[clang] c1468e9 - [Clang] Don't give up on an unsuccessful function instantiation (#126723)
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cfe-commits at lists.llvm.org
Tue Mar 4 19:50:41 PST 2025
Author: Younan Zhang
Date: 2025-03-05T11:50:37+08:00
New Revision: c1468e9cbca1002a24772af1a0e7a771f93f6910
URL: https://github.com/llvm/llvm-project/commit/c1468e9cbca1002a24772af1a0e7a771f93f6910
DIFF: https://github.com/llvm/llvm-project/commit/c1468e9cbca1002a24772af1a0e7a771f93f6910.diff
LOG: [Clang] Don't give up on an unsuccessful function instantiation (#126723)
For constexpr function templates, we immediately instantiate them upon
reference. However, if the function isn't defined at the time of
instantiation, even though it might be defined later, the instantiation
would forever fail.
This patch corrects the behavior by popping up failed instantiations
through PendingInstantiations, so that we are able to instantiate them
again in the future (e.g. at the end of TU.)
Fixes https://github.com/llvm/llvm-project/issues/125747
Added:
Modified:
clang/docs/ReleaseNotes.rst
clang/include/clang/Sema/Sema.h
clang/lib/Interpreter/IncrementalParser.cpp
clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
clang/test/CodeGenCXX/function-template-specialization.cpp
Removed:
################################################################################
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 37ea963bf337d..5098e5e983103 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -264,6 +264,8 @@ Bug Fixes to C++ Support
- Clang is now better at keeping track of friend function template instance contexts. (#GH55509)
- Clang now prints the correct instantiation context for diagnostics suppressed
by template argument deduction.
+- Clang is now better at instantiating the function definition after its use inside
+ of a constexpr lambda. (#GH125747)
- The initialization kind of elements of structured bindings
direct-list-initialized from an array is corrected to direct-initialization.
- Clang no longer crashes when a coroutine is declared ``[[noreturn]]``. (#GH127327)
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 2da5f5e311fc7..80177996b48b0 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -13657,12 +13657,16 @@ class Sema final : public SemaBase {
class LocalEagerInstantiationScope {
public:
- LocalEagerInstantiationScope(Sema &S) : S(S) {
+ LocalEagerInstantiationScope(Sema &S, bool AtEndOfTU)
+ : S(S), AtEndOfTU(AtEndOfTU) {
SavedPendingLocalImplicitInstantiations.swap(
S.PendingLocalImplicitInstantiations);
}
- void perform() { S.PerformPendingInstantiations(/*LocalOnly=*/true); }
+ void perform() {
+ S.PerformPendingInstantiations(/*LocalOnly=*/true,
+ /*AtEndOfTU=*/AtEndOfTU);
+ }
~LocalEagerInstantiationScope() {
assert(S.PendingLocalImplicitInstantiations.empty() &&
@@ -13673,6 +13677,7 @@ class Sema final : public SemaBase {
private:
Sema &S;
+ bool AtEndOfTU;
std::deque<PendingImplicitInstantiation>
SavedPendingLocalImplicitInstantiations;
};
@@ -13695,8 +13700,8 @@ class Sema final : public SemaBase {
class GlobalEagerInstantiationScope {
public:
- GlobalEagerInstantiationScope(Sema &S, bool Enabled)
- : S(S), Enabled(Enabled) {
+ GlobalEagerInstantiationScope(Sema &S, bool Enabled, bool AtEndOfTU)
+ : S(S), Enabled(Enabled), AtEndOfTU(AtEndOfTU) {
if (!Enabled)
return;
@@ -13710,7 +13715,8 @@ class Sema final : public SemaBase {
void perform() {
if (Enabled) {
S.DefineUsedVTables();
- S.PerformPendingInstantiations();
+ S.PerformPendingInstantiations(/*LocalOnly=*/false,
+ /*AtEndOfTU=*/AtEndOfTU);
}
}
@@ -13725,7 +13731,8 @@ class Sema final : public SemaBase {
S.SavedVTableUses.pop_back();
// Restore the set of pending implicit instantiations.
- if (S.TUKind != TU_Prefix || !S.LangOpts.PCHInstantiateTemplates) {
+ if ((S.TUKind != TU_Prefix || !S.LangOpts.PCHInstantiateTemplates) &&
+ AtEndOfTU) {
assert(S.PendingInstantiations.empty() &&
"PendingInstantiations should be empty before it is discarded.");
S.PendingInstantiations.swap(S.SavedPendingInstantiations.back());
@@ -13744,6 +13751,7 @@ class Sema final : public SemaBase {
private:
Sema &S;
bool Enabled;
+ bool AtEndOfTU;
};
ExplicitSpecifier instantiateExplicitSpecifier(
@@ -13929,7 +13937,8 @@ class Sema final : public SemaBase {
/// Performs template instantiation for all implicit template
/// instantiations we have seen until this point.
- void PerformPendingInstantiations(bool LocalOnly = false);
+ void PerformPendingInstantiations(bool LocalOnly = false,
+ bool AtEndOfTU = true);
TemplateParameterList *
SubstTemplateParams(TemplateParameterList *Params, DeclContext *Owner,
diff --git a/clang/lib/Interpreter/IncrementalParser.cpp b/clang/lib/Interpreter/IncrementalParser.cpp
index e43cea1baf43a..41d6304bd5f65 100644
--- a/clang/lib/Interpreter/IncrementalParser.cpp
+++ b/clang/lib/Interpreter/IncrementalParser.cpp
@@ -41,8 +41,9 @@ llvm::Expected<TranslationUnitDecl *>
IncrementalParser::ParseOrWrapTopLevelDecl() {
// Recover resources if we crash before exiting this method.
llvm::CrashRecoveryContextCleanupRegistrar<Sema> CleanupSema(&S);
- Sema::GlobalEagerInstantiationScope GlobalInstantiations(S, /*Enabled=*/true);
- Sema::LocalEagerInstantiationScope LocalInstantiations(S);
+ Sema::GlobalEagerInstantiationScope GlobalInstantiations(S, /*Enabled=*/true,
+ /*AtEndOfTU=*/true);
+ Sema::LocalEagerInstantiationScope LocalInstantiations(S, /*AtEndOfTU=*/true);
// Add a new PTU.
ASTContext &C = S.getASTContext();
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index dd894df851488..82e049c9c13b9 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -2362,7 +2362,8 @@ Decl *TemplateDeclInstantiator::VisitCXXRecordDecl(CXXRecordDecl *D) {
// DR1484 clarifies that the members of a local class are instantiated as part
// of the instantiation of their enclosing entity.
if (D->isCompleteDefinition() && D->isLocalClass()) {
- Sema::LocalEagerInstantiationScope LocalInstantiations(SemaRef);
+ Sema::LocalEagerInstantiationScope LocalInstantiations(SemaRef,
+ /*AtEndOfTU=*/false);
SemaRef.InstantiateClass(D->getLocation(), Record, D, TemplateArgs,
TSK_ImplicitInstantiation,
@@ -5344,8 +5345,10 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
// This has to happen before LateTemplateParser below is called, so that
// it marks vtables used in late parsed templates as used.
GlobalEagerInstantiationScope GlobalInstantiations(*this,
- /*Enabled=*/Recursive);
- LocalEagerInstantiationScope LocalInstantiations(*this);
+ /*Enabled=*/Recursive,
+ /*AtEndOfTU=*/AtEndOfTU);
+ LocalEagerInstantiationScope LocalInstantiations(*this,
+ /*AtEndOfTU=*/AtEndOfTU);
// Call the LateTemplateParser callback if there is a need to late parse
// a templated function definition.
@@ -5919,10 +5922,12 @@ void Sema::InstantiateVariableDefinition(SourceLocation PointOfInstantiation,
// If we're performing recursive template instantiation, create our own
// queue of pending implicit instantiations that we will instantiate
// later, while we're still within our own instantiation context.
- GlobalEagerInstantiationScope GlobalInstantiations(*this,
- /*Enabled=*/Recursive);
+ GlobalEagerInstantiationScope GlobalInstantiations(
+ *this,
+ /*Enabled=*/Recursive, /*AtEndOfTU=*/AtEndOfTU);
LocalInstantiationScope Local(*this);
- LocalEagerInstantiationScope LocalInstantiations(*this);
+ LocalEagerInstantiationScope LocalInstantiations(*this,
+ /*AtEndOfTU=*/AtEndOfTU);
// Enter the scope of this instantiation. We don't use
// PushDeclContext because we don't have a scope.
@@ -6019,14 +6024,16 @@ void Sema::InstantiateVariableDefinition(SourceLocation PointOfInstantiation,
// queue of pending implicit instantiations that we will instantiate later,
// while we're still within our own instantiation context.
GlobalEagerInstantiationScope GlobalInstantiations(*this,
- /*Enabled=*/Recursive);
+ /*Enabled=*/Recursive,
+ /*AtEndOfTU=*/AtEndOfTU);
// Enter the scope of this instantiation. We don't use
// PushDeclContext because we don't have a scope.
ContextRAII PreviousContext(*this, Var->getDeclContext());
LocalInstantiationScope Local(*this);
- LocalEagerInstantiationScope LocalInstantiations(*this);
+ LocalEagerInstantiationScope LocalInstantiations(*this,
+ /*AtEndOfTU=*/AtEndOfTU);
VarDecl *OldVar = Var;
if (Def->isStaticDataMember() && !Def->isOutOfLine()) {
@@ -6774,18 +6781,20 @@ NamedDecl *Sema::FindInstantiatedDecl(SourceLocation Loc, NamedDecl *D,
return D;
}
-void Sema::PerformPendingInstantiations(bool LocalOnly) {
- std::deque<PendingImplicitInstantiation> delayedPCHInstantiations;
+void Sema::PerformPendingInstantiations(bool LocalOnly, bool AtEndOfTU) {
+ std::deque<PendingImplicitInstantiation> DelayedImplicitInstantiations;
while (!PendingLocalImplicitInstantiations.empty() ||
(!LocalOnly && !PendingInstantiations.empty())) {
PendingImplicitInstantiation Inst;
+ bool LocalInstantiation = false;
if (PendingLocalImplicitInstantiations.empty()) {
Inst = PendingInstantiations.front();
PendingInstantiations.pop_front();
} else {
Inst = PendingLocalImplicitInstantiations.front();
PendingLocalImplicitInstantiations.pop_front();
+ LocalInstantiation = true;
}
// Instantiate function definitions
@@ -6794,22 +6803,26 @@ void Sema::PerformPendingInstantiations(bool LocalOnly) {
TSK_ExplicitInstantiationDefinition;
if (Function->isMultiVersion()) {
getASTContext().forEachMultiversionedFunctionVersion(
- Function, [this, Inst, DefinitionRequired](FunctionDecl *CurFD) {
+ Function,
+ [this, Inst, DefinitionRequired, AtEndOfTU](FunctionDecl *CurFD) {
InstantiateFunctionDefinition(/*FIXME:*/ Inst.second, CurFD, true,
- DefinitionRequired, true);
+ DefinitionRequired, AtEndOfTU);
if (CurFD->isDefined())
CurFD->setInstantiationIsPending(false);
});
} else {
InstantiateFunctionDefinition(/*FIXME:*/ Inst.second, Function, true,
- DefinitionRequired, true);
+ DefinitionRequired, AtEndOfTU);
if (Function->isDefined())
Function->setInstantiationIsPending(false);
}
// Definition of a PCH-ed template declaration may be available only in the TU.
if (!LocalOnly && LangOpts.PCHInstantiateTemplates &&
TUKind == TU_Prefix && Function->instantiationIsPending())
- delayedPCHInstantiations.push_back(Inst);
+ DelayedImplicitInstantiations.push_back(Inst);
+ else if (!AtEndOfTU && Function->instantiationIsPending() &&
+ !LocalInstantiation)
+ DelayedImplicitInstantiations.push_back(Inst);
continue;
}
@@ -6853,11 +6866,11 @@ void Sema::PerformPendingInstantiations(bool LocalOnly) {
// Instantiate static data member definitions or variable template
// specializations.
InstantiateVariableDefinition(/*FIXME:*/ Inst.second, Var, true,
- DefinitionRequired, true);
+ DefinitionRequired, AtEndOfTU);
}
- if (!LocalOnly && LangOpts.PCHInstantiateTemplates)
- PendingInstantiations.swap(delayedPCHInstantiations);
+ if (!DelayedImplicitInstantiations.empty())
+ PendingInstantiations.swap(DelayedImplicitInstantiations);
}
void Sema::PerformDependentDiagnostics(const DeclContext *Pattern,
diff --git a/clang/test/CodeGenCXX/function-template-specialization.cpp b/clang/test/CodeGenCXX/function-template-specialization.cpp
index 7728f3dc74624..31c78358d014c 100644
--- a/clang/test/CodeGenCXX/function-template-specialization.cpp
+++ b/clang/test/CodeGenCXX/function-template-specialization.cpp
@@ -1,4 +1,5 @@
-// RUN: %clang_cc1 -emit-llvm -triple %itanium_abi_triple %s -o - | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm -Wundefined-func-template -verify -triple %itanium_abi_triple %s -o - | FileCheck %s
+// expected-no-diagnostics
// CHECK-DAG: _ZZN7PR219047GetDataIiEERKibE1i = internal global i32 4
// CHECK-DAG: _ZZN7PR219047GetDataIiEERKibE1i_0 = internal global i32 2
@@ -43,3 +44,19 @@ const int &GetData<int>(bool b) {
return i;
}
}
+
+namespace GH125747 {
+
+template<typename F> constexpr int visit(F f) { return f(0); }
+
+template <class T> int G(T t);
+
+int main() { return visit([](auto s) -> int { return G(s); }); }
+
+template <class T> int G(T t) {
+ return 0;
+}
+
+// CHECK: define {{.*}} @_ZN8GH1257471GIiEEiT_
+
+}
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