Initial implementation of function overloading in C.
This commit adds a new attribute, "overloadable", that enables C++
function overloading in C. The attribute can only be added to function
declarations, e.g.,
int *f(int) __attribute__((overloadable));
If the "overloadable" attribute exists on a function with a given
name, *all* functions with that name (and in that scope) must have the
"overloadable" attribute. Sets of overloaded functions with the
"overloadable" attribute then follow the normal C++ rules for
overloaded functions, e.g., overloads must have different
parameter-type-lists from each other.
When calling an overloaded function in C, we follow the same
overloading rules as C++, with three extensions to the set of standard
conversions:
- A value of a given struct or union type T can be converted to the
type T. This is just the identity conversion. (In C++, this would
go through a copy constructor).
- A value of pointer type T* can be converted to a value of type U*
if T and U are compatible types. This conversion has Conversion
rank (it's considered a pointer conversion in C).
- A value of type T can be converted to a value of type U if T and U
are compatible (and are not both pointer types). This conversion
has Conversion rank (it's considered to be a new kind of
conversion unique to C, a "compatible" conversion).
Known defects (and, therefore, next steps):
1) The standard-conversion handling does not understand conversions
involving _Complex or vector extensions, so it is likely to get
these wrong. We need to add these conversions.
2) All overloadable functions with the same name will have the same
linkage name, which means we'll get a collision in the linker (if
not sooner). We'll need to mangle the names of these functions.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@64336 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Parse/AttributeList.cpp b/lib/Parse/AttributeList.cpp
index eb0527d..954e93e 100644
--- a/lib/Parse/AttributeList.cpp
+++ b/lib/Parse/AttributeList.cpp
@@ -98,6 +98,9 @@
if (!memcmp(Str, "constructor", 11)) return AT_constructor;
if (!memcmp(Str, "unavailable", 11)) return AT_unavailable;
break;
+ case 12:
+ if (!memcmp(Str, "overloadable", 12)) return AT_overloadable;
+ break;
case 13:
if (!memcmp(Str, "address_space", 13)) return AT_address_space;
if (!memcmp(Str, "always_inline", 13)) return AT_always_inline;
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index a3e0232..de06ca6 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -113,6 +113,25 @@
CurContext = getContainingDC(CurContext);
}
+/// \brief Determine whether we allow overloading of the function
+/// PrevDecl with another declaration.
+///
+/// This routine determines whether overloading is possible, not
+/// whether some new function is actually an overload. It will return
+/// true in C++ (where we can always provide overloads) or, as an
+/// extension, in C when the previous function is already an
+/// overloaded function declaration or has the "overloadable"
+/// attribute.
+static bool AllowOverloadingOfFunction(Decl *PrevDecl, ASTContext &Context) {
+ if (Context.getLangOptions().CPlusPlus)
+ return true;
+
+ if (isa<OverloadedFunctionDecl>(PrevDecl))
+ return true;
+
+ return PrevDecl->getAttr<OverloadableAttr>() != 0;
+}
+
/// Add this decl to the scope shadowed decl chains.
void Sema::PushOnScopeChains(NamedDecl *D, Scope *S) {
// Move up the scope chain until we find the nearest enclosing
@@ -173,7 +192,8 @@
return;
}
}
- } else if (getLangOptions().CPlusPlus && isa<FunctionDecl>(D)) {
+ } else if (isa<FunctionDecl>(D) &&
+ AllowOverloadingOfFunction(D, Context)) {
// We are pushing the name of a function, which might be an
// overloaded name.
FunctionDecl *FD = cast<FunctionDecl>(D);
@@ -1637,15 +1657,16 @@
// Merge the decl with the existing one if appropriate. Since C functions
// are in a flat namespace, make sure we consider decls in outer scopes.
+ bool OverloadableAttrRequired = false;
bool Redeclaration = false;
if (PrevDecl &&
(!getLangOptions().CPlusPlus||isDeclInScope(PrevDecl, DC, S))) {
- // If C++, determine whether NewFD is an overload of PrevDecl or
+ // Determine whether NewFD is an overload of PrevDecl or
// a declaration that requires merging. If it's an overload,
// there's no more work to do here; we'll just add the new
// function to the scope.
OverloadedFunctionDecl::function_iterator MatchedDecl;
- if (!getLangOptions().CPlusPlus ||
+ if (!AllowOverloadingOfFunction(PrevDecl, Context) ||
!IsOverload(NewFD, PrevDecl, MatchedDecl)) {
Decl *OldDecl = PrevDecl;
@@ -1672,6 +1693,12 @@
}
}
}
+
+ // If we're in C, this new declaration better have the
+ // "overloadable" attribute on it.
+ if (!getLangOptions().CPlusPlus &&
+ PrevDecl->getAttr<OverloadableAttr>())
+ OverloadableAttrRequired = true;
}
if (D.getCXXScopeSpec().isSet() &&
@@ -1712,6 +1739,17 @@
// (for example to check for conflicts, etc).
ProcessDeclAttributes(NewFD, D);
+ if (OverloadableAttrRequired && !NewFD->getAttr<OverloadableAttr>()) {
+ // If a function name is overloadable in C, then every function
+ // with that name must be marked "overloadable".
+ Diag(NewFD->getLocation(), diag::err_attribute_overloadable_missing)
+ << NewFD;
+ if (PrevDecl)
+ Diag(PrevDecl->getLocation(),
+ diag::note_attribute_overloadable_prev_overload);
+ NewFD->addAttr(new OverloadableAttr);
+ }
+
if (getLangOptions().CPlusPlus) {
// In C++, check default arguments now that we have merged decls. Unless
// the lexical context is the class, because in this case this is done
diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index 2a6da06..b4e3dd9 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -593,6 +593,21 @@
d->addAttr(new ObjCNSObjectAttr);
}
+static void
+HandleOverloadableAttr(Decl *D, const AttributeList &Attr, Sema &S) {
+ if (Attr.getNumArgs() != 0) {
+ S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments) << 1;
+ return;
+ }
+
+ if (!isa<FunctionDecl>(D)) {
+ S.Diag(Attr.getLoc(), diag::err_attribute_overloadable_not_function);
+ return;
+ }
+
+ D->addAttr(new OverloadableAttr);
+}
+
static void HandleBlocksAttr(Decl *d, const AttributeList &Attr, Sema &S) {
if (!Attr.getParameterName()) {
S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_string)
@@ -1301,6 +1316,7 @@
HandleTransparentUnionAttr(D, Attr, S);
break;
case AttributeList::AT_objc_gc: HandleObjCGCAttr (D, Attr, S); break;
+ case AttributeList::AT_overloadable:HandleOverloadableAttr(D, Attr, S); break;
case AttributeList::AT_nsobject: HandleObjCNSObject (D, Attr, S); break;
case AttributeList::AT_blocks: HandleBlocksAttr (D, Attr, S); break;
case AttributeList::AT_sentinel: HandleSentinelAttr (D, Attr, S); break;
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index c2051a5..4ac7214 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -1909,12 +1909,16 @@
Ovl = dyn_cast<OverloadedFunctionDecl>(DRExpr->getDecl());
}
- if (getLangOptions().CPlusPlus && (FDecl || Ovl || UnqualifiedName)) {
+ if (Ovl || (getLangOptions().CPlusPlus && (FDecl || UnqualifiedName))) {
// We don't perform ADL for builtins.
if (FDecl && FDecl->getIdentifier() &&
FDecl->getIdentifier()->getBuiltinID())
ADL = false;
+ // We don't perform ADL in C.
+ if (!getLangOptions().CPlusPlus)
+ ADL = false;
+
if (Ovl || ADL) {
FDecl = ResolveOverloadedCallFn(Fn, DRExpr? DRExpr->getDecl() : 0,
UnqualifiedName, LParenLoc, Args,
diff --git a/lib/Sema/SemaExprCXX.cpp b/lib/Sema/SemaExprCXX.cpp
index 4bfd4fa..6ce8331 100644
--- a/lib/Sema/SemaExprCXX.cpp
+++ b/lib/Sema/SemaExprCXX.cpp
@@ -809,6 +809,8 @@
case ICK_Integral_Conversion:
case ICK_Floating_Conversion:
case ICK_Floating_Integral:
+ case ICK_Compatible_Conversion:
+ // FIXME: Go deeper to get the unqualified type!
FromType = ToType.getUnqualifiedType();
ImpCastExprToType(From, FromType);
break;
diff --git a/lib/Sema/SemaLookup.cpp b/lib/Sema/SemaLookup.cpp
index ee4c14d..f4bfe5c 100644
--- a/lib/Sema/SemaLookup.cpp
+++ b/lib/Sema/SemaLookup.cpp
@@ -776,8 +776,29 @@
for (IdentifierResolver::iterator I = IdResolver.begin(Name),
IEnd = IdResolver.end();
I != IEnd; ++I)
- if ((*I)->isInIdentifierNamespace(IDNS))
+ if ((*I)->isInIdentifierNamespace(IDNS)) {
+ if ((*I)->getAttr<OverloadableAttr>()) {
+ // If this declaration has the "overloadable" attribute, we
+ // might have a set of overloaded functions.
+
+ // Figure out what scope the identifier is in.
+ while (!(S->getFlags() & Scope::DeclScope) || !S->isDeclScope(*I))
+ S = S->getParent();
+
+ // Find the last declaration in this scope (with the same
+ // name, naturally).
+ IdentifierResolver::iterator LastI = I;
+ for (++LastI; LastI != IEnd; ++LastI) {
+ if (!S->isDeclScope(*LastI))
+ break;
+ }
+
+ return LookupResult::CreateLookupResult(Context, I, LastI);
+ }
+
+ // We have a single lookup result.
return LookupResult::CreateLookupResult(Context, *I);
+ }
} else {
// Perform C++ unqualified name lookup.
std::pair<bool, LookupResult> MaybeResult =
diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index e40455b..e1939d3 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -45,6 +45,7 @@
ICC_Conversion,
ICC_Conversion,
ICC_Conversion,
+ ICC_Conversion,
ICC_Conversion
};
return Category[(int)Kind];
@@ -68,6 +69,7 @@
ICR_Conversion,
ICR_Conversion,
ICR_Conversion,
+ ICR_Conversion,
ICR_Conversion
};
return Rank[(int)Kind];
@@ -90,6 +92,7 @@
"Pointer conversion",
"Pointer-to-member conversion",
"Boolean conversion",
+ "Compatible-types conversion",
"Derived-to-base conversion"
};
return Name[Kind];
@@ -371,7 +374,8 @@
ImplicitConversionSequence ICS;
if (IsStandardConversion(From, ToType, ICS.Standard))
ICS.ConversionKind = ImplicitConversionSequence::StandardConversion;
- else if (IsUserDefinedConversion(From, ToType, ICS.UserDefined,
+ else if (getLangOptions().CPlusPlus &&
+ IsUserDefinedConversion(From, ToType, ICS.UserDefined,
!SuppressUserConversions, AllowExplicit)) {
ICS.ConversionKind = ImplicitConversionSequence::UserDefinedConversion;
// C++ [over.ics.user]p4:
@@ -429,10 +433,6 @@
{
QualType FromType = From->getType();
- // There are no standard conversions for class types, so abort early.
- if (FromType->isRecordType() || ToType->isRecordType())
- return false;
-
// Standard conversions (C++ [conv])
SCS.setAsIdentityConversion();
SCS.Deprecated = false;
@@ -440,6 +440,15 @@
SCS.FromTypePtr = FromType.getAsOpaquePtr();
SCS.CopyConstructor = 0;
+ // There are no standard conversions for class types in C++, so
+ // abort early. When overloading in C, however, we do permit
+ if (FromType->isRecordType() || ToType->isRecordType()) {
+ if (getLangOptions().CPlusPlus)
+ return false;
+
+ // When we're overloading in C, we allow, as standard conversions,
+ }
+
// The first conversion can be an lvalue-to-rvalue conversion,
// array-to-pointer conversion, or function-to-pointer conversion
// (C++ 4p1).
@@ -455,7 +464,10 @@
// If T is a non-class type, the type of the rvalue is the
// cv-unqualified version of T. Otherwise, the type of the rvalue
- // is T (C++ 4.1p1).
+ // is T (C++ 4.1p1). C++ can't get here with class types; in C, we
+ // just strip the qualifiers because they don't matter.
+
+ // FIXME: Doesn't see through to qualifiers behind a typedef!
FromType = FromType.getUnqualifiedType();
}
// Array-to-pointer conversion (C++ 4.2)
@@ -522,9 +534,10 @@
// point promotion, integral conversion, floating point conversion,
// floating-integral conversion, pointer conversion,
// pointer-to-member conversion, or boolean conversion (C++ 4p1).
+ // For overloading in C, this can also be a "compatible-type"
+ // conversion.
bool IncompatibleObjC = false;
- if (Context.getCanonicalType(FromType).getUnqualifiedType() ==
- Context.getCanonicalType(ToType).getUnqualifiedType()) {
+ if (Context.hasSameUnqualifiedType(FromType, ToType)) {
// The unqualified versions of the types are the same: there's no
// conversion to do.
SCS.Second = ICK_Identity;
@@ -580,6 +593,11 @@
FromType->isMemberPointerType())) {
SCS.Second = ICK_Boolean_Conversion;
FromType = Context.BoolTy;
+ }
+ // Compatible conversions (Clang extension for C function overloading)
+ else if (!getLangOptions().CPlusPlus &&
+ Context.typesAreCompatible(ToType, FromType)) {
+ SCS.Second = ICK_Compatible_Conversion;
} else {
// No second conversion required.
SCS.Second = ICK_Identity;
@@ -847,6 +865,16 @@
return true;
}
+ // When we're overloading in C, we allow a special kind of pointer
+ // conversion for compatible-but-not-identical pointee types.
+ if (!getLangOptions().CPlusPlus &&
+ Context.typesAreCompatible(FromPointeeType, ToPointeeType)) {
+ ConvertedType = BuildSimilarlyQualifiedPointerType(FromTypePtr,
+ ToPointeeType,
+ ToType, Context);
+ return true;
+ }
+
// C++ [conv.ptr]p3:
//
// An rvalue of type "pointer to cv D," where D is a class type,
@@ -860,7 +888,8 @@
//
// Note that we do not check for ambiguity or inaccessibility
// here. That is handled by CheckPointerConversion.
- if (FromPointeeType->isRecordType() && ToPointeeType->isRecordType() &&
+ if (getLangOptions().CPlusPlus &&
+ FromPointeeType->isRecordType() && ToPointeeType->isRecordType() &&
IsDerivedFrom(FromPointeeType, ToPointeeType)) {
ConvertedType = BuildSimilarlyQualifiedPointerType(FromTypePtr,
ToPointeeType,
@@ -1756,18 +1785,7 @@
ImplicitConversionSequence
Sema::TryCopyInitialization(Expr *From, QualType ToType,
bool SuppressUserConversions) {
- if (!getLangOptions().CPlusPlus) {
- // In C, copy initialization is the same as performing an assignment.
- AssignConvertType ConvTy =
- CheckSingleAssignmentConstraints(ToType, From);
- ImplicitConversionSequence ICS;
- if (getLangOptions().NoExtensions? ConvTy != Compatible
- : ConvTy == Incompatible)
- ICS.ConversionKind = ImplicitConversionSequence::BadConversion;
- else
- ICS.ConversionKind = ImplicitConversionSequence::StandardConversion;
- return ICS;
- } else if (ToType->isReferenceType()) {
+ if (ToType->isReferenceType()) {
ImplicitConversionSequence ICS;
CheckReferenceInit(From, ToType, &ICS, SuppressUserConversions);
return ICS;
diff --git a/lib/Sema/SemaOverload.h b/lib/Sema/SemaOverload.h
index 096bbf5..2511c2d 100644
--- a/lib/Sema/SemaOverload.h
+++ b/lib/Sema/SemaOverload.h
@@ -26,21 +26,22 @@
/// match with Table 9 of (C++ 13.3.3.1.1) and are listed such that
/// better conversion kinds have smaller values.
enum ImplicitConversionKind {
- ICK_Identity = 0, ///< Identity conversion (no conversion)
- ICK_Lvalue_To_Rvalue, ///< Lvalue-to-rvalue conversion (C++ 4.1)
- ICK_Array_To_Pointer, ///< Array-to-pointer conversion (C++ 4.2)
- ICK_Function_To_Pointer, ///< Function-to-pointer (C++ 4.3)
- ICK_Qualification, ///< Qualification conversions (C++ 4.4)
- ICK_Integral_Promotion, ///< Integral promotions (C++ 4.5)
- ICK_Floating_Promotion, ///< Floating point promotions (C++ 4.6)
- ICK_Integral_Conversion, ///< Integral conversions (C++ 4.7)
- ICK_Floating_Conversion, ///< Floating point conversions (C++ 4.8)
- ICK_Floating_Integral, ///< Floating-integral conversions (C++ 4.9)
- ICK_Pointer_Conversion, ///< Pointer conversions (C++ 4.10)
- ICK_Pointer_Member, ///< Pointer-to-member conversions (C++ 4.11)
- ICK_Boolean_Conversion, ///< Boolean conversions (C++ 4.12)
- ICK_Derived_To_Base, ///< Derived-to-base (C++ [over.best.ics][)
- ICK_Num_Conversion_Kinds ///< The number of conversion kinds
+ ICK_Identity = 0, ///< Identity conversion (no conversion)
+ ICK_Lvalue_To_Rvalue, ///< Lvalue-to-rvalue conversion (C++ 4.1)
+ ICK_Array_To_Pointer, ///< Array-to-pointer conversion (C++ 4.2)
+ ICK_Function_To_Pointer, ///< Function-to-pointer (C++ 4.3)
+ ICK_Qualification, ///< Qualification conversions (C++ 4.4)
+ ICK_Integral_Promotion, ///< Integral promotions (C++ 4.5)
+ ICK_Floating_Promotion, ///< Floating point promotions (C++ 4.6)
+ ICK_Integral_Conversion, ///< Integral conversions (C++ 4.7)
+ ICK_Floating_Conversion, ///< Floating point conversions (C++ 4.8)
+ ICK_Floating_Integral, ///< Floating-integral conversions (C++ 4.9)
+ ICK_Pointer_Conversion, ///< Pointer conversions (C++ 4.10)
+ ICK_Pointer_Member, ///< Pointer-to-member conversions (C++ 4.11)
+ ICK_Boolean_Conversion, ///< Boolean conversions (C++ 4.12)
+ ICK_Compatible_Conversion, ///< Conversions between compatible types in C99
+ ICK_Derived_To_Base, ///< Derived-to-base (C++ [over.best.ics])
+ ICK_Num_Conversion_Kinds ///< The number of conversion kinds
};
/// ImplicitConversionCategory - The category of an implicit