[clang] Add unique_ptr <T[]> accesses to -Wunsafe-buffer-usage (PR #156773)
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cfe-commits at lists.llvm.org
Mon Sep 8 10:50:32 PDT 2025
https://github.com/shreya-jain updated https://github.com/llvm/llvm-project/pull/156773
>From 927b2f61b8f5e0163c065ee4cbbf7ebb6956c34b Mon Sep 17 00:00:00 2001
From: shreya-jain <jainshreya at google.com>
Date: Wed, 3 Sep 2025 00:36:02 -0700
Subject: [PATCH 1/8] Update UnsafeBufferUsage.h
---
clang/include/clang/Analysis/Analyses/UnsafeBufferUsage.h | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/clang/include/clang/Analysis/Analyses/UnsafeBufferUsage.h b/clang/include/clang/Analysis/Analyses/UnsafeBufferUsage.h
index 9b53f1dc1d759..ea41eb3becfcf 100644
--- a/clang/include/clang/Analysis/Analyses/UnsafeBufferUsage.h
+++ b/clang/include/clang/Analysis/Analyses/UnsafeBufferUsage.h
@@ -14,6 +14,7 @@
#ifndef LLVM_CLANG_ANALYSIS_ANALYSES_UNSAFEBUFFERUSAGE_H
#define LLVM_CLANG_ANALYSIS_ANALYSES_UNSAFEBUFFERUSAGE_H
+#include "clang/AST/ASTTypeTraits.h"
#include "clang/AST/Decl.h"
#include "clang/AST/Expr.h"
#include "clang/AST/Stmt.h"
@@ -139,6 +140,12 @@ class UnsafeBufferUsageHandler {
FixItList &&Fixes, const Decl *D,
const FixitStrategy &VarTargetTypes) = 0;
+ // Invoked when an array subscript operator[] is used on a
+ // std::unique_ptr<T[]>.
+ virtual void handleUnsafeUniquePtrArrayAccess(const DynTypedNode &Node,
+ bool IsRelatedToDecl,
+ ASTContext &Ctx) = 0;
+
#ifndef NDEBUG
public:
bool areDebugNotesRequested() {
>From bae5f2ee3e04cc2bb54a5a863b9a8113aca227aa Mon Sep 17 00:00:00 2001
From: shreya-jain <jainshreya at google.com>
Date: Wed, 3 Sep 2025 00:38:29 -0700
Subject: [PATCH 2/8] Update UnsafeBufferUsageGadgets.def
---
.../include/clang/Analysis/Analyses/UnsafeBufferUsageGadgets.def | 1 +
1 file changed, 1 insertion(+)
diff --git a/clang/include/clang/Analysis/Analyses/UnsafeBufferUsageGadgets.def b/clang/include/clang/Analysis/Analyses/UnsafeBufferUsageGadgets.def
index 09fa510bc0472..fae5f8b8aa8e3 100644
--- a/clang/include/clang/Analysis/Analyses/UnsafeBufferUsageGadgets.def
+++ b/clang/include/clang/Analysis/Analyses/UnsafeBufferUsageGadgets.def
@@ -38,6 +38,7 @@ WARNING_GADGET(PointerArithmetic)
WARNING_GADGET(UnsafeBufferUsageAttr)
WARNING_GADGET(UnsafeBufferUsageCtorAttr)
WARNING_GADGET(DataInvocation)
+WARNING_GADGET(UniquePtrArrayAccess)
WARNING_OPTIONAL_GADGET(UnsafeLibcFunctionCall)
WARNING_OPTIONAL_GADGET(SpanTwoParamConstructor) // Uses of `std::span(arg0, arg1)`
FIXABLE_GADGET(ULCArraySubscript) // `DRE[any]` in an Unspecified Lvalue Context
>From 284c26214a0758346f78db02c81bfe953a9cd2ae Mon Sep 17 00:00:00 2001
From: shreya-jain <jainshreya at google.com>
Date: Wed, 3 Sep 2025 00:45:48 -0700
Subject: [PATCH 3/8] Update DiagnosticGroups.td
---
clang/include/clang/Basic/DiagnosticGroups.td | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index 0c994e0b5ca4d..4b27a42c6dd81 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -1750,7 +1750,8 @@ def ReadOnlyPlacementChecks : DiagGroup<"read-only-types">;
// Warnings and fixes to support the "safe buffers" programming model.
def UnsafeBufferUsageInContainer : DiagGroup<"unsafe-buffer-usage-in-container">;
def UnsafeBufferUsageInLibcCall : DiagGroup<"unsafe-buffer-usage-in-libc-call">;
-def UnsafeBufferUsage : DiagGroup<"unsafe-buffer-usage", [UnsafeBufferUsageInContainer, UnsafeBufferUsageInLibcCall]>;
+def UnsafeBufferUsageInUniquePtrArrayAccess : DiagGroup<"unsafe-buffer-usage-in-unique-ptr-array-access">;
+def UnsafeBufferUsage : DiagGroup<"unsafe-buffer-usage", [UnsafeBufferUsageInContainer, UnsafeBufferUsageInLibcCall, UnsafeBufferUsageInUniquePtrArrayAccess]>;
// Warnings and notes InstallAPI verification.
def InstallAPIViolation : DiagGroup<"installapi-violation">;
>From 980a75e56bd40fe2f58f5f4e5b4d671fd4448e84 Mon Sep 17 00:00:00 2001
From: shreya-jain <jainshreya at google.com>
Date: Wed, 3 Sep 2025 00:47:47 -0700
Subject: [PATCH 4/8] Update DiagnosticSemaKinds.td
---
clang/include/clang/Basic/DiagnosticSemaKinds.td | 2 ++
1 file changed, 2 insertions(+)
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index c76385ad73a91..117ba3b79eacc 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -13240,6 +13240,8 @@ def note_safe_buffer_usage_suggestions_disabled : Note<
def warn_unsafe_buffer_usage_in_container : Warning<
"the two-parameter std::span construction is unsafe as it can introduce mismatch between buffer size and the bound information">,
InGroup<UnsafeBufferUsageInContainer>, DefaultIgnore;
+def warn_unsafe_buffer_usage_unique_ptr_array_access : Warning<"direct access using operator[] on std::unique_ptr<T[]> is unsafe due to lack of bounds checking">,
+ InGroup<UnsafeBufferUsageInUniquePtrArray>, DefaultIgnore;
#ifndef NDEBUG
// Not a user-facing diagnostic. Useful for debugging false negatives in
// -fsafe-buffer-usage-suggestions (i.e. lack of -Wunsafe-buffer-usage fixits).
>From 11fc596ef00a9e47eca04724b8ae7e35f7aa12d1 Mon Sep 17 00:00:00 2001
From: shreya-jain <jainshreya at google.com>
Date: Wed, 3 Sep 2025 00:53:56 -0700
Subject: [PATCH 5/8] Update UnsafeBufferUsage.cpp
---
clang/lib/Analysis/UnsafeBufferUsage.cpp | 104 +++++++++++++++++++++++
1 file changed, 104 insertions(+)
diff --git a/clang/lib/Analysis/UnsafeBufferUsage.cpp b/clang/lib/Analysis/UnsafeBufferUsage.cpp
index 1d7b8722103aa..3dbf4e9a3535b 100644
--- a/clang/lib/Analysis/UnsafeBufferUsage.cpp
+++ b/clang/lib/Analysis/UnsafeBufferUsage.cpp
@@ -13,6 +13,7 @@
#include "clang/AST/Attr.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
+#include "clang/AST/DeclTemplate.h"
#include "clang/AST/DynamicRecursiveASTVisitor.h"
#include "clang/AST/Expr.h"
#include "clang/AST/FormatString.h"
@@ -1318,6 +1319,105 @@ static bool isSupportedVariable(const DeclRefExpr &Node) {
return D != nullptr && isa<VarDecl>(D);
}
+static bool isUniquePtrArray(const CXXRecordDecl *RecordDecl) {
+ if (!RecordDecl || !RecordDecl->isInStdNamespace() ||
+ RecordDecl->getNameAsString() != "unique_ptr") {
+ return false;
+ }
+
+ const ClassTemplateSpecializationDecl *class_template_specialization_decl =
+ dyn_cast<ClassTemplateSpecializationDecl>(RecordDecl);
+ if (!class_template_specialization_decl) {
+ return false;
+ }
+
+ const TemplateArgumentList &template_args =
+ class_template_specialization_decl->getTemplateArgs();
+
+ if (template_args.size() == 0) {
+ return false;
+ }
+
+ const TemplateArgument &first_arg = template_args[0];
+
+ if (first_arg.getKind() != TemplateArgument::Type) {
+ return false;
+ }
+
+ QualType referred_type = first_arg.getAsType();
+
+ if (referred_type->isArrayType()) {
+ return true;
+ }
+
+ return false;
+}
+
+class UniquePtrArrayAccessGadget : public WarningGadget {
+ static constexpr const char *const AccessorTag = "unique_ptr_array_access";
+ const CXXOperatorCallExpr *TheAccessorExpr;
+
+public:
+ UniquePtrArrayAccessGadget(const MatchResult &Result)
+ : WarningGadget(Kind::UniquePtrArrayAccess),
+ TheAccessorExpr(Result.getNodeAs<CXXOperatorCallExpr>(AccessorTag)) {
+ assert(TheAccessorExpr &&
+ "UniquePtrArrayAccessGadget requires a matched CXXOperatorCallExpr");
+ }
+
+ static bool classof(const Gadget *G) {
+ return G->getKind() == Kind::UniquePtrArrayAccess;
+ }
+
+ static bool matches(const Stmt *S, const ASTContext &Ctx,
+ MatchResult &Result) {
+
+ const CXXOperatorCallExpr *OpCall = dyn_cast<CXXOperatorCallExpr>(S);
+ if (!OpCall || OpCall->getOperator() != OO_Subscript) {
+ return false;
+ }
+
+ const Expr *Callee = OpCall->getCallee()->IgnoreParenImpCasts();
+ if (!Callee) {
+ return false;
+ }
+
+ const CXXMethodDecl *Method =
+ dyn_cast_or_null<CXXMethodDecl>(OpCall->getDirectCallee());
+ if (!Method) {
+ return false;
+ }
+
+ if (Method->getNameAsString() != "operator[]") {
+ return false;
+ }
+
+ const CXXRecordDecl *RecordDecl = Method->getParent();
+ if (!isUniquePtrArray(RecordDecl)) {
+ return false;
+ }
+
+ Result.addNode(AccessorTag, DynTypedNode::create(*OpCall));
+ return true;
+ }
+ void handleUnsafeOperation(UnsafeBufferUsageHandler &Handler,
+ bool IsRelatedToDecl,
+ ASTContext &Ctx) const override {
+ Handler.handleUnsafeUniquePtrArrayAccess(
+ DynTypedNode::create(*TheAccessorExpr), IsRelatedToDecl, Ctx);
+ }
+
+ SourceLocation getSourceLoc() const override {
+ if (TheAccessorExpr) {
+ return TheAccessorExpr->getOperatorLoc();
+ }
+ return SourceLocation();
+ }
+
+ DeclUseList getClaimedVarUseSites() const override { return {}; }
+ SmallVector<const Expr *, 1> getUnsafePtrs() const override { return {}; }
+};
+
using FixableGadgetList = std::vector<std::unique_ptr<FixableGadget>>;
using WarningGadgetList = std::vector<std::unique_ptr<WarningGadget>>;
@@ -2647,6 +2747,10 @@ std::set<const Expr *> clang::findUnsafePointers(const FunctionDecl *FD) {
}
};
+ void handleUnsafeUniquePtrArrayAccess(const DynTypedNode &Node,
+ bool IsRelatedToDecl,
+ ASTContext &Ctx) override {}
+
FixableGadgetList FixableGadgets;
WarningGadgetList WarningGadgets;
DeclUseTracker Tracker;
>From 800d39379f3fca299c5e5ca8f0eee2c9ec9ad7b2 Mon Sep 17 00:00:00 2001
From: shreya-jain <jainshreya at google.com>
Date: Wed, 3 Sep 2025 00:56:33 -0700
Subject: [PATCH 6/8] Update AnalysisBasedWarnings.cpp
---
clang/lib/Sema/AnalysisBasedWarnings.cpp | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/clang/lib/Sema/AnalysisBasedWarnings.cpp b/clang/lib/Sema/AnalysisBasedWarnings.cpp
index 1b66d83df5171..5f51d38c6cfb9 100644
--- a/clang/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/clang/lib/Sema/AnalysisBasedWarnings.cpp
@@ -2606,6 +2606,19 @@ class UnsafeBufferUsageReporter : public UnsafeBufferUsageHandler {
#endif
}
+ void handleUnsafeUniquePtrArrayAccess(const DynTypedNode &Node,
+ bool IsRelatedToDecl,
+ ASTContext &Ctx) override {
+ SourceLocation Loc;
+ std::string Message;
+
+ Loc = Node.get<Stmt>()->getBeginLoc();
+ Message = "Direct operator[] access on std::unique_ptr<T[]> is unsafe "
+ "(no bounds check).";
+ S.Diag(Loc, diag::warn_unsafe_buffer_usage_unique_ptr_array_access)
+ << Message << Node.getSourceRange();
+ }
+
bool isSafeBufferOptOut(const SourceLocation &Loc) const override {
return S.PP.isSafeBufferOptOut(S.getSourceManager(), Loc);
}
>From 4c959720dfa0d5889e7f57e4333745902d43a7be Mon Sep 17 00:00:00 2001
From: shreya-jain <jainshreya at google.com>
Date: Wed, 3 Sep 2025 00:58:07 -0700
Subject: [PATCH 7/8] Update warn-unsafe-buffer-usage-debug-unclaimed.cpp
---
.../warn-unsafe-buffer-usage-debug-unclaimed.cpp | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/warn-unsafe-buffer-usage-debug-unclaimed.cpp b/clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/warn-unsafe-buffer-usage-debug-unclaimed.cpp
index ab3d925753d47..563f27a97739d 100644
--- a/clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/warn-unsafe-buffer-usage-debug-unclaimed.cpp
+++ b/clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/warn-unsafe-buffer-usage-debug-unclaimed.cpp
@@ -32,6 +32,21 @@ void test_unclaimed_use(int *p) { // expected-warning{{'p' is an unsafe pointer
p[5] = 5; // expected-note{{used in buffer access here}}
}
+namespace std {
+inline namespace __1 {
+template <class T> class unique_ptr {
+public:
+ T &operator[](long long i) const;
+};
+} // namespace __1
+} // namespace std
+
+void basic_unique_ptr() {
+ std::unique_ptr<int[]> p1;
+ p1[0]; // expected-warning{{direct access using operator[] on
+ // std::unique_ptr<T[]> is unsafe due to lack of bounds checking}}
+}
+
// CHECK: Root # 1
// CHECK: |- DeclRefExpr # 4
// CHECK: |-- UnaryOperator(++) # 1
>From 38a2d442253070c76719d06c8abc642d0452db61 Mon Sep 17 00:00:00 2001
From: Shreya Jain <jainshreya at google.com>
Date: Wed, 3 Sep 2025 23:01:48 +0000
Subject: [PATCH 8/8] fix compilation issues and test
---
clang/include/clang/Basic/DiagnosticSemaKinds.td | 2 +-
clang/lib/Analysis/UnsafeBufferUsage.cpp | 11 +++++------
.../warn-unsafe-buffer-usage-debug-unclaimed.cpp | 3 +--
3 files changed, 7 insertions(+), 9 deletions(-)
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 117ba3b79eacc..6bdebde1ec19e 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -13241,7 +13241,7 @@ def warn_unsafe_buffer_usage_in_container : Warning<
"the two-parameter std::span construction is unsafe as it can introduce mismatch between buffer size and the bound information">,
InGroup<UnsafeBufferUsageInContainer>, DefaultIgnore;
def warn_unsafe_buffer_usage_unique_ptr_array_access : Warning<"direct access using operator[] on std::unique_ptr<T[]> is unsafe due to lack of bounds checking">,
- InGroup<UnsafeBufferUsageInUniquePtrArray>, DefaultIgnore;
+ InGroup<UnsafeBufferUsageInUniquePtrArrayAccess>, DefaultIgnore;
#ifndef NDEBUG
// Not a user-facing diagnostic. Useful for debugging false negatives in
// -fsafe-buffer-usage-suggestions (i.e. lack of -Wunsafe-buffer-usage fixits).
diff --git a/clang/lib/Analysis/UnsafeBufferUsage.cpp b/clang/lib/Analysis/UnsafeBufferUsage.cpp
index 3dbf4e9a3535b..7a0a0ee7fb694 100644
--- a/clang/lib/Analysis/UnsafeBufferUsage.cpp
+++ b/clang/lib/Analysis/UnsafeBufferUsage.cpp
@@ -2732,10 +2732,13 @@ std::set<const Expr *> clang::findUnsafePointers(const FunctionDecl *FD) {
const VariableGroupsManager &, FixItList &&,
const Decl *,
const FixitStrategy &) override {}
- bool isSafeBufferOptOut(const SourceLocation &) const override {
+ void handleUnsafeUniquePtrArrayAccess(const DynTypedNode &Node,
+ bool IsRelatedToDecl,
+ ASTContext &Ctx) override {}
+ bool ignoreUnsafeBufferInContainer(const SourceLocation &) const override {
return false;
}
- bool ignoreUnsafeBufferInContainer(const SourceLocation &) const override {
+ bool isSafeBufferOptOut(const SourceLocation &) const override {
return false;
}
bool ignoreUnsafeBufferInLibcCall(const SourceLocation &) const override {
@@ -2747,10 +2750,6 @@ std::set<const Expr *> clang::findUnsafePointers(const FunctionDecl *FD) {
}
};
- void handleUnsafeUniquePtrArrayAccess(const DynTypedNode &Node,
- bool IsRelatedToDecl,
- ASTContext &Ctx) override {}
-
FixableGadgetList FixableGadgets;
WarningGadgetList WarningGadgets;
DeclUseTracker Tracker;
diff --git a/clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/warn-unsafe-buffer-usage-debug-unclaimed.cpp b/clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/warn-unsafe-buffer-usage-debug-unclaimed.cpp
index 563f27a97739d..e504d1f97ada3 100644
--- a/clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/warn-unsafe-buffer-usage-debug-unclaimed.cpp
+++ b/clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/warn-unsafe-buffer-usage-debug-unclaimed.cpp
@@ -43,8 +43,7 @@ template <class T> class unique_ptr {
void basic_unique_ptr() {
std::unique_ptr<int[]> p1;
- p1[0]; // expected-warning{{direct access using operator[] on
- // std::unique_ptr<T[]> is unsafe due to lack of bounds checking}}
+ p1[0]; // expected-warning{{direct access using operator[] on std::unique_ptr<T[]> is unsafe due to lack of bounds checking}}
}
// CHECK: Root # 1
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