[Clang] Make the result type of sizeof/pointer subtraction/size_t lit…

clang/include/clang/AST/ASTContext.h

@@ -2442,6 +2442,10 @@ class ASTContext : public RefCountedBase<ASTContext> {
   QualType GetBuiltinType(unsigned ID, GetBuiltinTypeError &Error,
                           unsigned *IntegerConstantArgs = nullptr) const;
 
+  QualType getCGlobalCXXStdNSTypedef(const NamespaceDecl *StdNS,
+                                     StringRef DefName,
+                                     QualType FallBack = {}) const;
+
   /// Types and expressions required to build C++2a three-way comparisons
   /// using operator<=>, including the values return by builtin <=> operators.
   ComparisonCategories CompCategories;

clang/lib/AST/ASTContext.cpp

@@ -12556,6 +12556,35 @@ QualType ASTContext::GetBuiltinType(unsigned Id,
   return getFunctionType(ResType, ArgTypes, EPI);
 }
 
+QualType ASTContext::getCGlobalCXXStdNSTypedef(const NamespaceDecl *StdNS,
+                                               StringRef DefName,
+                                               QualType FallBack) const {
+  DeclContextLookupResult Lookup;
+  if (getLangOpts().C99) {
+    Lookup = getTranslationUnitDecl()->lookup(&Idents.get(DefName));
+  } else if (getLangOpts().CPlusPlus) {
+    if (StdNS == nullptr) {
+      auto LookupStdNS = getTranslationUnitDecl()->lookup(&Idents.get("std"));
+      if (!LookupStdNS.empty()) {
+        StdNS = dyn_cast<NamespaceDecl>(LookupStdNS.front());
+      }
+    }
+    if (StdNS) {
+      Lookup = StdNS->lookup(&Idents.get(DefName));
+    } else {
+      Lookup = getTranslationUnitDecl()->lookup(&Idents.get(DefName));
+    }
+  }
+  if (!Lookup.empty()) {
+    if (auto *TD = dyn_cast<TypedefNameDecl>(Lookup.front())) {
+      if (auto Result = getTypeDeclType(TD); !Result.isNull()) {
+        return Result;
+      }
+    }
+  }
+  return FallBack;
+}
+
 static GVALinkage basicGVALinkageForFunction(const ASTContext &Context,
                                              const FunctionDecl *FD) {
   if (!FD->isExternallyVisible())

clang/lib/AST/ComparisonCategories.cpp

@@ -87,37 +87,17 @@ ComparisonCategoryInfo::ValueInfo *ComparisonCategoryInfo::lookupValueInfo(
   return &Objects.back();
 }
 
-static const NamespaceDecl *lookupStdNamespace(const ASTContext &Ctx,
-                                               NamespaceDecl *&StdNS) {
-  if (!StdNS) {
-    DeclContextLookupResult Lookup =
-        Ctx.getTranslationUnitDecl()->lookup(&Ctx.Idents.get("std"));
-    if (!Lookup.empty())
-      StdNS = dyn_cast<NamespaceDecl>(Lookup.front());
-  }
-  return StdNS;
-}
-
-static const CXXRecordDecl *lookupCXXRecordDecl(const ASTContext &Ctx,
-                                                const NamespaceDecl *StdNS,
-                                                ComparisonCategoryType Kind) {
-  StringRef Name = ComparisonCategories::getCategoryString(Kind);
-  DeclContextLookupResult Lookup = StdNS->lookup(&Ctx.Idents.get(Name));
-  if (!Lookup.empty())
-    if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(Lookup.front()))
-      return RD;
-  return nullptr;
-}
-
 const ComparisonCategoryInfo *
 ComparisonCategories::lookupInfo(ComparisonCategoryType Kind) const {
   auto It = Data.find(static_cast<char>(Kind));
   if (It != Data.end())
     return &It->second;
-
-  if (const NamespaceDecl *NS = lookupStdNamespace(Ctx, StdNS))
-    if (const CXXRecordDecl *RD = lookupCXXRecordDecl(Ctx, NS, Kind))
+  if (auto QT = Ctx.getCGlobalCXXStdNSTypedef(
+          nullptr, ComparisonCategories::getCategoryString(Kind));
+      !QT.isNull()) {
+    if (const auto *RD = QT->getAsCXXRecordDecl())
       return &Data.try_emplace((char)Kind, Ctx, RD, Kind).first->second;
+  }
 
   return nullptr;
 }

clang/lib/AST/ExprCXX.cpp

@@ -1700,8 +1700,10 @@ SizeOfPackExpr *SizeOfPackExpr::Create(ASTContext &Context,
                                        ArrayRef<TemplateArgument> PartialArgs) {
   void *Storage =
       Context.Allocate(totalSizeToAlloc<TemplateArgument>(PartialArgs.size()));
-  return new (Storage) SizeOfPackExpr(Context.getSizeType(), OperatorLoc, Pack,
-                                      PackLoc, RParenLoc, Length, PartialArgs);
+  return new (Storage) SizeOfPackExpr(
+      Context.getCGlobalCXXStdNSTypedef(nullptr, "size_t",
+                                        Context.getSizeType()),
+      OperatorLoc, Pack, PackLoc, RParenLoc, Length, PartialArgs);
 }
 
 SizeOfPackExpr *SizeOfPackExpr::CreateDeserialized(ASTContext &Context,

clang/lib/Sema/SemaExpr.cpp

@@ -4026,10 +4026,20 @@ ExprResult Sema::ActOnNumericConstant(const Token &Tok, Scope *UDLScope) {
         // Does it fit in size_t?
         if (ResultVal.isIntN(SizeTSize)) {
           // Does it fit in ssize_t?
-          if (!Literal.isUnsigned && ResultVal[SizeTSize - 1] == 0)
-            Ty = Context.getSignedSizeType();
-          else if (AllowUnsigned)
-            Ty = Context.getSizeType();
+          if (!Literal.isUnsigned && ResultVal[SizeTSize - 1] == 0) {
+            auto SignedSize = Context.getSignedSizeType();
+            if (auto PtrDiff = Context.getCGlobalCXXStdNSTypedef(
+                    getStdNamespace(), "ptrdiff_t");
+                Context.hasSameType(PtrDiff, SignedSize))
+              Ty = PtrDiff;
+            else if (auto SSize = Context.getCGlobalCXXStdNSTypedef(
+                         getStdNamespace(), "ssize_t");
+                     Context.hasSameType(SSize, SignedSize))
+              Ty = SSize;
+          } else if (AllowUnsigned) {
+            Ty = Context.getCGlobalCXXStdNSTypedef(getStdNamespace(), "size_t",
+                                                   Context.getSizeType());
+          }
           Width = SizeTSize;
         }
       }
@@ -4702,7 +4712,10 @@ ExprResult Sema::CreateUnaryExprOrTypeTraitExpr(TypeSourceInfo *TInfo,
 
   // C99 6.5.3.4p4: the type (an unsigned integer type) is size_t.
   return new (Context) UnaryExprOrTypeTraitExpr(
-      ExprKind, TInfo, Context.getSizeType(), OpLoc, R.getEnd());
+      ExprKind, TInfo,
+      Context.getCGlobalCXXStdNSTypedef(getStdNamespace(), "size_t",
+                                        Context.getSizeType()),
+      OpLoc, R.getEnd());
 }
 
 ExprResult
@@ -4745,7 +4758,10 @@ Sema::CreateUnaryExprOrTypeTraitExpr(Expr *E, SourceLocation OpLoc,
 
   // C99 6.5.3.4p4: the type (an unsigned integer type) is size_t.
   return new (Context) UnaryExprOrTypeTraitExpr(
-      ExprKind, E, Context.getSizeType(), OpLoc, E->getSourceRange().getEnd());
+      ExprKind, E,
+      Context.getCGlobalCXXStdNSTypedef(getStdNamespace(), "size_t",
+                                        Context.getSizeType()),
+      OpLoc, E->getSourceRange().getEnd());
 }
 
 ExprResult
@@ -11353,8 +11369,10 @@ QualType Sema::CheckSubtractionOperands(ExprResult &LHS, ExprResult &RHS,
         }
       }
 
-      if (CompLHSTy) *CompLHSTy = LHS.get()->getType();
-      return Context.getPointerDiffType();
+      if (CompLHSTy)
+        *CompLHSTy = LHS.get()->getType();
+      return Context.getCGlobalCXXStdNSTypedef(getStdNamespace(), "ptrdiff_t",
+                                               Context.getPointerDiffType());
     }
   }