[clang] Reland: [clang] Diagnose dangling issues for the "Container<GSLPointer>" case. #107213 (PR #108344)
Haojian Wu via cfe-commits
cfe-commits at lists.llvm.org
Thu Sep 12 02:48:30 PDT 2024
https://github.com/hokein updated https://github.com/llvm/llvm-project/pull/108344
>From d1096323a87897b917ede2c29afd42c9f2674cd7 Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein.wu at gmail.com>
Date: Thu, 12 Sep 2024 09:27:03 +0200
Subject: [PATCH 1/2] Reapply "[clang] Diagnose dangling issues for the
"Container<GSLPointer>" case. (#107213)"
This reverts commit 0683c4e839524c37fe4ddfa1bce1e31ba556041b.
---
clang/docs/ReleaseNotes.rst | 2 +
clang/include/clang/Basic/AttrDocs.td | 14 ++++
clang/lib/Sema/CheckExprLifetime.cpp | 42 +++++++---
.../Sema/warn-lifetime-analysis-nocfg.cpp | 77 +++++++++++++++++++
4 files changed, 126 insertions(+), 9 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 22749e96a7e3d3..9860b25f2e7fa6 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -301,6 +301,8 @@ Improvements to Clang's diagnostics
- Clang now warns for u8 character literals used in C23 with ``-Wpre-c23-compat`` instead of ``-Wpre-c++17-compat``.
+- Clang now diagnoses cases where a dangling ``GSLOwner<GSLPointer>`` object is constructed, e.g. ``std::vector<string_view> v = {std::string()};`` (#GH100526).
+
Improvements to Clang's time-trace
----------------------------------
diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
index 546e5100b79dd9..9f72456d2da678 100644
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/clang/include/clang/Basic/AttrDocs.td
@@ -6690,6 +6690,20 @@ When the Owner's lifetime ends, it will consider the Pointer to be dangling.
P.getInt(); // P is dangling
}
+If a template class is annotated with ``[[gsl::Owner]]``, and the first
+instantiated template argument is a pointer type (raw pointer, or ``[[gsl::Pointer]]``),
+the analysis will consider the instantiated class as a container of the pointer.
+When constructing such an object from a GSL owner object, the analysis will
+assume that the container holds a pointer to the owner object. Consequently,
+when the owner object is destroyed, the pointer will be considered dangling.
+
+.. code-block:: c++
+
+ int f() {
+ std::vector<std::string_view> v = {std::string()}; // v holds a dangling pointer.
+ std::optional<std::string_view> o = std::string(); // o holds a dangling pointer.
+ }
+
}];
}
diff --git a/clang/lib/Sema/CheckExprLifetime.cpp b/clang/lib/Sema/CheckExprLifetime.cpp
index f62e18543851c1..77c73f47658fe1 100644
--- a/clang/lib/Sema/CheckExprLifetime.cpp
+++ b/clang/lib/Sema/CheckExprLifetime.cpp
@@ -267,6 +267,26 @@ static bool isInStlNamespace(const Decl *D) {
return DC->isStdNamespace();
}
+// Returns true if the given Record decl is a form of `GSLOwner<Pointer>`
+// type, e.g. std::vector<string_view>, std::optional<string_view>.
+static bool isContainerOfPointer(const RecordDecl *Container) {
+ if (const auto *CTSD =
+ dyn_cast_if_present<ClassTemplateSpecializationDecl>(Container)) {
+ if (!CTSD->hasAttr<OwnerAttr>()) // Container must be a GSL owner type.
+ return false;
+ const auto &TAs = CTSD->getTemplateArgs();
+ return TAs.size() > 0 && TAs[0].getKind() == TemplateArgument::Type &&
+ (isRecordWithAttr<PointerAttr>(TAs[0].getAsType()) ||
+ TAs[0].getAsType()->isPointerType());
+ }
+ return false;
+}
+
+static bool isGSLOwner(QualType T) {
+ return isRecordWithAttr<OwnerAttr>(T) &&
+ !isContainerOfPointer(T->getAsRecordDecl());
+}
+
static bool shouldTrackImplicitObjectArg(const CXXMethodDecl *Callee) {
if (auto *Conv = dyn_cast_or_null<CXXConversionDecl>(Callee))
if (isRecordWithAttr<PointerAttr>(Conv->getConversionType()))
@@ -275,7 +295,7 @@ static bool shouldTrackImplicitObjectArg(const CXXMethodDecl *Callee) {
return false;
if (!isRecordWithAttr<PointerAttr>(
Callee->getFunctionObjectParameterType()) &&
- !isRecordWithAttr<OwnerAttr>(Callee->getFunctionObjectParameterType()))
+ !isGSLOwner(Callee->getFunctionObjectParameterType()))
return false;
if (Callee->getReturnType()->isPointerType() ||
isRecordWithAttr<PointerAttr>(Callee->getReturnType())) {
@@ -413,7 +433,7 @@ static void visitFunctionCallArguments(IndirectLocalPath &Path, Expr *Call,
// Once we initialized a value with a non gsl-owner reference, it can no
// longer dangle.
if (ReturnType->isReferenceType() &&
- !isRecordWithAttr<OwnerAttr>(ReturnType->getPointeeType())) {
+ !isGSLOwner(ReturnType->getPointeeType())) {
for (const IndirectLocalPathEntry &PE : llvm::reverse(Path)) {
if (PE.Kind == IndirectLocalPathEntry::GslReferenceInit ||
PE.Kind == IndirectLocalPathEntry::LifetimeBoundCall)
@@ -468,12 +488,17 @@ static void visitFunctionCallArguments(IndirectLocalPath &Path, Expr *Call,
if (CheckCoroCall || Callee->getParamDecl(I)->hasAttr<LifetimeBoundAttr>())
VisitLifetimeBoundArg(Callee->getParamDecl(I), Args[I]);
else if (EnableGSLAnalysis && I == 0) {
+ // Perform GSL analysis for the first argument
if (shouldTrackFirstArgument(Callee)) {
VisitGSLPointerArg(Callee, Args[0]);
- } else if (auto *CCE = dyn_cast<CXXConstructExpr>(Call);
- CCE &&
- CCE->getConstructor()->getParent()->hasAttr<PointerAttr>()) {
- VisitGSLPointerArg(CCE->getConstructor(), Args[0]);
+ } else if (auto *Ctor = dyn_cast<CXXConstructExpr>(Call)) {
+ const auto *ClassD = Ctor->getConstructor()->getParent();
+ // Two cases:
+ // a GSL pointer, e.g. std::string_view
+ // a container of GSL pointer, e.g. std::vector<string_view>
+ if (ClassD->hasAttr<PointerAttr>() ||
+ (isContainerOfPointer(ClassD) && Callee->getNumParams() == 1))
+ VisitGSLPointerArg(Ctor->getConstructor(), Args[0]);
}
}
}
@@ -985,13 +1010,12 @@ static void checkExprLifetimeImpl(Sema &SemaRef,
// int &p = *localUniquePtr;
// someContainer.add(std::move(localUniquePtr));
// return p;
- IsLocalGslOwner = isRecordWithAttr<OwnerAttr>(L->getType());
+ IsLocalGslOwner = isGSLOwner(L->getType());
if (pathContainsInit(Path) || !IsLocalGslOwner)
return false;
} else {
IsGslPtrValueFromGslTempOwner =
- MTE && !MTE->getExtendingDecl() &&
- isRecordWithAttr<OwnerAttr>(MTE->getType());
+ MTE && !MTE->getExtendingDecl() && isGSLOwner(MTE->getType());
// Skipping a chain of initializing gsl::Pointer annotated objects.
// We are looking only for the final source to find out if it was
// a local or temporary owner or the address of a local variable/param.
diff --git a/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp b/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
index 59357d0730a7d9..234e06f069074b 100644
--- a/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
+++ b/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
@@ -158,17 +158,30 @@ auto begin(C &c) -> decltype(c.begin());
template<typename T, int N>
T *begin(T (&array)[N]);
+using size_t = decltype(sizeof(0));
+
+template<typename T>
+struct initializer_list {
+ const T* ptr; size_t sz;
+};
template <typename T>
struct vector {
typedef __gnu_cxx::basic_iterator<T> iterator;
iterator begin();
iterator end();
const T *data() const;
+ vector();
+ vector(initializer_list<T> __l);
+
+ template<typename InputIterator>
+ vector(InputIterator first, InputIterator __last);
+
T &at(int n);
};
template<typename T>
struct basic_string_view {
+ basic_string_view();
basic_string_view(const T *);
const T *begin() const;
};
@@ -203,11 +216,21 @@ template<typename T>
struct optional {
optional();
optional(const T&);
+
+ template<typename U = T>
+ optional(U&& t);
+
+ template<typename U>
+ optional(optional<U>&& __t);
+
T &operator*() &;
T &&operator*() &&;
T &value() &;
T &&value() &&;
};
+template<typename T>
+optional<__decay(T)> make_optional(T&&);
+
template<typename T>
struct stack {
@@ -553,3 +576,57 @@ void test() {
std::string_view svjkk1 = ReturnStringView(StrCat("bar", "x")); // expected-warning {{object backing the pointer will be destroyed at the end of the full-expression}}
}
} // namespace GH100549
+
+namespace GH100526 {
+void test() {
+ std::vector<std::string_view> v1({std::string()}); // expected-warning {{object backing the pointer will be destroyed at the end}}
+ std::vector<std::string_view> v2({
+ std::string(), // expected-warning {{object backing the pointer will be destroyed at the end}}
+ std::string_view()
+ });
+ std::vector<std::string_view> v3({
+ std::string_view(),
+ std::string() // expected-warning {{object backing the pointer will be destroyed at the end}}
+ });
+
+ std::optional<std::string_view> o1 = std::string(); // expected-warning {{object backing the pointer}}
+
+ std::string s;
+ // This is a tricky use-after-free case, what it does:
+ // 1. make_optional creates a temporary "optional<string>"" object
+ // 2. the temporary object owns the underlying string which is copied from s.
+ // 3. the t3 object holds the view to the underlying string of the temporary object.
+ std::optional<std::string_view> o2 = std::make_optional(s); // expected-warning {{object backing the pointer}}
+ std::optional<std::string_view> o3 = std::optional<std::string>(s); // expected-warning {{object backing the pointer}}
+ std::optional<std::string_view> o4 = std::optional<std::string_view>(s);
+
+ // FIXME: should work for assignment cases
+ v1 = {std::string()};
+ o1 = std::string();
+
+ // no warning on copying pointers.
+ std::vector<std::string_view> n1 = {std::string_view()};
+ std::optional<std::string_view> n2 = {std::string_view()};
+ std::optional<std::string_view> n3 = std::string_view();
+ std::optional<std::string_view> n4 = std::make_optional(std::string_view());
+ const char* b = "";
+ std::optional<std::string_view> n5 = std::make_optional(b);
+ std::optional<std::string_view> n6 = std::make_optional("test");
+}
+
+std::vector<std::string_view> test2(int i) {
+ std::vector<std::string_view> t;
+ if (i)
+ return t; // this is fine, no dangling
+ return std::vector<std::string_view>(t.begin(), t.end());
+}
+
+std::optional<std::string_view> test3(int i) {
+ std::string s;
+ std::string_view sv;
+ if (i)
+ return s; // expected-warning {{address of stack memory associated}}
+ return sv; // fine
+}
+
+} // namespace GH100526
>From 69d669a923655bf457ed8ca0520d94ba7e9d0258 Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein.wu at gmail.com>
Date: Thu, 12 Sep 2024 10:18:46 +0200
Subject: [PATCH 2/2] Fix the false positive for make_optional(nullptr);
We should also consider isNullPtrType as the pointer type.
---
clang/lib/Sema/CheckExprLifetime.cpp | 3 ++-
clang/test/Sema/warn-lifetime-analysis-nocfg.cpp | 4 ++++
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/clang/lib/Sema/CheckExprLifetime.cpp b/clang/lib/Sema/CheckExprLifetime.cpp
index 77c73f47658fe1..5525dbcb688bff 100644
--- a/clang/lib/Sema/CheckExprLifetime.cpp
+++ b/clang/lib/Sema/CheckExprLifetime.cpp
@@ -277,7 +277,8 @@ static bool isContainerOfPointer(const RecordDecl *Container) {
const auto &TAs = CTSD->getTemplateArgs();
return TAs.size() > 0 && TAs[0].getKind() == TemplateArgument::Type &&
(isRecordWithAttr<PointerAttr>(TAs[0].getAsType()) ||
- TAs[0].getAsType()->isPointerType());
+ TAs[0].getAsType()->isPointerType() ||
+ TAs[0].getAsType()->isNullPtrType());
}
return false;
}
diff --git a/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp b/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
index 234e06f069074b..81f75fd49860bc 100644
--- a/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
+++ b/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
@@ -629,4 +629,8 @@ std::optional<std::string_view> test3(int i) {
return sv; // fine
}
+std::optional<int*> test4(int a) {
+ return std::make_optional(nullptr); // fine
+}
+
} // namespace GH100526
More information about the cfe-commits
mailing list