https://github.com/zyn0217 created
https://github.com/llvm/llvm-project/pull/128845
This fixes a potential integer overflow bug that has been around for many
versions and was exposed by my patch recently. So we think it warrants a
backport.
Backports b8d1f3d62.
>From 4adb975ae689d575dcd329ccd24d2cd0355bb61b Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7...@gmail.com>
Date: Wed, 26 Feb 2025 16:54:19 +0800
Subject: [PATCH] [Clang] Fix an integer overflow issue in computing CTAD's
parameter depth (#128704)
Backports b8d1f3d62.
This fixes a potential integer overflow bug that has been around for
many versions and was exposed by my patch recently. So we think it
warrants a backport
---
clang/docs/ReleaseNotes.rst | 1 +
clang/lib/Sema/SemaTemplateDeductionGuide.cpp | 9 +++++-
clang/test/SemaTemplate/deduction-guide.cpp | 32 +++++++++++++++++++
3 files changed, 41 insertions(+), 1 deletion(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 153afdb3d59e3..7537b2b8d42d8 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -1058,6 +1058,7 @@ Bug Fixes to C++ Support
- Fixed a substitution bug in transforming CTAD aliases when the type alias
contains a non-pack template argument
corresponding to a pack parameter (#GH124715)
- Clang is now better at keeping track of friend function template instance
contexts. (#GH55509)
+- Fixed an integer overflow bug in computing template parameter depths when
synthesizing CTAD guides. (#GH128691)
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaTemplateDeductionGuide.cpp
b/clang/lib/Sema/SemaTemplateDeductionGuide.cpp
index 00c5dfd3d7a43..b424de9c8a945 100644
--- a/clang/lib/Sema/SemaTemplateDeductionGuide.cpp
+++ b/clang/lib/Sema/SemaTemplateDeductionGuide.cpp
@@ -377,8 +377,15 @@ struct ConvertConstructorToDeductionGuideTransform {
if (NestedPattern)
Args.addOuterRetainedLevels(NestedPattern->getTemplateDepth());
auto [Depth, Index] = getDepthAndIndex(Param);
+ // Depth can still be 0 if FTD belongs to an explicit class template
+ // specialization with an empty template parameter list. In that case,
+ // we don't want the NewDepth to overflow, and it should remain 0.
+ assert(Depth ||
+ cast<ClassTemplateSpecializationDecl>(FTD->getDeclContext())
+ ->isExplicitSpecialization());
NamedDecl *NewParam = transformTemplateParameter(
- SemaRef, DC, Param, Args, Index + Depth1IndexAdjustment, Depth -
1);
+ SemaRef, DC, Param, Args, Index + Depth1IndexAdjustment,
+ Depth ? Depth - 1 : 0);
if (!NewParam)
return nullptr;
// Constraints require that we substitute depth-1 arguments
diff --git a/clang/test/SemaTemplate/deduction-guide.cpp
b/clang/test/SemaTemplate/deduction-guide.cpp
index a4c523595fca2..ecd152abebd74 100644
--- a/clang/test/SemaTemplate/deduction-guide.cpp
+++ b/clang/test/SemaTemplate/deduction-guide.cpp
@@ -691,3 +691,35 @@ Test test(42);
// CHECK-NEXT: | `-ParmVarDecl {{.*}} 'auto:1'
} // namespace GH122134
+
+namespace GH128691 {
+
+template <typename = void>
+class NewDeleteAllocator;
+
+template <>
+struct NewDeleteAllocator<> {
+ template <typename T>
+ NewDeleteAllocator(T); // expected-note {{candidate template ignored}} \
+ // expected-note {{implicit deduction guide declared
as}}
+};
+
+template <typename>
+struct NewDeleteAllocator : NewDeleteAllocator<> { // expected-note
{{candidate template ignored}} \
+ // expected-note {{implicit
deduction guide declared as}}
+ using NewDeleteAllocator<>::NewDeleteAllocator;
+};
+
+void test() { NewDeleteAllocator abc(42); } // expected-error {{no viable
constructor or deduction guide}}
+
+// CHECK-LABEL: Dumping GH128691::<deduction guide for NewDeleteAllocator>:
+// CHECK-NEXT: FunctionTemplateDecl {{.+}} <deduction guide for
NewDeleteAllocator>
+// CHECK-NEXT: |-TemplateTypeParmDecl {{.+}} typename depth 0 index 0
+// CHECK-NEXT: | `-TemplateArgument type 'void'
+// CHECK-NEXT: | |-inherited from TemplateTypeParm {{.+}} depth 0 index 0
+// CHECK-NEXT: | `-BuiltinType {{.+}} 'void'
+// CHECK-NEXT: |-TemplateTypeParmDecl {{.+}} typename depth 0 index 1 T
+// CHECK-NEXT: `-CXXDeductionGuideDecl {{.+}} <deduction guide for
NewDeleteAllocator> 'auto (T) -> NewDeleteAllocator<type-parameter-0-0>'
+// CHECK-NEXT: `-ParmVarDecl {{.+}} 'T'
+
+} // namespace GH128691
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