chrisbazley created this revision.
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The semantics of the unary & operator are modified
so that if its operand has type "type" then its
result has type "pointer to type", with the omission
of any _Optional qualifier of the pointed-to type.
Also added a new helper method,
ASTContext::getNonOptionalType.
Rationale:
A new idiom &* is proposed to allow removal of the
_Optional qualifier from a pointee whilst allowing
static analyzers to check the validity of such
conversions. This is merely the simplest expression
that incorporates a semantic dereference without
actually accessing the pointed-to object.
There is only one way to get the address of an object
(excepting arithmetic), whereas there are many ways
to dereference a pointer. This is why the semantics
of & are modified rather than modifying *, [] and ->.
The operand of & is already treated specially, being
exempt from implicit conversion of an array type into
a pointer, for example.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D142734
Files:
clang/include/clang/AST/ASTContext.h
clang/lib/Sema/SemaExpr.cpp
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -14585,10 +14585,18 @@
if (getLangOpts().C99) {
// Implement C99-only parts of addressof rules.
if (UnaryOperator* uOp = dyn_cast<UnaryOperator>(op)) {
- if (uOp->getOpcode() == UO_Deref)
+ if (uOp->getOpcode() == UO_Deref) {
// Per C99 6.5.3.2, the address of a deref always returns a valid result
// (assuming the deref expression is valid).
- return uOp->getSubExpr()->getType();
+ auto Result = uOp->getSubExpr()->getType();
+ if (const PointerType *PT = Result->getAs<PointerType>()) {
+ // A dereferenced pointer is not a null pointer (by definition).
+ auto PointeeType = PT->getPointeeType();
+ Result =
+ Context.getPointerType(Context.getNonOptionalType(PointeeType));
+ }
+ return Result;
+ }
}
// Technically, there should be a check for array subscript
// expressions here, but the result of one is always an lvalue anyway.
@@ -14602,6 +14610,7 @@
Expr::LValueClassification lval = op->ClassifyLValue(Context);
unsigned AddressOfError = AO_No_Error;
+ QualType Ty = Context.getNonOptionalType(op->getType());
if (lval == Expr::LV_ClassTemporary || lval == Expr::LV_ArrayTemporary) {
bool sfinae = (bool)isSFINAEContext();
@@ -14611,10 +14620,9 @@
if (sfinae)
return QualType();
// Materialize the temporary as an lvalue so that we can take its address.
- OrigOp = op =
- CreateMaterializeTemporaryExpr(op->getType(), OrigOp.get(), true);
+ OrigOp = op = CreateMaterializeTemporaryExpr(Ty, OrigOp.get(), true);
} else if (isa<ObjCSelectorExpr>(op)) {
- return Context.getPointerType(op->getType());
+ return Context.getPointerType(Ty);
} else if (lval == Expr::LV_MemberFunction) {
// If it's an instance method, make a member pointer.
// The expression must have exactly the form &A::foo.
@@ -14652,7 +14660,7 @@
Diag(OpLoc, diag::err_typecheck_addrof_dtor) << op->getSourceRange();
QualType MPTy = Context.getMemberPointerType(
- op->getType(), Context.getTypeDeclType(MD->getParent()).getTypePtr());
+ Ty, Context.getTypeDeclType(MD->getParent()).getTypePtr());
// Under the MS ABI, lock down the inheritance model now.
if (Context.getTargetInfo().getCXXABI().isMicrosoft())
(void)isCompleteType(OpLoc, MPTy);
@@ -14660,7 +14668,7 @@
} else if (lval != Expr::LV_Valid && lval != Expr::LV_IncompleteVoidType) {
// C99 6.5.3.2p1
// The operand must be either an l-value or a function designator
- if (!op->getType()->isFunctionType()) {
+ if (!Ty->isFunctionType()) {
// Use a special diagnostic for loads from property references.
if (isa<PseudoObjectExpr>(op)) {
AddressOfError = AO_Property_Expansion;
@@ -14711,8 +14719,7 @@
Ctx = Ctx->getParent();
QualType MPTy = Context.getMemberPointerType(
- op->getType(),
- Context.getTypeDeclType(cast<RecordDecl>(Ctx)).getTypePtr());
+ Ty, Context.getTypeDeclType(cast<RecordDecl>(Ctx)).getTypePtr());
// Under the MS ABI, lock down the inheritance model now.
if (Context.getTargetInfo().getCXXABI().isMicrosoft())
(void)isCompleteType(OpLoc, MPTy);
@@ -14737,12 +14744,12 @@
}
// If the operand has type "type", the result has type "pointer to type".
- if (op->getType()->isObjCObjectType())
- return Context.getObjCObjectPointerType(op->getType());
+ if (Ty->isObjCObjectType())
+ return Context.getObjCObjectPointerType(Ty);
CheckAddressOfPackedMember(op);
- return Context.getPointerType(op->getType());
+ return Context.getPointerType(Ty);
}
static void RecordModifiableNonNullParam(Sema &S, const Expr *Exp) {
Index: clang/include/clang/AST/ASTContext.h
===================================================================
--- clang/include/clang/AST/ASTContext.h
+++ clang/include/clang/AST/ASTContext.h
@@ -2151,6 +2151,18 @@
return getQualifiedType(type.getUnqualifiedType(), Qs);
}
+ /// Return a type without the optional qualifier.
+ QualType getNonOptionalType(QualType type) const {
+ if (type.isLocalOptionalQualified()) {
+ type.removeLocalOptional();
+ } else if (type.isOptionalQualified()) {
+ Qualifiers Qs = type.getQualifiers();
+ Qs.removeOptional();
+ type = getQualifiedType(type.getUnqualifiedType(), Qs);
+ }
+ return type;
+ }
+
unsigned char getFixedPointScale(QualType Ty) const;
unsigned char getFixedPointIBits(QualType Ty) const;
llvm::FixedPointSemantics getFixedPointSemantics(QualType Ty) const;
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