https://github.com/zwuis created
https://github.com/llvm/llvm-project/pull/134522
Fixes #51347
>From ccab3dc1f18ffeda9acb07c0bd5f80f65cc788b9 Mon Sep 17 00:00:00 2001
From: Yanzuo Liu <zw...@outlook.com>
Date: Sun, 6 Apr 2025 15:06:56 +0800
Subject: [PATCH] Handle invalid variable template specialization whose type
depends on itself
---
clang/docs/ReleaseNotes.rst | 2 ++
.../include/clang/Basic/DiagnosticSemaKinds.td | 3 +++
clang/lib/Sema/SemaTemplate.cpp | 7 +++++++
.../SemaTemplate/instantiate-var-template.cpp | 18 ++++++++++++++++++
4 files changed, 30 insertions(+)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 5217e04b5e83f..9e0fe8a94729b 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -414,6 +414,8 @@ Bug Fixes to C++ Support
- Clang now issues an error when placement new is used to modify a
const-qualified variable
in a ``constexpr`` function. (#GH131432)
- Clang now emits a warning when class template argument deduction for alias
templates is used in C++17. (#GH133806)
+- No longer crashes when instantiating invalid variable template specialization
+ whose type depends on itself. (#GH51347)
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 393bfecf9a36b..0c1da40dba388 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5259,6 +5259,9 @@ def err_template_member_noparams : Error<
"extraneous 'template<>' in declaration of member %0">;
def err_template_tag_noparams : Error<
"extraneous 'template<>' in declaration of %0 %1">;
+def err_var_template_spec_type_depends_on_self : Error<
+ "the type of variable template specialization %0 declared with deduced type "
+ "%1 depends on itself">;
def warn_unqualified_call_to_std_cast_function : Warning<
"unqualified call to '%0'">, InGroup<DiagGroup<"unqualified-std-cast-call">>;
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 153f44f8ec67a..ce54dbbb3b9fe 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -4377,6 +4377,13 @@ Sema::CheckVarTemplateId(VarTemplateDecl *Template,
SourceLocation TemplateLoc,
if (VarTemplateSpecializationDecl *Spec =
Template->findSpecialization(CTAI.CanonicalConverted, InsertPos)) {
checkSpecializationReachability(TemplateNameLoc, Spec);
+ if (Spec->getType()->isUndeducedType()) {
+ // We are substituting the initializer of this variable template
+ // specialization.
+ Diag(TemplateNameLoc, diag::err_var_template_spec_type_depends_on_self)
+ << Spec << Spec->getType();
+ return true;
+ }
// If we already have a variable template specialization, return it.
return Spec;
}
diff --git a/clang/test/SemaTemplate/instantiate-var-template.cpp
b/clang/test/SemaTemplate/instantiate-var-template.cpp
index 60d3bd3b59f53..34a1b9710814b 100644
--- a/clang/test/SemaTemplate/instantiate-var-template.cpp
+++ b/clang/test/SemaTemplate/instantiate-var-template.cpp
@@ -47,3 +47,21 @@ namespace InvalidInsertPos {
template<> int v<int, 0>;
int k = v<int, 500>;
}
+
+namespace GH51347 {
+ template <typename T>
+ auto p = p<T>; // expected-error {{the type of variable template
specialization 'p<int>'}}
+
+ auto x = p<int>; // expected-note {{in instantiation of variable template
specialization 'GH51347::p'}}
+}
+
+namespace GH97881_comment {
+ template <bool B>
+ auto g = sizeof(g<!B>);
+ // expected-error@-1 {{the type of variable template specialization
'g<false>'}}
+ // expected-note@-2 {{in instantiation of variable template specialization
'GH97881_comment::g'}}
+
+ void test() {
+ (void)sizeof(g<false>); // expected-note {{in instantiation of variable
template specialization 'GH97881_comment::g'}}
+ }
+}
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