Implement support for comparing pointers with <, >, <=, >=, ==, and !=
in C++, taking into account conversions to the "composite pointer
type" so that we can compare, e.g., a pointer to a derived class to a
pointer to a base class.
Also, upgrade the "comparing distinct pointer types" from a warning to
an error for C++, since this is clearly an error. Turns out that we
hadn't gone through and audited this code for C++, ever.
Fixes <rdar://problem/6816420>.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@70829 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 36ec9c6..a4eeb9f 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -3653,7 +3653,7 @@
return LHSTy;
}
-// C99 6.5.8
+// C99 6.5.8, C++ [expr.rel]
QualType Sema::CheckCompareOperands(Expr *&lex, Expr *&rex, SourceLocation Loc,
unsigned OpaqueOpc, bool isRelational) {
BinaryOperator::Opcode Opc = (BinaryOperator::Opcode)OpaqueOpc;
@@ -3758,6 +3758,31 @@
QualType RCanPointeeTy =
Context.getCanonicalType(rType->getAsPointerType()->getPointeeType());
+ // Simple check: if the pointee types are identical, we're done.
+ if (LCanPointeeTy == RCanPointeeTy)
+ return ResultTy;
+
+ if (getLangOptions().CPlusPlus) {
+ // C++ [expr.rel]p2:
+ // [...] Pointer conversions (4.10) and qualification
+ // conversions (4.4) are performed on pointer operands (or on
+ // a pointer operand and a null pointer constant) to bring
+ // them to their composite pointer type. [...]
+ //
+ // C++ [expr.eq]p2 uses the same notion for (in)equality
+ // comparisons of pointers.
+ QualType T = CompositePointerType(lex, rex, LHSIsNull, RHSIsNull);
+ if (T.isNull()) {
+ Diag(Loc, diag::err_typecheck_comparison_of_distinct_pointers)
+ << lType << rType << lex->getSourceRange() << rex->getSourceRange();
+ return QualType();
+ }
+
+ ImpCastExprToType(lex, T);
+ ImpCastExprToType(rex, T);
+ return ResultTy;
+ }
+
if (!LHSIsNull && !RHSIsNull && // C99 6.5.9p2
!LCanPointeeTy->isVoidType() && !RCanPointeeTy->isVoidType() &&
!Context.typesAreCompatible(LCanPointeeTy.getUnqualifiedType(),