Implement checks for bool in increment and decrement.

llvm-svn: 61275

clang/include/clang/Basic/DiagnosticKinds.def

@@ -1298,6 +1298,10 @@ DIAG(err_delete_operand, ERROR,
      "cannot delete expression of type %0")
 DIAG(warn_delete_incomplete, WARNING,
      "deleting pointer to incomplete type %0 may cause undefined behaviour")
+DIAG(err_decrement_bool, ERROR,
+     "cannot decrement expression of type bool")
+DIAG(warn_increment_bool, WARNING,
+     "incrementing expression of type bool is deprecated")
 
 DIAG(err_invalid_use_of_function_type, ERROR,
      "a function type is not allowed here")

clang/lib/Sema/Sema.h

@@ -1306,7 +1306,8 @@ public:
   
   /// type checking unary operators (subroutines of ActOnUnaryOp).
   /// C99 6.5.3.1, 6.5.3.2, 6.5.3.4
-  QualType CheckIncrementDecrementOperand(Expr *op, SourceLocation OpLoc);   
+  QualType CheckIncrementDecrementOperand(Expr *op, SourceLocation OpLoc,
+                                          bool isInc);
   QualType CheckAddressOfOperand(Expr *op, SourceLocation OpLoc);
   QualType CheckIndirectionOperand(Expr *op, SourceLocation OpLoc);
   QualType CheckRealImagOperand(Expr *&Op, SourceLocation OpLoc);

clang/lib/Sema/SemaExpr.cpp

@@ -952,7 +952,8 @@ Action::ExprResult Sema::ActOnPostfixUnaryOp(Scope *S, SourceLocation OpLoc,
     // build a built-in operation.
   }
 
-  QualType result = CheckIncrementDecrementOperand(Arg, OpLoc);
+  QualType result = CheckIncrementDecrementOperand(Arg, OpLoc,
+                                                 Opc == UnaryOperator::PostInc);
   if (result.isNull())
     return true;
   return new UnaryOperator(Arg, Opc, result, OpLoc);
@@ -2762,12 +2763,20 @@ QualType Sema::CheckCommaOperands(Expr *LHS, Expr *&RHS, SourceLocation Loc) {
 
 /// CheckIncrementDecrementOperand - unlike most "Check" methods, this routine
 /// doesn't need to call UsualUnaryConversions or UsualArithmeticConversions.
-QualType Sema::CheckIncrementDecrementOperand(Expr *Op, SourceLocation OpLoc) {
+QualType Sema::CheckIncrementDecrementOperand(Expr *Op, SourceLocation OpLoc,
+                                              bool isInc) {
   QualType ResType = Op->getType();
   assert(!ResType.isNull() && "no type for increment/decrement expression");
 
-  // C99 6.5.2.4p1: We allow complex as a GCC extension.
-  if (ResType->isRealType()) {
+  if (getLangOptions().CPlusPlus && ResType->isBooleanType()) {
+    // Decrement of bool is not allowed.
+    if (!isInc) {
+      Diag(OpLoc, diag::err_decrement_bool) << Op->getSourceRange();
+      return QualType();
+    }
+    // Increment of bool sets it to true, but is deprecated.
+    Diag(OpLoc, diag::warn_increment_bool) << Op->getSourceRange();
+  } else if (ResType->isRealType()) {
     // OK!
   } else if (const PointerType *PT = ResType->getAsPointerType()) {
     // C99 6.5.2.4p2, 6.5.6p2
@@ -3350,7 +3359,8 @@ Action::ExprResult Sema::ActOnUnaryOp(Scope *S, SourceLocation OpLoc,
     assert(0 && "Unimplemented unary expr!");
   case UnaryOperator::PreInc:
   case UnaryOperator::PreDec:
-    resultType = CheckIncrementDecrementOperand(Input, OpLoc);
+    resultType = CheckIncrementDecrementOperand(Input, OpLoc,
+                                                Opc == UnaryOperator::PreInc);
     break;
   case UnaryOperator::AddrOf: 
     resultType = CheckAddressOfOperand(Input, OpLoc);

clang/test/SemaCXX/bool.cpp

@@ -5,3 +5,12 @@ enum {
   ReadWrite = false,
   ReadOnly = true
 };
+
+// bool cannot be decremented, and gives a warning on increment
+void test(bool b)
+{
+  ++b; // expected-warning {{incrementing expression of type bool is deprecated}}
+  b++; // expected-warning {{incrementing expression of type bool is deprecated}}
+  --b; // expected-error {{cannot decrement expression of type bool}}
+  b--; // expected-error {{cannot decrement expression of type bool}}
+}

clang/www/cxx_status.html

@@ -548,9 +548,9 @@ welcome!</p>
   <td>&nbsp;&nbsp;&nbsp;&nbsp;5.2.6 [expr.post.incr]</td>
   <td class="complete" align="center">&#x2713;</td>
   <td class="complete" align="center">&#x2713;</td>
-  <td class="advanced"></td>
+  <td class="complete" align="center">&#x2713;</td>
+  <td></td>
   <td></td>
-  <td>Decrement of bool is accepted, increment not warned about</td>
 </tr>
 <tr>
   <td>&nbsp;&nbsp;&nbsp;&nbsp;5.2.7 [expr.dynamic.cast]</td>
@@ -646,9 +646,9 @@ welcome!</p>
   <td>&nbsp;&nbsp;&nbsp;&nbsp;5.3.2 [expr.pre.incr]</td>
   <td class="complete" align="center">&#x2713;</td>
   <td class="complete" align="center">&#x2713;</td>
-  <td class="advanced"></td>
+  <td class="complete" align="center">&#x2713;</td>
+  <td></td>
   <td></td>
-  <td>Decrement of bool is accepted, increment not warned about</td>
 </tr>
 <tr>
   <td>&nbsp;&nbsp;&nbsp;&nbsp;5.3.3 [expr.sizeof]</td>