
+      DeclContext *DC = CurContext;
+      if (isa<FunctionDecl>(DC))
+        DC = DC->getParent();
+      if (auto *CTSD = dyn_cast<ClassTemplateSpecializationDecl>(DC)) {
+        if (CTSD->isInStdNamespace() &&
+            llvm::StringSwitch<bool>(CTSD->getName())
+                .Cases("less", "less_equal", "greater", "greater_equal", true)
+                .Default(false)) {
+          if (RHSType->isNullPtrType())
+            RHS = ImpCastExprToType(RHS.get(), LHSType, CK_NullToPointer);
+          else
+            LHS = ImpCastExprToType(LHS.get(), RHSType, CK_NullToPointer);
+          return ResultTy;
+        }
+      }
+    }
+
+    // C++ [expr.eq]p2:
+    //   If at least one operand is a pointer to member, [...] bring them to
+    //   their composite pointer type.
     if (!IsRelational &&
-        LHSType->isMemberPointerType() && RHSType->isMemberPointerType()) {
+        (LHSType->isMemberPointerType() || RHSType->isMemberPointerType())) {
       if (convertPointersToCompositeType(*this, Loc, LHS, RHS))
         return QualType();
       else
@@ -9531,15 +9556,19 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
       // Under a debugger, allow the comparison of pointers to integers,
       // since users tend to want to compare addresses.
     } else if ((LHSIsNull && LHSType->isIntegerType()) ||
-        (RHSIsNull && RHSType->isIntegerType())) {
-      if (IsRelational && !getLangOpts().CPlusPlus)
-        DiagID = diag::ext_typecheck_ordered_comparison_of_pointer_and_zero;
-    } else if (IsRelational && !getLangOpts().CPlusPlus)
-      DiagID = diag::ext_typecheck_ordered_comparison_of_pointer_integer;
-    else if (getLangOpts().CPlusPlus) {
+               (RHSIsNull && RHSType->isIntegerType())) {
+      if (IsRelational) {
+        isError = getLangOpts().CPlusPlus;
+        DiagID =
+          isError ? diag::err_typecheck_ordered_comparison_of_pointer_and_zero
+                  : diag::ext_typecheck_ordered_comparison_of_pointer_and_zero;
+      }
+    } else if (getLangOpts().CPlusPlus) {
       DiagID = diag::err_typecheck_comparison_of_pointer_integer;
       isError = true;
-    } else
+    } else if (IsRelational)
+      DiagID = diag::ext_typecheck_ordered_comparison_of_pointer_integer;
+    else
       DiagID = diag::ext_typecheck_comparison_of_pointer_integer;
 
     if (DiagID) {