[modules ts] Basic for module linkage.
In addition to the formal linkage rules, the Modules TS includes cases where
internal-linkage symbols within a module interface unit can be referenced from
outside the module via exported inline functions / templates. We give such
declarations "module-internal linkage", which is formally internal linkage, but
results in an externally-visible symbol.
llvm-svn: 307434
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 24d9983..573a98e 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -573,6 +573,44 @@
return false;
}
+static bool isExportedFromModuleIntefaceUnit(const NamedDecl *D) {
+ switch (D->getModuleOwnershipKind()) {
+ case Decl::ModuleOwnershipKind::Unowned:
+ case Decl::ModuleOwnershipKind::ModulePrivate:
+ return false;
+ case Decl::ModuleOwnershipKind::Visible:
+ case Decl::ModuleOwnershipKind::VisibleWhenImported:
+ if (auto *M = D->getOwningModule())
+ return M->Kind == Module::ModuleInterfaceUnit;
+ }
+ llvm_unreachable("unexpected module ownership kind");
+}
+
+static LinkageInfo getInternalLinkageFor(const NamedDecl *D) {
+ // Internal linkage declarations within a module interface unit are modeled
+ // as "module-internal linkage", which means that they have internal linkage
+ // formally but can be indirectly accessed from outside the module via inline
+ // functions and templates defined within the module.
+ if (auto *M = D->getOwningModule())
+ if (M->Kind == Module::ModuleInterfaceUnit)
+ return LinkageInfo(ModuleInternalLinkage, DefaultVisibility, false);
+
+ return LinkageInfo::internal();
+}
+
+static LinkageInfo getExternalLinkageFor(const NamedDecl *D) {
+ // C++ Modules TS [basic.link]/6.8:
+ // - A name declared at namespace scope that does not have internal linkage
+ // by the previous rules and that is introduced by a non-exported
+ // declaration has module linkage.
+ if (auto *M = D->getOwningModule())
+ if (M->Kind == Module::ModuleInterfaceUnit)
+ if (!isExportedFromModuleIntefaceUnit(D))
+ return LinkageInfo(ModuleLinkage, DefaultVisibility, false);
+
+ return LinkageInfo::external();
+}
+
static LinkageInfo getLVForNamespaceScopeDecl(const NamedDecl *D,
LVComputationKind computation) {
assert(D->getDeclContext()->getRedeclContext()->isFileContext() &&
@@ -588,16 +626,18 @@
if (const auto *Var = dyn_cast<VarDecl>(D)) {
// Explicitly declared static.
if (Var->getStorageClass() == SC_Static)
- return LinkageInfo::internal();
+ return getInternalLinkageFor(Var);
// - a non-inline, non-volatile object or reference that is explicitly
// declared const or constexpr and neither explicitly declared extern
// nor previously declared to have external linkage; or (there is no
// equivalent in C99)
+ // The C++ modules TS adds "non-exported" to this list.
if (Context.getLangOpts().CPlusPlus &&
Var->getType().isConstQualified() &&
!Var->getType().isVolatileQualified() &&
- !Var->isInline()) {
+ !Var->isInline() &&
+ !isExportedFromModuleIntefaceUnit(Var)) {
const VarDecl *PrevVar = Var->getPreviousDecl();
if (PrevVar)
return getLVForDecl(PrevVar, computation);
@@ -605,7 +645,7 @@
if (Var->getStorageClass() != SC_Extern &&
Var->getStorageClass() != SC_PrivateExtern &&
!isSingleLineLanguageLinkage(*Var))
- return LinkageInfo::internal();
+ return getInternalLinkageFor(Var);
}
for (const VarDecl *PrevVar = Var->getPreviousDecl(); PrevVar;
@@ -615,7 +655,7 @@
return PrevVar->getLinkageAndVisibility();
// Explicitly declared static.
if (PrevVar->getStorageClass() == SC_Static)
- return LinkageInfo::internal();
+ return getInternalLinkageFor(Var);
}
} else if (const FunctionDecl *Function = D->getAsFunction()) {
// C++ [temp]p4:
@@ -624,7 +664,7 @@
// Explicitly declared static.
if (Function->getCanonicalDecl()->getStorageClass() == SC_Static)
- return LinkageInfo(InternalLinkage, DefaultVisibility, false);
+ return getInternalLinkageFor(Function);
} else if (const auto *IFD = dyn_cast<IndirectFieldDecl>(D)) {
// - a data member of an anonymous union.
const VarDecl *VD = IFD->getVarDecl();
@@ -637,7 +677,12 @@
const auto *Var = dyn_cast<VarDecl>(D);
const auto *Func = dyn_cast<FunctionDecl>(D);
// FIXME: In C++11 onwards, anonymous namespaces should give decls
- // within them internal linkage, not unique external linkage.
+ // within them (including those inside extern "C" contexts) internal
+ // linkage, not unique external linkage:
+ //
+ // C++11 [basic.link]p4:
+ // An unnamed namespace or a namespace declared directly or indirectly
+ // within an unnamed namespace has internal linkage.
if ((!Var || !isFirstInExternCContext(Var)) &&
(!Func || !isFirstInExternCContext(Func)))
return LinkageInfo::uniqueExternal();
@@ -718,7 +763,8 @@
// because of this, but unique-external linkage suits us.
if (Context.getLangOpts().CPlusPlus && !isFirstInExternCContext(Var)) {
LinkageInfo TypeLV = getLVForType(*Var->getType(), computation);
- if (TypeLV.getLinkage() != ExternalLinkage)
+ if (TypeLV.getLinkage() != ExternalLinkage &&
+ TypeLV.getLinkage() != ModuleLinkage)
return LinkageInfo::uniqueExternal();
if (!LV.isVisibilityExplicit())
LV.mergeVisibility(TypeLV);
@@ -816,7 +862,9 @@
// - a namespace (7.3), unless it is declared within an unnamed
// namespace.
- } else if (isa<NamespaceDecl>(D) && !D->isInAnonymousNamespace()) {
+ //
+ // We handled names in anonymous namespaces above.
+ } else if (isa<NamespaceDecl>(D)) {
return LV;
// By extension, we assign external linkage to Objective-C
@@ -1125,6 +1173,8 @@
if (const auto *ND = dyn_cast<NamedDecl>(DC))
return getLVForDecl(ND, computation);
+ // FIXME: We have a closure at TU scope with no context declaration. This
+ // should probably have no linkage.
return LinkageInfo::external();
}
@@ -1137,7 +1187,7 @@
// This is a "void f();" which got merged with a file static.
if (Function->getCanonicalDecl()->getStorageClass() == SC_Static)
- return LinkageInfo::internal();
+ return getInternalLinkageFor(Function);
LinkageInfo LV;
if (!hasExplicitVisibilityAlready(computation)) {
@@ -1226,7 +1276,7 @@
LVComputationKind computation) {
// Internal_linkage attribute overrides other considerations.
if (D->hasAttr<InternalLinkageAttr>())
- return LinkageInfo::internal();
+ return getInternalLinkageFor(D);
// Objective-C: treat all Objective-C declarations as having external
// linkage.
@@ -1275,14 +1325,14 @@
case Decl::ObjCProperty:
case Decl::ObjCPropertyImpl:
case Decl::ObjCProtocol:
- return LinkageInfo::external();
+ return getExternalLinkageFor(D);
case Decl::CXXRecord: {
const auto *Record = cast<CXXRecordDecl>(D);
if (Record->isLambda()) {
if (!Record->getLambdaManglingNumber()) {
// This lambda has no mangling number, so it's internal.
- return LinkageInfo::internal();
+ return getInternalLinkageFor(D);
}
// This lambda has its linkage/visibility determined:
@@ -1298,7 +1348,7 @@
const CXXRecordDecl *OuterMostLambda =
getOutermostEnclosingLambda(Record);
if (!OuterMostLambda->getLambdaManglingNumber())
- return LinkageInfo::internal();
+ return getInternalLinkageFor(D);
return getLVForClosure(
OuterMostLambda->getDeclContext()->getRedeclContext(),
@@ -1349,7 +1399,7 @@
LVComputationKind computation) {
// Internal_linkage attribute overrides other considerations.
if (D->hasAttr<InternalLinkageAttr>())
- return LinkageInfo::internal();
+ return getInternalLinkageFor(D);
if (computation == LVForLinkageOnly && D->hasCachedLinkage())
return LinkageInfo(D->getCachedLinkage(), DefaultVisibility, false);