[clang] Reland: [clang] Track function template instantiation from definition (PR #125266)
Matheus Izvekov via cfe-commits
cfe-commits at lists.llvm.org
Wed Feb 5 08:25:07 PST 2025
https://github.com/mizvekov updated https://github.com/llvm/llvm-project/pull/125266
>From 1282f6a3181fa37e8649e407fabd72893a01103a Mon Sep 17 00:00:00 2001
From: Matheus Izvekov <mizvekov at gmail.com>
Date: Sat, 28 Sep 2024 14:28:58 -0300
Subject: [PATCH] [clang] Track function template instantiation from definition
This fixes instantiation of definition for friend function templates,
when the declaration found and the one containing the definition
have different template contexts.
In these cases, the the function declaration corresponding to the
definition is not available; it may not even be instantiated at all.
So this patch adds a bit which tracks which function template
declaration was instantiated from the member template.
It's used to find which primary template serves as a context
for the purpose of obtainining the template arguments needed
to instantiate the definition.
Fixes #55509
---
clang/docs/ReleaseNotes.rst | 2 +
clang/include/clang/AST/Decl.h | 7 ++
clang/include/clang/AST/DeclBase.h | 10 +-
clang/include/clang/AST/DeclTemplate.h | 20 ++++
clang/lib/AST/Decl.cpp | 1 +
clang/lib/Sema/SemaTemplateDeduction.cpp | 17 +--
clang/lib/Sema/SemaTemplateInstantiate.cpp | 9 +-
.../lib/Sema/SemaTemplateInstantiateDecl.cpp | 27 ++++-
clang/lib/Serialization/ASTReaderDecl.cpp | 1 +
clang/lib/Serialization/ASTWriterDecl.cpp | 3 +-
clang/test/SemaTemplate/GH55509.cpp | 112 ++++++++++++++++++
11 files changed, 181 insertions(+), 28 deletions(-)
create mode 100644 clang/test/SemaTemplate/GH55509.cpp
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index f7feca0089f94d..21c1ff25d2862b 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -145,6 +145,8 @@ Bug Fixes to Attribute Support
Bug Fixes to C++ Support
^^^^^^^^^^^^^^^^^^^^^^^^
+- Clang is now better at keeping track of friend function template instance contexts. (#GH55509)
+
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
index 499d27a9be5a8a..f305cbbce4c609 100644
--- a/clang/include/clang/AST/Decl.h
+++ b/clang/include/clang/AST/Decl.h
@@ -2298,6 +2298,13 @@ class FunctionDecl : public DeclaratorDecl,
FunctionDeclBits.IsLateTemplateParsed = ILT;
}
+ bool isInstantiatedFromMemberTemplate() const {
+ return FunctionDeclBits.IsInstantiatedFromMemberTemplate;
+ }
+ void setInstantiatedFromMemberTemplate(bool Val = true) {
+ FunctionDeclBits.IsInstantiatedFromMemberTemplate = Val;
+ }
+
/// Whether this function is "trivial" in some specialized C++ senses.
/// Can only be true for default constructors, copy constructors,
/// copy assignment operators, and destructors. Not meaningful until
diff --git a/clang/include/clang/AST/DeclBase.h b/clang/include/clang/AST/DeclBase.h
index 3bb82c1572ef9c..648dae2838e036 100644
--- a/clang/include/clang/AST/DeclBase.h
+++ b/clang/include/clang/AST/DeclBase.h
@@ -1780,6 +1780,8 @@ class DeclContext {
uint64_t HasImplicitReturnZero : 1;
LLVM_PREFERRED_TYPE(bool)
uint64_t IsLateTemplateParsed : 1;
+ LLVM_PREFERRED_TYPE(bool)
+ uint64_t IsInstantiatedFromMemberTemplate : 1;
/// Kind of contexpr specifier as defined by ConstexprSpecKind.
LLVM_PREFERRED_TYPE(ConstexprSpecKind)
@@ -1830,7 +1832,7 @@ class DeclContext {
};
/// Number of inherited and non-inherited bits in FunctionDeclBitfields.
- enum { NumFunctionDeclBits = NumDeclContextBits + 31 };
+ enum { NumFunctionDeclBits = NumDeclContextBits + 32 };
/// Stores the bits used by CXXConstructorDecl. If modified
/// NumCXXConstructorDeclBits and the accessor
@@ -1841,12 +1843,12 @@ class DeclContext {
LLVM_PREFERRED_TYPE(FunctionDeclBitfields)
uint64_t : NumFunctionDeclBits;
- /// 20 bits to fit in the remaining available space.
+ /// 19 bits to fit in the remaining available space.
/// Note that this makes CXXConstructorDeclBitfields take
/// exactly 64 bits and thus the width of NumCtorInitializers
/// will need to be shrunk if some bit is added to NumDeclContextBitfields,
/// NumFunctionDeclBitfields or CXXConstructorDeclBitfields.
- uint64_t NumCtorInitializers : 17;
+ uint64_t NumCtorInitializers : 16;
LLVM_PREFERRED_TYPE(bool)
uint64_t IsInheritingConstructor : 1;
@@ -1860,7 +1862,7 @@ class DeclContext {
};
/// Number of inherited and non-inherited bits in CXXConstructorDeclBitfields.
- enum { NumCXXConstructorDeclBits = NumFunctionDeclBits + 20 };
+ enum { NumCXXConstructorDeclBits = NumFunctionDeclBits + 19 };
/// Stores the bits used by ObjCMethodDecl.
/// If modified NumObjCMethodDeclBits and the accessor
diff --git a/clang/include/clang/AST/DeclTemplate.h b/clang/include/clang/AST/DeclTemplate.h
index 87406b0e030df1..a30ae798a99bc6 100644
--- a/clang/include/clang/AST/DeclTemplate.h
+++ b/clang/include/clang/AST/DeclTemplate.h
@@ -1011,6 +1011,26 @@ class FunctionTemplateDecl : public RedeclarableTemplateDecl {
return getTemplatedDecl()->isThisDeclarationADefinition();
}
+ bool isCompatibleWithDefinition() const {
+ return getTemplatedDecl()->isInstantiatedFromMemberTemplate() ||
+ isThisDeclarationADefinition();
+ }
+
+ // This bit closely tracks 'RedeclarableTemplateDecl::InstantiatedFromMember',
+ // except this is per declaration, while the redeclarable field is
+ // per chain. This indicates a template redeclaration which
+ // is compatible with the definition, in the non-trivial case
+ // where this is not already a definition.
+ // This is only really needed for instantiating the definition of friend
+ // function templates, which can have redeclarations in different template
+ // contexts.
+ // The bit is actually stored in the FunctionDecl for space efficiency
+ // reasons.
+ void setInstantiatedFromMemberTemplate(FunctionTemplateDecl *D) {
+ getTemplatedDecl()->setInstantiatedFromMemberTemplate();
+ RedeclarableTemplateDecl::setInstantiatedFromMemberTemplate(D);
+ }
+
/// Return the specialization with the provided arguments if it exists,
/// otherwise return the insertion point.
FunctionDecl *findSpecialization(ArrayRef<TemplateArgument> Args,
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 7e8a172ae4c37f..610207cf8b9a4a 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -3065,6 +3065,7 @@ FunctionDecl::FunctionDecl(Kind DK, ASTContext &C, DeclContext *DC,
FunctionDeclBits.IsIneligibleOrNotSelected = false;
FunctionDeclBits.HasImplicitReturnZero = false;
FunctionDeclBits.IsLateTemplateParsed = false;
+ FunctionDeclBits.IsInstantiatedFromMemberTemplate = false;
FunctionDeclBits.ConstexprKind = static_cast<uint64_t>(ConstexprKind);
FunctionDeclBits.BodyContainsImmediateEscalatingExpression = false;
FunctionDeclBits.InstantiationIsPending = false;
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 096844f55374bc..eb70dd743c8be5 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -4072,22 +4072,7 @@ TemplateDeductionResult Sema::FinishTemplateArgumentDeduction(
if (FunctionTemplate->getFriendObjectKind())
Owner = FunctionTemplate->getLexicalDeclContext();
FunctionDecl *FD = FunctionTemplate->getTemplatedDecl();
- // additional check for inline friend,
- // ```
- // template <class F1> int foo(F1 X);
- // template <int A1> struct A {
- // template <class F1> friend int foo(F1 X) { return A1; }
- // };
- // template struct A<1>;
- // int a = foo(1.0);
- // ```
- const FunctionDecl *FDFriend;
- if (FD->getFriendObjectKind() == Decl::FriendObjectKind::FOK_None &&
- FD->isDefined(FDFriend, /*CheckForPendingFriendDefinition*/ true) &&
- FDFriend->getFriendObjectKind() != Decl::FriendObjectKind::FOK_None) {
- FD = const_cast<FunctionDecl *>(FDFriend);
- Owner = FD->getLexicalDeclContext();
- }
+
MultiLevelTemplateArgumentList SubstArgs(
FunctionTemplate, CanonicalDeducedArgumentList->asArray(),
/*Final=*/false);
diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index 85301d696bccdd..d9a47ca3daa20c 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -479,9 +479,6 @@ MultiLevelTemplateArgumentList Sema::getTemplateInstantiationArgs(
using namespace TemplateInstArgsHelpers;
const Decl *CurDecl = ND;
- if (!CurDecl)
- CurDecl = Decl::castFromDeclContext(DC);
-
if (Innermost) {
Result.addOuterTemplateArguments(const_cast<NamedDecl *>(ND), *Innermost,
Final);
@@ -495,8 +492,10 @@ MultiLevelTemplateArgumentList Sema::getTemplateInstantiationArgs(
// has a depth of 0.
if (const auto *TTP = dyn_cast<TemplateTemplateParmDecl>(CurDecl))
HandleDefaultTempArgIntoTempTempParam(TTP, Result);
- CurDecl = Response::UseNextDecl(CurDecl).NextDecl;
- }
+ CurDecl = DC ? Decl::castFromDeclContext(DC)
+ : Response::UseNextDecl(CurDecl).NextDecl;
+ } else if (!CurDecl)
+ CurDecl = Decl::castFromDeclContext(DC);
while (!CurDecl->isFileContextDecl()) {
Response R;
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 595369661917ce..1f42f9500959e5 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -12,6 +12,7 @@
#include "TreeTransform.h"
#include "clang/AST/ASTConsumer.h"
#include "clang/AST/ASTContext.h"
+#include "clang/AST/ASTLambda.h"
#include "clang/AST/ASTMutationListener.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/DependentDiagnostic.h"
@@ -5276,9 +5277,31 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
RebuildTypeSourceInfoForDefaultSpecialMembers();
SetDeclDefaulted(Function, PatternDecl->getLocation());
} else {
+ NamedDecl *ND = Function;
+ DeclContext *DC = ND->getLexicalDeclContext();
+ std::optional<ArrayRef<TemplateArgument>> Innermost;
+ if (auto *Primary = Function->getPrimaryTemplate();
+ Primary &&
+ !isGenericLambdaCallOperatorOrStaticInvokerSpecialization(Function) &&
+ Function->getTemplateSpecializationKind() !=
+ TSK_ExplicitSpecialization) {
+ auto It = llvm::find_if(Primary->redecls(),
+ [](const RedeclarableTemplateDecl *RTD) {
+ return cast<FunctionTemplateDecl>(RTD)
+ ->isCompatibleWithDefinition();
+ });
+ assert(It != Primary->redecls().end() &&
+ "Should't get here without a definition");
+ if (FunctionDecl *Def = cast<FunctionTemplateDecl>(*It)
+ ->getTemplatedDecl()
+ ->getDefinition())
+ DC = Def->getLexicalDeclContext();
+ else
+ DC = (*It)->getLexicalDeclContext();
+ Innermost.emplace(Function->getTemplateSpecializationArgs()->asArray());
+ }
MultiLevelTemplateArgumentList TemplateArgs = getTemplateInstantiationArgs(
- Function, Function->getLexicalDeclContext(), /*Final=*/false,
- /*Innermost=*/std::nullopt, false, PatternDecl);
+ Function, DC, /*Final=*/false, Innermost, false, PatternDecl);
// Substitute into the qualifier; we can get a substitution failure here
// through evil use of alias templates.
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 28db3d355237ac..df834cd862f737 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -1064,6 +1064,7 @@ void ASTDeclReader::VisitFunctionDecl(FunctionDecl *FD) {
FD->setHasImplicitReturnZero(FunctionDeclBits.getNextBit());
FD->setIsMultiVersion(FunctionDeclBits.getNextBit());
FD->setLateTemplateParsed(FunctionDeclBits.getNextBit());
+ FD->setInstantiatedFromMemberTemplate(FunctionDeclBits.getNextBit());
FD->setFriendConstraintRefersToEnclosingTemplate(
FunctionDeclBits.getNextBit());
FD->setUsesSEHTry(FunctionDeclBits.getNextBit());
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index d8ce3c2fb964a7..b25dadab656b0e 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -679,7 +679,7 @@ void ASTDeclWriter::VisitDeclaratorDecl(DeclaratorDecl *D) {
}
void ASTDeclWriter::VisitFunctionDecl(FunctionDecl *D) {
- static_assert(DeclContext::NumFunctionDeclBits == 44,
+ static_assert(DeclContext::NumFunctionDeclBits == 45,
"You need to update the serializer after you change the "
"FunctionDeclBits");
@@ -785,6 +785,7 @@ void ASTDeclWriter::VisitFunctionDecl(FunctionDecl *D) {
FunctionDeclBits.addBit(D->hasImplicitReturnZero());
FunctionDeclBits.addBit(D->isMultiVersion());
FunctionDeclBits.addBit(D->isLateTemplateParsed());
+ FunctionDeclBits.addBit(D->isInstantiatedFromMemberTemplate());
FunctionDeclBits.addBit(D->FriendConstraintRefersToEnclosingTemplate());
FunctionDeclBits.addBit(D->usesSEHTry());
Record.push_back(FunctionDeclBits);
diff --git a/clang/test/SemaTemplate/GH55509.cpp b/clang/test/SemaTemplate/GH55509.cpp
new file mode 100644
index 00000000000000..773a84305a0cda
--- /dev/null
+++ b/clang/test/SemaTemplate/GH55509.cpp
@@ -0,0 +1,112 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 %s
+
+namespace t1 {
+ template<int N> struct A {
+ template<class C> friend auto cica(const A<N-1>&, C) {
+ return N;
+ }
+ };
+
+ template<> struct A<0> {
+ template<class C> friend auto cica(const A<0>&, C);
+ // expected-note at -1 {{declared here}}
+ };
+
+ void test() {
+ cica(A<0>{}, 0);
+ // expected-error at -1 {{function 'cica<int>' with deduced return type cannot be used before it is defined}}
+
+ (void)A<1>{};
+ cica(A<0>{}, 0);
+ }
+} // namespace t1
+namespace t2 {
+ template<int N> struct A {
+ template<class C> friend auto cica(const A<N-1>&, C) {
+ return N;
+ }
+ };
+
+ template<> struct A<0> {
+ template<class C> friend auto cica(const A<0>&, C);
+ };
+
+ template <int N, class = decltype(cica(A<N>{}, nullptr))>
+ void MakeCica();
+ // expected-note at -1 {{candidate function}}
+
+ template <int N> void MakeCica(A<N+1> = {});
+ // expected-note at -1 {{candidate function}}
+
+ void test() {
+ MakeCica<0>();
+
+ MakeCica<0>();
+ // expected-error at -1 {{call to 'MakeCica' is ambiguous}}
+ }
+} // namespace t2
+namespace t3 {
+ template<int N> struct A {
+ template<class C> friend auto cica(const A<N-1>&, C) {
+ return N-1;
+ }
+ };
+
+ template<> struct A<0> {
+ template<class C> friend auto cica(const A<0>&, C);
+ };
+
+ template <int N, class AT, class = decltype(cica(AT{}, nullptr))>
+ static constexpr bool MakeCica(int);
+
+ template <int N, class AT>
+ static constexpr bool MakeCica(short, A<N+1> = {});
+
+ template <int N, class AT = A<N>, class Val = decltype(MakeCica<N, AT>(0))>
+ static constexpr bool has_cica = Val{};
+
+ constexpr bool cica2 = has_cica<0> || has_cica<0>;
+} // namespace t3
+namespace t4 {
+ template<int N> struct A {
+ template<class C> friend auto cica(const A<N-1>&, C);
+ };
+
+ template<> struct A<0> {
+ template<class C> friend auto cica(const A<0>&, C) {
+ C a;
+ }
+ };
+
+ template struct A<1>;
+
+ void test() {
+ cica(A<0>{}, 0);
+ }
+} // namespace t4
+namespace regression1 {
+ template <class> class A;
+
+ template <class T> [[gnu::abi_tag("TAG")]] void foo(A<T>);
+
+ template <class> struct A {
+ friend void foo <>(A);
+ };
+
+ template struct A<int>;
+
+ template <class T> [[gnu::abi_tag("TAG")]] void foo(A<T>) {}
+
+ template void foo<int>(A<int>);
+} // namespace regression1
+namespace regression2 {
+ template <class> struct A {
+ template <class T> static void f() {
+ A<int>::f<T>();
+ }
+ };
+ template <> template <class T> void A<int>::f() {
+ static_assert(__is_same(T, long));
+ }
+ template void A<void>::f<long>();
+} // namespace regression2
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