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llvm-project/clang/lib/Sema/SemaCoroutine.cpp

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//===-- SemaCoroutine.cpp - Semantic Analysis for Coroutines --------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements semantic analysis for C++ Coroutines.
//
// This file contains references to sections of the Coroutines TS, which
// can be found at http://wg21.link/coroutines.
//
//===----------------------------------------------------------------------===//
#include "CoroutineStmtBuilder.h"
#include "clang/AST/ASTLambda.h"
#include "clang/AST/Decl.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/StmtCXX.h"
#include "clang/Basic/Builtins.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Sema/Initialization.h"
#include "clang/Sema/Overload.h"
#include "clang/Sema/ScopeInfo.h"
#include "clang/Sema/SemaInternal.h"
#include "llvm/ADT/SmallSet.h"
using namespace clang;
using namespace sema;
static LookupResult lookupMember(Sema &S, const char *Name, CXXRecordDecl *RD,
SourceLocation Loc, bool &Res) {
DeclarationName DN = S.PP.getIdentifierInfo(Name);
LookupResult LR(S, DN, Loc, Sema::LookupMemberName);
// Suppress diagnostics when a private member is selected. The same warnings
// will be produced again when building the call.
LR.suppressDiagnostics();
Res = S.LookupQualifiedName(LR, RD);
return LR;
}
static bool lookupMember(Sema &S, const char *Name, CXXRecordDecl *RD,
SourceLocation Loc) {
bool Res;
lookupMember(S, Name, RD, Loc, Res);
return Res;
}
/// Look up the std::coroutine_traits<...>::promise_type for the given
/// function type.
static QualType lookupPromiseType(Sema &S, const FunctionDecl *FD,
SourceLocation KwLoc) {
const FunctionProtoType *FnType = FD->getType()->castAs<FunctionProtoType>();
const SourceLocation FuncLoc = FD->getLocation();
NamespaceDecl *CoroNamespace = nullptr;
ClassTemplateDecl *CoroTraits =
S.lookupCoroutineTraits(KwLoc, FuncLoc, CoroNamespace);
if (!CoroTraits) {
return QualType();
}
// Form template argument list for coroutine_traits<R, P1, P2, ...> according
// to [dcl.fct.def.coroutine]3
TemplateArgumentListInfo Args(KwLoc, KwLoc);
auto AddArg = [&](QualType T) {
Args.addArgument(TemplateArgumentLoc(
TemplateArgument(T), S.Context.getTrivialTypeSourceInfo(T, KwLoc)));
};
AddArg(FnType->getReturnType());
// If the function is a non-static member function, add the type
// of the implicit object parameter before the formal parameters.
if (auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
if (MD->isInstance()) {
// [over.match.funcs]4
// For non-static member functions, the type of the implicit object
// parameter is
// -- "lvalue reference to cv X" for functions declared without a
// ref-qualifier or with the & ref-qualifier
// -- "rvalue reference to cv X" for functions declared with the &&
// ref-qualifier
QualType T = MD->getThisType()->castAs<PointerType>()->getPointeeType();
T = FnType->getRefQualifier() == RQ_RValue
? S.Context.getRValueReferenceType(T)
: S.Context.getLValueReferenceType(T, /*SpelledAsLValue*/ true);
AddArg(T);
}
}
for (QualType T : FnType->getParamTypes())
AddArg(T);
// Build the template-id.
QualType CoroTrait =
S.CheckTemplateIdType(TemplateName(CoroTraits), KwLoc, Args);
if (CoroTrait.isNull())
return QualType();
if (S.RequireCompleteType(KwLoc, CoroTrait,
diag::err_coroutine_type_missing_specialization))
return QualType();
auto *RD = CoroTrait->getAsCXXRecordDecl();
assert(RD && "specialization of class template is not a class?");
// Look up the ::promise_type member.
LookupResult R(S, &S.PP.getIdentifierTable().get("promise_type"), KwLoc,
Sema::LookupOrdinaryName);
S.LookupQualifiedName(R, RD);
auto *Promise = R.getAsSingle<TypeDecl>();
if (!Promise) {
S.Diag(FuncLoc,
diag::err_implied_std_coroutine_traits_promise_type_not_found)
<< RD;
return QualType();
}
// The promise type is required to be a class type.
QualType PromiseType = S.Context.getTypeDeclType(Promise);
auto buildElaboratedType = [&]() {
auto *NNS = NestedNameSpecifier::Create(S.Context, nullptr, CoroNamespace);
NNS = NestedNameSpecifier::Create(S.Context, NNS, false,
CoroTrait.getTypePtr());
return S.Context.getElaboratedType(ETK_None, NNS, PromiseType);
};
if (!PromiseType->getAsCXXRecordDecl()) {
S.Diag(FuncLoc,
diag::err_implied_std_coroutine_traits_promise_type_not_class)
<< buildElaboratedType();
return QualType();
}
if (S.RequireCompleteType(FuncLoc, buildElaboratedType(),
diag::err_coroutine_promise_type_incomplete))
return QualType();
return PromiseType;
}
/// Look up the std::coroutine_handle<PromiseType>.
static QualType lookupCoroutineHandleType(Sema &S, QualType PromiseType,
SourceLocation Loc) {
if (PromiseType.isNull())
return QualType();
NamespaceDecl *CoroNamespace = S.getCachedCoroNamespace();
assert(CoroNamespace && "Should already be diagnosed");
LookupResult Result(S, &S.PP.getIdentifierTable().get("coroutine_handle"),
Loc, Sema::LookupOrdinaryName);
if (!S.LookupQualifiedName(Result, CoroNamespace)) {
S.Diag(Loc, diag::err_implied_coroutine_type_not_found)
<< "std::coroutine_handle";
return QualType();
}
ClassTemplateDecl *CoroHandle = Result.getAsSingle<ClassTemplateDecl>();
if (!CoroHandle) {
Result.suppressDiagnostics();
// We found something weird. Complain about the first thing we found.
NamedDecl *Found = *Result.begin();
S.Diag(Found->getLocation(), diag::err_malformed_std_coroutine_handle);
return QualType();
}
// Form template argument list for coroutine_handle<Promise>.
TemplateArgumentListInfo Args(Loc, Loc);
Args.addArgument(TemplateArgumentLoc(
TemplateArgument(PromiseType),
S.Context.getTrivialTypeSourceInfo(PromiseType, Loc)));
// Build the template-id.
QualType CoroHandleType =
S.CheckTemplateIdType(TemplateName(CoroHandle), Loc, Args);
if (CoroHandleType.isNull())
return QualType();
if (S.RequireCompleteType(Loc, CoroHandleType,
diag::err_coroutine_type_missing_specialization))
return QualType();
return CoroHandleType;
}
static bool isValidCoroutineContext(Sema &S, SourceLocation Loc,
StringRef Keyword) {
// [expr.await]p2 dictates that 'co_await' and 'co_yield' must be used within
// a function body.
// FIXME: This also covers [expr.await]p2: "An await-expression shall not
// appear in a default argument." But the diagnostic QoI here could be
// improved to inform the user that default arguments specifically are not
// allowed.
auto *FD = dyn_cast<FunctionDecl>(S.CurContext);
if (!FD) {
S.Diag(Loc, isa<ObjCMethodDecl>(S.CurContext)
? diag::err_coroutine_objc_method
: diag::err_coroutine_outside_function) << Keyword;
return false;
}
// An enumeration for mapping the diagnostic type to the correct diagnostic
// selection index.
enum InvalidFuncDiag {
DiagCtor = 0,
DiagDtor,
DiagMain,
DiagConstexpr,
DiagAutoRet,
DiagVarargs,
DiagConsteval,
};
bool Diagnosed = false;
auto DiagInvalid = [&](InvalidFuncDiag ID) {
S.Diag(Loc, diag::err_coroutine_invalid_func_context) << ID << Keyword;
Diagnosed = true;
return false;
};
// Diagnose when a constructor, destructor
// or the function 'main' are declared as a coroutine.
auto *MD = dyn_cast<CXXMethodDecl>(FD);
// [class.ctor]p11: "A constructor shall not be a coroutine."
if (MD && isa<CXXConstructorDecl>(MD))
return DiagInvalid(DiagCtor);
// [class.dtor]p17: "A destructor shall not be a coroutine."
else if (MD && isa<CXXDestructorDecl>(MD))
return DiagInvalid(DiagDtor);
// [basic.start.main]p3: "The function main shall not be a coroutine."
else if (FD->isMain())
return DiagInvalid(DiagMain);
// Emit a diagnostics for each of the following conditions which is not met.
// [expr.const]p2: "An expression e is a core constant expression unless the
// evaluation of e [...] would evaluate one of the following expressions:
// [...] an await-expression [...] a yield-expression."
if (FD->isConstexpr())
DiagInvalid(FD->isConsteval() ? DiagConsteval : DiagConstexpr);
// [dcl.spec.auto]p15: "A function declared with a return type that uses a
// placeholder type shall not be a coroutine."
if (FD->getReturnType()->isUndeducedType())
DiagInvalid(DiagAutoRet);
// [dcl.fct.def.coroutine]p1
// The parameter-declaration-clause of the coroutine shall not terminate with
// an ellipsis that is not part of a parameter-declaration.
if (FD->isVariadic())
DiagInvalid(DiagVarargs);
return !Diagnosed;
}
static ExprResult buildOperatorCoawaitLookupExpr(Sema &SemaRef, Scope *S,
SourceLocation Loc) {
DeclarationName OpName =
SemaRef.Context.DeclarationNames.getCXXOperatorName(OO_Coawait);
LookupResult Operators(SemaRef, OpName, SourceLocation(),
Sema::LookupOperatorName);
SemaRef.LookupName(Operators, S);
assert(!Operators.isAmbiguous() && "Operator lookup cannot be ambiguous");
const auto &Functions = Operators.asUnresolvedSet();
bool IsOverloaded =
Functions.size() > 1 ||
(Functions.size() == 1 && isa<FunctionTemplateDecl>(*Functions.begin()));
Expr *CoawaitOp = UnresolvedLookupExpr::Create(
SemaRef.Context, /*NamingClass*/ nullptr, NestedNameSpecifierLoc(),
DeclarationNameInfo(OpName, Loc), /*RequiresADL*/ true, IsOverloaded,
Functions.begin(), Functions.end());
assert(CoawaitOp);
return CoawaitOp;
}
/// Build a call to 'operator co_await' if there is a suitable operator for
/// the given expression.
static ExprResult buildOperatorCoawaitCall(Sema &SemaRef, SourceLocation Loc,
Expr *E,
UnresolvedLookupExpr *Lookup) {
UnresolvedSet<16> Functions;
Functions.append(Lookup->decls_begin(), Lookup->decls_end());
return SemaRef.CreateOverloadedUnaryOp(Loc, UO_Coawait, Functions, E);
}
static ExprResult buildOperatorCoawaitCall(Sema &SemaRef, Scope *S,
SourceLocation Loc, Expr *E) {
ExprResult R = buildOperatorCoawaitLookupExpr(SemaRef, S, Loc);
if (R.isInvalid())
return ExprError();
return buildOperatorCoawaitCall(SemaRef, Loc, E,
cast<UnresolvedLookupExpr>(R.get()));
}
static ExprResult buildCoroutineHandle(Sema &S, QualType PromiseType,
SourceLocation Loc) {
QualType CoroHandleType = lookupCoroutineHandleType(S, PromiseType, Loc);
if (CoroHandleType.isNull())
return ExprError();
DeclContext *LookupCtx = S.computeDeclContext(CoroHandleType);
LookupResult Found(S, &S.PP.getIdentifierTable().get("from_address"), Loc,
Sema::LookupOrdinaryName);
if (!S.LookupQualifiedName(Found, LookupCtx)) {
S.Diag(Loc, diag::err_coroutine_handle_missing_member)
<< "from_address";
return ExprError();
}
Expr *FramePtr =
S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_frame, {});
CXXScopeSpec SS;
ExprResult FromAddr =
S.BuildDeclarationNameExpr(SS, Found, /*NeedsADL=*/false);
if (FromAddr.isInvalid())
return ExprError();
return S.BuildCallExpr(nullptr, FromAddr.get(), Loc, FramePtr, Loc);
}
struct ReadySuspendResumeResult {
enum AwaitCallType { ACT_Ready, ACT_Suspend, ACT_Resume };
Expr *Results[3];
OpaqueValueExpr *OpaqueValue;
bool IsInvalid;
};
static ExprResult buildMemberCall(Sema &S, Expr *Base, SourceLocation Loc,
StringRef Name, MultiExprArg Args) {
DeclarationNameInfo NameInfo(&S.PP.getIdentifierTable().get(Name), Loc);
// FIXME: Fix BuildMemberReferenceExpr to take a const CXXScopeSpec&.
CXXScopeSpec SS;
ExprResult Result = S.BuildMemberReferenceExpr(
Base, Base->getType(), Loc, /*IsPtr=*/false, SS,
SourceLocation(), nullptr, NameInfo, /*TemplateArgs=*/nullptr,
/*Scope=*/nullptr);
if (Result.isInvalid())
return ExprError();
// We meant exactly what we asked for. No need for typo correction.
if (auto *TE = dyn_cast<TypoExpr>(Result.get())) {
S.clearDelayedTypo(TE);
S.Diag(Loc, diag::err_no_member)
<< NameInfo.getName() << Base->getType()->getAsCXXRecordDecl()
<< Base->getSourceRange();
return ExprError();
}
return S.BuildCallExpr(nullptr, Result.get(), Loc, Args, Loc, nullptr);
}
// See if return type is coroutine-handle and if so, invoke builtin coro-resume
// on its address. This is to enable experimental support for coroutine-handle
// returning await_suspend that results in a guaranteed tail call to the target
// coroutine.
static Expr *maybeTailCall(Sema &S, QualType RetType, Expr *E,
SourceLocation Loc) {
if (RetType->isReferenceType())
return nullptr;
Type const *T = RetType.getTypePtr();
if (!T->isClassType() && !T->isStructureType())
return nullptr;
// FIXME: Add convertability check to coroutine_handle<>. Possibly via
// EvaluateBinaryTypeTrait(BTT_IsConvertible, ...) which is at the moment
// a private function in SemaExprCXX.cpp
ExprResult AddressExpr = buildMemberCall(S, E, Loc, "address", None);
if (AddressExpr.isInvalid())
return nullptr;
Expr *JustAddress = AddressExpr.get();
// Check that the type of AddressExpr is void*
if (!JustAddress->getType().getTypePtr()->isVoidPointerType())
S.Diag(cast<CallExpr>(JustAddress)->getCalleeDecl()->getLocation(),
diag::warn_coroutine_handle_address_invalid_return_type)
<< JustAddress->getType();
// Clean up temporary objects so that they don't live across suspension points
// unnecessarily. We choose to clean up before the call to
// __builtin_coro_resume so that the cleanup code are not inserted in-between
// the resume call and return instruction, which would interfere with the
// musttail call contract.
JustAddress = S.MaybeCreateExprWithCleanups(JustAddress);
return S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_resume,
JustAddress);
}
/// Build calls to await_ready, await_suspend, and await_resume for a co_await
/// expression.
/// The generated AST tries to clean up temporary objects as early as
/// possible so that they don't live across suspension points if possible.
/// Having temporary objects living across suspension points unnecessarily can
/// lead to large frame size, and also lead to memory corruptions if the
/// coroutine frame is destroyed after coming back from suspension. This is done
/// by wrapping both the await_ready call and the await_suspend call with
/// ExprWithCleanups. In the end of this function, we also need to explicitly
/// set cleanup state so that the CoawaitExpr is also wrapped with an
/// ExprWithCleanups to clean up the awaiter associated with the co_await
/// expression.
static ReadySuspendResumeResult buildCoawaitCalls(Sema &S, VarDecl *CoroPromise,
SourceLocation Loc, Expr *E) {
OpaqueValueExpr *Operand = new (S.Context)
OpaqueValueExpr(Loc, E->getType(), VK_LValue, E->getObjectKind(), E);
// Assume valid until we see otherwise.
// Further operations are responsible for setting IsInalid to true.
ReadySuspendResumeResult Calls = {{}, Operand, /*IsInvalid=*/false};
using ACT = ReadySuspendResumeResult::AwaitCallType;
auto BuildSubExpr = [&](ACT CallType, StringRef Func,
MultiExprArg Arg) -> Expr * {
ExprResult Result = buildMemberCall(S, Operand, Loc, Func, Arg);
if (Result.isInvalid()) {
Calls.IsInvalid = true;
return nullptr;
}
Calls.Results[CallType] = Result.get();
return Result.get();
};
CallExpr *AwaitReady =
cast_or_null<CallExpr>(BuildSubExpr(ACT::ACT_Ready, "await_ready", None));
if (!AwaitReady)
return Calls;
if (!AwaitReady->getType()->isDependentType()) {
// [expr.await]p3 [...]
// — await-ready is the expression e.await_ready(), contextually converted
// to bool.
ExprResult Conv = S.PerformContextuallyConvertToBool(AwaitReady);
if (Conv.isInvalid()) {
S.Diag(AwaitReady->getDirectCallee()->getBeginLoc(),
diag::note_await_ready_no_bool_conversion);
S.Diag(Loc, diag::note_coroutine_promise_call_implicitly_required)
<< AwaitReady->getDirectCallee() << E->getSourceRange();
Calls.IsInvalid = true;
} else
Calls.Results[ACT::ACT_Ready] = S.MaybeCreateExprWithCleanups(Conv.get());
}
ExprResult CoroHandleRes =
buildCoroutineHandle(S, CoroPromise->getType(), Loc);
if (CoroHandleRes.isInvalid()) {
Calls.IsInvalid = true;
return Calls;
}
Expr *CoroHandle = CoroHandleRes.get();
CallExpr *AwaitSuspend = cast_or_null<CallExpr>(
BuildSubExpr(ACT::ACT_Suspend, "await_suspend", CoroHandle));
if (!AwaitSuspend)
return Calls;
if (!AwaitSuspend->getType()->isDependentType()) {
// [expr.await]p3 [...]
// - await-suspend is the expression e.await_suspend(h), which shall be
// a prvalue of type void, bool, or std::coroutine_handle<Z> for some
// type Z.
QualType RetType = AwaitSuspend->getCallReturnType(S.Context);
// Experimental support for coroutine_handle returning await_suspend.
if (Expr *TailCallSuspend =
maybeTailCall(S, RetType, AwaitSuspend, Loc))
// Note that we don't wrap the expression with ExprWithCleanups here
// because that might interfere with tailcall contract (e.g. inserting
// clean up instructions in-between tailcall and return). Instead
// ExprWithCleanups is wrapped within maybeTailCall() prior to the resume
// call.
Calls.Results[ACT::ACT_Suspend] = TailCallSuspend;
else {
// non-class prvalues always have cv-unqualified types
if (RetType->isReferenceType() ||
(!RetType->isBooleanType() && !RetType->isVoidType())) {
S.Diag(AwaitSuspend->getCalleeDecl()->getLocation(),
diag::err_await_suspend_invalid_return_type)
<< RetType;
S.Diag(Loc, diag::note_coroutine_promise_call_implicitly_required)
<< AwaitSuspend->getDirectCallee();
Calls.IsInvalid = true;
} else
Calls.Results[ACT::ACT_Suspend] =
S.MaybeCreateExprWithCleanups(AwaitSuspend);
}
}
BuildSubExpr(ACT::ACT_Resume, "await_resume", None);
// Make sure the awaiter object gets a chance to be cleaned up.
S.Cleanup.setExprNeedsCleanups(true);
return Calls;
}
static ExprResult buildPromiseCall(Sema &S, VarDecl *Promise,
SourceLocation Loc, StringRef Name,
MultiExprArg Args) {
// Form a reference to the promise.
ExprResult PromiseRef = S.BuildDeclRefExpr(
Promise, Promise->getType().getNonReferenceType(), VK_LValue, Loc);
if (PromiseRef.isInvalid())
return ExprError();
return buildMemberCall(S, PromiseRef.get(), Loc, Name, Args);
}
VarDecl *Sema::buildCoroutinePromise(SourceLocation Loc) {
assert(isa<FunctionDecl>(CurContext) && "not in a function scope");
auto *FD = cast<FunctionDecl>(CurContext);
bool IsThisDependentType = [&] {
if (auto *MD = dyn_cast_or_null<CXXMethodDecl>(FD))
return MD->isInstance() && MD->getThisType()->isDependentType();
else
return false;
}();
QualType T = FD->getType()->isDependentType() || IsThisDependentType
? Context.DependentTy
: lookupPromiseType(*this, FD, Loc);
if (T.isNull())
return nullptr;
auto *VD = VarDecl::Create(Context, FD, FD->getLocation(), FD->getLocation(),
&PP.getIdentifierTable().get("__promise"), T,
Context.getTrivialTypeSourceInfo(T, Loc), SC_None);
VD->setImplicit();
CheckVariableDeclarationType(VD);
if (VD->isInvalidDecl())
return nullptr;
auto *ScopeInfo = getCurFunction();
// Build a list of arguments, based on the coroutine function's arguments,
// that if present will be passed to the promise type's constructor.
llvm::SmallVector<Expr *, 4> CtorArgExprs;
// Add implicit object parameter.
if (auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
if (MD->isInstance() && !isLambdaCallOperator(MD)) {
ExprResult ThisExpr = ActOnCXXThis(Loc);
if (ThisExpr.isInvalid())
return nullptr;
ThisExpr = CreateBuiltinUnaryOp(Loc, UO_Deref, ThisExpr.get());
if (ThisExpr.isInvalid())
return nullptr;
CtorArgExprs.push_back(ThisExpr.get());
}
}
// Add the coroutine function's parameters.
auto &Moves = ScopeInfo->CoroutineParameterMoves;
for (auto *PD : FD->parameters()) {
if (PD->getType()->isDependentType())
continue;
auto RefExpr = ExprEmpty();
auto Move = Moves.find(PD);
assert(Move != Moves.end() &&
"Coroutine function parameter not inserted into move map");
// If a reference to the function parameter exists in the coroutine
// frame, use that reference.
auto *MoveDecl =
cast<VarDecl>(cast<DeclStmt>(Move->second)->getSingleDecl());
RefExpr =
BuildDeclRefExpr(MoveDecl, MoveDecl->getType().getNonReferenceType(),
ExprValueKind::VK_LValue, FD->getLocation());
if (RefExpr.isInvalid())
return nullptr;
CtorArgExprs.push_back(RefExpr.get());
}
// If we have a non-zero number of constructor arguments, try to use them.
// Otherwise, fall back to the promise type's default constructor.
if (!CtorArgExprs.empty()) {
// Create an initialization sequence for the promise type using the
// constructor arguments, wrapped in a parenthesized list expression.
Expr *PLE = ParenListExpr::Create(Context, FD->getLocation(),
CtorArgExprs, FD->getLocation());
InitializedEntity Entity = InitializedEntity::InitializeVariable(VD);
InitializationKind Kind = InitializationKind::CreateForInit(
VD->getLocation(), /*DirectInit=*/true, PLE);
InitializationSequence InitSeq(*this, Entity, Kind, CtorArgExprs,
/*TopLevelOfInitList=*/false,
/*TreatUnavailableAsInvalid=*/false);
// [dcl.fct.def.coroutine]5.7
// promise-constructor-arguments is determined as follows: overload
// resolution is performed on a promise constructor call created by
// assembling an argument list q_1 ... q_n . If a viable constructor is
// found ([over.match.viable]), then promise-constructor-arguments is ( q_1
// , ..., q_n ), otherwise promise-constructor-arguments is empty.
if (InitSeq) {
ExprResult Result = InitSeq.Perform(*this, Entity, Kind, CtorArgExprs);
if (Result.isInvalid()) {
VD->setInvalidDecl();
} else if (Result.get()) {
VD->setInit(MaybeCreateExprWithCleanups(Result.get()));
VD->setInitStyle(VarDecl::CallInit);
CheckCompleteVariableDeclaration(VD);
}
} else
ActOnUninitializedDecl(VD);
} else
ActOnUninitializedDecl(VD);
FD->addDecl(VD);
return VD;
}
/// Check that this is a context in which a coroutine suspension can appear.
static FunctionScopeInfo *checkCoroutineContext(Sema &S, SourceLocation Loc,
StringRef Keyword,
bool IsImplicit = false) {
if (!isValidCoroutineContext(S, Loc, Keyword))
return nullptr;
assert(isa<FunctionDecl>(S.CurContext) && "not in a function scope");
auto *ScopeInfo = S.getCurFunction();
assert(ScopeInfo && "missing function scope for function");
if (ScopeInfo->FirstCoroutineStmtLoc.isInvalid() && !IsImplicit)
ScopeInfo->setFirstCoroutineStmt(Loc, Keyword);
if (ScopeInfo->CoroutinePromise)
return ScopeInfo;
if (!S.buildCoroutineParameterMoves(Loc))
return nullptr;
ScopeInfo->CoroutinePromise = S.buildCoroutinePromise(Loc);
if (!ScopeInfo->CoroutinePromise)
return nullptr;
return ScopeInfo;
}
/// Recursively check \p E and all its children to see if any call target
/// (including constructor call) is declared noexcept. Also any value returned
/// from the call has a noexcept destructor.
static void checkNoThrow(Sema &S, const Stmt *E,
llvm::SmallPtrSetImpl<const Decl *> &ThrowingDecls) {
auto checkDeclNoexcept = [&](const Decl *D, bool IsDtor = false) {
// In the case of dtor, the call to dtor is implicit and hence we should
// pass nullptr to canCalleeThrow.
if (Sema::canCalleeThrow(S, IsDtor ? nullptr : cast<Expr>(E), D)) {
if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
// co_await promise.final_suspend() could end up calling
// __builtin_coro_resume for symmetric transfer if await_suspend()
// returns a handle. In that case, even __builtin_coro_resume is not
// declared as noexcept and may throw, it does not throw _into_ the
// coroutine that just suspended, but rather throws back out from
// whoever called coroutine_handle::resume(), hence we claim that
// logically it does not throw.
if (FD->getBuiltinID() == Builtin::BI__builtin_coro_resume)
return;
}
if (ThrowingDecls.empty()) {
// [dcl.fct.def.coroutine]p15
// The expression co_await promise.final_suspend() shall not be
// potentially-throwing ([except.spec]).
//
// First time seeing an error, emit the error message.
S.Diag(cast<FunctionDecl>(S.CurContext)->getLocation(),
diag::err_coroutine_promise_final_suspend_requires_nothrow);
}
ThrowingDecls.insert(D);
}
};
if (auto *CE = dyn_cast<CXXConstructExpr>(E)) {
CXXConstructorDecl *Ctor = CE->getConstructor();
checkDeclNoexcept(Ctor);
// Check the corresponding destructor of the constructor.
checkDeclNoexcept(Ctor->getParent()->getDestructor(), /*IsDtor=*/true);
} else if (auto *CE = dyn_cast<CallExpr>(E)) {
if (CE->isTypeDependent())
return;
checkDeclNoexcept(CE->getCalleeDecl());
QualType ReturnType = CE->getCallReturnType(S.getASTContext());
// Check the destructor of the call return type, if any.
if (ReturnType.isDestructedType() ==
QualType::DestructionKind::DK_cxx_destructor) {
const auto *T =
cast<RecordType>(ReturnType.getCanonicalType().getTypePtr());
checkDeclNoexcept(cast<CXXRecordDecl>(T->getDecl())->getDestructor(),
/*IsDtor=*/true);
}
} else
for (const auto *Child : E->children()) {
if (!Child)
continue;
checkNoThrow(S, Child, ThrowingDecls);
}
}
bool Sema::checkFinalSuspendNoThrow(const Stmt *FinalSuspend) {
llvm::SmallPtrSet<const Decl *, 4> ThrowingDecls;
// We first collect all declarations that should not throw but not declared
// with noexcept. We then sort them based on the location before printing.
// This is to avoid emitting the same note multiple times on the same
// declaration, and also provide a deterministic order for the messages.
checkNoThrow(*this, FinalSuspend, ThrowingDecls);
auto SortedDecls = llvm::SmallVector<const Decl *, 4>{ThrowingDecls.begin(),
ThrowingDecls.end()};
sort(SortedDecls, [](const Decl *A, const Decl *B) {
return A->getEndLoc() < B->getEndLoc();
});
for (const auto *D : SortedDecls) {
Diag(D->getEndLoc(), diag::note_coroutine_function_declare_noexcept);
}
return ThrowingDecls.empty();
}
bool Sema::ActOnCoroutineBodyStart(Scope *SC, SourceLocation KWLoc,
StringRef Keyword) {
if (!checkCoroutineContext(*this, KWLoc, Keyword))
return false;
auto *ScopeInfo = getCurFunction();
assert(ScopeInfo->CoroutinePromise);
// If we have existing coroutine statements then we have already built
// the initial and final suspend points.
if (!ScopeInfo->NeedsCoroutineSuspends)
return true;
ScopeInfo->setNeedsCoroutineSuspends(false);
auto *Fn = cast<FunctionDecl>(CurContext);
SourceLocation Loc = Fn->getLocation();
// Build the initial suspend point
auto buildSuspends = [&](StringRef Name) mutable -> StmtResult {
ExprResult Suspend =
buildPromiseCall(*this, ScopeInfo->CoroutinePromise, Loc, Name, None);
if (Suspend.isInvalid())
return StmtError();
Suspend = buildOperatorCoawaitCall(*this, SC, Loc, Suspend.get());
if (Suspend.isInvalid())
return StmtError();
Suspend = BuildResolvedCoawaitExpr(Loc, Suspend.get(),
/*IsImplicit*/ true);
Suspend = ActOnFinishFullExpr(Suspend.get(), /*DiscardedValue*/ false);
if (Suspend.isInvalid()) {
Diag(Loc, diag::note_coroutine_promise_suspend_implicitly_required)
<< ((Name == "initial_suspend") ? 0 : 1);
Diag(KWLoc, diag::note_declared_coroutine_here) << Keyword;
return StmtError();
}
return cast<Stmt>(Suspend.get());
};
StmtResult InitSuspend = buildSuspends("initial_suspend");
if (InitSuspend.isInvalid())
return true;
StmtResult FinalSuspend = buildSuspends("final_suspend");
if (FinalSuspend.isInvalid() || !checkFinalSuspendNoThrow(FinalSuspend.get()))
return true;
ScopeInfo->setCoroutineSuspends(InitSuspend.get(), FinalSuspend.get());
return true;
}
// Recursively walks up the scope hierarchy until either a 'catch' or a function
// scope is found, whichever comes first.
static bool isWithinCatchScope(Scope *S) {
// 'co_await' and 'co_yield' keywords are disallowed within catch blocks, but
// lambdas that use 'co_await' are allowed. The loop below ends when a
// function scope is found in order to ensure the following behavior:
//
// void foo() { // <- function scope
// try { //
// co_await x; // <- 'co_await' is OK within a function scope
// } catch { // <- catch scope
// co_await x; // <- 'co_await' is not OK within a catch scope
// []() { // <- function scope
// co_await x; // <- 'co_await' is OK within a function scope
// }();
// }
// }
while (S && !S->isFunctionScope()) {
if (S->isCatchScope())
return true;
S = S->getParent();
}
return false;
}
// [expr.await]p2, emphasis added: "An await-expression shall appear only in
// a *potentially evaluated* expression within the compound-statement of a
// function-body *outside of a handler* [...] A context within a function
// where an await-expression can appear is called a suspension context of the
// function."
static void checkSuspensionContext(Sema &S, SourceLocation Loc,
StringRef Keyword) {
// First emphasis of [expr.await]p2: must be a potentially evaluated context.
// That is, 'co_await' and 'co_yield' cannot appear in subexpressions of
// \c sizeof.
if (S.isUnevaluatedContext())
S.Diag(Loc, diag::err_coroutine_unevaluated_context) << Keyword;
// Second emphasis of [expr.await]p2: must be outside of an exception handler.
if (isWithinCatchScope(S.getCurScope()))
S.Diag(Loc, diag::err_coroutine_within_handler) << Keyword;
}
ExprResult Sema::ActOnCoawaitExpr(Scope *S, SourceLocation Loc, Expr *E) {
if (!ActOnCoroutineBodyStart(S, Loc, "co_await")) {
CorrectDelayedTyposInExpr(E);
return ExprError();
}
checkSuspensionContext(*this, Loc, "co_await");
if (E->hasPlaceholderType()) {
ExprResult R = CheckPlaceholderExpr(E);
if (R.isInvalid()) return ExprError();
E = R.get();
}
ExprResult Lookup = buildOperatorCoawaitLookupExpr(*this, S, Loc);
if (Lookup.isInvalid())
return ExprError();
return BuildUnresolvedCoawaitExpr(Loc, E,
cast<UnresolvedLookupExpr>(Lookup.get()));
}
ExprResult Sema::BuildUnresolvedCoawaitExpr(SourceLocation Loc, Expr *E,
UnresolvedLookupExpr *Lookup) {
auto *FSI = checkCoroutineContext(*this, Loc, "co_await");
if (!FSI)
return ExprError();
if (E->hasPlaceholderType()) {
ExprResult R = CheckPlaceholderExpr(E);
if (R.isInvalid())
return ExprError();
E = R.get();
}
auto *Promise = FSI->CoroutinePromise;
if (Promise->getType()->isDependentType()) {
Expr *Res =
new (Context) DependentCoawaitExpr(Loc, Context.DependentTy, E, Lookup);
return Res;
}
auto *RD = Promise->getType()->getAsCXXRecordDecl();
if (lookupMember(*this, "await_transform", RD, Loc)) {
ExprResult R = buildPromiseCall(*this, Promise, Loc, "await_transform", E);
if (R.isInvalid()) {
Diag(Loc,
diag::note_coroutine_promise_implicit_await_transform_required_here)
<< E->getSourceRange();
return ExprError();
}
E = R.get();
}
ExprResult Awaitable = buildOperatorCoawaitCall(*this, Loc, E, Lookup);
if (Awaitable.isInvalid())
return ExprError();
return BuildResolvedCoawaitExpr(Loc, Awaitable.get());
}
ExprResult Sema::BuildResolvedCoawaitExpr(SourceLocation Loc, Expr *E,
bool IsImplicit) {
auto *Coroutine = checkCoroutineContext(*this, Loc, "co_await", IsImplicit);
if (!Coroutine)
return ExprError();
if (E->hasPlaceholderType()) {
ExprResult R = CheckPlaceholderExpr(E);
if (R.isInvalid()) return ExprError();
E = R.get();
}
if (E->getType()->isDependentType()) {
Expr *Res = new (Context)
CoawaitExpr(Loc, Context.DependentTy, E, IsImplicit);
return Res;
}
// If the expression is a temporary, materialize it as an lvalue so that we
// can use it multiple times.
if (E->isPRValue())
E = CreateMaterializeTemporaryExpr(E->getType(), E, true);
// The location of the `co_await` token cannot be used when constructing
// the member call expressions since it's before the location of `Expr`, which
// is used as the start of the member call expression.
SourceLocation CallLoc = E->getExprLoc();
// Build the await_ready, await_suspend, await_resume calls.
ReadySuspendResumeResult RSS = buildCoawaitCalls(
*this, Coroutine->CoroutinePromise, CallLoc, E);
if (RSS.IsInvalid)
return ExprError();
Expr *Res =
new (Context) CoawaitExpr(Loc, E, RSS.Results[0], RSS.Results[1],
RSS.Results[2], RSS.OpaqueValue, IsImplicit);
return Res;
}
ExprResult Sema::ActOnCoyieldExpr(Scope *S, SourceLocation Loc, Expr *E) {
if (!ActOnCoroutineBodyStart(S, Loc, "co_yield")) {
CorrectDelayedTyposInExpr(E);
return ExprError();
}
checkSuspensionContext(*this, Loc, "co_yield");
// Build yield_value call.
ExprResult Awaitable = buildPromiseCall(
*this, getCurFunction()->CoroutinePromise, Loc, "yield_value", E);
if (Awaitable.isInvalid())
return ExprError();
// Build 'operator co_await' call.
Awaitable = buildOperatorCoawaitCall(*this, S, Loc, Awaitable.get());
if (Awaitable.isInvalid())
return ExprError();
return BuildCoyieldExpr(Loc, Awaitable.get());
}
ExprResult Sema::BuildCoyieldExpr(SourceLocation Loc, Expr *E) {
auto *Coroutine = checkCoroutineContext(*this, Loc, "co_yield");
if (!Coroutine)
return ExprError();
if (E->hasPlaceholderType()) {
ExprResult R = CheckPlaceholderExpr(E);
if (R.isInvalid()) return ExprError();
E = R.get();
}
if (E->getType()->isDependentType()) {
Expr *Res = new (Context) CoyieldExpr(Loc, Context.DependentTy, E);
return Res;
}
// If the expression is a temporary, materialize it as an lvalue so that we
// can use it multiple times.
if (E->isPRValue())
E = CreateMaterializeTemporaryExpr(E->getType(), E, true);
// Build the await_ready, await_suspend, await_resume calls.
ReadySuspendResumeResult RSS = buildCoawaitCalls(
*this, Coroutine->CoroutinePromise, Loc, E);
if (RSS.IsInvalid)
return ExprError();
Expr *Res =
new (Context) CoyieldExpr(Loc, E, RSS.Results[0], RSS.Results[1],
RSS.Results[2], RSS.OpaqueValue);
return Res;
}
StmtResult Sema::ActOnCoreturnStmt(Scope *S, SourceLocation Loc, Expr *E) {
if (!ActOnCoroutineBodyStart(S, Loc, "co_return")) {
CorrectDelayedTyposInExpr(E);
return StmtError();
}
return BuildCoreturnStmt(Loc, E);
}
StmtResult Sema::BuildCoreturnStmt(SourceLocation Loc, Expr *E,
bool IsImplicit) {
auto *FSI = checkCoroutineContext(*this, Loc, "co_return", IsImplicit);
if (!FSI)
return StmtError();
if (E && E->hasPlaceholderType() &&
!E->hasPlaceholderType(BuiltinType::Overload)) {
ExprResult R = CheckPlaceholderExpr(E);
if (R.isInvalid()) return StmtError();
E = R.get();
}
VarDecl *Promise = FSI->CoroutinePromise;
ExprResult PC;
if (E && (isa<InitListExpr>(E) || !E->getType()->isVoidType())) {
getNamedReturnInfo(E, SimplerImplicitMoveMode::ForceOn);
PC = buildPromiseCall(*this, Promise, Loc, "return_value", E);
} else {
E = MakeFullDiscardedValueExpr(E).get();
PC = buildPromiseCall(*this, Promise, Loc, "return_void", None);
}
if (PC.isInvalid())
return StmtError();
Expr *PCE = ActOnFinishFullExpr(PC.get(), /*DiscardedValue*/ false).get();
Stmt *Res = new (Context) CoreturnStmt(Loc, E, PCE, IsImplicit);
return Res;
}
/// Look up the std::nothrow object.
static Expr *buildStdNoThrowDeclRef(Sema &S, SourceLocation Loc) {
NamespaceDecl *Std = S.getStdNamespace();
assert(Std && "Should already be diagnosed");
LookupResult Result(S, &S.PP.getIdentifierTable().get("nothrow"), Loc,
Sema::LookupOrdinaryName);
if (!S.LookupQualifiedName(Result, Std)) {
// <coroutine> is not requred to include <new>, so we couldn't omit
// the check here.
S.Diag(Loc, diag::err_implicit_coroutine_std_nothrow_type_not_found);
return nullptr;
}
auto *VD = Result.getAsSingle<VarDecl>();
if (!VD) {
Result.suppressDiagnostics();
// We found something weird. Complain about the first thing we found.
NamedDecl *Found = *Result.begin();
S.Diag(Found->getLocation(), diag::err_malformed_std_nothrow);
return nullptr;
}
ExprResult DR = S.BuildDeclRefExpr(VD, VD->getType(), VK_LValue, Loc);
if (DR.isInvalid())
return nullptr;
return DR.get();
}
// Find an appropriate delete for the promise.
static FunctionDecl *findDeleteForPromise(Sema &S, SourceLocation Loc,
QualType PromiseType) {
FunctionDecl *OperatorDelete = nullptr;
DeclarationName DeleteName =
S.Context.DeclarationNames.getCXXOperatorName(OO_Delete);
auto *PointeeRD = PromiseType->getAsCXXRecordDecl();
assert(PointeeRD && "PromiseType must be a CxxRecordDecl type");
// [dcl.fct.def.coroutine]p12
// The deallocation function's name is looked up by searching for it in the
// scope of the promise type. If nothing is found, a search is performed in
// the global scope.
if (S.FindDeallocationFunction(Loc, PointeeRD, DeleteName, OperatorDelete))
return nullptr;
// FIXME: We didn't implement following selection:
// [dcl.fct.def.coroutine]p12
// If both a usual deallocation function with only a pointer parameter and a
// usual deallocation function with both a pointer parameter and a size
// parameter are found, then the selected deallocation function shall be the
// one with two parameters. Otherwise, the selected deallocation function
// shall be the function with one parameter.
if (!OperatorDelete) {
// Look for a global declaration.
const bool CanProvideSize = S.isCompleteType(Loc, PromiseType);
const bool Overaligned = false;
OperatorDelete = S.FindUsualDeallocationFunction(Loc, CanProvideSize,
Overaligned, DeleteName);
}
S.MarkFunctionReferenced(Loc, OperatorDelete);
return OperatorDelete;
}
void Sema::CheckCompletedCoroutineBody(FunctionDecl *FD, Stmt *&Body) {
FunctionScopeInfo *Fn = getCurFunction();
assert(Fn && Fn->isCoroutine() && "not a coroutine");
if (!Body) {
assert(FD->isInvalidDecl() &&
"a null body is only allowed for invalid declarations");
return;
}
// We have a function that uses coroutine keywords, but we failed to build
// the promise type.
if (!Fn->CoroutinePromise)
return FD->setInvalidDecl();
if (isa<CoroutineBodyStmt>(Body)) {
// Nothing todo. the body is already a transformed coroutine body statement.
return;
}
// The always_inline attribute doesn't reliably apply to a coroutine,
// because the coroutine will be split into pieces and some pieces
// might be called indirectly, as in a virtual call. Even the ramp
// function cannot be inlined at -O0, due to pipeline ordering
// problems (see https://llvm.org/PR53413). Tell the user about it.
if (FD->hasAttr<AlwaysInlineAttr>())
Diag(FD->getLocation(), diag::warn_always_inline_coroutine);
// [stmt.return.coroutine]p1:
// A coroutine shall not enclose a return statement ([stmt.return]).
if (Fn->FirstReturnLoc.isValid()) {
assert(Fn->FirstCoroutineStmtLoc.isValid() &&
"first coroutine location not set");
Diag(Fn->FirstReturnLoc, diag::err_return_in_coroutine);
Diag(Fn->FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
<< Fn->getFirstCoroutineStmtKeyword();
}
CoroutineStmtBuilder Builder(*this, *FD, *Fn, Body);
if (Builder.isInvalid() || !Builder.buildStatements())
return FD->setInvalidDecl();
// Build body for the coroutine wrapper statement.
Body = CoroutineBodyStmt::Create(Context, Builder);
}
CoroutineStmtBuilder::CoroutineStmtBuilder(Sema &S, FunctionDecl &FD,
sema::FunctionScopeInfo &Fn,
Stmt *Body)
: S(S), FD(FD), Fn(Fn), Loc(FD.getLocation()),
IsPromiseDependentType(
!Fn.CoroutinePromise ||
Fn.CoroutinePromise->getType()->isDependentType()) {
this->Body = Body;
for (auto KV : Fn.CoroutineParameterMoves)
this->ParamMovesVector.push_back(KV.second);
this->ParamMoves = this->ParamMovesVector;
if (!IsPromiseDependentType) {
PromiseRecordDecl = Fn.CoroutinePromise->getType()->getAsCXXRecordDecl();
assert(PromiseRecordDecl && "Type should have already been checked");
}
this->IsValid = makePromiseStmt() && makeInitialAndFinalSuspend();
}
bool CoroutineStmtBuilder::buildStatements() {
assert(this->IsValid && "coroutine already invalid");
this->IsValid = makeReturnObject();
if (this->IsValid && !IsPromiseDependentType)
buildDependentStatements();
return this->IsValid;
}
bool CoroutineStmtBuilder::buildDependentStatements() {
assert(this->IsValid && "coroutine already invalid");
assert(!this->IsPromiseDependentType &&
"coroutine cannot have a dependent promise type");
this->IsValid = makeOnException() && makeOnFallthrough() &&
makeGroDeclAndReturnStmt() && makeReturnOnAllocFailure() &&
makeNewAndDeleteExpr();
return this->IsValid;
}
bool CoroutineStmtBuilder::makePromiseStmt() {
// Form a declaration statement for the promise declaration, so that AST
// visitors can more easily find it.
StmtResult PromiseStmt =
S.ActOnDeclStmt(S.ConvertDeclToDeclGroup(Fn.CoroutinePromise), Loc, Loc);
if (PromiseStmt.isInvalid())
return false;
this->Promise = PromiseStmt.get();
return true;
}
bool CoroutineStmtBuilder::makeInitialAndFinalSuspend() {
if (Fn.hasInvalidCoroutineSuspends())
return false;
this->InitialSuspend = cast<Expr>(Fn.CoroutineSuspends.first);
this->FinalSuspend = cast<Expr>(Fn.CoroutineSuspends.second);
return true;
}
static bool diagReturnOnAllocFailure(Sema &S, Expr *E,
CXXRecordDecl *PromiseRecordDecl,
FunctionScopeInfo &Fn) {
auto Loc = E->getExprLoc();
if (auto *DeclRef = dyn_cast_or_null<DeclRefExpr>(E)) {
auto *Decl = DeclRef->getDecl();
if (CXXMethodDecl *Method = dyn_cast_or_null<CXXMethodDecl>(Decl)) {
if (Method->isStatic())
return true;
else
Loc = Decl->getLocation();
}
}
S.Diag(
Loc,
diag::err_coroutine_promise_get_return_object_on_allocation_failure)
<< PromiseRecordDecl;
S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
<< Fn.getFirstCoroutineStmtKeyword();
return false;
}
bool CoroutineStmtBuilder::makeReturnOnAllocFailure() {
assert(!IsPromiseDependentType &&
"cannot make statement while the promise type is dependent");
// [dcl.fct.def.coroutine]p10
// If a search for the name get_return_object_on_allocation_failure in
// the scope of the promise type ([class.member.lookup]) finds any
// declarations, then the result of a call to an allocation function used to
// obtain storage for the coroutine state is assumed to return nullptr if it
// fails to obtain storage, ... If the allocation function returns nullptr,
// ... and the return value is obtained by a call to
// T::get_return_object_on_allocation_failure(), where T is the
// promise type.
DeclarationName DN =
S.PP.getIdentifierInfo("get_return_object_on_allocation_failure");
LookupResult Found(S, DN, Loc, Sema::LookupMemberName);
if (!S.LookupQualifiedName(Found, PromiseRecordDecl))
return true;
CXXScopeSpec SS;
ExprResult DeclNameExpr =
S.BuildDeclarationNameExpr(SS, Found, /*NeedsADL=*/false);
if (DeclNameExpr.isInvalid())
return false;
if (!diagReturnOnAllocFailure(S, DeclNameExpr.get(), PromiseRecordDecl, Fn))
return false;
ExprResult ReturnObjectOnAllocationFailure =
S.BuildCallExpr(nullptr, DeclNameExpr.get(), Loc, {}, Loc);
if (ReturnObjectOnAllocationFailure.isInvalid())
return false;
StmtResult ReturnStmt =
S.BuildReturnStmt(Loc, ReturnObjectOnAllocationFailure.get());
if (ReturnStmt.isInvalid()) {
S.Diag(Found.getFoundDecl()->getLocation(), diag::note_member_declared_here)
<< DN;
S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
<< Fn.getFirstCoroutineStmtKeyword();
return false;
}
this->ReturnStmtOnAllocFailure = ReturnStmt.get();
return true;
}
bool CoroutineStmtBuilder::makeNewAndDeleteExpr() {
// Form and check allocation and deallocation calls.
assert(!IsPromiseDependentType &&
"cannot make statement while the promise type is dependent");
QualType PromiseType = Fn.CoroutinePromise->getType();
if (S.RequireCompleteType(Loc, PromiseType, diag::err_incomplete_type))
return false;
const bool RequiresNoThrowAlloc = ReturnStmtOnAllocFailure != nullptr;
// According to [dcl.fct.def.coroutine]p9, Lookup allocation functions using a
// parameter list composed of the requested size of the coroutine state being
// allocated, followed by the coroutine function's arguments. If a matching
// allocation function exists, use it. Otherwise, use an allocation function
// that just takes the requested size.
FunctionDecl *OperatorNew = nullptr;
FunctionDecl *OperatorDelete = nullptr;
FunctionDecl *UnusedResult = nullptr;
bool PassAlignment = false;
SmallVector<Expr *, 1> PlacementArgs;
// [dcl.fct.def.coroutine]p9
// An implementation may need to allocate additional storage for a
// coroutine.
// This storage is known as the coroutine state and is obtained by calling a
// non-array allocation function ([basic.stc.dynamic.allocation]). The
// allocation function's name is looked up by searching for it in the scope of
// the promise type.
// - If any declarations are found, overload resolution is performed on a
// function call created by assembling an argument list. The first argument is
// the amount of space requested, and has type std::size_t. The
// lvalues p1 ... pn are the succeeding arguments.
//
// ...where "p1 ... pn" are defined earlier as:
//
// [dcl.fct.def.coroutine]p3
// The promise type of a coroutine is `std::coroutine_traits<R, P1, ...,
// Pn>`
// , where R is the return type of the function, and `P1, ..., Pn` are the
// sequence of types of the non-object function parameters, preceded by the
// type of the object parameter ([dcl.fct]) if the coroutine is a non-static
// member function. [dcl.fct.def.coroutine]p4 In the following, p_i is an
// lvalue of type P_i, where p1 denotes the object parameter and p_i+1 denotes
// the i-th non-object function parameter for a non-static member function,
// and p_i denotes the i-th function parameter otherwise. For a non-static
// member function, q_1 is an lvalue that denotes *this; any other q_i is an
// lvalue that denotes the parameter copy corresponding to p_i.
if (auto *MD = dyn_cast<CXXMethodDecl>(&FD)) {
if (MD->isInstance() && !isLambdaCallOperator(MD)) {
ExprResult ThisExpr = S.ActOnCXXThis(Loc);
if (ThisExpr.isInvalid())
return false;
ThisExpr = S.CreateBuiltinUnaryOp(Loc, UO_Deref, ThisExpr.get());
if (ThisExpr.isInvalid())
return false;
PlacementArgs.push_back(ThisExpr.get());
}
}
for (auto *PD : FD.parameters()) {
if (PD->getType()->isDependentType())
continue;
// Build a reference to the parameter.
auto PDLoc = PD->getLocation();
ExprResult PDRefExpr =
S.BuildDeclRefExpr(PD, PD->getOriginalType().getNonReferenceType(),
ExprValueKind::VK_LValue, PDLoc);
if (PDRefExpr.isInvalid())
return false;
PlacementArgs.push_back(PDRefExpr.get());
}
S.FindAllocationFunctions(Loc, SourceRange(), /*NewScope*/ Sema::AFS_Class,
/*DeleteScope*/ Sema::AFS_Both, PromiseType,
/*isArray*/ false, PassAlignment, PlacementArgs,
OperatorNew, UnusedResult, /*Diagnose*/ false);
// [dcl.fct.def.coroutine]p9
// If no viable function is found ([over.match.viable]), overload resolution
// is performed again on a function call created by passing just the amount of
// space required as an argument of type std::size_t.
if (!OperatorNew && !PlacementArgs.empty()) {
PlacementArgs.clear();
S.FindAllocationFunctions(Loc, SourceRange(), /*NewScope*/ Sema::AFS_Class,
/*DeleteScope*/ Sema::AFS_Both, PromiseType,
/*isArray*/ false, PassAlignment, PlacementArgs,
OperatorNew, UnusedResult, /*Diagnose*/ false);
}
// [dcl.fct.def.coroutine]p9
// The allocation function's name is looked up by searching for it in the
// scope of the promise type.
// - If any declarations are found, ...
// - Otherwise, a search is performed in the global scope.
if (!OperatorNew) {
S.FindAllocationFunctions(Loc, SourceRange(), /*NewScope*/ Sema::AFS_Global,
/*DeleteScope*/ Sema::AFS_Both, PromiseType,
/*isArray*/ false, PassAlignment, PlacementArgs,
OperatorNew, UnusedResult);
}
bool IsGlobalOverload =
OperatorNew && !isa<CXXRecordDecl>(OperatorNew->getDeclContext());
// If we didn't find a class-local new declaration and non-throwing new
// was is required then we need to lookup the non-throwing global operator
// instead.
if (RequiresNoThrowAlloc && (!OperatorNew || IsGlobalOverload)) {
auto *StdNoThrow = buildStdNoThrowDeclRef(S, Loc);
if (!StdNoThrow)
return false;
PlacementArgs = {StdNoThrow};
OperatorNew = nullptr;
S.FindAllocationFunctions(Loc, SourceRange(), /*NewScope*/ Sema::AFS_Both,
/*DeleteScope*/ Sema::AFS_Both, PromiseType,
/*isArray*/ false, PassAlignment, PlacementArgs,
OperatorNew, UnusedResult);
}
if (!OperatorNew)
return false;
if (RequiresNoThrowAlloc) {
const auto *FT = OperatorNew->getType()->castAs<FunctionProtoType>();
if (!FT->isNothrow(/*ResultIfDependent*/ false)) {
S.Diag(OperatorNew->getLocation(),
diag::err_coroutine_promise_new_requires_nothrow)
<< OperatorNew;
S.Diag(Loc, diag::note_coroutine_promise_call_implicitly_required)
<< OperatorNew;
return false;
}
}
if ((OperatorDelete = findDeleteForPromise(S, Loc, PromiseType)) == nullptr) {
// FIXME: We should add an error here. According to:
// [dcl.fct.def.coroutine]p12
// If no usual deallocation function is found, the program is ill-formed.
return false;
}
Expr *FramePtr =
S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_frame, {});
Expr *FrameSize =
S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_size, {});
// Make new call.
ExprResult NewRef =
S.BuildDeclRefExpr(OperatorNew, OperatorNew->getType(), VK_LValue, Loc);
if (NewRef.isInvalid())
return false;
SmallVector<Expr *, 2> NewArgs(1, FrameSize);
llvm::append_range(NewArgs, PlacementArgs);
ExprResult NewExpr =
S.BuildCallExpr(S.getCurScope(), NewRef.get(), Loc, NewArgs, Loc);
NewExpr = S.ActOnFinishFullExpr(NewExpr.get(), /*DiscardedValue*/ false);
if (NewExpr.isInvalid())
return false;
// Make delete call.
QualType OpDeleteQualType = OperatorDelete->getType();
ExprResult DeleteRef =
S.BuildDeclRefExpr(OperatorDelete, OpDeleteQualType, VK_LValue, Loc);
if (DeleteRef.isInvalid())
return false;
Expr *CoroFree =
S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_free, {FramePtr});
SmallVector<Expr *, 2> DeleteArgs{CoroFree};
// [dcl.fct.def.coroutine]p12
// The selected deallocation function shall be called with the address of
// the block of storage to be reclaimed as its first argument. If a
// deallocation function with a parameter of type std::size_t is
// used, the size of the block is passed as the corresponding argument.
const auto *OpDeleteType =
OpDeleteQualType.getTypePtr()->castAs<FunctionProtoType>();
if (OpDeleteType->getNumParams() > 1)
DeleteArgs.push_back(FrameSize);
ExprResult DeleteExpr =
S.BuildCallExpr(S.getCurScope(), DeleteRef.get(), Loc, DeleteArgs, Loc);
DeleteExpr =
S.ActOnFinishFullExpr(DeleteExpr.get(), /*DiscardedValue*/ false);
if (DeleteExpr.isInvalid())
return false;
this->Allocate = NewExpr.get();
this->Deallocate = DeleteExpr.get();
return true;
}
bool CoroutineStmtBuilder::makeOnFallthrough() {
assert(!IsPromiseDependentType &&
"cannot make statement while the promise type is dependent");
// [dcl.fct.def.coroutine]/p6
// If searches for the names return_void and return_value in the scope of
// the promise type each find any declarations, the program is ill-formed.
// [Note 1: If return_void is found, flowing off the end of a coroutine is
// equivalent to a co_return with no operand. Otherwise, flowing off the end
// of a coroutine results in undefined behavior ([stmt.return.coroutine]). —
// end note]
bool HasRVoid, HasRValue;
LookupResult LRVoid =
lookupMember(S, "return_void", PromiseRecordDecl, Loc, HasRVoid);
LookupResult LRValue =
lookupMember(S, "return_value", PromiseRecordDecl, Loc, HasRValue);
StmtResult Fallthrough;
if (HasRVoid && HasRValue) {
// FIXME Improve this diagnostic
S.Diag(FD.getLocation(),
diag::err_coroutine_promise_incompatible_return_functions)
<< PromiseRecordDecl;
S.Diag(LRVoid.getRepresentativeDecl()->getLocation(),
diag::note_member_first_declared_here)
<< LRVoid.getLookupName();
S.Diag(LRValue.getRepresentativeDecl()->getLocation(),
diag::note_member_first_declared_here)
<< LRValue.getLookupName();
return false;
} else if (!HasRVoid && !HasRValue) {
// We need to set 'Fallthrough'. Otherwise the other analysis part might
// think the coroutine has defined a return_value method. So it might emit
// **false** positive warning. e.g.,
//
// promise_without_return_func foo() {
// co_await something();
// }
//
// Then AnalysisBasedWarning would emit a warning about `foo()` lacking a
// co_return statements, which isn't correct.
Fallthrough = S.ActOnNullStmt(PromiseRecordDecl->getLocation());
if (Fallthrough.isInvalid())
return false;
} else if (HasRVoid) {
Fallthrough = S.BuildCoreturnStmt(FD.getLocation(), nullptr,
/*IsImplicit*/false);
Fallthrough = S.ActOnFinishFullStmt(Fallthrough.get());
if (Fallthrough.isInvalid())
return false;
}
this->OnFallthrough = Fallthrough.get();
return true;
}
bool CoroutineStmtBuilder::makeOnException() {
// Try to form 'p.unhandled_exception();'
assert(!IsPromiseDependentType &&
"cannot make statement while the promise type is dependent");
const bool RequireUnhandledException = S.getLangOpts().CXXExceptions;
if (!lookupMember(S, "unhandled_exception", PromiseRecordDecl, Loc)) {
auto DiagID =
RequireUnhandledException
? diag::err_coroutine_promise_unhandled_exception_required
: diag::
warn_coroutine_promise_unhandled_exception_required_with_exceptions;
S.Diag(Loc, DiagID) << PromiseRecordDecl;
S.Diag(PromiseRecordDecl->getLocation(), diag::note_defined_here)
<< PromiseRecordDecl;
return !RequireUnhandledException;
}
// If exceptions are disabled, don't try to build OnException.
if (!S.getLangOpts().CXXExceptions)
return true;
ExprResult UnhandledException = buildPromiseCall(S, Fn.CoroutinePromise, Loc,
"unhandled_exception", None);
UnhandledException = S.ActOnFinishFullExpr(UnhandledException.get(), Loc,
/*DiscardedValue*/ false);
if (UnhandledException.isInvalid())
return false;
// Since the body of the coroutine will be wrapped in try-catch, it will
// be incompatible with SEH __try if present in a function.
if (!S.getLangOpts().Borland && Fn.FirstSEHTryLoc.isValid()) {
S.Diag(Fn.FirstSEHTryLoc, diag::err_seh_in_a_coroutine_with_cxx_exceptions);
S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
<< Fn.getFirstCoroutineStmtKeyword();
return false;
}
this->OnException = UnhandledException.get();
return true;
}
bool CoroutineStmtBuilder::makeReturnObject() {
// [dcl.fct.def.coroutine]p7
// The expression promise.get_return_object() is used to initialize the
// returned reference or prvalue result object of a call to a coroutine.
ExprResult ReturnObject =
buildPromiseCall(S, Fn.CoroutinePromise, Loc, "get_return_object", None);
if (ReturnObject.isInvalid())
return false;
this->ReturnValue = ReturnObject.get();
return true;
}
static void noteMemberDeclaredHere(Sema &S, Expr *E, FunctionScopeInfo &Fn) {
if (auto *MbrRef = dyn_cast<CXXMemberCallExpr>(E)) {
auto *MethodDecl = MbrRef->getMethodDecl();
S.Diag(MethodDecl->getLocation(), diag::note_member_declared_here)
<< MethodDecl;
}
S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
<< Fn.getFirstCoroutineStmtKeyword();
}
bool CoroutineStmtBuilder::makeGroDeclAndReturnStmt() {
assert(!IsPromiseDependentType &&
"cannot make statement while the promise type is dependent");
assert(this->ReturnValue && "ReturnValue must be already formed");
QualType const GroType = this->ReturnValue->getType();
assert(!GroType->isDependentType() &&
"get_return_object type must no longer be dependent");
QualType const FnRetType = FD.getReturnType();
assert(!FnRetType->isDependentType() &&
"get_return_object type must no longer be dependent");
if (FnRetType->isVoidType()) {
ExprResult Res =
S.ActOnFinishFullExpr(this->ReturnValue, Loc, /*DiscardedValue*/ false);
if (Res.isInvalid())
return false;
return true;
}
if (GroType->isVoidType()) {
// Trigger a nice error message.
InitializedEntity Entity =
InitializedEntity::InitializeResult(Loc, FnRetType);
S.PerformCopyInitialization(Entity, SourceLocation(), ReturnValue);
noteMemberDeclaredHere(S, ReturnValue, Fn);
return false;
}
StmtResult ReturnStmt = S.BuildReturnStmt(Loc, ReturnValue);
if (ReturnStmt.isInvalid()) {
noteMemberDeclaredHere(S, ReturnValue, Fn);
return false;
}
this->ReturnStmt = ReturnStmt.get();
return true;
}
// Create a static_cast\<T&&>(expr).
static Expr *castForMoving(Sema &S, Expr *E, QualType T = QualType()) {
if (T.isNull())
T = E->getType();
QualType TargetType = S.BuildReferenceType(
T, /*SpelledAsLValue*/ false, SourceLocation(), DeclarationName());
SourceLocation ExprLoc = E->getBeginLoc();
TypeSourceInfo *TargetLoc =
S.Context.getTrivialTypeSourceInfo(TargetType, ExprLoc);
return S
.BuildCXXNamedCast(ExprLoc, tok::kw_static_cast, TargetLoc, E,
SourceRange(ExprLoc, ExprLoc), E->getSourceRange())
.get();
}
/// Build a variable declaration for move parameter.
static VarDecl *buildVarDecl(Sema &S, SourceLocation Loc, QualType Type,
IdentifierInfo *II) {
TypeSourceInfo *TInfo = S.Context.getTrivialTypeSourceInfo(Type, Loc);
VarDecl *Decl = VarDecl::Create(S.Context, S.CurContext, Loc, Loc, II, Type,
TInfo, SC_None);
Decl->setImplicit();
return Decl;
}
// Build statements that move coroutine function parameters to the coroutine
// frame, and store them on the function scope info.
bool Sema::buildCoroutineParameterMoves(SourceLocation Loc) {
assert(isa<FunctionDecl>(CurContext) && "not in a function scope");
auto *FD = cast<FunctionDecl>(CurContext);
auto *ScopeInfo = getCurFunction();
if (!ScopeInfo->CoroutineParameterMoves.empty())
return false;
// [dcl.fct.def.coroutine]p13
// When a coroutine is invoked, after initializing its parameters
// ([expr.call]), a copy is created for each coroutine parameter. For a
// parameter of type cv T, the copy is a variable of type cv T with
// automatic storage duration that is direct-initialized from an xvalue of
// type T referring to the parameter.
for (auto *PD : FD->parameters()) {
if (PD->getType()->isDependentType())
continue;
ExprResult PDRefExpr =
BuildDeclRefExpr(PD, PD->getType().getNonReferenceType(),
ExprValueKind::VK_LValue, Loc); // FIXME: scope?
if (PDRefExpr.isInvalid())
return false;
Expr *CExpr = nullptr;
if (PD->getType()->getAsCXXRecordDecl() ||
PD->getType()->isRValueReferenceType())
CExpr = castForMoving(*this, PDRefExpr.get());
else
CExpr = PDRefExpr.get();
// [dcl.fct.def.coroutine]p13
// The initialization and destruction of each parameter copy occurs in the
// context of the called coroutine.
auto D = buildVarDecl(*this, Loc, PD->getType(), PD->getIdentifier());
AddInitializerToDecl(D, CExpr, /*DirectInit=*/true);
// Convert decl to a statement.
StmtResult Stmt = ActOnDeclStmt(ConvertDeclToDeclGroup(D), Loc, Loc);
if (Stmt.isInvalid())
return false;
ScopeInfo->CoroutineParameterMoves.insert(std::make_pair(PD, Stmt.get()));
}
return true;
}
StmtResult Sema::BuildCoroutineBodyStmt(CoroutineBodyStmt::CtorArgs Args) {
CoroutineBodyStmt *Res = CoroutineBodyStmt::Create(Context, Args);
if (!Res)
return StmtError();
return Res;
}
ClassTemplateDecl *Sema::lookupCoroutineTraits(SourceLocation KwLoc,
SourceLocation FuncLoc,
NamespaceDecl *&Namespace) {
if (!StdCoroutineTraitsCache) {
// Because coroutines moved from std::experimental in the TS to std in
// C++20, we look in both places to give users time to transition their
// TS-specific code to C++20. Diagnostics are given when the TS usage is
// discovered.
// TODO: Become stricter when <experimental/coroutine> is removed.
auto const &TraitIdent = PP.getIdentifierTable().get("coroutine_traits");
NamespaceDecl *StdSpace = getStdNamespace();
LookupResult ResStd(*this, &TraitIdent, FuncLoc, LookupOrdinaryName);
bool InStd = StdSpace && LookupQualifiedName(ResStd, StdSpace);
NamespaceDecl *ExpSpace = lookupStdExperimentalNamespace();
LookupResult ResExp(*this, &TraitIdent, FuncLoc, LookupOrdinaryName);
bool InExp = ExpSpace && LookupQualifiedName(ResExp, ExpSpace);
if (!InStd && !InExp) {
// The goggles, they found nothing!
Diag(KwLoc, diag::err_implied_coroutine_type_not_found)
<< "std::coroutine_traits";
return nullptr;
}
// Prefer ::std to std::experimental.
auto &Result = InStd ? ResStd : ResExp;
CoroTraitsNamespaceCache = InStd ? StdSpace : ExpSpace;
// coroutine_traits is required to be a class template.
StdCoroutineTraitsCache = Result.getAsSingle<ClassTemplateDecl>();
if (!StdCoroutineTraitsCache) {
Result.suppressDiagnostics();
NamedDecl *Found = *Result.begin();
Diag(Found->getLocation(), diag::err_malformed_std_coroutine_traits);
return nullptr;
}
if (InExp) {
// Found in std::experimental
Diag(KwLoc, diag::warn_deprecated_coroutine_namespace)
<< "coroutine_traits";
ResExp.suppressDiagnostics();
auto *Found = *ResExp.begin();
Diag(Found->getLocation(), diag::note_entity_declared_at) << Found;
if (InStd &&
StdCoroutineTraitsCache != ResExp.getAsSingle<ClassTemplateDecl>()) {
// Also found something different in std
Diag(KwLoc,
diag::err_mixed_use_std_and_experimental_namespace_for_coroutine);
Diag(StdCoroutineTraitsCache->getLocation(),
diag::note_entity_declared_at)
<< StdCoroutineTraitsCache;
return nullptr;
}
}
}
Namespace = CoroTraitsNamespaceCache;
return StdCoroutineTraitsCache;
}
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