P0012R1: Make exception specifications be part of the type system. This
implements the bulk of the change (modifying the type system to include
exception specifications), but not all the details just yet.
llvm-svn: 284337
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 709de43..34eced3 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -3193,6 +3193,34 @@
return CanResultType;
}
+static bool isCanonicalExceptionSpecification(
+ const FunctionProtoType::ExceptionSpecInfo &ESI, bool NoexceptInType) {
+ if (ESI.Type == EST_None)
+ return true;
+ if (!NoexceptInType)
+ return false;
+
+ // C++17 onwards: exception specification is part of the type, as a simple
+ // boolean "can this function type throw".
+ if (ESI.Type == EST_BasicNoexcept)
+ return true;
+
+ // A dynamic exception specification is canonical if it only contains pack
+ // expansions (so we can't tell whether it's non-throwing).
+ if (ESI.Type == EST_Dynamic) {
+ for (QualType ET : ESI.Exceptions)
+ if (!ET->getAs<PackExpansionType>())
+ return false;
+ return true;
+ }
+
+ // A noexcept(expr) specification is canonical if expr is value-dependent.
+ if (ESI.Type == EST_ComputedNoexcept)
+ return ESI.NoexceptExpr && ESI.NoexceptExpr->isValueDependent();
+
+ return false;
+}
+
QualType
ASTContext::getFunctionType(QualType ResultTy, ArrayRef<QualType> ArgArray,
const FunctionProtoType::ExtProtoInfo &EPI) const {
@@ -3209,10 +3237,14 @@
FunctionProtoTypes.FindNodeOrInsertPos(ID, InsertPos))
return QualType(FTP, 0);
+ bool NoexceptInType = getLangOpts().CPlusPlus1z;
+
+ bool IsCanonicalExceptionSpec =
+ isCanonicalExceptionSpecification(EPI.ExceptionSpec, NoexceptInType);
+
// Determine whether the type being created is already canonical or not.
- bool isCanonical =
- EPI.ExceptionSpec.Type == EST_None && isCanonicalResultType(ResultTy) &&
- !EPI.HasTrailingReturn;
+ bool isCanonical = IsCanonicalExceptionSpec &&
+ isCanonicalResultType(ResultTy) && !EPI.HasTrailingReturn;
for (unsigned i = 0; i != NumArgs && isCanonical; ++i)
if (!ArgArray[i].isCanonicalAsParam())
isCanonical = false;
@@ -3228,7 +3260,45 @@
FunctionProtoType::ExtProtoInfo CanonicalEPI = EPI;
CanonicalEPI.HasTrailingReturn = false;
- CanonicalEPI.ExceptionSpec = FunctionProtoType::ExceptionSpecInfo();
+
+ if (IsCanonicalExceptionSpec) {
+ // Exception spec is already OK.
+ } else if (NoexceptInType) {
+ switch (EPI.ExceptionSpec.Type) {
+ case EST_Unparsed: case EST_Unevaluated: case EST_Uninstantiated:
+ // We don't know yet. It shouldn't matter what we pick here; no-one
+ // should ever look at this.
+ LLVM_FALLTHROUGH;
+ case EST_None: case EST_MSAny: case EST_Dynamic:
+ // If we get here for EST_Dynamic, there is at least one
+ // non-pack-expansion type, so this is not non-throwing.
+ CanonicalEPI.ExceptionSpec.Type = EST_None;
+ break;
+
+ case EST_DynamicNone: case EST_BasicNoexcept:
+ CanonicalEPI.ExceptionSpec.Type = EST_BasicNoexcept;
+ break;
+
+ case EST_ComputedNoexcept:
+ llvm::APSInt Value(1);
+ auto *E = CanonicalEPI.ExceptionSpec.NoexceptExpr;
+ if (!E || !E->isIntegerConstantExpr(Value, *this, nullptr,
+ /*IsEvaluated*/false)) {
+ // This noexcept specification is invalid.
+ // FIXME: Should this be able to happen?
+ CanonicalEPI.ExceptionSpec.Type = EST_None;
+ break;
+ }
+
+ CanonicalEPI.ExceptionSpec.Type =
+ Value.getBoolValue() ? EST_BasicNoexcept : EST_None;
+ break;
+ }
+ assert(isCanonicalExceptionSpecification(CanonicalEPI.ExceptionSpec,
+ NoexceptInType));
+ } else {
+ CanonicalEPI.ExceptionSpec = FunctionProtoType::ExceptionSpecInfo();
+ }
// Adjust the canonical function result type.
CanQualType CanResultTy = getCanonicalFunctionResultType(ResultTy);
diff --git a/clang/lib/AST/Type.cpp b/clang/lib/AST/Type.cpp
index 113974c..2601fa4 100644
--- a/clang/lib/AST/Type.cpp
+++ b/clang/lib/AST/Type.cpp
@@ -2717,8 +2717,9 @@
QualType *exnSlot = argSlot + NumParams;
unsigned I = 0;
for (QualType ExceptionType : epi.ExceptionSpec.Exceptions) {
- // Note that a dependent exception specification does *not* make
- // a type dependent; it's not even part of the C++ type system.
+ // Note that, before C++17, a dependent exception specification does
+ // *not* make a type dependent; it's not even part of the C++ type
+ // system.
if (ExceptionType->isInstantiationDependentType())
setInstantiationDependent();
@@ -2757,6 +2758,19 @@
slot[0] = epi.ExceptionSpec.SourceDecl;
}
+ // If this is a canonical type, and its exception specification is dependent,
+ // then it's a dependent type. This only happens in C++17 onwards.
+ if (isCanonicalUnqualified()) {
+ if (getExceptionSpecType() == EST_Dynamic ||
+ getExceptionSpecType() == EST_ComputedNoexcept) {
+ assert(hasDependentExceptionSpec() && "type should not be canonical");
+ setDependent();
+ }
+ } else if (getCanonicalTypeInternal()->isDependentType()) {
+ // Ask our canonical type whether our exception specification was dependent.
+ setDependent();
+ }
+
if (epi.ExtParameterInfos) {
ExtParameterInfo *extParamInfos =
const_cast<ExtParameterInfo *>(getExtParameterInfosBuffer());
@@ -2801,29 +2815,28 @@
return value.getBoolValue() ? NR_Nothrow : NR_Throw;
}
-bool FunctionProtoType::isNothrow(const ASTContext &Ctx,
- bool ResultIfDependent) const {
+CanThrowResult FunctionProtoType::canThrow(const ASTContext &Ctx) const {
ExceptionSpecificationType EST = getExceptionSpecType();
assert(EST != EST_Unevaluated && EST != EST_Uninstantiated);
if (EST == EST_DynamicNone || EST == EST_BasicNoexcept)
- return true;
+ return CT_Cannot;
- if (EST == EST_Dynamic && ResultIfDependent) {
+ if (EST == EST_Dynamic) {
// A dynamic exception specification is throwing unless every exception
// type is an (unexpanded) pack expansion type.
for (unsigned I = 0, N = NumExceptions; I != N; ++I)
if (!getExceptionType(I)->getAs<PackExpansionType>())
- return false;
- return ResultIfDependent;
+ return CT_Can;
+ return CT_Dependent;
}
if (EST != EST_ComputedNoexcept)
- return false;
+ return CT_Can;
NoexceptResult NR = getNoexceptSpec(Ctx);
if (NR == NR_Dependent)
- return ResultIfDependent;
- return NR == NR_Nothrow;
+ return CT_Dependent;
+ return NR == NR_Nothrow ? CT_Cannot : CT_Can;
}
bool FunctionProtoType::isTemplateVariadic() const {
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index efdf8a3..54b56b3 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -2933,10 +2933,20 @@
}
if (getLangOpts().CPlusPlus) {
- // (C++98 13.1p2):
+ // C++1z [over.load]p2
// Certain function declarations cannot be overloaded:
- // -- Function declarations that differ only in the return type
- // cannot be overloaded.
+ // -- Function declarations that differ only in the return type,
+ // the exception specification, or both cannot be overloaded.
+
+ // Check the exception specifications match. This may recompute the type of
+ // both Old and New if it resolved exception specifications, so grab the
+ // types again after this. Because this updates the type, we do this before
+ // any of the other checks below, which may update the "de facto" NewQType
+ // but do not necessarily update the type of New.
+ if (CheckEquivalentExceptionSpec(Old, New))
+ return true;
+ OldQType = Context.getCanonicalType(Old->getType());
+ NewQType = Context.getCanonicalType(New->getType());
// Go back to the type source info to compare the declared return types,
// per C++1y [dcl.type.auto]p13:
@@ -2951,10 +2961,10 @@
(New->getTypeSourceInfo()
? New->getTypeSourceInfo()->getType()->castAs<FunctionType>()
: NewType)->getReturnType();
- QualType ResQT;
if (!Context.hasSameType(OldDeclaredReturnType, NewDeclaredReturnType) &&
!((NewQType->isDependentType() || OldQType->isDependentType()) &&
New->isLocalExternDecl())) {
+ QualType ResQT;
if (NewDeclaredReturnType->isObjCObjectPointerType() &&
OldDeclaredReturnType->isObjCObjectPointerType())
ResQT = Context.mergeObjCGCQualifiers(NewQType, OldQType);
@@ -3092,7 +3102,7 @@
// noreturn should now match unless the old type info didn't have it.
QualType OldQTypeForComparison = OldQType;
if (!OldTypeInfo.getNoReturn() && NewTypeInfo.getNoReturn()) {
- assert(OldQType == QualType(OldType, 0));
+ auto *OldType = OldQType->castAs<FunctionProtoType>();
const FunctionType *OldTypeForComparison
= Context.adjustFunctionType(OldType, OldTypeInfo.withNoReturn(true));
OldQTypeForComparison = QualType(OldTypeForComparison, 0);
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 93e626f..f86b793 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -659,9 +659,6 @@
Invalid = true;
}
- if (CheckEquivalentExceptionSpec(Old, New))
- Invalid = true;
-
return Invalid;
}
diff --git a/clang/lib/Sema/SemaExceptionSpec.cpp b/clang/lib/Sema/SemaExceptionSpec.cpp
index f8e75b2..a81ef51 100644
--- a/clang/lib/Sema/SemaExceptionSpec.cpp
+++ b/clang/lib/Sema/SemaExceptionSpec.cpp
@@ -130,6 +130,11 @@
/// to member to a function with an exception specification. This means that
/// it is invalid to add another level of indirection.
bool Sema::CheckDistantExceptionSpec(QualType T) {
+ // C++17 removes this rule in favor of putting exception specifications into
+ // the type system.
+ if (getLangOpts().CPlusPlus1z)
+ return false;
+
if (const PointerType *PT = T->getAs<PointerType>())
T = PT->getPointeeType();
else if (const MemberPointerType *PT = T->getAs<MemberPointerType>())
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index ec7f7bc..206a704 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -7288,7 +7288,7 @@
return Sema::IncompatiblePointer;
}
if (!S.getLangOpts().CPlusPlus &&
- S.IsNoReturnConversion(ltrans, rtrans, ltrans))
+ S.IsFunctionConversion(ltrans, rtrans, ltrans))
return Sema::IncompatiblePointer;
return ConvTy;
}
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 4de7fc3..56f5934 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -3610,7 +3610,7 @@
// Nothing else to do.
break;
- case ICK_NoReturn_Adjustment:
+ case ICK_Function_Conversion:
// If both sides are functions (or pointers/references to them), there could
// be incompatible exception declarations.
if (CheckExceptionSpecCompatibility(From, ToType))
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 082a6f9..460e53f 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -150,7 +150,7 @@
"Lvalue-to-rvalue",
"Array-to-pointer",
"Function-to-pointer",
- "Noreturn adjustment",
+ "Function pointer conversion",
"Qualification",
"Integral promotion",
"Floating point promotion",
@@ -1390,13 +1390,15 @@
}
/// \brief Determine whether the conversion from FromType to ToType is a valid
-/// conversion that strips "noreturn" off the nested function type.
-bool Sema::IsNoReturnConversion(QualType FromType, QualType ToType,
+/// conversion that strips "noexcept" or "noreturn" off the nested function
+/// type.
+bool Sema::IsFunctionConversion(QualType FromType, QualType ToType,
QualType &ResultTy) {
if (Context.hasSameUnqualifiedType(FromType, ToType))
return false;
// Permit the conversion F(t __attribute__((noreturn))) -> F(t)
+ // or F(t noexcept) -> F(t)
// where F adds one of the following at most once:
// - a pointer
// - a member pointer
@@ -1425,11 +1427,37 @@
return false;
}
- const FunctionType *FromFn = cast<FunctionType>(CanFrom);
- FunctionType::ExtInfo EInfo = FromFn->getExtInfo();
- if (!EInfo.getNoReturn()) return false;
+ const auto *FromFn = cast<FunctionType>(CanFrom);
+ FunctionType::ExtInfo FromEInfo = FromFn->getExtInfo();
- FromFn = Context.adjustFunctionType(FromFn, EInfo.withNoReturn(false));
+ const auto *ToFn = dyn_cast<FunctionProtoType>(CanTo);
+ FunctionType::ExtInfo ToEInfo = ToFn->getExtInfo();
+
+ bool Changed = false;
+
+ // Drop 'noreturn' if not present in target type.
+ if (FromEInfo.getNoReturn() && !ToEInfo.getNoReturn()) {
+ FromFn = Context.adjustFunctionType(FromFn, FromEInfo.withNoReturn(false));
+ Changed = true;
+ }
+
+ // Drop 'noexcept' if not present in target type.
+ if (const auto *FromFPT = dyn_cast<FunctionProtoType>(FromFn)) {
+ const auto *ToFPT = dyn_cast<FunctionProtoType>(ToFn);
+ if (FromFPT->isNothrow(Context) && !ToFPT->isNothrow(Context)) {
+ FromFn = cast<FunctionType>(
+ Context.getFunctionType(FromFPT->getReturnType(),
+ FromFPT->getParamTypes(),
+ FromFPT->getExtProtoInfo().withExceptionSpec(
+ FunctionProtoType::ExceptionSpecInfo()))
+ .getTypePtr());
+ Changed = true;
+ }
+ }
+
+ if (!Changed)
+ return false;
+
assert(QualType(FromFn, 0).isCanonical());
if (QualType(FromFn, 0) != CanTo) return false;
@@ -1534,7 +1562,7 @@
S.ExtractUnqualifiedFunctionType(ToType), FromType)) {
QualType resultTy;
// if the function type matches except for [[noreturn]], it's ok
- if (!S.IsNoReturnConversion(FromType,
+ if (!S.IsFunctionConversion(FromType,
S.ExtractUnqualifiedFunctionType(ToType), resultTy))
// otherwise, only a boolean conversion is standard
if (!ToType->isBooleanType())
@@ -1727,9 +1755,10 @@
// Compatible conversions (Clang extension for C function overloading)
SCS.Second = ICK_Compatible_Conversion;
FromType = ToType.getUnqualifiedType();
- } else if (S.IsNoReturnConversion(FromType, ToType, FromType)) {
- // Treat a conversion that strips "noreturn" as an identity conversion.
- SCS.Second = ICK_NoReturn_Adjustment;
+ } else if (S.IsFunctionConversion(FromType, ToType, FromType)) {
+ // Function pointer conversions (removing 'noexcept') including removal of
+ // 'noreturn' (Clang extension).
+ SCS.Second = ICK_Function_Conversion;
} else if (IsTransparentUnionStandardConversion(S, From, ToType,
InOverloadResolution,
SCS, CStyle)) {
@@ -2615,7 +2644,8 @@
ft_parameter_arity,
ft_parameter_mismatch,
ft_return_type,
- ft_qualifer_mismatch
+ ft_qualifer_mismatch,
+ ft_noexcept
};
/// Attempts to get the FunctionProtoType from a Type. Handles
@@ -2715,6 +2745,16 @@
return;
}
+ // Handle exception specification differences on canonical type (in C++17
+ // onwards).
+ if (cast<FunctionProtoType>(FromFunction->getCanonicalTypeUnqualified())
+ ->isNothrow(Context) !=
+ cast<FunctionProtoType>(ToFunction->getCanonicalTypeUnqualified())
+ ->isNothrow(Context)) {
+ PDiag << ft_noexcept;
+ return;
+ }
+
// Unable to find a difference, so add no extra info.
PDiag << ft_default;
}
@@ -5096,7 +5136,7 @@
// conversions are fine.
switch (SCS.Second) {
case ICK_Identity:
- case ICK_NoReturn_Adjustment:
+ case ICK_Function_Conversion:
case ICK_Integral_Promotion:
case ICK_Integral_Conversion: // Narrowing conversions are checked elsewhere.
return true;
@@ -10428,7 +10468,7 @@
bool candidateHasExactlyCorrectType(const FunctionDecl *FD) {
QualType Discard;
return Context.hasSameUnqualifiedType(TargetFunctionType, FD->getType()) ||
- S.IsNoReturnConversion(FD->getType(), TargetFunctionType, Discard);
+ S.IsFunctionConversion(FD->getType(), TargetFunctionType, Discard);
}
/// \return true if A is considered a better overload candidate for the
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 4f76a02..2e4b9ca 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -956,9 +956,9 @@
if (!ParamFunction || !ArgFunction)
return Param == Arg;
- // Noreturn adjustment.
+ // Noreturn and noexcept adjustment.
QualType AdjustedParam;
- if (IsNoReturnConversion(Param, Arg, AdjustedParam))
+ if (IsFunctionConversion(Param, Arg, AdjustedParam))
return Arg == Context.getCanonicalType(AdjustedParam);
// FIXME: Compatible calling conventions.
@@ -2757,18 +2757,17 @@
}
// - The transformed A can be another pointer or pointer to member
- // type that can be converted to the deduced A via a qualification
- // conversion.
+ // type that can be converted to the deduced A via a function pointer
+ // conversion and/or a qualification conversion.
//
// Also allow conversions which merely strip [[noreturn]] from function types
// (recursively) as an extension.
- // FIXME: Currently, this doesn't play nicely with qualification conversions.
bool ObjCLifetimeConversion = false;
QualType ResultTy;
if ((A->isAnyPointerType() || A->isMemberPointerType()) &&
(S.IsQualificationConversion(A, DeducedA, false,
ObjCLifetimeConversion) ||
- S.IsNoReturnConversion(A, DeducedA, ResultTy)))
+ S.IsFunctionConversion(A, DeducedA, ResultTy)))
return false;
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index cfbfc3b..b1daab4 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -4142,7 +4142,7 @@
// Exception specs are not allowed in typedefs. Complain, but add it
// anyway.
- if (IsTypedefName && FTI.getExceptionSpecType())
+ if (IsTypedefName && FTI.getExceptionSpecType() && !LangOpts.CPlusPlus1z)
S.Diag(FTI.getExceptionSpecLocBeg(),
diag::err_exception_spec_in_typedef)
<< (D.getContext() == Declarator::AliasDeclContext ||
