[clang] Revert "[Clang] Warn about ignored dllimport on explicit instantiations" (PR #224971)
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Sun Sep 20 14:40:57 PDT 2026
llvmorg-github-actions[bot] wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: Tomohiro Kashiwada (kikairoya)
<details>
<summary>Changes</summary>
Reverts llvm/llvm-project#<!-- -->191392
Causes wrong warnings on libc++ (https://github.com/llvm/llvm-project/pull/191392#issuecomment-5752359615).
---
Patch is 22.26 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/224971.diff
4 Files Affected:
- (modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (-6)
- (modified) clang/lib/Sema/SemaTemplate.cpp (+36-64)
- (modified) clang/test/SemaCXX/dllexport.cpp (-55)
- (modified) clang/test/SemaCXX/dllimport.cpp (-50)
``````````diff
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index fca68f292f6671..9074dc7a822c58 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3880,9 +3880,6 @@ def warn_dllimport_dropped_from_inline_function : Warning<
def warn_nothrow_attribute_ignored : Warning<"'nothrow' attribute conflicts with"
" exception specification; attribute ignored">,
InGroup<IgnoredAttributes>;
-def warn_dllattr_ignored_already_instantiated : Warning<
- "%0 attribute ignored; class template is already instantiated">,
- InGroup<IgnoredAttributes>;
def warn_dllattr_ignored_exclusion_takes_precedence : Warning<
"%0 attribute ignored; %1 takes precedence">,
InGroup<IgnoredAttributes>;
@@ -4006,9 +4003,6 @@ def err_attribute_dllimport_static_field_definition : Error<
def warn_attribute_dllimport_static_field_definition : Warning<
"definition of dllimport static field">,
InGroup<DiagGroup<"dllimport-static-field-def">>;
-def warn_attribute_dllimport_explicit_instantiation_def : Warning<
- "'dllimport' attribute ignored on explicit instantiation definition">,
- InGroup<IgnoredAttributes>;
def warn_attribute_dllexport_explicit_instantiation_decl : Warning<
"explicit instantiation declaration should not be 'dllexport'">,
InGroup<DllexportExplicitInstantiationDecl>;
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 50ff56ff7811ee..b8b0c71894daac 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -10294,32 +10294,23 @@ DeclResult Sema::ActOnExplicitInstantiation(
? TSK_ExplicitInstantiationDefinition
: TSK_ExplicitInstantiationDeclaration;
- bool DLLAttrAffected = false;
- const ParsedAttr *AttachedExportAttr = nullptr;
- const ParsedAttr *AttachedImportAttr = nullptr;
- for (const ParsedAttr &AL : Attr) {
- if (AL.getKind() == ParsedAttr::AT_DLLExport)
- AttachedExportAttr = &AL;
- else if (AL.getKind() == ParsedAttr::AT_DLLImport)
- AttachedImportAttr = &AL;
- }
-
if (TSK == TSK_ExplicitInstantiationDeclaration &&
!Context.getTargetInfo().getTriple().isOSCygMing()) {
// Check for dllexport class template instantiation declarations,
// except for MinGW mode.
- if (AttachedExportAttr) {
- Diag(ExternLoc,
- diag::warn_attribute_dllexport_explicit_instantiation_decl);
- Diag(AttachedExportAttr->getLoc(), diag::note_attribute);
- DLLAttrAffected = true;
+ for (const ParsedAttr &AL : Attr) {
+ if (AL.getKind() == ParsedAttr::AT_DLLExport) {
+ Diag(ExternLoc,
+ diag::warn_attribute_dllexport_explicit_instantiation_decl);
+ Diag(AL.getLoc(), diag::note_attribute);
+ break;
+ }
}
if (auto *A = ClassTemplate->getTemplatedDecl()->getAttr<DLLExportAttr>()) {
Diag(ExternLoc,
diag::warn_attribute_dllexport_explicit_instantiation_decl);
Diag(A->getLocation(), diag::note_attribute);
- DLLAttrAffected = true;
}
}
@@ -10327,12 +10318,20 @@ DeclResult Sema::ActOnExplicitInstantiation(
// instantiation declarations for most purposes.
bool DLLImportExplicitInstantiationDef = false;
if (TSK == TSK_ExplicitInstantiationDefinition &&
- Context.getTargetInfo().shouldDLLImportComdatSymbols()) {
+ Context.getTargetInfo().getCXXABI().isMicrosoft()) {
// Check for dllimport class template instantiation definitions.
bool DLLImport =
ClassTemplate->getTemplatedDecl()->getAttr<DLLImportAttr>();
- // dllexport trumps dllimport.
- if ((DLLImport || AttachedImportAttr) && !AttachedExportAttr) {
+ for (const ParsedAttr &AL : Attr) {
+ if (AL.getKind() == ParsedAttr::AT_DLLImport)
+ DLLImport = true;
+ if (AL.getKind() == ParsedAttr::AT_DLLExport) {
+ // dllexport trumps dllimport here.
+ DLLImport = false;
+ break;
+ }
+ }
+ if (DLLImport) {
TSK = TSK_ExplicitInstantiationDeclaration;
DLLImportExplicitInstantiationDef = true;
}
@@ -10364,30 +10363,28 @@ DeclResult Sema::ActOnExplicitInstantiation(
Context.getTargetInfo().getTriple().isOSCygMing()) {
// Check for dllexport class template instantiation definitions in MinGW
// mode, if a previous declaration of the instantiation was seen.
- if (AttachedExportAttr) {
- if (PrevDecl->hasAttr<DLLExportAttr>()) {
- Diag(AttachedExportAttr->getLoc(),
- diag::warn_attr_dllexport_explicit_inst_def);
- } else {
- Diag(AttachedExportAttr->getLoc(),
- diag::warn_attr_dllexport_explicit_inst_def_mismatch);
- Diag(PrevDecl->getLocation(), diag::note_prev_decl_missing_dllexport);
+ for (const ParsedAttr &AL : Attr) {
+ if (AL.getKind() == ParsedAttr::AT_DLLExport) {
+ if (PrevDecl->hasAttr<DLLExportAttr>()) {
+ Diag(AL.getLoc(), diag::warn_attr_dllexport_explicit_inst_def);
+ } else {
+ Diag(AL.getLoc(),
+ diag::warn_attr_dllexport_explicit_inst_def_mismatch);
+ Diag(PrevDecl->getLocation(), diag::note_prev_decl_missing_dllexport);
+ }
+ break;
}
- DLLAttrAffected = true;
- } else if (AttachedImportAttr) {
- Diag(AttachedImportAttr->getLoc(),
- diag::warn_attribute_dllimport_explicit_instantiation_def);
- DLLAttrAffected = true;
}
}
if (TSK == TSK_ExplicitInstantiationDefinition && PrevDecl &&
!Context.getTargetInfo().getTriple().isWindowsGNUEnvironment() &&
- !AttachedExportAttr) {
+ llvm::none_of(Attr, [](const ParsedAttr &AL) {
+ return AL.getKind() == ParsedAttr::AT_DLLExport;
+ })) {
if (const auto *DEA = PrevDecl->getAttr<DLLExportOnDeclAttr>()) {
Diag(TemplateLoc, diag::warn_dllexport_on_decl_ignored);
Diag(DEA->getLoc(), diag::note_dllexport_on_decl);
- DLLAttrAffected = true;
}
}
@@ -10459,10 +10456,7 @@ DeclResult Sema::ActOnExplicitInstantiation(
Specialization->setTemplateKeywordLoc(TemplateLoc);
Specialization->setBraceRange(SourceRange());
- bool PreviouslyDLLExported = Specialization->hasAttr<DLLExportAttr>() ||
- (PrevDecl && PrevDecl->hasAttr<DLLExportAttr>());
- bool PreviouslyDLLImported = Specialization->hasAttr<DLLImportAttr>() ||
- (PrevDecl && PrevDecl->hasAttr<DLLImportAttr>());
+ bool PreviouslyDLLExported = Specialization->hasAttr<DLLExportAttr>();
ProcessDeclAttributeList(S, Specialization, Attr);
ProcessAPINotes(Specialization);
@@ -10498,12 +10492,11 @@ DeclResult Sema::ActOnExplicitInstantiation(
ClassTemplateSpecializationDecl *Def
= cast_or_null<ClassTemplateSpecializationDecl>(
Specialization->getDefinition());
- if (!Def) {
+ if (!Def)
InstantiateClassTemplateSpecialization(TemplateNameLoc, Specialization, TSK,
/*Complain=*/true,
CTAI.StrictPackMatch);
- DLLAttrAffected = true;
- } else if (TSK == TSK_ExplicitInstantiationDefinition) {
+ else if (TSK == TSK_ExplicitInstantiationDefinition) {
MarkVTableUsed(TemplateNameLoc, Specialization, true);
Specialization->setPointOfInstantiation(Def->getPointOfInstantiation());
}
@@ -10531,16 +10524,13 @@ DeclResult Sema::ActOnExplicitInstantiation(
A->setInherited(true);
Def->addAttr(A);
dllExportImportClassTemplateSpecialization(*this, Def);
- DLLAttrAffected = true;
}
}
// Fix a TSK_ImplicitInstantiation followed by a
// TSK_ExplicitInstantiationDefinition
- bool NewlyDLLExported = !PreviouslyDLLExported && AttachedExportAttr &&
- Specialization->hasAttr<DLLExportAttr>();
- bool NewlyDLLImported = !PreviouslyDLLImported && AttachedImportAttr &&
- Specialization->hasAttr<DLLImportAttr>();
+ bool NewlyDLLExported =
+ !PreviouslyDLLExported && Specialization->hasAttr<DLLExportAttr>();
if (Old_TSK == TSK_ImplicitInstantiation && NewlyDLLExported &&
Context.getTargetInfo().shouldDLLImportComdatSymbols()) {
// An explicit instantiation definition can add a dll attribute to a
@@ -10558,7 +10548,6 @@ DeclResult Sema::ActOnExplicitInstantiation(
assert(Def == Specialization &&
"Def and Specialization should match for implicit instantiation");
dllExportImportClassTemplateSpecialization(*this, Def);
- DLLAttrAffected = true;
}
// In MinGW mode, export the template instantiation if the declaration
@@ -10567,23 +10556,6 @@ DeclResult Sema::ActOnExplicitInstantiation(
Context.getTargetInfo().getTriple().isOSCygMing() &&
PrevDecl->hasAttr<DLLExportAttr>()) {
dllExportImportClassTemplateSpecialization(*this, Def);
- DLLAttrAffected = true;
- }
-
- if (!DLLAttrAffected && (NewlyDLLExported || NewlyDLLImported)) {
- if (Context.getTargetInfo().getTriple().isOSCygMing() &&
- TSK == TSK_ExplicitInstantiationDeclaration && NewlyDLLImported) {
- // In MinGW mode, all undefined symbols are also searched from DLLs
- // even if they were not declared with dllimport, so doesn't warn
- // about ignoring dllimport.
- } else {
- const ParsedAttr *A =
- AttachedExportAttr ? AttachedExportAttr : AttachedImportAttr;
- Diag(A->getLoc(), diag::warn_dllattr_ignored_already_instantiated) << A;
- Diag(Def->getPointOfInstantiation(),
- diag::note_instantiation_required_here)
- << /*implicit|explicit=*/0;
- }
}
// Set the template specialization kind. Make sure it is set before
diff --git a/clang/test/SemaCXX/dllexport.cpp b/clang/test/SemaCXX/dllexport.cpp
index 51c37e0d53eda9..70e7f1398ad052 100644
--- a/clang/test/SemaCXX/dllexport.cpp
+++ b/clang/test/SemaCXX/dllexport.cpp
@@ -1063,61 +1063,6 @@ template<typename T> __declspec(dllexport) constexpr int CTMR<T>::ConstexprField
// dllexport.
template <> void ExportClassTmplMembers<int>::normalDecl() = delete; // non-gnu-error {{attribute 'dllexport' cannot be applied to a deleted function}}
-struct InstTrig {
- struct Spec;
- struct Impl;
- struct Decl;
-};
-template<bool InstDef, typename... Triggers>
-struct ClassTmplSpecializedMember { // gnu-note 5 {{'dllexport' attribute is missing on previous declaration}}
- void specializedMember1();
- void specializedMember2();
- void instantiatedMember1();
- void instantiatedMember2();
- void member() {}
-};
-
-template <> void ClassTmplSpecializedMember<false, InstTrig::Spec>::specializedMember1(); // gnu-note{{implicit instantiation first required here}}
-extern template struct __declspec(dllexport) ClassTmplSpecializedMember<false, InstTrig::Spec>; // non-gnu-warning{{explicit instantiation declaration should not be 'dllexport'}} \
- non-gnu-note{{attribute is here}} \
- gnu-warning{{'dllexport' attribute ignored; class template is already instantiated}}
-template <> void ClassTmplSpecializedMember<true, InstTrig::Spec>::specializedMember1();
-template struct __declspec(dllexport) ClassTmplSpecializedMember<true, InstTrig::Spec>; // gnu-warning{{'dllexport' attribute ignored on explicit instantiation definition}}
-
-void anchor(ClassTmplSpecializedMember<false, InstTrig::Impl> &x) { x.instantiatedMember1(); } // gnu-note{{implicit instantiation first required here}}
-extern template struct __declspec(dllexport) ClassTmplSpecializedMember<false, InstTrig::Impl>; // non-gnu-warning{{explicit instantiation declaration should not be 'dllexport'}} \
- non-gnu-note{{attribute is here}} \
- gnu-warning{{'dllexport' attribute ignored; class template is already instantiated}}
-void anchor(ClassTmplSpecializedMember<true, InstTrig::Impl> &x) { x.instantiatedMember1(); }
-template struct __declspec(dllexport) ClassTmplSpecializedMember<true, InstTrig::Impl>; // gnu-warning{{'dllexport' attribute ignored on explicit instantiation definition}}
-
-template <> void ClassTmplSpecializedMember<false, InstTrig::Spec, InstTrig::Spec>::specializedMember1(); // gnu-note{{implicit instantiation first required here}}
-template <> void ClassTmplSpecializedMember<false, InstTrig::Spec, InstTrig::Spec>::specializedMember2();
-extern template struct __declspec(dllexport) ClassTmplSpecializedMember<false, InstTrig::Spec, InstTrig::Spec>; // non-gnu-warning{{explicit instantiation declaration should not be 'dllexport'}} \
- non-gnu-note{{attribute is here}} \
- gnu-warning{{'dllexport' attribute ignored; class template is already instantiated}}
-template <> void ClassTmplSpecializedMember<true, InstTrig::Spec, InstTrig::Spec>::specializedMember1();
-template <> void ClassTmplSpecializedMember<true, InstTrig::Spec, InstTrig::Spec>::specializedMember2();
-template struct __declspec(dllexport) ClassTmplSpecializedMember<true, InstTrig::Spec, InstTrig::Spec>; // gnu-warning{{'dllexport' attribute ignored on explicit instantiation definition}}
-
-template <> void ClassTmplSpecializedMember<false, InstTrig::Spec, InstTrig::Impl>::specializedMember1(); // gnu-note{{implicit instantiation first required here}}
-void anchor(ClassTmplSpecializedMember<false, InstTrig::Spec, InstTrig::Impl> &x) { x.instantiatedMember1(); }
-extern template struct __declspec(dllexport) ClassTmplSpecializedMember<false, InstTrig::Spec, InstTrig::Impl>; // non-gnu-warning{{explicit instantiation declaration should not be 'dllexport'}} \
- non-gnu-note{{attribute is here}} \
- gnu-warning{{'dllexport' attribute ignored; class template is already instantiated}}
-template <> void ClassTmplSpecializedMember<true, InstTrig::Spec, InstTrig::Impl>::specializedMember1();
-void anchor(ClassTmplSpecializedMember<true, InstTrig::Spec, InstTrig::Impl> &x) { x.instantiatedMember1(); }
-template struct __declspec(dllexport) ClassTmplSpecializedMember<true, InstTrig::Spec, InstTrig::Impl>; // gnu-warning{{'dllexport' attribute ignored on explicit instantiation definition}}
-
-void anchor(ClassTmplSpecializedMember<false, InstTrig::Impl, InstTrig::Spec> &x) { x.instantiatedMember1(); } // gnu-note{{implicit instantiation first required here}}
-template <> void ClassTmplSpecializedMember<false, InstTrig::Impl, InstTrig::Spec>::specializedMember1();
-extern template struct __declspec(dllexport) ClassTmplSpecializedMember<false, InstTrig::Impl, InstTrig::Spec>; // non-gnu-warning{{explicit instantiation declaration should not be 'dllexport'}} \
- non-gnu-note{{attribute is here}} \
- gnu-warning{{'dllexport' attribute ignored; class template is already instantiated}}
-void anchor(ClassTmplSpecializedMember<true, InstTrig::Impl, InstTrig::Spec> &x) { x.instantiatedMember1(); }
-template <> void ClassTmplSpecializedMember<true, InstTrig::Impl, InstTrig::Spec>::specializedMember1();
-template struct __declspec(dllexport) ClassTmplSpecializedMember<true, InstTrig::Impl, InstTrig::Spec>; // gnu-warning{{'dllexport' attribute ignored on explicit instantiation definition}}
-
//===----------------------------------------------------------------------===//
// Class template member templates
diff --git a/clang/test/SemaCXX/dllimport.cpp b/clang/test/SemaCXX/dllimport.cpp
index c0266be95cd62b..deb0574cb5e68a 100644
--- a/clang/test/SemaCXX/dllimport.cpp
+++ b/clang/test/SemaCXX/dllimport.cpp
@@ -999,56 +999,6 @@ template<> void ClassTmpl<int>::importedStatic() {} // non-gnu-error{{cannot def
template <> void ImportClassTmplMembers<int>::normalDecl() = delete; // non-gnu-error{{cannot define non-inline dllimport template specialization}} \
non-gnu-error{{attribute 'dllimport' cannot be applied to a deleted function}}
-struct InstTrig {
- struct Spec;
- struct Impl;
- struct Decl;
-};
-template<bool InstDef, typename... Triggers>
-struct ClassTmplSpecializedMember {
- void specializedMember1();
- void specializedMember2();
- void instantiatedMember1();
- void instantiatedMember2();
- void member() {}
-};
-
-template <> void ClassTmplSpecializedMember<false, InstTrig::Spec>::specializedMember1(); // non-gnu-note{{implicit instantiation first required here}}
-extern template struct __declspec(dllimport) ClassTmplSpecializedMember<false, InstTrig::Spec>; // non-gnu-warning{{'dllimport' attribute ignored; class template is already instantiated}}
-template <> void ClassTmplSpecializedMember<true, InstTrig::Spec>::specializedMember1(); // non-gnu-note{{implicit instantiation first required here}}
-template struct __declspec(dllimport) ClassTmplSpecializedMember<true, InstTrig::Spec>; // non-gnu-warning{{'dllimport' attribute ignored; class template is already instantiated}} \
- gnu-warning{{'dllimport' attribute ignored on explicit instantiation definition}}
-
-void anchor(ClassTmplSpecializedMember<false, InstTrig::Impl> &x) { x.instantiatedMember1(); } // non-gnu-note{{implicit instantiation first required here}}
-extern template struct __declspec(dllimport) ClassTmplSpecializedMember<false, InstTrig::Impl>; // non-gnu-warning{{'dllimport' attribute ignored; class template is already instantiated}}
-void anchor(ClassTmplSpecializedMember<true, InstTrig::Impl> &x) { x.instantiatedMember1(); } // non-gnu-note{{implicit instantiation first required here}}
-template struct __declspec(dllimport) ClassTmplSpecializedMember<true, InstTrig::Impl>; // non-gnu-warning{{'dllimport' attribute ignored; class template is already instantiated}} \
- gnu-warning{{'dllimport' attribute ignored on explicit instantiation definition}}
-
-template <> void ClassTmplSpecializedMember<false, InstTrig::Spec, InstTrig::Spec>::specializedMember1(); // non-gnu-note{{implicit instantiation first required here}}
-template <> void ClassTmplSpecializedMember<false, InstTrig::Spec, InstTrig::Spec>::specializedMember2();
-extern template struct __declspec(dllimport) ClassTmplSpecializedMember<false, InstTrig::Spec, InstTrig::Spec>; // non-gnu-warning{{'dllimport' attribute ignored; class template is already instantiated}}
-template <> void ClassTmplSpecializedMember<true, InstTrig::Spec, InstTrig::Spec>::specializedMember1(); // non-gnu-note{{implicit instantiation first required here}}
-template <> void ClassTmplSpecializedMember<true, InstTrig::Spec, InstTrig::Spec>::specializedMember2();
-template struct __declspec(dllimport) ClassTmplSpecializedMember<true, InstTrig::Spec, InstTrig::Spec>; // non-gnu-warning{{'dllimport' attribute ignored; class template is already instantiated}} \
- gnu-warning{{'dllimport' attribute ignored on explicit instantiation definition}}
-
-template <> void ClassTmplSpecializedMember<false, InstTrig::Spec, InstTrig::Impl>::specializedMember1(); // non-gnu...
[truncated]
``````````
</details>
https://github.com/llvm/llvm-project/pull/224971
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