[c++20] P1143R2: Add support for the C++20 'constinit' keyword.
This is mostly the same as the
[[clang::require_constant_initialization]] attribute, but has a couple
of additional syntactic and semantic restrictions.
In passing, I added a warning for the attribute form being added after
we have already seen the initialization of the variable (but before we
see the definition); that case previously slipped between the cracks and
the attribute was silently ignored.
llvm-svn: 370972
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 21dd542..6c0c828 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -2220,6 +2220,22 @@
return Init.getAddrOfPtr1();
}
+VarDecl *VarDecl::getInitializingDeclaration() {
+ VarDecl *Def = nullptr;
+ for (auto I : redecls()) {
+ if (I->hasInit())
+ return I;
+
+ if (I->isThisDeclarationADefinition()) {
+ if (isStaticDataMember())
+ return I;
+ else
+ Def = I;
+ }
+ }
+ return Def;
+}
+
bool VarDecl::isOutOfLine() const {
if (Decl::isOutOfLine())
return true;
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 6eafe81..95d9f62 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -541,8 +541,10 @@
Builder.defineMacro("__cpp_template_template_args", "201611L");
// C++20 features.
- if (LangOpts.CPlusPlus2a)
+ if (LangOpts.CPlusPlus2a) {
Builder.defineMacro("__cpp_conditional_explicit", "201806L");
+ Builder.defineMacro("__cpp_constinit", "201907L");
+ }
if (LangOpts.Char8)
Builder.defineMacro("__cpp_char8_t", "201811L");
Builder.defineMacro("__cpp_impl_destroying_delete", "201806L");
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index c4c5045..d66c539 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -2514,7 +2514,7 @@
// Issue diagnostic and remove constexpr specifier if present.
if (DS.hasConstexprSpecifier() && DSC != DeclSpecContext::DSC_condition) {
Diag(DS.getConstexprSpecLoc(), diag::err_typename_invalid_constexpr)
- << (DS.getConstexprSpecifier() == CSK_consteval);
+ << DS.getConstexprSpecifier();
DS.ClearConstexprSpec();
}
}
@@ -3653,15 +3653,16 @@
isInvalid = DS.setModulePrivateSpec(Loc, PrevSpec, DiagID);
break;
- // constexpr
+ // constexpr, consteval, constinit specifiers
case tok::kw_constexpr:
isInvalid = DS.SetConstexprSpec(CSK_constexpr, Loc, PrevSpec, DiagID);
break;
-
- // consteval
case tok::kw_consteval:
isInvalid = DS.SetConstexprSpec(CSK_consteval, Loc, PrevSpec, DiagID);
break;
+ case tok::kw_constinit:
+ isInvalid = DS.SetConstexprSpec(CSK_constinit, Loc, PrevSpec, DiagID);
+ break;
// type-specifier
case tok::kw_short:
@@ -5080,8 +5081,9 @@
case tok::annot_decltype:
case tok::kw_constexpr:
- // C++20 consteval.
+ // C++20 consteval and constinit.
case tok::kw_consteval:
+ case tok::kw_constinit:
// C11 _Atomic
case tok::kw__Atomic:
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index cf03ed6..529c09a 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -1313,6 +1313,8 @@
case tok::kw_mutable: // struct foo {...} mutable x;
case tok::kw_thread_local: // struct foo {...} thread_local x;
case tok::kw_constexpr: // struct foo {...} constexpr x;
+ case tok::kw_consteval: // struct foo {...} consteval x;
+ case tok::kw_constinit: // struct foo {...} constinit x;
// As shown above, type qualifiers and storage class specifiers absolutely
// can occur after class specifiers according to the grammar. However,
// almost no one actually writes code like this. If we see one of these,
diff --git a/clang/lib/Parse/ParseTentative.cpp b/clang/lib/Parse/ParseTentative.cpp
index 8e56e0c..2eee15b 100644
--- a/clang/lib/Parse/ParseTentative.cpp
+++ b/clang/lib/Parse/ParseTentative.cpp
@@ -1408,6 +1408,7 @@
case tok::kw_typedef:
case tok::kw_constexpr:
case tok::kw_consteval:
+ case tok::kw_constinit:
// storage-class-specifier
case tok::kw_register:
case tok::kw_static:
diff --git a/clang/lib/Sema/DeclSpec.cpp b/clang/lib/Sema/DeclSpec.cpp
index 77e5eb0..639231c 100644
--- a/clang/lib/Sema/DeclSpec.cpp
+++ b/clang/lib/Sema/DeclSpec.cpp
@@ -569,6 +569,7 @@
case CSK_unspecified: return "unspecified";
case CSK_constexpr: return "constexpr";
case CSK_consteval: return "consteval";
+ case CSK_constinit: return "constinit";
}
llvm_unreachable("Unknown ConstexprSpecKind");
}
@@ -1036,13 +1037,9 @@
bool DeclSpec::SetConstexprSpec(ConstexprSpecKind ConstexprKind,
SourceLocation Loc, const char *&PrevSpec,
unsigned &DiagID) {
- if (getConstexprSpecifier() != CSK_unspecified) {
- if (getConstexprSpecifier() == CSK_consteval || ConstexprKind == CSK_consteval)
- return BadSpecifier(ConstexprKind, getConstexprSpecifier(), PrevSpec, DiagID);
- DiagID = diag::warn_duplicate_declspec;
- PrevSpec = "constexpr";
- return true;
- }
+ if (getConstexprSpecifier() != CSK_unspecified)
+ return BadSpecifier(ConstexprKind, getConstexprSpecifier(), PrevSpec,
+ DiagID);
ConstexprSpecifier = ConstexprKind;
ConstexprLoc = Loc;
return false;
@@ -1291,8 +1288,10 @@
<< (TypeSpecType == TST_char16 ? "char16_t" : "char32_t");
if (getConstexprSpecifier() == CSK_constexpr)
S.Diag(ConstexprLoc, diag::warn_cxx98_compat_constexpr);
- if (getConstexprSpecifier() == CSK_consteval)
+ else if (getConstexprSpecifier() == CSK_consteval)
S.Diag(ConstexprLoc, diag::warn_cxx20_compat_consteval);
+ else if (getConstexprSpecifier() == CSK_constinit)
+ S.Diag(ConstexprLoc, diag::warn_cxx20_compat_constinit);
// C++ [class.friend]p6:
// No storage-class-specifier shall appear in the decl-specifier-seq
// of a friend declaration.
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index a96f0d2..a270822 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -2661,6 +2661,60 @@
}
}
+static void diagnoseMissingConstinit(Sema &S, const VarDecl *InitDecl,
+ const ConstInitAttr *CIAttr,
+ bool AttrBeforeInit) {
+ SourceLocation InsertLoc = InitDecl->getInnerLocStart();
+
+ // Figure out a good way to write this specifier on the old declaration.
+ // FIXME: We should just use the spelling of CIAttr, but we don't preserve
+ // enough of the attribute list spelling information to extract that without
+ // heroics.
+ std::string SuitableSpelling;
+ if (S.getLangOpts().CPlusPlus2a)
+ SuitableSpelling =
+ S.PP.getLastMacroWithSpelling(InsertLoc, {tok::kw_constinit});
+ if (SuitableSpelling.empty() && S.getLangOpts().CPlusPlus11)
+ SuitableSpelling = S.PP.getLastMacroWithSpelling(
+ InsertLoc,
+ {tok::l_square, tok::l_square, S.PP.getIdentifierInfo("clang"),
+ tok::coloncolon,
+ S.PP.getIdentifierInfo("require_constant_initialization"),
+ tok::r_square, tok::r_square});
+ if (SuitableSpelling.empty())
+ SuitableSpelling = S.PP.getLastMacroWithSpelling(
+ InsertLoc,
+ {tok::kw___attribute, tok::l_paren, tok::r_paren,
+ S.PP.getIdentifierInfo("require_constant_initialization"),
+ tok::r_paren, tok::r_paren});
+ if (SuitableSpelling.empty() && S.getLangOpts().CPlusPlus2a)
+ SuitableSpelling = "constinit";
+ if (SuitableSpelling.empty() && S.getLangOpts().CPlusPlus11)
+ SuitableSpelling = "[[clang::require_constant_initialization]]";
+ if (SuitableSpelling.empty())
+ SuitableSpelling = "__attribute__((require_constant_initialization))";
+ SuitableSpelling += " ";
+
+ if (AttrBeforeInit) {
+ // extern constinit int a;
+ // int a = 0; // error (missing 'constinit'), accepted as extension
+ assert(CIAttr->isConstinit() && "should not diagnose this for attribute");
+ S.Diag(InitDecl->getLocation(), diag::ext_constinit_missing)
+ << InitDecl << FixItHint::CreateInsertion(InsertLoc, SuitableSpelling);
+ S.Diag(CIAttr->getLocation(), diag::note_constinit_specified_here);
+ } else {
+ // int a = 0;
+ // constinit extern int a; // error (missing 'constinit')
+ S.Diag(CIAttr->getLocation(),
+ CIAttr->isConstinit() ? diag::err_constinit_added_too_late
+ : diag::warn_require_const_init_added_too_late)
+ << FixItHint::CreateRemoval(SourceRange(CIAttr->getLocation()));
+ S.Diag(InitDecl->getLocation(), diag::note_constinit_missing_here)
+ << CIAttr->isConstinit()
+ << FixItHint::CreateInsertion(InsertLoc, SuitableSpelling);
+ }
+}
+
/// mergeDeclAttributes - Copy attributes from the Old decl to the New one.
void Sema::mergeDeclAttributes(NamedDecl *New, Decl *Old,
AvailabilityMergeKind AMK) {
@@ -2673,6 +2727,41 @@
if (!Old->hasAttrs() && !New->hasAttrs())
return;
+ // [dcl.constinit]p1:
+ // If the [constinit] specifier is applied to any declaration of a
+ // variable, it shall be applied to the initializing declaration.
+ const auto *OldConstInit = Old->getAttr<ConstInitAttr>();
+ const auto *NewConstInit = New->getAttr<ConstInitAttr>();
+ if (bool(OldConstInit) != bool(NewConstInit)) {
+ const auto *OldVD = cast<VarDecl>(Old);
+ auto *NewVD = cast<VarDecl>(New);
+
+ // Find the initializing declaration. Note that we might not have linked
+ // the new declaration into the redeclaration chain yet.
+ const VarDecl *InitDecl = OldVD->getInitializingDeclaration();
+ if (!InitDecl &&
+ (NewVD->hasInit() || NewVD->isThisDeclarationADefinition()))
+ InitDecl = NewVD;
+
+ if (InitDecl == NewVD) {
+ // This is the initializing declaration. If it would inherit 'constinit',
+ // that's ill-formed. (Note that we do not apply this to the attribute
+ // form).
+ if (OldConstInit && OldConstInit->isConstinit())
+ diagnoseMissingConstinit(*this, NewVD, OldConstInit,
+ /*AttrBeforeInit=*/true);
+ } else if (NewConstInit) {
+ // This is the first time we've been told that this declaration should
+ // have a constant initializer. If we already saw the initializing
+ // declaration, this is too late.
+ if (InitDecl && InitDecl != NewVD) {
+ diagnoseMissingConstinit(*this, InitDecl, NewConstInit,
+ /*AttrBeforeInit=*/false);
+ NewVD->dropAttr<ConstInitAttr>();
+ }
+ }
+ }
+
// Attributes declared post-definition are currently ignored.
checkNewAttributesAfterDef(*this, New, Old);
@@ -4315,13 +4404,13 @@
// and definitions of functions and variables.
// C++2a [dcl.constexpr]p1: The consteval specifier shall be applied only to
// the declaration of a function or function template
- bool IsConsteval = DS.getConstexprSpecifier() == CSK_consteval;
if (Tag)
Diag(DS.getConstexprSpecLoc(), diag::err_constexpr_tag)
- << GetDiagnosticTypeSpecifierID(DS.getTypeSpecType()) << IsConsteval;
+ << GetDiagnosticTypeSpecifierID(DS.getTypeSpecType())
+ << DS.getConstexprSpecifier();
else
Diag(DS.getConstexprSpecLoc(), diag::err_constexpr_wrong_decl_kind)
- << IsConsteval;
+ << DS.getConstexprSpecifier();
// Don't emit warnings after this error.
return TagD;
}
@@ -5776,7 +5865,7 @@
<< getLangOpts().CPlusPlus17;
if (D.getDeclSpec().hasConstexprSpecifier())
Diag(D.getDeclSpec().getConstexprSpecLoc(), diag::err_invalid_constexpr)
- << 1 << (D.getDeclSpec().getConstexprSpecifier() == CSK_consteval);
+ << 1 << D.getDeclSpec().getConstexprSpecifier();
if (D.getName().Kind != UnqualifiedIdKind::IK_Identifier) {
if (D.getName().Kind == UnqualifiedIdKind::IK_DeductionGuideName)
@@ -6671,19 +6760,6 @@
if (TemplateParamLists.size() > VDTemplateParamLists)
NewVD->setTemplateParameterListsInfo(
Context, TemplateParamLists.drop_back(VDTemplateParamLists));
-
- if (D.getDeclSpec().hasConstexprSpecifier()) {
- NewVD->setConstexpr(true);
- // C++1z [dcl.spec.constexpr]p1:
- // A static data member declared with the constexpr specifier is
- // implicitly an inline variable.
- if (NewVD->isStaticDataMember() && getLangOpts().CPlusPlus17)
- NewVD->setImplicitlyInline();
- if (D.getDeclSpec().getConstexprSpecifier() == CSK_consteval)
- Diag(D.getDeclSpec().getConstexprSpecLoc(),
- diag::err_constexpr_wrong_decl_kind)
- << /*consteval*/ 1;
- }
}
if (D.getDeclSpec().isInlineSpecified()) {
@@ -6749,6 +6825,36 @@
NewVD->setTSCSpec(TSCS);
}
+ switch (D.getDeclSpec().getConstexprSpecifier()) {
+ case CSK_unspecified:
+ break;
+
+ case CSK_consteval:
+ Diag(D.getDeclSpec().getConstexprSpecLoc(),
+ diag::err_constexpr_wrong_decl_kind)
+ << D.getDeclSpec().getConstexprSpecifier();
+ LLVM_FALLTHROUGH;
+
+ case CSK_constexpr:
+ NewVD->setConstexpr(true);
+ // C++1z [dcl.spec.constexpr]p1:
+ // A static data member declared with the constexpr specifier is
+ // implicitly an inline variable.
+ if (NewVD->isStaticDataMember() && getLangOpts().CPlusPlus17)
+ NewVD->setImplicitlyInline();
+ break;
+
+ case CSK_constinit:
+ if (!NewVD->hasGlobalStorage())
+ Diag(D.getDeclSpec().getConstexprSpecLoc(),
+ diag::err_constinit_local_variable);
+ else
+ NewVD->addAttr(::new (Context) ConstInitAttr(
+ SourceRange(D.getDeclSpec().getConstexprSpecLoc()), Context,
+ ConstInitAttr::Keyword_constinit));
+ break;
+ }
+
// C99 6.7.4p3
// An inline definition of a function with external linkage shall
// not contain a definition of a modifiable object with static or
@@ -7989,7 +8095,7 @@
return SC_None;
}
-static FunctionDecl* CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
+static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
DeclContext *DC, QualType &R,
TypeSourceInfo *TInfo,
StorageClass SC,
@@ -8021,7 +8127,16 @@
}
ExplicitSpecifier ExplicitSpecifier = D.getDeclSpec().getExplicitSpecifier();
+
ConstexprSpecKind ConstexprKind = D.getDeclSpec().getConstexprSpecifier();
+ if (ConstexprKind == CSK_constinit) {
+ SemaRef.Diag(D.getDeclSpec().getConstexprSpecLoc(),
+ diag::err_constexpr_wrong_decl_kind)
+ << ConstexprKind;
+ ConstexprKind = CSK_unspecified;
+ D.getMutableDeclSpec().ClearConstexprSpec();
+ }
+
// Check that the return type is not an abstract class type.
// For record types, this is done by the AbstractClassUsageDiagnoser once
// the class has been completely parsed.
@@ -8452,7 +8567,6 @@
bool isInline = D.getDeclSpec().isInlineSpecified();
bool isVirtual = D.getDeclSpec().isVirtualSpecified();
bool hasExplicit = D.getDeclSpec().hasExplicitSpecifier();
- ConstexprSpecKind ConstexprKind = D.getDeclSpec().getConstexprSpecifier();
isFriend = D.getDeclSpec().isFriendSpecified();
if (isFriend && !isInline && D.isFunctionDefinition()) {
// C++ [class.friend]p5
@@ -8651,7 +8765,8 @@
}
}
- if (ConstexprKind != CSK_unspecified) {
+ if (ConstexprSpecKind ConstexprKind =
+ D.getDeclSpec().getConstexprSpecifier()) {
// C++11 [dcl.constexpr]p2: constexpr functions and constexpr constructors
// are implicitly inline.
NewFD->setImplicitlyInline();
@@ -8659,9 +8774,10 @@
// C++11 [dcl.constexpr]p3: functions declared constexpr are required to
// be either constructors or to return a literal type. Therefore,
// destructors cannot be declared constexpr.
- if (isa<CXXDestructorDecl>(NewFD))
+ if (isa<CXXDestructorDecl>(NewFD)) {
Diag(D.getDeclSpec().getConstexprSpecLoc(), diag::err_constexpr_dtor)
- << (ConstexprKind == CSK_consteval);
+ << ConstexprKind;
+ }
}
// If __module_private__ was specified, mark the function accordingly.
@@ -12043,17 +12159,17 @@
// Don't emit further diagnostics about constexpr globals since they
// were just diagnosed.
- if (!var->isConstexpr() && GlobalStorage &&
- var->hasAttr<RequireConstantInitAttr>()) {
+ if (!var->isConstexpr() && GlobalStorage && var->hasAttr<ConstInitAttr>()) {
// FIXME: Need strict checking in C++03 here.
bool DiagErr = getLangOpts().CPlusPlus11
? !var->checkInitIsICE() : !checkConstInit();
if (DiagErr) {
- auto attr = var->getAttr<RequireConstantInitAttr>();
+ auto *Attr = var->getAttr<ConstInitAttr>();
Diag(var->getLocation(), diag::err_require_constant_init_failed)
<< Init->getSourceRange();
- Diag(attr->getLocation(), diag::note_declared_required_constant_init_here)
- << attr->getRange();
+ Diag(Attr->getLocation(),
+ diag::note_declared_required_constant_init_here)
+ << Attr->getRange() << Attr->isConstinit();
if (getLangOpts().CPlusPlus11) {
APValue Value;
SmallVector<PartialDiagnosticAt, 8> Notes;
@@ -12546,7 +12662,7 @@
<< getLangOpts().CPlusPlus17;
if (DS.hasConstexprSpecifier())
Diag(DS.getConstexprSpecLoc(), diag::err_invalid_constexpr)
- << 0 << (D.getDeclSpec().getConstexprSpecifier() == CSK_consteval);
+ << 0 << D.getDeclSpec().getConstexprSpecifier();
DiagnoseFunctionSpecifiers(DS);
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 2a72f7d..2890f90 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -7057,8 +7057,8 @@
case ParsedAttr::AT_VecTypeHint:
handleVecTypeHint(S, D, AL);
break;
- case ParsedAttr::AT_RequireConstantInit:
- handleSimpleAttribute<RequireConstantInitAttr>(S, D, AL);
+ case ParsedAttr::AT_ConstInit:
+ handleSimpleAttribute<ConstInitAttr>(S, D, AL);
break;
case ParsedAttr::AT_InitPriority:
handleInitPriorityAttr(S, D, AL);
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index 4b16a09..f9c36e0 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -5146,9 +5146,9 @@
// C++0x [dcl.constexpr]p9:
// A constexpr specifier used in an object declaration declares the object
// as const.
- if (D.getDeclSpec().hasConstexprSpecifier() && T->isObjectType()) {
+ if (D.getDeclSpec().getConstexprSpecifier() == CSK_constexpr &&
+ T->isObjectType())
T.addConst();
- }
// If there was an ellipsis in the declarator, the declaration declares a
// parameter pack whose type may be a pack expansion type.