Factor out (some of) the checking for invalid forms of pointer

arithmetic into a couple of common routines. Use these to make the
messages more consistent in the various contexts, especially in terms of
consistently diagnosing binary operators with invalid types on both the
left- and right-hand side. Also, improve the grammar and wording of the
messages some, handling both two pointers and two (different) types.

The wording of function pointer arithmetic diagnostics still strikes me
as poorly phrased, and I worry this makes them slightly more awkward if
more consistent. I'm hoping to fix that with a follow-on patch and test
case that will also make them more helpful when a typedef or template
type parameter makes the type completely opaque.

Suggestions on better wording are very welcome, thanks to Richard Smith
for some initial help on that front.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@133906 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 151 insertions, 126 deletions

diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 892b882df5..d644e55989 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -3092,8 +3092,9 @@ Sema::CreateBuiltinArraySubscriptExpr(Expr *Base, SourceLocation LLoc,
 
   if (ResultType->isVoidType() && !getLangOptions().CPlusPlus) {
     // GNU extension: subscripting on pointer to void
+    // FIXME: Use a better warning for this.
     Diag(LLoc, diag::ext_gnu_void_ptr)
-      << BaseExpr->getSourceRange();
+      << 0 << BaseExpr->getSourceRange();
 
     // C forbids expressions of unqualified void type from being l-values.
     // See IsCForbiddenLValueType.
@@ -5595,6 +5596,145 @@ QualType Sema::CheckRemainderOperands(
   return compType;
 }
 
+/// \brief Diagnose invalid arithmetic on two void pointers.
+static void diagnoseArithmeticOnTwoVoidPointers(Sema &S, SourceLocation Loc,
+                                                Expr *LHS, Expr *RHS) {
+  S.Diag(Loc, S.getLangOptions().CPlusPlus
+                ? diag::err_typecheck_pointer_arith_void_type
+                : diag::ext_gnu_void_ptr)
+    << 1 /* two pointers */ << LHS->getSourceRange() << RHS->getSourceRange();
+}
+
+/// \brief Diagnose invalid arithmetic on a void pointer.
+static void diagnoseArithmeticOnVoidPointer(Sema &S, SourceLocation Loc,
+                                            Expr *Pointer) {
+  S.Diag(Loc, S.getLangOptions().CPlusPlus
+                ? diag::err_typecheck_pointer_arith_void_type
+                : diag::ext_gnu_void_ptr)
+    << 0 /* one pointer */ << Pointer->getSourceRange();
+}
+
+/// \brief Diagnose invalid arithmetic on two function pointers.
+static void diagnoseArithmeticOnTwoFunctionPointers(Sema &S, SourceLocation Loc,
+                                                    Expr *LHS, Expr *RHS) {
+  assert(LHS->getType()->isAnyPointerType());
+  assert(RHS->getType()->isAnyPointerType());
+  S.Diag(Loc, S.getLangOptions().CPlusPlus
+                ? diag::err_typecheck_pointer_arith_function_type
+                : diag::ext_gnu_ptr_func_arith)
+    << 1 /* two pointers */ << LHS->getType()->getPointeeType()
+    // We only show the second type if it differs from the first.
+    << (unsigned)!S.Context.hasSameUnqualifiedType(LHS->getType(),
+                                                   RHS->getType())
+    << RHS->getType()->getPointeeType()
+    << LHS->getSourceRange() << RHS->getSourceRange();
+}
+
+/// \brief Diagnose invalid arithmetic on a function pointer.
+static void diagnoseArithmeticOnFunctionPointer(Sema &S, SourceLocation Loc,
+                                                Expr *Pointer) {
+  assert(Pointer->getType()->isAnyPointerType());
+  S.Diag(Loc, S.getLangOptions().CPlusPlus
+                ? diag::err_typecheck_pointer_arith_function_type
+                : diag::ext_gnu_ptr_func_arith)
+    << 0 /* one pointer */ << Pointer->getType()->getPointeeType()
+    << 0 /* one pointer, so only one type */
+    << Pointer->getSourceRange();
+}
+
+/// \brief Check the validity of an arithmetic pointer operand.
+///
+/// If the operand has pointer type, this code will check for pointer types
+/// which are invalid in arithmetic operations. These will be diagnosed
+/// appropriately, including whether or not the use is supported as an
+/// extension.
+///
+/// \returns True when the operand is valid to use (even if as an extension).
+static bool checkArithmeticOpPointerOperand(Sema &S, SourceLocation Loc,
+                                            Expr *Operand) {
+  if (!Operand->getType()->isAnyPointerType()) return true;
+
+  QualType PointeeTy = Operand->getType()->getPointeeType();
+  if (PointeeTy->isVoidType()) {
+    diagnoseArithmeticOnVoidPointer(S, Loc, Operand);
+    return !S.getLangOptions().CPlusPlus;
+  }
+  if (PointeeTy->isFunctionType()) {
+    diagnoseArithmeticOnFunctionPointer(S, Loc, Operand);
+    return !S.getLangOptions().CPlusPlus;
+  }
+
+  if ((Operand->getType()->isPointerType() &&
+       !Operand->getType()->isDependentType()) ||
+      Operand->getType()->isObjCObjectPointerType()) {
+    QualType PointeeTy = Operand->getType()->getPointeeType();
+    if (S.RequireCompleteType(
+          Loc, PointeeTy,
+          S.PDiag(diag::err_typecheck_arithmetic_incomplete_type)
+            << PointeeTy << Operand->getSourceRange()))
+      return false;
+  }
+
+  return true;
+}
+
+/// \brief Check the validity of a binary arithmetic operation w.r.t. pointer
+/// operands.
+///
+/// This routine will diagnose any invalid arithmetic on pointer operands much
+/// like \see checkArithmeticOpPointerOperand. However, it has special logic
+/// for emitting a single diagnostic even for operations where both LHS and RHS
+/// are (potentially problematic) pointers.
+///
+/// \returns True when the operand is valid to use (even if as an extension).
+static bool checkArithmeticBinOpPointerOperands(Sema &S, SourceLocation Loc,
+                                                Expr *LHS, Expr *RHS) {
+  bool isLHSPointer = LHS->getType()->isAnyPointerType();
+  bool isRHSPointer = RHS->getType()->isAnyPointerType();
+  if (!isLHSPointer && !isRHSPointer) return true;
+
+  QualType LHSPointeeTy, RHSPointeeTy;
+  if (isLHSPointer) LHSPointeeTy = LHS->getType()->getPointeeType();
+  if (isRHSPointer) RHSPointeeTy = RHS->getType()->getPointeeType();
+
+  // Check for arithmetic on pointers to incomplete types.
+  bool isLHSVoidPtr = isLHSPointer && LHSPointeeTy->isVoidType();
+  bool isRHSVoidPtr = isRHSPointer && RHSPointeeTy->isVoidType();
+  if (isLHSVoidPtr || isRHSVoidPtr) {
+    if (!isRHSVoidPtr) diagnoseArithmeticOnVoidPointer(S, Loc, LHS);
+    else if (!isLHSVoidPtr) diagnoseArithmeticOnVoidPointer(S, Loc, RHS);
+    else diagnoseArithmeticOnTwoVoidPointers(S, Loc, LHS, RHS);
+
+    return !S.getLangOptions().CPlusPlus;
+  }
+
+  bool isLHSFuncPtr = isLHSPointer && LHSPointeeTy->isFunctionType();
+  bool isRHSFuncPtr = isRHSPointer && RHSPointeeTy->isFunctionType();
+  if (isLHSFuncPtr || isRHSFuncPtr) {
+    if (!isRHSFuncPtr) diagnoseArithmeticOnFunctionPointer(S, Loc, LHS);
+    else if (!isLHSFuncPtr) diagnoseArithmeticOnFunctionPointer(S, Loc, RHS);
+    else diagnoseArithmeticOnTwoFunctionPointers(S, Loc, LHS, RHS);
+
+    return !S.getLangOptions().CPlusPlus;
+  }
+
+  Expr *Operands[] = { LHS, RHS };
+  for (unsigned i = 0; i < 2; ++i) {
+    Expr *Operand = Operands[i];
+    if ((Operand->getType()->isPointerType() &&
+         !Operand->getType()->isDependentType()) ||
+        Operand->getType()->isObjCObjectPointerType()) {
+      QualType PointeeTy = Operand->getType()->getPointeeType();
+      if (S.RequireCompleteType(
+            Loc, PointeeTy,
+            S.PDiag(diag::err_typecheck_arithmetic_incomplete_type)
+              << PointeeTy << Operand->getSourceRange()))
+        return false;
+    }
+  }
+  return true;
+}
+
 QualType Sema::CheckAdditionOperands( // C99 6.5.6
   ExprResult &lex, ExprResult &rex, SourceLocation Loc, QualType* CompLHSTy) {
   if (lex.get()->getType()->isVectorType() || rex.get()->getType()->isVectorType()) {
@@ -5620,42 +5760,12 @@ QualType Sema::CheckAdditionOperands( // C99 6.5.6
     std::swap(PExp, IExp);
 
   if (PExp->getType()->isAnyPointerType()) {
-
     if (IExp->getType()->isIntegerType()) {
-      QualType PointeeTy = PExp->getType()->getPointeeType();
-
-      // Check for arithmetic on pointers to incomplete types.
-      if (PointeeTy->isVoidType()) {
-        if (getLangOptions().CPlusPlus) {
-          Diag(Loc, diag::err_typecheck_pointer_arith_void_type)
-            << lex.get()->getSourceRange() << rex.get()->getSourceRange();
-          return QualType();
-        }
+      if (!checkArithmeticOpPointerOperand(*this, Loc, PExp))
+        return QualType();
 
-        // GNU extension: arithmetic on pointer to void
-        Diag(Loc, diag::ext_gnu_void_ptr)
-          << lex.get()->getSourceRange() << rex.get()->getSourceRange();
-      } else if (PointeeTy->isFunctionType()) {
-        if (getLangOptions().CPlusPlus) {
-          Diag(Loc, diag::err_typecheck_pointer_arith_function_type)
-            << PExp->getType() << PExp->getSourceRange();
-          return QualType();
-        }
+      QualType PointeeTy = PExp->getType()->getPointeeType();
 
-        // GNU extension: arithmetic on pointer to function
-        Diag(Loc, diag::ext_gnu_ptr_func_arith)
-          << PExp->getType() << PExp->getSourceRange();
-      } else {
-        // Check if we require a complete type.
-        if (((PExp->getType()->isPointerType() &&
-              !PExp->getType()->isDependentType()) ||
-              PExp->getType()->isObjCObjectPointerType()) &&
-             RequireCompleteType(Loc, PointeeTy,
-                           PDiag(diag::err_typecheck_arithmetic_incomplete_type)
-                             << PExp->getSourceRange()
-                             << PExp->getType()))
-          return QualType();
-      }
       // Diagnose bad cases where we step over interface counts.
       if (PointeeTy->isObjCObjectType() && LangOpts.ObjCNonFragileABI) {
         Diag(Loc, diag::err_arithmetic_nonfragile_interface)
@@ -5705,35 +5815,6 @@ QualType Sema::CheckSubtractionOperands(ExprResult &lex, ExprResult &rex,
   if (lex.get()->getType()->isAnyPointerType()) {
     QualType lpointee = lex.get()->getType()->getPointeeType();
 
-    // The LHS must be an completely-defined object type.
-
-    bool ComplainAboutVoid = false;
-    Expr *ComplainAboutFunc = 0;
-    if (lpointee->isVoidType()) {
-      if (getLangOptions().CPlusPlus) {
-        Diag(Loc, diag::err_typecheck_pointer_arith_void_type)
-          << lex.get()->getSourceRange() << rex.get()->getSourceRange();
-        return QualType();
-      }
-
-      // GNU C extension: arithmetic on pointer to void
-      ComplainAboutVoid = true;
-    } else if (lpointee->isFunctionType()) {
-      if (getLangOptions().CPlusPlus) {
-        Diag(Loc, diag::err_typecheck_pointer_arith_function_type)
-          << lex.get()->getType() << lex.get()->getSourceRange();
-        return QualType();
-      }
-
-      // GNU C extension: arithmetic on pointer to function
-      ComplainAboutFunc = lex.get();
-    } else if (!lpointee->isDependentType() &&
-               RequireCompleteType(Loc, lpointee,
-                                   PDiag(diag::err_typecheck_sub_ptr_object)
-                                     << lex.get()->getSourceRange()
-                                     << lex.get()->getType()))
-      return QualType();
-
     // Diagnose bad cases where we step over interface counts.
     if (lpointee->isObjCObjectType() && LangOpts.ObjCNonFragileABI) {
       Diag(Loc, diag::err_arithmetic_nonfragile_interface)
@@ -5743,13 +5824,8 @@ QualType Sema::CheckSubtractionOperands(ExprResult &lex, ExprResult &rex,
 
     // The result type of a pointer-int computation is the pointer type.
     if (rex.get()->getType()->isIntegerType()) {
-      if (ComplainAboutVoid)
-        Diag(Loc, diag::ext_gnu_void_ptr)
-          << lex.get()->getSourceRange() << rex.get()->getSourceRange();
-      if (ComplainAboutFunc)
-        Diag(Loc, diag::ext_gnu_ptr_func_arith)
-          << ComplainAboutFunc->getType()
-          << ComplainAboutFunc->getSourceRange();
+      if (!checkArithmeticOpPointerOperand(*this, Loc, lex.get()))
+        return QualType();
 
       if (CompLHSTy) *CompLHSTy = lex.get()->getType();
       return lex.get()->getType();
@@ -5759,33 +5835,6 @@ QualType Sema::CheckSubtractionOperands(ExprResult &lex, ExprResult &rex,
     if (const PointerType *RHSPTy = rex.get()->getType()->getAs<PointerType>()) {
       QualType rpointee = RHSPTy->getPointeeType();
 
-      // RHS must be a completely-type object type.
-      // Handle the GNU void* extension.
-      if (rpointee->isVoidType()) {
-        if (getLangOptions().CPlusPlus) {
-          Diag(Loc, diag::err_typecheck_pointer_arith_void_type)
-            << lex.get()->getSourceRange() << rex.get()->getSourceRange();
-          return QualType();
-        }
-
-        ComplainAboutVoid = true;
-      } else if (rpointee->isFunctionType()) {
-        if (getLangOptions().CPlusPlus) {
-          Diag(Loc, diag::err_typecheck_pointer_arith_function_type)
-            << rex.get()->getType() << rex.get()->getSourceRange();
-          return QualType();
-        }
-
-        // GNU extension: arithmetic on pointer to function
-        if (!ComplainAboutFunc)
-          ComplainAboutFunc = rex.get();
-      } else if (!rpointee->isDependentType() &&
-                 RequireCompleteType(Loc, rpointee,
-                                     PDiag(diag::err_typecheck_sub_ptr_object)
-                                       << rex.get()->getSourceRange()
-                                       << rex.get()->getType()))
-        return QualType();
-
       if (getLangOptions().CPlusPlus) {
         // Pointee types must be the same: C++ [expr.add]
         if (!Context.hasSameUnqualifiedType(lpointee, rpointee)) {
@@ -5806,13 +5855,9 @@ QualType Sema::CheckSubtractionOperands(ExprResult &lex, ExprResult &rex,
         }
       }
 
-      if (ComplainAboutVoid)
-        Diag(Loc, diag::ext_gnu_void_ptr)
-          << lex.get()->getSourceRange() << rex.get()->getSourceRange();
-      if (ComplainAboutFunc)
-        Diag(Loc, diag::ext_gnu_ptr_func_arith)
-          << ComplainAboutFunc->getType()
-          << ComplainAboutFunc->getSourceRange();
+      if (!checkArithmeticBinOpPointerOperands(*this, Loc,
+                                               lex.get(), rex.get()))
+        return QualType();
 
       if (CompLHSTy) *CompLHSTy = lex.get()->getType();
       return Context.getPointerDiffType();
@@ -6819,29 +6864,9 @@ static QualType CheckIncrementDecrementOperand(Sema &S, Expr *Op,
     QualType PointeeTy = ResType->getPointeeType();
 
     // C99 6.5.2.4p2, 6.5.6p2
-    if (PointeeTy->isVoidType()) {
-      if (S.getLangOptions().CPlusPlus) {
-        S.Diag(OpLoc, diag::err_typecheck_pointer_arith_void_type)
-          << Op->getSourceRange();
-        return QualType();
-      }
-
-      // Pointer to void is a GNU extension in C.
-      S.Diag(OpLoc, diag::ext_gnu_void_ptr) << Op->getSourceRange();
-    } else if (PointeeTy->isFunctionType()) {
-      if (S.getLangOptions().CPlusPlus) {
-        S.Diag(OpLoc, diag::err_typecheck_pointer_arith_function_type)
-          << Op->getType() << Op->getSourceRange();
-        return QualType();
-      }
-
-      S.Diag(OpLoc, diag::ext_gnu_ptr_func_arith)
-        << ResType << Op->getSourceRange();
-    } else if (S.RequireCompleteType(OpLoc, PointeeTy,
-                 S.PDiag(diag::err_typecheck_arithmetic_incomplete_type)
-                             << Op->getSourceRange()
-                             << ResType))
+    if (!checkArithmeticOpPointerOperand(S, OpLoc, Op))
       return QualType();
+
     // Diagnose bad cases where we step over interface counts.
     else if (PointeeTy->isObjCObjectType() && S.LangOpts.ObjCNonFragileABI) {
       S.Diag(OpLoc, diag::err_arithmetic_nonfragile_interface)