Don't suppress instantiation of definitions for variables subject to explicit
instantiation declarations if they are usable from constant expressions.
We are permitted to instantiate in these cases, and required to do so in order
to have an initializer available for use within constant evaluation.
llvm-svn: 316136
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index c92d0aa..1d8b9bc 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -14823,9 +14823,10 @@
TemplateSpecializationKind TSK = Var->getTemplateSpecializationKind();
bool OdrUseContext = isOdrUseContext(SemaRef);
+ bool UsableInConstantExpr =
+ Var->isUsableInConstantExpressions(SemaRef.Context);
bool NeedDefinition =
- OdrUseContext || (isEvaluatableContext(SemaRef) &&
- Var->isUsableInConstantExpressions(SemaRef.Context));
+ OdrUseContext || (isEvaluatableContext(SemaRef) && UsableInConstantExpr);
VarTemplateSpecializationDecl *VarSpec =
dyn_cast<VarTemplateSpecializationDecl>(Var);
@@ -14844,14 +14845,19 @@
// instantiations of variable templates, except for those that could be used
// in a constant expression.
if (NeedDefinition && isTemplateInstantiation(TSK)) {
- bool TryInstantiating = TSK == TSK_ImplicitInstantiation;
+ // Per C++17 [temp.explicit]p10, we may instantiate despite an explicit
+ // instantiation declaration if a variable is usable in a constant
+ // expression (among other cases).
+ bool TryInstantiating =
+ TSK == TSK_ImplicitInstantiation ||
+ (TSK == TSK_ExplicitInstantiationDeclaration && UsableInConstantExpr);
if (TryInstantiating && !isa<VarTemplateSpecializationDecl>(Var)) {
if (Var->getPointOfInstantiation().isInvalid()) {
// This is a modification of an existing AST node. Notify listeners.
if (ASTMutationListener *L = SemaRef.getASTMutationListener())
L->StaticDataMemberInstantiated(Var);
- } else if (!Var->isUsableInConstantExpressions(SemaRef.Context))
+ } else if (!UsableInConstantExpr)
// Don't bother trying to instantiate it again, unless we might need
// its initializer before we get to the end of the TU.
TryInstantiating = false;
@@ -14870,7 +14876,7 @@
// Do not instantiate specializations that are still type-dependent.
if (IsNonDependent) {
- if (Var->isUsableInConstantExpressions(SemaRef.Context)) {
+ if (UsableInConstantExpr) {
// Do not defer instantiations of variables which could be used in a
// constant expression.
SemaRef.InstantiateVariableDefinition(PointOfInstantiation, Var);
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 3800ea6..186a618 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -4359,10 +4359,12 @@
return;
// C++11 [temp.explicit]p10:
- // Except for inline functions, [...] explicit instantiation declarations
+ // Except for inline functions, const variables of literal types, variables
+ // of reference types, [...] explicit instantiation declarations
// have the effect of suppressing the implicit instantiation of the entity
// to which they refer.
- if (TSK == TSK_ExplicitInstantiationDeclaration)
+ if (TSK == TSK_ExplicitInstantiationDeclaration &&
+ !Var->isUsableInConstantExpressions(getASTContext()))
return;
// Make sure to pass the instantiated variable to the consumer at the end.
diff --git a/clang/test/CodeGenCXX/dllimport-members.cpp b/clang/test/CodeGenCXX/dllimport-members.cpp
index 19d9e1d..ff78683 100644
--- a/clang/test/CodeGenCXX/dllimport-members.cpp
+++ b/clang/test/CodeGenCXX/dllimport-members.cpp
@@ -836,7 +836,7 @@
// Import explicit instantiation declaration of an imported member variable
// template.
-// MSC-DAG: @"\01??$ImportedStaticVar@UExplicitDecl_Imported@@@MemVarTmpl@@2HB" = external dllimport constant i32
+// MSC-DAG: @"\01??$ImportedStaticVar@UExplicitDecl_Imported@@@MemVarTmpl@@2HB" = available_externally dllimport constant i32 1
// GNU-DAG: @_ZN10MemVarTmpl17ImportedStaticVarI21ExplicitDecl_ImportedEE = external dllimport constant i32
extern template const int MemVarTmpl::ImportedStaticVar<ExplicitDecl_Imported>;
USEMV(MemVarTmpl, ImportedStaticVar<ExplicitDecl_Imported>)
@@ -861,7 +861,7 @@
// Import explicit instantiation declaration of a non-imported member variable
// template.
-// MSC-DAG: @"\01??$StaticVar@UExplicitDecl_Imported@@@MemVarTmpl@@2HB" = external dllimport constant i32
+// MSC-DAG: @"\01??$StaticVar@UExplicitDecl_Imported@@@MemVarTmpl@@2HB" = available_externally dllimport constant i32 1
// GNU-DAG: @_ZN10MemVarTmpl9StaticVarI21ExplicitDecl_ImportedEE = external dllimport constant i32
extern template __declspec(dllimport) const int MemVarTmpl::StaticVar<ExplicitDecl_Imported>;
USEMV(MemVarTmpl, StaticVar<ExplicitDecl_Imported>)
diff --git a/clang/test/SemaTemplate/cxx17-inline-variables.cpp b/clang/test/SemaTemplate/cxx17-inline-variables.cpp
new file mode 100644
index 0000000..c018050
--- /dev/null
+++ b/clang/test/SemaTemplate/cxx17-inline-variables.cpp
@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -std=c++17 -verify %s
+// expected-no-diagnostics
+template<bool> struct DominatorTreeBase {
+ static constexpr bool IsPostDominator = true;
+};
+extern template class DominatorTreeBase<false>;
+constexpr bool k = DominatorTreeBase<false>::IsPostDominator;
diff --git a/clang/test/SemaTemplate/extern-templates.cpp b/clang/test/SemaTemplate/extern-templates.cpp
index 5eb9c9d..acbc9d5 100644
--- a/clang/test/SemaTemplate/extern-templates.cpp
+++ b/clang/test/SemaTemplate/extern-templates.cpp
@@ -71,3 +71,10 @@
void g_X1_2(X1<const void *> x1, const void *ptr) {
x1.g(ptr);
}
+
+namespace static_const_member {
+ template <typename T> struct A { static const int n; };
+ template <typename T> const int A<T>::n = 3;
+ extern template struct A<int>;
+ int arr[A<int>::n];
+}