Implement semantic checking of static_cast and dynamic_cast.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@58509 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaExprCXX.cpp b/lib/Sema/SemaExprCXX.cpp
index 209914b..2c5c264 100644
--- a/lib/Sema/SemaExprCXX.cpp
+++ b/lib/Sema/SemaExprCXX.cpp
@@ -12,6 +12,7 @@
//===----------------------------------------------------------------------===//
#include "Sema.h"
+#include "SemaInherit.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ASTContext.h"
#include "clang/Parse/DeclSpec.h"
@@ -40,6 +41,8 @@
DestType, OpLoc);
case tok::kw_dynamic_cast:
+ CheckDynamicCast(OpLoc, Ex, DestType,
+ SourceRange(LAngleBracketLoc, RAngleBracketLoc));
return new CXXDynamicCastExpr(DestType.getNonReferenceType(), Ex,
DestType, OpLoc);
@@ -49,10 +52,11 @@
DestType, OpLoc);
case tok::kw_static_cast:
+ CheckStaticCast(OpLoc, Ex, DestType);
return new CXXStaticCastExpr(DestType.getNonReferenceType(), Ex,
DestType, OpLoc);
}
-
+
return true;
}
@@ -325,41 +329,347 @@
}
/// CheckStaticCast - Check that a static_cast\<DestType\>(SrcExpr) is valid.
+/// Refer to C++ 5.2.9 for details. Static casts are mostly used for making
+/// implicit conversions explicit and getting rid of data loss warnings.
void
Sema::CheckStaticCast(SourceLocation OpLoc, Expr *&SrcExpr, QualType DestType)
{
-#if 0
- // 5.2.9/1 sets the ground rule of disallowing casting away constness.
- // 5.2.9/2 permits everything allowed for direct-init, deferring to 8.5.
- // Note: for class destination, that's overload resolution over dest's
- // constructors. Src's conversions are only considered in overload choice.
- // For any other destination, that's just the clause 4 standards convs.
- // 5.2.9/4 permits static_cast<cv void>(anything), which is a no-op.
- // 5.2.9/5 permits explicit non-dynamic downcasts for lvalue-to-reference.
- // 5.2.9/6 permits reversing all implicit conversions except lvalue-to-rvalue,
- // function-to-pointer, array decay and to-bool, with some further
- // restrictions. Defers to 4.
- // 5.2.9/7 permits integer-to-enum conversion. Interesting note: if the
- // integer does not correspond to an enum value, the result is unspecified -
- // but it still has to be some value of the enum. I don't think any compiler
- // complies with that.
- // 5.2.9/8 is 5.2.9/5 for pointers.
- // 5.2.9/9 messes with member pointers. TODO. No need to think about that yet.
- // 5.2.9/10 permits void* to T*.
-
QualType OrigDestType = DestType, OrigSrcType = SrcExpr->getType();
- DestType = Context.getCanonicalType(DestType);
- // Tests are ordered by simplicity and a wild guess at commonness.
- if (const BuiltinType *BuiltinDest = DestType->getAsBuiltinType()) {
- // 5.2.9/4
- if (BuiltinDest->getKind() == BuiltinType::Void) {
+ // Conversions are tried roughly in the order the standard specifies them.
+ // This is necessary because there are some conversions that can be
+ // interpreted in more than one way, and the order disambiguates.
+ // DR 427 specifies that paragraph 5 is to be applied before paragraph 2.
+
+ // This option is unambiguous and simple, so put it here.
+ // C++ 5.2.9p4: Any expression can be explicitly converted to type "cv void".
+ if (DestType->isVoidType()) {
+ return;
+ }
+
+ DestType = Context.getCanonicalType(DestType);
+
+ // C++ 5.2.9p5, reference downcast.
+ // See the function for details.
+ if (IsStaticReferenceDowncast(SrcExpr, DestType)) {
+ return;
+ }
+
+ // C++ 5.2.9p2: An expression e can be explicitly converted to a type T
+ // [...] if the declaration "T t(e);" is well-formed, [...].
+ ImplicitConversionSequence ICS = TryDirectInitialization(SrcExpr, DestType);
+ if (ICS.ConversionKind != ImplicitConversionSequence::BadConversion) {
+ if (ICS.ConversionKind == ImplicitConversionSequence::StandardConversion &&
+ ICS.Standard.First != ICK_Identity)
+ {
+ DefaultFunctionArrayConversion(SrcExpr);
+ }
+ return;
+ }
+ // FIXME: Missing the validation of the conversion, e.g. for an accessible
+ // base.
+
+ // C++ 5.2.9p6: May apply the reverse of any standard conversion, except
+ // lvalue-to-rvalue, array-to-pointer, function-to-pointer, and boolean
+ // conversions, subject to further restrictions.
+ // Also, C++ 5.2.9p1 forbids casting away constness, which makes reversal
+ // of qualification conversions impossible.
+
+ // The lvalue-to-rvalue, array-to-pointer and function-to-pointer conversions
+ // are applied to the expression.
+ DefaultFunctionArrayConversion(SrcExpr);
+
+ QualType SrcType = Context.getCanonicalType(SrcExpr->getType());
+
+ // Reverse integral promotion/conversion. All such conversions are themselves
+ // again integral promotions or conversions and are thus already handled by
+ // p2 (TryDirectInitialization above).
+ // (Note: any data loss warnings should be suppressed.)
+ // The exception is the reverse of enum->integer, i.e. integer->enum (and
+ // enum->enum). See also C++ 5.2.9p7.
+ // The same goes for reverse floating point promotion/conversion and
+ // floating-integral conversions. Again, only floating->enum is relevant.
+ if (DestType->isEnumeralType()) {
+ if (SrcType->isComplexType() || SrcType->isVectorType()) {
+ // Fall through - these cannot be converted.
+ } else if (SrcType->isArithmeticType() || SrcType->isEnumeralType()) {
return;
}
-
- // Primitive conversions for 5.2.9/2 and 6.
}
-#endif
+
+ // Reverse pointer upcast. C++ 4.10p3 specifies pointer upcast.
+ // C++ 5.2.9p8 additionally disallows a cast path through virtual inheritance.
+ if (IsStaticPointerDowncast(SrcType, DestType)) {
+ return;
+ }
+
+ // Reverse member pointer conversion. C++ 5.11 specifies member pointer
+ // conversion. C++ 5.2.9p9 has additional information.
+ // DR54's access restrictions apply here also.
+ // FIXME: Don't have member pointers yet.
+
+ // Reverse pointer conversion to void*. C++ 4.10.p2 specifies conversion to
+ // void*. C++ 5.2.9p10 specifies additional restrictions, which really is
+ // just the usual constness stuff.
+ if (const PointerType *SrcPointer = SrcType->getAsPointerType()) {
+ QualType SrcPointee = SrcPointer->getPointeeType();
+ if (SrcPointee->isVoidType()) {
+ if (const PointerType *DestPointer = DestType->getAsPointerType()) {
+ QualType DestPointee = DestPointer->getPointeeType();
+ if (DestPointee->isObjectType() &&
+ DestPointee.isAtLeastAsQualifiedAs(SrcPointee))
+ {
+ return;
+ }
+ }
+ }
+ }
+
+ // We tried everything. Everything! Nothing works! :-(
+ // FIXME: Error reporting could be a lot better. Should store the reason
+ // why every substep failed and, at the end, select the most specific and
+ // report that.
+ Diag(OpLoc, diag::err_bad_cxx_cast_generic, "static_cast",
+ OrigDestType.getAsString(), OrigSrcType.getAsString());
+}
+
+/// Tests whether a conversion according to C++ 5.2.9p5 is valid.
+bool
+Sema::IsStaticReferenceDowncast(Expr *SrcExpr, QualType DestType)
+{
+ // C++ 5.2.9p5: An lvalue of type "cv1 B", where B is a class type, can be
+ // cast to type "reference to cv2 D", where D is a class derived from B,
+ // if a valid standard conversion from "pointer to D" to "pointer to B"
+ // exists, cv2 >= cv1, and B is not a virtual base class of D.
+ // In addition, DR54 clarifies that the base must be accessible in the
+ // current context. Although the wording of DR54 only applies to the pointer
+ // variant of this rule, the intent is clearly for it to apply to the this
+ // conversion as well.
+
+ if (SrcExpr->isLvalue(Context) != Expr::LV_Valid) {
+ return false;
+ }
+
+ DestType = Context.getCanonicalType(DestType);
+ const ReferenceType *DestReference = DestType->getAsReferenceType();
+ if (!DestReference) {
+ return false;
+ }
+ QualType DestPointee = DestReference->getPointeeType();
+
+ QualType SrcType = Context.getCanonicalType(SrcExpr->getType());
+
+ return IsStaticDowncast(SrcType, DestPointee);
+}
+
+/// Tests whether a conversion according to C++ 5.2.9p8 is valid.
+bool
+Sema::IsStaticPointerDowncast(QualType SrcType, QualType DestType)
+{
+ // C++ 5.2.9p8: An rvalue of type "pointer to cv1 B", where B is a class
+ // type, can be converted to an rvalue of type "pointer to cv2 D", where D
+ // is a class derived from B, if a valid standard conversion from "pointer
+ // to D" to "pointer to B" exists, cv2 >= cv1, and B is not a virtual base
+ // class of D.
+ // In addition, DR54 clarifies that the base must be accessible in the
+ // current context.
+
+ SrcType = Context.getCanonicalType(SrcType);
+ const PointerType *SrcPointer = SrcType->getAsPointerType();
+ if (!SrcPointer) {
+ return false;
+ }
+
+ DestType = Context.getCanonicalType(DestType);
+ const PointerType *DestPointer = DestType->getAsPointerType();
+ if (!DestPointer) {
+ return false;
+ }
+
+ return IsStaticDowncast(SrcPointer->getPointeeType(),
+ DestPointer->getPointeeType());
+}
+
+/// IsStaticDowncast - Common functionality of IsStaticReferenceDowncast and
+/// IsStaticPointerDowncast. Tests whether a static downcast from SrcType to
+/// DestType, both of which must be canonical, is possible and allowed.
+bool
+Sema::IsStaticDowncast(QualType SrcType, QualType DestType)
+{
+ assert(SrcType->isCanonical());
+ assert(DestType->isCanonical());
+
+ if (!DestType->isRecordType()) {
+ return false;
+ }
+
+ if (!SrcType->isRecordType()) {
+ return false;
+ }
+
+ // Comparing cv is cheaper, so do it first.
+ if (!DestType.isAtLeastAsQualifiedAs(SrcType)) {
+ return false;
+ }
+
+ BasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/false,
+ /*DetectVirtual=*/true);
+ if (!IsDerivedFrom(DestType, SrcType, Paths)) {
+ return false;
+ }
+
+ if (Paths.isAmbiguous(SrcType.getUnqualifiedType())) {
+ return false;
+ }
+
+ if (Paths.getDetectedVirtual() != 0) {
+ return false;
+ }
+
+ // FIXME: Test accessibility.
+
+ return true;
+}
+
+/// TryDirectInitialization - Attempt to direct-initialize a value of the
+/// given type (DestType) from the given expression (SrcExpr), as one would
+/// do when creating an object with new with parameters. This function returns
+/// an implicit conversion sequence that can be used to perform the
+/// initialization.
+/// This routine is very similar to TryCopyInitialization; the differences
+/// between the two (C++ 8.5p12 and C++ 8.5p14) are:
+/// 1) In direct-initialization, all constructors of the target type are
+/// considered, including those marked as explicit.
+/// 2) In direct-initialization, overload resolution is performed over the
+/// constructors of the target type. In copy-initialization, overload
+/// resolution is performed over all conversion functions that result in
+/// the target type. This can lead to different functions used.
+ImplicitConversionSequence
+Sema::TryDirectInitialization(Expr *SrcExpr, QualType DestType)
+{
+ if (!DestType->isRecordType()) {
+ // For non-class types, copy and direct initialization are identical.
+ // C++ 8.5p11
+ // FIXME: Those parts should be in a common function, actually.
+ return TryCopyInitialization(SrcExpr, DestType);
+ }
+
+ // Not enough support for the rest yet, actually.
+ ImplicitConversionSequence ICS;
+ ICS.ConversionKind = ImplicitConversionSequence::BadConversion;
+ return ICS;
+}
+
+/// CheckDynamicCast - Check that a dynamic_cast\<DestType\>(SrcExpr) is valid.
+/// Refer to C++ 5.2.7 for details. Dynamic casts are used mostly for runtime-
+/// checked downcasts in class hierarchies.
+void
+Sema::CheckDynamicCast(SourceLocation OpLoc, Expr *&SrcExpr, QualType DestType,
+ const SourceRange &DestRange)
+{
+ QualType OrigDestType = DestType, OrigSrcType = SrcExpr->getType();
+ DestType = Context.getCanonicalType(DestType);
+
+ // C++ 5.2.7p1: T shall be a pointer or reference to a complete class type,
+ // or "pointer to cv void".
+
+ QualType DestPointee;
+ const PointerType *DestPointer = DestType->getAsPointerType();
+ const ReferenceType *DestReference = DestType->getAsReferenceType();
+ if (DestPointer) {
+ DestPointee = DestPointer->getPointeeType();
+ } else if (DestReference) {
+ DestPointee = DestReference->getPointeeType();
+ } else {
+ Diag(OpLoc, diag::err_bad_dynamic_cast_operand,
+ OrigDestType.getAsString(), "not a reference or pointer", DestRange);
+ return;
+ }
+
+ const RecordType *DestRecord = DestPointee->getAsRecordType();
+ if (DestPointee->isVoidType()) {
+ assert(DestPointer && "Reference to void is not possible");
+ } else if (DestRecord) {
+ if (!DestRecord->getDecl()->isDefinition()) {
+ Diag(OpLoc, diag::err_bad_dynamic_cast_operand,
+ DestPointee.getUnqualifiedType().getAsString(),
+ "incomplete", DestRange);
+ return;
+ }
+ } else {
+ Diag(OpLoc, diag::err_bad_dynamic_cast_operand,
+ DestPointee.getUnqualifiedType().getAsString(),
+ "not a class", DestRange);
+ return;
+ }
+
+ // C++ 5.2.7p2: If T is a pointer type, v shall be an rvalue of a pointer to
+ // complete class type, [...]. If T is a reference type, v shall be an
+ // lvalue of a complete class type, [...].
+
+ QualType SrcType = Context.getCanonicalType(OrigSrcType);
+ QualType SrcPointee;
+ if (DestPointer) {
+ if (const PointerType *SrcPointer = SrcType->getAsPointerType()) {
+ SrcPointee = SrcPointer->getPointeeType();
+ } else {
+ Diag(OpLoc, diag::err_bad_dynamic_cast_operand,
+ OrigSrcType.getAsString(), "not a pointer", SrcExpr->getSourceRange());
+ return;
+ }
+ } else {
+ if (SrcExpr->isLvalue(Context) != Expr::LV_Valid) {
+ Diag(OpLoc, diag::err_bad_dynamic_cast_operand,
+ OrigDestType.getAsString(), "not an lvalue", SrcExpr->getSourceRange());
+ }
+ SrcPointee = SrcType;
+ }
+
+ const RecordType *SrcRecord = SrcPointee->getAsRecordType();
+ if (SrcRecord) {
+ if (!SrcRecord->getDecl()->isDefinition()) {
+ Diag(OpLoc, diag::err_bad_dynamic_cast_operand,
+ SrcPointee.getUnqualifiedType().getAsString(), "incomplete",
+ SrcExpr->getSourceRange());
+ return;
+ }
+ } else {
+ Diag(OpLoc, diag::err_bad_dynamic_cast_operand,
+ SrcPointee.getUnqualifiedType().getAsString(), "not a class",
+ SrcExpr->getSourceRange());
+ return;
+ }
+
+ // Assumptions to this point.
+ assert(DestPointer || DestReference);
+ assert(DestRecord || DestPointee->isVoidType());
+ assert(SrcRecord);
+
+ // C++ 5.2.7p1: The dynamic_cast operator shall not cast away constness.
+ if (!DestPointee.isAtLeastAsQualifiedAs(SrcPointee)) {
+ Diag(OpLoc, diag::err_bad_cxx_cast_const_away, "dynamic_cast",
+ OrigDestType.getAsString(), OrigSrcType.getAsString());
+ return;
+ }
+
+ // C++ 5.2.7p3: If the type of v is the same as the required result type,
+ // [except for cv].
+ if (DestRecord == SrcRecord) {
+ return;
+ }
+
+ // C++ 5.2.7p5
+ // Upcasts are resolved statically.
+ if (DestRecord && IsDerivedFrom(SrcPointee, DestPointee)) {
+ CheckDerivedToBaseConversion(SrcPointee, DestPointee, OpLoc, SourceRange());
+ // Diagnostic already emitted on error.
+ return;
+ }
+
+ // C++ 5.2.7p6: Otherwise, v shall be [polymorphic].
+ // FIXME: Information not yet available.
+
+ // Done. Everything else is run-time checks.
}
/// ActOnCXXBoolLiteral - Parse {true,false} literals.