rZhBoYao created this revision.
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According to dcl.fct.def.general p2
<https://eel.is/c++draft/dcl.fct.def.general#2.sentence-3> and this
<https://stackoverflow.com/questions/70410542/can-one-delete-a-function-returning-an-incomplete-type-in-c>,
deleted functions with incomplete return types and parameter types are
well-formed.
struct Incomplete; // expected-note{{forward declaration of
'Incomplete'}}
Incomplete f() = delete; // well-formed
Incomplete g(Incomplete a) = delete; // well-formed
Incomplete h() {} // expected-error{{incomplete result
type 'Incomplete' in function definition}}
Inspired by this tweet
<https://twitter.com/shafikyaghmour/status/1510069442302001157>.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D122981
Files:
clang/include/clang/Sema/Sema.h
clang/lib/Parse/Parser.cpp
clang/lib/Sema/SemaDecl.cpp
clang/test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.general/p2.cpp
Index: clang/test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.general/p2.cpp
===================================================================
--- /dev/null
+++ clang/test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.general/p2.cpp
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+struct Incomplete; // expected-note{{forward declaration of 'Incomplete'}}
+Incomplete f() = delete; // well-formed
+Incomplete g(Incomplete a) = delete; // well-formed
+Incomplete h() {} // expected-error{{incomplete result type 'Incomplete' in function definition}}
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -14169,7 +14169,7 @@
Decl *
Sema::ActOnStartOfFunctionDef(Scope *FnBodyScope, Declarator &D,
MultiTemplateParamsArg TemplateParameterLists,
- SkipBodyInfo *SkipBody) {
+ SkipBodyInfo *SkipBody, bool FnDeleted) {
assert(getCurFunctionDecl() == nullptr && "Function parsing confused");
assert(D.isFunctionDeclarator() && "Not a function declarator!");
Scope *ParentScope = FnBodyScope->getParent();
@@ -14188,7 +14188,7 @@
D.setFunctionDefinitionKind(FunctionDefinitionKind::Definition);
Decl *DP = HandleDeclarator(ParentScope, D, TemplateParameterLists);
- Decl *Dcl = ActOnStartOfFunctionDef(FnBodyScope, DP, SkipBody);
+ Decl *Dcl = ActOnStartOfFunctionDef(FnBodyScope, DP, SkipBody, FnDeleted);
if (!Bases.empty())
ActOnFinishedFunctionDefinitionInOpenMPDeclareVariantScope(Dcl, Bases);
@@ -14364,7 +14364,7 @@
}
Decl *Sema::ActOnStartOfFunctionDef(Scope *FnBodyScope, Decl *D,
- SkipBodyInfo *SkipBody) {
+ SkipBodyInfo *SkipBody, bool FnDeleted) {
if (!D) {
// Parsing the function declaration failed in some way. Push on a fake scope
// anyway so we can try to parse the function body.
@@ -14454,10 +14454,11 @@
}
// The return type of a function definition must be complete
- // (C99 6.9.1p3, C++ [dcl.fct]p6).
+ // unless the function is deleted
+ // (C99 6.9.1p3, C++ [dcl.fct.def.general]p2).
QualType ResultType = FD->getReturnType();
if (!ResultType->isDependentType() && !ResultType->isVoidType() &&
- !FD->isInvalidDecl() &&
+ !FD->isInvalidDecl() && !FnDeleted &&
RequireCompleteType(FD->getLocation(), ResultType,
diag::err_func_def_incomplete_result))
FD->setInvalidDecl();
@@ -14465,9 +14466,10 @@
if (FnBodyScope)
PushDeclContext(FnBodyScope, FD);
- // Check the validity of our function parameters
- CheckParmsForFunctionDef(FD->parameters(),
- /*CheckParameterNames=*/true);
+ if (!FnDeleted)
+ // Check the validity of our function parameters
+ CheckParmsForFunctionDef(FD->parameters(),
+ /*CheckParameterNames=*/true);
// Add non-parameter declarations already in the function to the current
// scope.
Index: clang/lib/Parse/Parser.cpp
===================================================================
--- clang/lib/Parse/Parser.cpp
+++ clang/lib/Parse/Parser.cpp
@@ -1302,11 +1302,15 @@
// Tell the actions module that we have entered a function definition with the
// specified Declarator for the function.
Sema::SkipBodyInfo SkipBody;
+ bool FnDeleted = GetLookAheadToken(0).getKind() == tok::equal &&
+ GetLookAheadToken(1).getKind() == tok::kw_delete
+ ? true
+ : false;
Decl *Res = Actions.ActOnStartOfFunctionDef(getCurScope(), D,
TemplateInfo.TemplateParams
? *TemplateInfo.TemplateParams
: MultiTemplateParamsArg(),
- &SkipBody);
+ &SkipBody, FnDeleted);
if (SkipBody.ShouldSkip) {
SkipFunctionBody();
Index: clang/include/clang/Sema/Sema.h
===================================================================
--- clang/include/clang/Sema/Sema.h
+++ clang/include/clang/Sema/Sema.h
@@ -2902,9 +2902,11 @@
SkipBodyInfo *SkipBody = nullptr);
Decl *ActOnStartOfFunctionDef(Scope *S, Declarator &D,
MultiTemplateParamsArg TemplateParamLists,
- SkipBodyInfo *SkipBody = nullptr);
+ SkipBodyInfo *SkipBody = nullptr,
+ bool FnDeleted = false);
Decl *ActOnStartOfFunctionDef(Scope *S, Decl *D,
- SkipBodyInfo *SkipBody = nullptr);
+ SkipBodyInfo *SkipBody = nullptr,
+ bool FnDeleted = false);
void ActOnStartTrailingRequiresClause(Scope *S, Declarator &D);
ExprResult ActOnFinishTrailingRequiresClause(ExprResult ConstraintExpr);
ExprResult ActOnRequiresClause(ExprResult ConstraintExpr);
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