[PATCH] Sema: Disallow taking the address of a bitfield coming from preincrement

[David Majnemer]

Hi rsmith,

Clang forgot that '++s.m' was a bitfield l-value and permit it's address
to be taken; this would crash at CodeGen-time.

Instead, propagate the object-kind when we see the prefix
increment/decrement.

http://reviews.llvm.org/D4733

Files:
  lib/Sema/SemaExpr.cpp
  test/CXX/drs/dr3xx.cpp

Index: lib/Sema/SemaExpr.cpp
===================================================================
--- lib/Sema/SemaExpr.cpp
+++ lib/Sema/SemaExpr.cpp
@@ -8764,6 +8764,7 @@
 /// doesn't need to call UsualUnaryConversions or UsualArithmeticConversions.
 static QualType CheckIncrementDecrementOperand(Sema &S, Expr *Op,
                                                ExprValueKind &VK,
+                                               ExprObjectKind &OK,
                                                SourceLocation OpLoc,
                                                bool IsInc, bool IsPrefix) {
   if (Op->isTypeDependent())
@@ -8809,7 +8810,7 @@
   } else if (ResType->isPlaceholderType()) {
     ExprResult PR = S.CheckPlaceholderExpr(Op);
     if (PR.isInvalid()) return QualType();
-    return CheckIncrementDecrementOperand(S, PR.get(), VK, OpLoc,
+    return CheckIncrementDecrementOperand(S, PR.get(), VK, OK, OpLoc,
                                           IsInc, IsPrefix);
   } else if (S.getLangOpts().AltiVec && ResType->isVectorType()) {
     // OK! ( C/C++ Language Extensions for CBEA(Version 2.6) 10.3 )
@@ -8830,6 +8831,7 @@
   // operand.
   if (IsPrefix && S.getLangOpts().CPlusPlus) {
     VK = VK_LValue;
+    OK = Op->getObjectKind();
     return ResType;
   } else {
     VK = VK_RValue;
@@ -9818,7 +9820,8 @@
   case UO_PreDec:
   case UO_PostInc:
   case UO_PostDec:
-    resultType = CheckIncrementDecrementOperand(*this, Input.get(), VK, OpLoc,
+    resultType = CheckIncrementDecrementOperand(*this, Input.get(), VK, OK,
+                                                OpLoc,
                                                 Opc == UO_PreInc ||
                                                 Opc == UO_PostInc,
                                                 Opc == UO_PreInc ||
Index: test/CXX/drs/dr3xx.cpp
===================================================================
--- test/CXX/drs/dr3xx.cpp
+++ test/CXX/drs/dr3xx.cpp
@@ -322,6 +322,7 @@
   int *f = &(true ? s.n : s.n); // expected-error {{address of bit-field}}
   int &g = (void(), s.n); // expected-error {{non-const reference cannot bind to bit-field}}
   int *h = &(void(), s.n); // expected-error {{address of bit-field}}
+  int *i = &++s.n; // expected-error {{address of bit-field}}
 }
 
 namespace dr326 { // dr326: yes
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