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When determining whether a lambda-expression is implicitly constexpr, 

check the formal rules rather than seeing if the normal checks produce a
diagnostic.

This fixes the handling of C++2a extensions in lambdas in C++17 mode,
as well as some corner cases in earlier language modes where we issue
diagnostics for things other than not satisfying the formal constexpr
requirements.

llvm-svn: 367254
This commit is contained in:
Richard Smith 2019-07-29 19:59:45 +00:00
parent 8e9516f2aa
commit a625da716c
6 changed files with 267 additions and 117 deletions
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12
clang/include/clang/Sema/Sema.h
View File

@ -2076,8 +2076,16 @@ public:
bool &AddToScope);
bool AddOverriddenMethods(CXXRecordDecl *DC, CXXMethodDecl *MD);
bool CheckConstexprFunctionDecl(const FunctionDecl *FD);
bool CheckConstexprFunctionBody(const FunctionDecl *FD, Stmt *Body);
enum class CheckConstexprKind {
/// Diagnose issues that are non-constant or that are extensions.
Diagnose,
/// Identify whether this function satisfies the formal rules for constexpr
/// functions in the current lanugage mode (with no extensions).
CheckValid
};
bool CheckConstexprFunctionDefinition(const FunctionDecl *FD,
CheckConstexprKind Kind);
void DiagnoseHiddenVirtualMethods(CXXMethodDecl *MD);
void FindHiddenVirtualMethods(CXXMethodDecl *MD,

3
clang/lib/Sema/SemaDecl.cpp
View File

@ -13532,8 +13532,7 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
}
if (!IsInstantiation && FD && FD->isConstexpr() && !FD->isInvalidDecl() &&
(!CheckConstexprFunctionDecl(FD) ||
!CheckConstexprFunctionBody(FD, Body)))
!CheckConstexprFunctionDefinition(FD, CheckConstexprKind::Diagnose))
FD->setInvalidDecl();
if (FD && FD->hasAttr<NakedAttr>()) {

330
clang/lib/Sema/SemaDeclCXX.cpp
View File

@ -1569,11 +1569,34 @@ void Sema::CheckCXXDefaultArguments(FunctionDecl *FD) {
}
}
/// Check that the given type is a literal type. Issue a diagnostic if not,
/// if Kind is Diagnose.
/// \return \c true if a problem has been found (and optionally diagnosed).
template <typename... Ts>
static bool CheckLiteralType(Sema &SemaRef, Sema::CheckConstexprKind Kind,
SourceLocation Loc, QualType T, unsigned DiagID,
Ts &&...DiagArgs) {
if (T->isDependentType())
return false;
switch (Kind) {
case Sema::CheckConstexprKind::Diagnose:
return SemaRef.RequireLiteralType(Loc, T, DiagID,
std::forward<Ts>(DiagArgs)...);
case Sema::CheckConstexprKind::CheckValid:
return !T->isLiteralType(SemaRef.Context);
}
llvm_unreachable("unknown CheckConstexprKind");
}
// CheckConstexprParameterTypes - Check whether a function's parameter types
// are all literal types. If so, return true. If not, produce a suitable
// diagnostic and return false.
static bool CheckConstexprParameterTypes(Sema &SemaRef,
const FunctionDecl *FD) {
const FunctionDecl *FD,
Sema::CheckConstexprKind Kind) {
unsigned ArgIndex = 0;
const FunctionProtoType *FT = FD->getType()->getAs<FunctionProtoType>();
for (FunctionProtoType::param_type_iterator i = FT->param_type_begin(),
@ -1581,11 +1604,10 @@ static bool CheckConstexprParameterTypes(Sema &SemaRef,
i != e; ++i, ++ArgIndex) {
const ParmVarDecl *PD = FD->getParamDecl(ArgIndex);
SourceLocation ParamLoc = PD->getLocation();
if (!(*i)->isDependentType() &&
SemaRef.RequireLiteralType(
ParamLoc, *i, diag::err_constexpr_non_literal_param, ArgIndex + 1,
PD->getSourceRange(), isa<CXXConstructorDecl>(FD),
FD->isConsteval()))
if (CheckLiteralType(SemaRef, Kind, ParamLoc, *i,
diag::err_constexpr_non_literal_param, ArgIndex + 1,
PD->getSourceRange(), isa<CXXConstructorDecl>(FD),
FD->isConsteval()))
return false;
}
return true;
@ -1605,13 +1627,18 @@ static unsigned getRecordDiagFromTagKind(TagTypeKind Tag) {
}
}
// CheckConstexprFunctionDecl - Check whether a function declaration satisfies
// the requirements of a constexpr function definition or a constexpr
// constructor definition. If so, return true. If not, produce appropriate
// diagnostics and return false.
static bool CheckConstexprFunctionBody(Sema &SemaRef, const FunctionDecl *Dcl,
Stmt *Body,
Sema::CheckConstexprKind Kind);
// Check whether a function declaration satisfies the requirements of a
// constexpr function definition or a constexpr constructor definition. If so,
// return true. If not, produce appropriate diagnostics (unless asked not to by
// Kind) and return false.
//
// This implements C++11 [dcl.constexpr]p3,4, as amended by DR1360.
bool Sema::CheckConstexprFunctionDecl(const FunctionDecl *NewFD) {
bool Sema::CheckConstexprFunctionDefinition(const FunctionDecl *NewFD,
CheckConstexprKind Kind) {
const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(NewFD);
if (MD && MD->isInstance()) {
// C++11 [dcl.constexpr]p4:
@ -1623,6 +1650,9 @@ bool Sema::CheckConstexprFunctionDecl(const FunctionDecl *NewFD) {
// functions.
const CXXRecordDecl *RD = MD->getParent();
if (RD->getNumVBases()) {
if (Kind == CheckConstexprKind::CheckValid)
return false;
Diag(NewFD->getLocation(), diag::err_constexpr_virtual_base)
<< isa<CXXConstructorDecl>(NewFD)
<< getRecordDiagFromTagKind(RD->getTagKind()) << RD->getNumVBases();
@ -1641,8 +1671,12 @@ bool Sema::CheckConstexprFunctionDecl(const FunctionDecl *NewFD) {
const CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(NewFD);
if (Method && Method->isVirtual()) {
if (getLangOpts().CPlusPlus2a) {
Diag(Method->getLocation(), diag::warn_cxx17_compat_constexpr_virtual);
if (Kind == CheckConstexprKind::Diagnose)
Diag(Method->getLocation(), diag::warn_cxx17_compat_constexpr_virtual);
} else {
if (Kind == CheckConstexprKind::CheckValid)
return false;
Method = Method->getCanonicalDecl();
Diag(Method->getLocation(), diag::err_constexpr_virtual);
@ -1660,18 +1694,20 @@ bool Sema::CheckConstexprFunctionDecl(const FunctionDecl *NewFD) {
// - its return type shall be a literal type;
QualType RT = NewFD->getReturnType();
if (!RT->isDependentType() &&
RequireLiteralType(NewFD->getLocation(), RT,
diag::err_constexpr_non_literal_return,
NewFD->isConsteval()))
if (CheckLiteralType(*this, Kind, NewFD->getLocation(), RT,
diag::err_constexpr_non_literal_return,
NewFD->isConsteval()))
return false;
}
// - each of its parameter types shall be a literal type;
if (!CheckConstexprParameterTypes(*this, NewFD))
if (!CheckConstexprParameterTypes(*this, NewFD, Kind))
return false;
return true;
Stmt *Body = NewFD->getBody();
assert(Body &&
"CheckConstexprFunctionDefinition called on function with no body");
return CheckConstexprFunctionBody(*this, NewFD, Body, Kind);
}
/// Check the given declaration statement is legal within a constexpr function
@ -1680,7 +1716,8 @@ bool Sema::CheckConstexprFunctionDecl(const FunctionDecl *NewFD) {
/// \return true if the body is OK (maybe only as an extension), false if we
/// have diagnosed a problem.
static bool CheckConstexprDeclStmt(Sema &SemaRef, const FunctionDecl *Dcl,
DeclStmt *DS, SourceLocation &Cxx1yLoc) {
DeclStmt *DS, SourceLocation &Cxx1yLoc,
Sema::CheckConstexprKind Kind) {
// C++11 [dcl.constexpr]p3 and p4:
// The definition of a constexpr function(p3) or constructor(p4) [...] shall
// contain only
@ -1704,10 +1741,12 @@ static bool CheckConstexprDeclStmt(Sema &SemaRef, const FunctionDecl *Dcl,
const auto *TN = cast<TypedefNameDecl>(DclIt);
if (TN->getUnderlyingType()->isVariablyModifiedType()) {
// Don't allow variably-modified types in constexpr functions.
TypeLoc TL = TN->getTypeSourceInfo()->getTypeLoc();
SemaRef.Diag(TL.getBeginLoc(), diag::err_constexpr_vla)
<< TL.getSourceRange() << TL.getType()
<< isa<CXXConstructorDecl>(Dcl);
if (Kind == Sema::CheckConstexprKind::Diagnose) {
TypeLoc TL = TN->getTypeSourceInfo()->getTypeLoc();
SemaRef.Diag(TL.getBeginLoc(), diag::err_constexpr_vla)
<< TL.getSourceRange() << TL.getType()
<< isa<CXXConstructorDecl>(Dcl);
}
return false;
}
continue;
@ -1716,12 +1755,17 @@ static bool CheckConstexprDeclStmt(Sema &SemaRef, const FunctionDecl *Dcl,
case Decl::Enum:
case Decl::CXXRecord:
// C++1y allows types to be defined, not just declared.
if (cast<TagDecl>(DclIt)->isThisDeclarationADefinition())
SemaRef.Diag(DS->getBeginLoc(),
SemaRef.getLangOpts().CPlusPlus14
? diag::warn_cxx11_compat_constexpr_type_definition
: diag::ext_constexpr_type_definition)
<< isa<CXXConstructorDecl>(Dcl);
if (cast<TagDecl>(DclIt)->isThisDeclarationADefinition()) {
if (Kind == Sema::CheckConstexprKind::Diagnose) {
SemaRef.Diag(DS->getBeginLoc(),
SemaRef.getLangOpts().CPlusPlus14
? diag::warn_cxx11_compat_constexpr_type_definition
: diag::ext_constexpr_type_definition)
<< isa<CXXConstructorDecl>(Dcl);
} else if (!SemaRef.getLangOpts().CPlusPlus14) {
return false;
}
}
continue;
case Decl::EnumConstant:
@ -1739,31 +1783,37 @@ static bool CheckConstexprDeclStmt(Sema &SemaRef, const FunctionDecl *Dcl,
const auto *VD = cast<VarDecl>(DclIt);
if (VD->isThisDeclarationADefinition()) {
if (VD->isStaticLocal()) {
SemaRef.Diag(VD->getLocation(),
diag::err_constexpr_local_var_static)
<< isa<CXXConstructorDecl>(Dcl)
<< (VD->getTLSKind() == VarDecl::TLS_Dynamic);
if (Kind == Sema::CheckConstexprKind::Diagnose) {
SemaRef.Diag(VD->getLocation(),
diag::err_constexpr_local_var_static)
<< isa<CXXConstructorDecl>(Dcl)
<< (VD->getTLSKind() == VarDecl::TLS_Dynamic);
}
return false;
}
if (!VD->getType()->isDependentType() &&
SemaRef.RequireLiteralType(
VD->getLocation(), VD->getType(),
diag::err_constexpr_local_var_non_literal_type,
isa<CXXConstructorDecl>(Dcl)))
if (CheckLiteralType(SemaRef, Kind, VD->getLocation(), VD->getType(),
diag::err_constexpr_local_var_non_literal_type,
isa<CXXConstructorDecl>(Dcl)))
return false;
if (!VD->getType()->isDependentType() &&
!VD->hasInit() && !VD->isCXXForRangeDecl()) {
SemaRef.Diag(VD->getLocation(),
diag::err_constexpr_local_var_no_init)
<< isa<CXXConstructorDecl>(Dcl);
if (Kind == Sema::CheckConstexprKind::Diagnose) {
SemaRef.Diag(VD->getLocation(),
diag::err_constexpr_local_var_no_init)
<< isa<CXXConstructorDecl>(Dcl);
}
return false;
}
}
SemaRef.Diag(VD->getLocation(),
SemaRef.getLangOpts().CPlusPlus14
? diag::warn_cxx11_compat_constexpr_local_var
: diag::ext_constexpr_local_var)
<< isa<CXXConstructorDecl>(Dcl);
if (Kind == Sema::CheckConstexprKind::Diagnose) {
SemaRef.Diag(VD->getLocation(),
SemaRef.getLangOpts().CPlusPlus14
? diag::warn_cxx11_compat_constexpr_local_var
: diag::ext_constexpr_local_var)
<< isa<CXXConstructorDecl>(Dcl);
} else if (!SemaRef.getLangOpts().CPlusPlus14) {
return false;
}
continue;
}
@ -1776,8 +1826,10 @@ static bool CheckConstexprDeclStmt(Sema &SemaRef, const FunctionDecl *Dcl,
continue;
default:
SemaRef.Diag(DS->getBeginLoc(), diag::err_constexpr_body_invalid_stmt)
<< isa<CXXConstructorDecl>(Dcl) << Dcl->isConsteval();
if (Kind == Sema::CheckConstexprKind::Diagnose) {
SemaRef.Diag(DS->getBeginLoc(), diag::err_constexpr_body_invalid_stmt)
<< isa<CXXConstructorDecl>(Dcl) << Dcl->isConsteval();
}
return false;
}
}
@ -1792,17 +1844,23 @@ static bool CheckConstexprDeclStmt(Sema &SemaRef, const FunctionDecl *Dcl,
/// struct or union nested within the class being checked.
/// \param Inits All declarations, including anonymous struct/union members and
/// indirect members, for which any initialization was provided.
/// \param Diagnosed Set to true if an error is produced.
static void CheckConstexprCtorInitializer(Sema &SemaRef,
/// \param Diagnosed Whether we've emitted the error message yet. Used to attach
/// multiple notes for different members to the same error.
/// \param Kind Whether we're diagnosing a constructor as written or determining
/// whether the formal requirements are satisfied.
/// \return \c false if we're checking for validity and the constructor does
/// not satisfy the requirements on a constexpr constructor.
static bool CheckConstexprCtorInitializer(Sema &SemaRef,
const FunctionDecl *Dcl,
FieldDecl *Field,
llvm::SmallSet<Decl*, 16> &Inits,
bool &Diagnosed) {
bool &Diagnosed,
Sema::CheckConstexprKind Kind) {
if (Field->isInvalidDecl())
return;
return true;
if (Field->isUnnamedBitfield())
return;
return true;
// Anonymous unions with no variant members and empty anonymous structs do not
// need to be explicitly initialized. FIXME: Anonymous structs that contain no
@ -1811,22 +1869,30 @@ static void CheckConstexprCtorInitializer(Sema &SemaRef,
(Field->getType()->isUnionType()
? !Field->getType()->getAsCXXRecordDecl()->hasVariantMembers()
: Field->getType()->getAsCXXRecordDecl()->isEmpty()))
return;
return true;
if (!Inits.count(Field)) {
if (!Diagnosed) {
SemaRef.Diag(Dcl->getLocation(), diag::err_constexpr_ctor_missing_init);
Diagnosed = true;
if (Kind == Sema::CheckConstexprKind::Diagnose) {
if (!Diagnosed) {
SemaRef.Diag(Dcl->getLocation(), diag::err_constexpr_ctor_missing_init);
Diagnosed = true;
}
SemaRef.Diag(Field->getLocation(),
diag::note_constexpr_ctor_missing_init);
} else {
return false;
}
SemaRef.Diag(Field->getLocation(), diag::note_constexpr_ctor_missing_init);
} else if (Field->isAnonymousStructOrUnion()) {
const RecordDecl *RD = Field->getType()->castAs<RecordType>()->getDecl();
for (auto *I : RD->fields())
// If an anonymous union contains an anonymous struct of which any member
// is initialized, all members must be initialized.
if (!RD->isUnion() || Inits.count(I))
CheckConstexprCtorInitializer(SemaRef, Dcl, I, Inits, Diagnosed);
if (!CheckConstexprCtorInitializer(SemaRef, Dcl, I, Inits, Diagnosed,
Kind))
return false;
}
return true;
}
/// Check the provided statement is allowed in a constexpr function
@ -1834,7 +1900,8 @@ static void CheckConstexprCtorInitializer(Sema &SemaRef,
static bool
CheckConstexprFunctionStmt(Sema &SemaRef, const FunctionDecl *Dcl, Stmt *S,
SmallVectorImpl<SourceLocation> &ReturnStmts,
SourceLocation &Cxx1yLoc, SourceLocation &Cxx2aLoc) {
SourceLocation &Cxx1yLoc, SourceLocation &Cxx2aLoc,
Sema::CheckConstexprKind Kind) {
// - its function-body shall be [...] a compound-statement that contains only
switch (S->getStmtClass()) {
case Stmt::NullStmtClass:
@ -1847,7 +1914,7 @@ CheckConstexprFunctionStmt(Sema &SemaRef, const FunctionDecl *Dcl, Stmt *S,
// - using-directives,
// - typedef declarations and alias-declarations that do not define
// classes or enumerations,
if (!CheckConstexprDeclStmt(SemaRef, Dcl, cast<DeclStmt>(S), Cxx1yLoc))
if (!CheckConstexprDeclStmt(SemaRef, Dcl, cast<DeclStmt>(S), Cxx1yLoc, Kind))
return false;
return true;
@ -1871,7 +1938,7 @@ CheckConstexprFunctionStmt(Sema &SemaRef, const FunctionDecl *Dcl, Stmt *S,
CompoundStmt *CompStmt = cast<CompoundStmt>(S);
for (auto *BodyIt : CompStmt->body()) {
if (!CheckConstexprFunctionStmt(SemaRef, Dcl, BodyIt, ReturnStmts,
Cxx1yLoc, Cxx2aLoc))
Cxx1yLoc, Cxx2aLoc, Kind))
return false;
}
return true;
@ -1889,11 +1956,11 @@ CheckConstexprFunctionStmt(Sema &SemaRef, const FunctionDecl *Dcl, Stmt *S,
IfStmt *If = cast<IfStmt>(S);
if (!CheckConstexprFunctionStmt(SemaRef, Dcl, If->getThen(), ReturnStmts,
Cxx1yLoc, Cxx2aLoc))
Cxx1yLoc, Cxx2aLoc, Kind))
return false;
if (If->getElse() &&
!CheckConstexprFunctionStmt(SemaRef, Dcl, If->getElse(), ReturnStmts,
Cxx1yLoc, Cxx2aLoc))
Cxx1yLoc, Cxx2aLoc, Kind))
return false;
return true;
}
@ -1912,7 +1979,7 @@ CheckConstexprFunctionStmt(Sema &SemaRef, const FunctionDecl *Dcl, Stmt *S,
for (Stmt *SubStmt : S->children())
if (SubStmt &&
!CheckConstexprFunctionStmt(SemaRef, Dcl, SubStmt, ReturnStmts,
Cxx1yLoc, Cxx2aLoc))
Cxx1yLoc, Cxx2aLoc, Kind))
return false;
return true;
@ -1927,7 +1994,7 @@ CheckConstexprFunctionStmt(Sema &SemaRef, const FunctionDecl *Dcl, Stmt *S,
for (Stmt *SubStmt : S->children())
if (SubStmt &&
!CheckConstexprFunctionStmt(SemaRef, Dcl, SubStmt, ReturnStmts,
Cxx1yLoc, Cxx2aLoc))
Cxx1yLoc, Cxx2aLoc, Kind))
return false;
return true;
@ -1937,7 +2004,7 @@ CheckConstexprFunctionStmt(Sema &SemaRef, const FunctionDecl *Dcl, Stmt *S,
for (Stmt *SubStmt : S->children()) {
if (SubStmt &&
!CheckConstexprFunctionStmt(SemaRef, Dcl, SubStmt, ReturnStmts,
Cxx1yLoc, Cxx2aLoc))
Cxx1yLoc, Cxx2aLoc, Kind))
return false;
}
return true;
@ -1947,7 +2014,7 @@ CheckConstexprFunctionStmt(Sema &SemaRef, const FunctionDecl *Dcl, Stmt *S,
// try block check).
if (!CheckConstexprFunctionStmt(SemaRef, Dcl,
cast<CXXCatchStmt>(S)->getHandlerBlock(),
ReturnStmts, Cxx1yLoc, Cxx2aLoc))
ReturnStmts, Cxx1yLoc, Cxx2aLoc, Kind))
return false;
return true;
@ -1961,16 +2028,21 @@ CheckConstexprFunctionStmt(Sema &SemaRef, const FunctionDecl *Dcl, Stmt *S,
return true;
}
SemaRef.Diag(S->getBeginLoc(), diag::err_constexpr_body_invalid_stmt)
<< isa<CXXConstructorDecl>(Dcl) << Dcl->isConsteval();
if (Kind == Sema::CheckConstexprKind::Diagnose) {
SemaRef.Diag(S->getBeginLoc(), diag::err_constexpr_body_invalid_stmt)
<< isa<CXXConstructorDecl>(Dcl) << Dcl->isConsteval();
}
return false;
}
/// Check the body for the given constexpr function declaration only contains
/// the permitted types of statement. C++11 [dcl.constexpr]p3,p4.
///
/// \return true if the body is OK, false if we have diagnosed a problem.
bool Sema::CheckConstexprFunctionBody(const FunctionDecl *Dcl, Stmt *Body) {
/// \return true if the body is OK, false if we have found or diagnosed a
/// problem.
static bool CheckConstexprFunctionBody(Sema &SemaRef, const FunctionDecl *Dcl,
Stmt *Body,
Sema::CheckConstexprKind Kind) {
SmallVector<SourceLocation, 4> ReturnStmts;
if (isa<CXXTryStmt>(Body)) {
@ -1986,11 +2058,20 @@ bool Sema::CheckConstexprFunctionBody(const FunctionDecl *Dcl, Stmt *Body) {
//
// This restriction is lifted in C++2a, as long as inner statements also
// apply the general constexpr rules.
Diag(Body->getBeginLoc(),
!getLangOpts().CPlusPlus2a
? diag::ext_constexpr_function_try_block_cxx2a
: diag::warn_cxx17_compat_constexpr_function_try_block)
<< isa<CXXConstructorDecl>(Dcl);
switch (Kind) {
case Sema::CheckConstexprKind::CheckValid:
if (!SemaRef.getLangOpts().CPlusPlus2a)
return false;
break;
case Sema::CheckConstexprKind::Diagnose:
SemaRef.Diag(Body->getBeginLoc(),
!SemaRef.getLangOpts().CPlusPlus2a
? diag::ext_constexpr_function_try_block_cxx2a
: diag::warn_cxx17_compat_constexpr_function_try_block)
<< isa<CXXConstructorDecl>(Dcl);
break;
}
}
// - its function-body shall be [...] a compound-statement that contains only
@ -2001,23 +2082,30 @@ bool Sema::CheckConstexprFunctionBody(const FunctionDecl *Dcl, Stmt *Body) {
SourceLocation Cxx1yLoc, Cxx2aLoc;
for (Stmt *SubStmt : Body->children()) {
if (SubStmt &&
!CheckConstexprFunctionStmt(*this, Dcl, SubStmt, ReturnStmts,
Cxx1yLoc, Cxx2aLoc))
!CheckConstexprFunctionStmt(SemaRef, Dcl, SubStmt, ReturnStmts,
Cxx1yLoc, Cxx2aLoc, Kind))
return false;
}
if (Cxx2aLoc.isValid())
Diag(Cxx2aLoc,
getLangOpts().CPlusPlus2a
if (Kind == Sema::CheckConstexprKind::CheckValid) {
// If this is only valid as an extension, report that we don't satisfy the
// constraints of the current language.
if ((Cxx2aLoc.isValid() && !SemaRef.getLangOpts().CPlusPlus2a) ||
(Cxx1yLoc.isValid() && !SemaRef.getLangOpts().CPlusPlus17))
return false;
} else if (Cxx2aLoc.isValid()) {
SemaRef.Diag(Cxx2aLoc,
SemaRef.getLangOpts().CPlusPlus2a
? diag::warn_cxx17_compat_constexpr_body_invalid_stmt
: diag::ext_constexpr_body_invalid_stmt_cxx2a)
<< isa<CXXConstructorDecl>(Dcl);
if (Cxx1yLoc.isValid())
Diag(Cxx1yLoc,
getLangOpts().CPlusPlus14
} else if (Cxx1yLoc.isValid()) {
SemaRef.Diag(Cxx1yLoc,
SemaRef.getLangOpts().CPlusPlus14
? diag::warn_cxx11_compat_constexpr_body_invalid_stmt
: diag::ext_constexpr_body_invalid_stmt)
<< isa<CXXConstructorDecl>(Dcl);
}
if (const CXXConstructorDecl *Constructor
= dyn_cast<CXXConstructorDecl>(Dcl)) {
@ -2031,7 +2119,9 @@ bool Sema::CheckConstexprFunctionBody(const FunctionDecl *Dcl, Stmt *Body) {
if (RD->isUnion()) {
if (Constructor->getNumCtorInitializers() == 0 &&
RD->hasVariantMembers()) {
Diag(Dcl->getLocation(), diag::err_constexpr_union_ctor_no_init);
if (Kind == Sema::CheckConstexprKind::Diagnose)
SemaRef.Diag(Dcl->getLocation(),
diag::err_constexpr_union_ctor_no_init);
return false;
}
} else if (!Constructor->isDependentContext() &&
@ -2068,9 +2158,9 @@ bool Sema::CheckConstexprFunctionBody(const FunctionDecl *Dcl, Stmt *Body) {
bool Diagnosed = false;
for (auto *I : RD->fields())
CheckConstexprCtorInitializer(*this, Dcl, I, Inits, Diagnosed);
if (Diagnosed)
return false;
if (!CheckConstexprCtorInitializer(SemaRef, Dcl, I, Inits, Diagnosed,
Kind))
return false;
}
}
} else {
@ -2079,22 +2169,45 @@ bool Sema::CheckConstexprFunctionBody(const FunctionDecl *Dcl, Stmt *Body) {
// statement. We still do, unless the return type might be void, because
// otherwise if there's no return statement, the function cannot
// be used in a core constant expression.
bool OK = getLangOpts().CPlusPlus14 &&
bool OK = SemaRef.getLangOpts().CPlusPlus14 &&
(Dcl->getReturnType()->isVoidType() ||
Dcl->getReturnType()->isDependentType());
Diag(Dcl->getLocation(),
OK ? diag::warn_cxx11_compat_constexpr_body_no_return
: diag::err_constexpr_body_no_return)
<< Dcl->isConsteval();
if (!OK)
return false;
switch (Kind) {
case Sema::CheckConstexprKind::Diagnose:
SemaRef.Diag(Dcl->getLocation(),
OK ? diag::warn_cxx11_compat_constexpr_body_no_return
: diag::err_constexpr_body_no_return)
<< Dcl->isConsteval();
if (!OK)
return false;
break;
case Sema::CheckConstexprKind::CheckValid:
// The formal requirements don't include this rule in C++14, even
// though the "must be able to produce a constant expression" rules
// still imply it in some cases.
if (!SemaRef.getLangOpts().CPlusPlus14)
return false;
break;
}
} else if (ReturnStmts.size() > 1) {
Diag(ReturnStmts.back(),
getLangOpts().CPlusPlus14
? diag::warn_cxx11_compat_constexpr_body_multiple_return
: diag::ext_constexpr_body_multiple_return);
for (unsigned I = 0; I < ReturnStmts.size() - 1; ++I)
Diag(ReturnStmts[I], diag::note_constexpr_body_previous_return);
switch (Kind) {
case Sema::CheckConstexprKind::Diagnose:
SemaRef.Diag(
ReturnStmts.back(),
SemaRef.getLangOpts().CPlusPlus14
? diag::warn_cxx11_compat_constexpr_body_multiple_return
: diag::ext_constexpr_body_multiple_return);
for (unsigned I = 0; I < ReturnStmts.size() - 1; ++I)
SemaRef.Diag(ReturnStmts[I],
diag::note_constexpr_body_previous_return);
break;
case Sema::CheckConstexprKind::CheckValid:
if (!SemaRef.getLangOpts().CPlusPlus14)
return false;
break;
}
}
}
@ -2108,12 +2221,17 @@ bool Sema::CheckConstexprFunctionBody(const FunctionDecl *Dcl, Stmt *Body) {
// C++11 [dcl.constexpr]p4:
// - every constructor involved in initializing non-static data members and
// base class sub-objects shall be a constexpr constructor.
//
// Note that this rule is distinct from the "requirements for a constexpr
// function", so is not checked in CheckValid mode.
SmallVector<PartialDiagnosticAt, 8> Diags;
if (!Expr::isPotentialConstantExpr(Dcl, Diags)) {
Diag(Dcl->getLocation(), diag::ext_constexpr_function_never_constant_expr)
<< isa<CXXConstructorDecl>(Dcl);
if (Kind == Sema::CheckConstexprKind::Diagnose &&
!Expr::isPotentialConstantExpr(Dcl, Diags)) {
SemaRef.Diag(Dcl->getLocation(),
diag::ext_constexpr_function_never_constant_expr)
<< isa<CXXConstructorDecl>(Dcl);
for (size_t I = 0, N = Diags.size(); I != N; ++I)
Diag(Diags[I].first, Diags[I].second);
SemaRef.Diag(Diags[I].first, Diags[I].second);
// Don't return false here: we allow this for compatibility in
// system headers.
}

5
clang/lib/Sema/SemaLambda.cpp
View File

@ -1776,10 +1776,9 @@ ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
!CallOperator->isConstexpr() &&
!isa<CoroutineBodyStmt>(CallOperator->getBody()) &&
!Class->getDeclContext()->isDependentContext()) {
TentativeAnalysisScope DiagnosticScopeGuard(*this);
CallOperator->setConstexprKind(
(CheckConstexprFunctionDecl(CallOperator) &&
CheckConstexprFunctionBody(CallOperator, CallOperator->getBody()))
CheckConstexprFunctionDefinition(CallOperator,
CheckConstexprKind::CheckValid)
? CSK_constexpr
: CSK_unspecified);
}

5
clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p3.cpp
View File

@ -157,11 +157,8 @@ constexpr int DisallowedStmtsCXX1Y_2_1() {
constexpr int DisallowedStmtsCXX1Y_3() {
// - a try-block,
try {} catch (...) {}
#ifndef CXX2A
#if !defined(CXX2A)
// expected-error@-2 {{use of this statement in a constexpr function is a C++2a extension}}
#ifndef CXX1Y
// expected-error@-4 {{use of this statement in a constexpr function is a C++14 extension}}
#endif
#endif
return 0;
}

29
clang/test/SemaCXX/cxx1z-constexpr-lambdas.cpp
View File

@ -1,4 +1,5 @@
// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks %s -fcxx-exceptions
// RUN: %clang_cc1 -std=c++2a -verify -fsyntax-only -fblocks %s -fcxx-exceptions
// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks -fdelayed-template-parsing %s -fcxx-exceptions
// RUN: %clang_cc1 -std=c++14 -verify -fsyntax-only -fblocks %s -DCPP14_AND_EARLIER -fcxx-exceptions
@ -25,6 +26,34 @@ namespace ns2 {
auto L = [](int I) constexpr { asm("non-constexpr"); }; //expected-error{{not allowed in constexpr function}}
} // end ns1
// This is not constexpr until C++20, as the requirements on constexpr
// functions don't permit try-catch blocks.
#if __cplusplus <= 201703L
// expected-error@#try-catch {{constant expression}}
// expected-note@#try-catch {{non-constexpr function 'operator()'}}
// expected-note@#try-catch {{declared here}}
#endif
constexpr int try_catch = [] { // #try-catch
try { return 0; } catch (...) { return 1; }
}();
// These lambdas have constexpr operator() even though they can never produce a
// constant expression.
auto never_constant_1 = [] { // expected-note {{here}}
volatile int n = 0;
return n;
};
auto never_constant_2 = [] () -> int { // expected-note {{here}}
};
struct test_never_constant {
#if __cplusplus >= 201703L
// expected-error@+3 {{non-constexpr declaration of 'operator()' follows constexpr declaration}}
// expected-error@+3 {{non-constexpr declaration of 'operator()' follows constexpr declaration}}
#endif
friend auto decltype(never_constant_1)::operator()() const;
friend int decltype(never_constant_2)::operator()() const;
};
} // end ns test_constexpr_checking
namespace test_constexpr_call {