https://github.com/usx95 updated
https://github.com/llvm/llvm-project/pull/111499
>From adaab9e5f549ae1625e8539334dfbc73a0559d8c Mon Sep 17 00:00:00 2001
From: Utkarsh Saxena <u...@google.com>
Date: Sun, 10 Nov 2024 07:42:49 +0000
Subject: [PATCH] Introduce [[clang::lifetime_capture_by]]
---
clang/docs/ReleaseNotes.rst | 3 +
clang/include/clang/Basic/Attr.td | 34 ++++++
clang/include/clang/Basic/AttrDocs.td | 62 +++++++++++
.../clang/Basic/DiagnosticSemaKinds.td | 12 ++
clang/include/clang/Sema/Sema.h | 4 +
clang/lib/AST/TypePrinter.cpp | 8 ++
clang/lib/Sema/SemaDecl.cpp | 1 +
clang/lib/Sema/SemaDeclAttr.cpp | 103 ++++++++++++++++++
.../test/SemaCXX/attr-lifetime-capture-by.cpp | 40 +++++++
9 files changed, 267 insertions(+)
create mode 100644 clang/test/SemaCXX/attr-lifetime-capture-by.cpp
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index c3424e0e6f34c9..93cce21156634d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -449,6 +449,9 @@ Attribute Changes in Clang
- Fix a bug where clang doesn't automatically apply the ``[[gsl::Owner]]`` or
``[[gsl::Pointer]]`` to STL explicit template specialization decls.
(#GH109442)
+- Clang now supports ``[[clang::lifetime_capture_by(X)]]``. Similar to
lifetimebound, this can be
+ used to specify when a reference to a function parameter is captured by
another capturing entity ``X``.
+
Improvements to Clang's diagnostics
-----------------------------------
diff --git a/clang/include/clang/Basic/Attr.td
b/clang/include/clang/Basic/Attr.td
index a631e81d40aa68..6884ec1b2a0663 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -1889,6 +1889,40 @@ def LifetimeBound : DeclOrTypeAttr {
let SimpleHandler = 1;
}
+def LifetimeCaptureBy : DeclOrTypeAttr {
+ let Spellings = [Clang<"lifetime_capture_by", 0>];
+ let Subjects = SubjectList<[ParmVar, ImplicitObjectParameter], ErrorDiag>;
+ let Args = [VariadicParamOrParamIdxArgument<"Params">];
+ let Documentation = [LifetimeCaptureByDocs];
+ let LangOpts = [CPlusPlus];
+ let AdditionalMembers = [{
+private:
+ SmallVector<IdentifierInfo*, 1> ArgIdents;
+ SmallVector<SourceLocation, 1> ArgLocs;
+
+public:
+ static constexpr int THIS = 0;
+ static constexpr int INVALID = -1;
+ static constexpr int UNKNOWN = -2;
+ static constexpr int GLOBAL = -3;
+
+ void setArgs(SmallVector<IdentifierInfo*, 1>&& Idents,
+ SmallVector<SourceLocation, 1>&& Locs) {
+ assert(Idents.size() == Locs.size());
+ assert(Idents.size() == params_Size);
+ ArgIdents = std::move(Idents);
+ ArgLocs = std::move(Locs);
+ }
+
+ ArrayRef<IdentifierInfo*> getArgIdents() const { return ArgIdents; }
+ ArrayRef<SourceLocation> getArgLocs() const { return ArgLocs; }
+ void setParamIdx(size_t Idx, int Val) {
+ assert(Idx < params_Size);
+ params_[Idx] = Val;
+ }
+}];
+}
+
def TrivialABI : InheritableAttr {
// This attribute does not have a C [[]] spelling because it requires the
// CPlusPlus language option.
diff --git a/clang/include/clang/Basic/AttrDocs.td
b/clang/include/clang/Basic/AttrDocs.td
index b64dbef6332e6a..9ba6b4e4993de3 100644
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/clang/include/clang/Basic/AttrDocs.td
@@ -3967,6 +3967,68 @@ Attribute ``trivial_abi`` has no effect in the following
cases:
}];
}
+
+def LifetimeCaptureByDocs : Documentation {
+ let Category = DocCatFunction;
+ let Content = [{
+ The ``lifetime_capture_by(X)`` attribute on a function parameter or
implicit object
+parameter indicates that references to arguments passed to such parameters may
be
+captured by the capturing entity ``X``.
+
+The capturing entity ``X`` can be one of the following:
+- Another (named) function parameter.
+
+ .. code-block:: c++
+
+ void addToSet(std::string_view a [[clang::lifetime_capture_by(s)]],
std::set<std::string_view>& s) {
+ s.insert(a);
+ }
+
+- ``this`` (in case of member functions).
+
+ .. code-block:: c++
+
+ class S {
+ void addToSet(std::string_view a [[clang::lifetime_capture_by(this)]]) {
+ s.insert(a);
+ }
+ std::set<std::string_view> s;
+ };
+
+- 'global', 'unknown' (without quotes).
+
+ .. code-block:: c++
+
+ std::set<std::string_view> s;
+ void addToSet(std::string_view a [[clang::lifetime_capture_by(global)]]) {
+ s.insert(a);
+ }
+ void addSomewhere(std::string_view a
[[clang::lifetime_capture_by(unknown)]]);
+
+The attribute can be applied to the implicit ``this`` parameter of a member
+function by writing the attribute after the function type:
+
+.. code-block:: c++
+
+ struct S {
+ const char *data(std::set<S*>& s) [[clang::lifetime_capture_by(s)]] {
+ s.insert(this);
+ }
+ };
+
+The attribute supports specifying more than one capturing entities:
+
+.. code-block:: c++
+ void addToSets(std::string_view a [[clang::lifetime_capture_by(s1, s2)]],
+ std::set<std::string_view>& s1,
+ std::set<std::string_view>& s2) {
+ s1.insert(a);
+ s2.insert(a);
+ }
+
+ .. _`lifetimebound`:
https://clang.llvm.org/docs/AttributeReference.html#lifetimebound
+ }];
+}
def MSInheritanceDocs : Documentation {
let Category = DocCatDecl;
let Heading = "__single_inheritance, __multiple_inheritance,
__virtual_inheritance";
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index a5d97d7e545ffd..b42dfce130f4c3 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3383,6 +3383,18 @@ def err_callback_callee_is_variadic : Error<
"'callback' attribute callee may not be variadic">;
def err_callback_implicit_this_not_available : Error<
"'callback' argument at position %0 references unavailable implicit 'this'">;
+
+def err_capture_by_attribute_multiple : Error<
+ "multiple 'lifetime_capture' attributes specified">;
+def err_capture_by_attribute_no_entity : Error<
+ "'lifetime_capture_by' attribute specifies no capturing entity">;
+def err_capture_by_implicit_this_not_available : Error<
+ "'lifetime_capture_by' argument references unavailable implicit 'this'">;
+def err_capture_by_attribute_argument_unknown : Error<
+ "'lifetime_capture_by' attribute argument %0 is not a known function
parameter"
+ "; must be a function parameter of one of 'this', 'global' or 'unknown'">;
+def err_capture_by_references_itself : Error<"'lifetime_capture_by' argument
references itself">;
+
def err_init_method_bad_return_type : Error<
"init methods must return an object pointer type, not %0">;
def err_attribute_invalid_size : Error<
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index fad446a05e782f..fb8cc994d3294e 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -1760,6 +1760,10 @@ class Sema final : public SemaBase {
/// Add [[gsl::Pointer]] attributes for std:: types.
void inferGslPointerAttribute(TypedefNameDecl *TD);
+ LifetimeCaptureByAttr *ParseLifetimeCaptureByAttr(const ParsedAttr &AL,
+ StringRef ParamName);
+ void LazyProcessLifetimeCaptureByParams(FunctionDecl *FD);
+
/// Add _Nullable attributes for std:: types.
void inferNullableClassAttribute(CXXRecordDecl *CRD);
diff --git a/clang/lib/AST/TypePrinter.cpp b/clang/lib/AST/TypePrinter.cpp
index 6d8db5cf4ffd22..802b2b0fb07e6b 100644
--- a/clang/lib/AST/TypePrinter.cpp
+++ b/clang/lib/AST/TypePrinter.cpp
@@ -25,6 +25,7 @@
#include "clang/AST/TextNodeDumper.h"
#include "clang/AST/Type.h"
#include "clang/Basic/AddressSpaces.h"
+#include "clang/Basic/AttrKinds.h"
#include "clang/Basic/ExceptionSpecificationType.h"
#include "clang/Basic/IdentifierTable.h"
#include "clang/Basic/LLVM.h"
@@ -1909,6 +1910,12 @@ void TypePrinter::printAttributedAfter(const
AttributedType *T,
OS << " [[clang::lifetimebound]]";
return;
}
+ if (T->getAttrKind() == attr::LifetimeCaptureBy) {
+ // FIXME: Print the attribute arguments once we have a way to retrieve
these
+ // here.
+ OS << " [[clang::lifetime_capture_by(...)";
+ return;
+ }
// The printing of the address_space attribute is handled by the qualifier
// since it is still stored in the qualifier. Return early to prevent
printing
@@ -1976,6 +1983,7 @@ void TypePrinter::printAttributedAfter(const
AttributedType *T,
case attr::SizedBy:
case attr::SizedByOrNull:
case attr::LifetimeBound:
+ case attr::LifetimeCaptureBy:
case attr::TypeNonNull:
case attr::TypeNullable:
case attr::TypeNullableResult:
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 61c29e320d5c73..a3bc8e4191c819 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -16687,6 +16687,7 @@ void Sema::AddKnownFunctionAttributes(FunctionDecl *FD)
{
}
}
+ LazyProcessLifetimeCaptureByParams(FD);
inferLifetimeBoundAttribute(FD);
AddKnownFunctionAttributesForReplaceableGlobalAllocationFunction(FD);
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index d05d326178e1b8..38e9421a456311 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -14,6 +14,7 @@
#include "clang/AST/ASTContext.h"
#include "clang/AST/ASTMutationListener.h"
#include "clang/AST/CXXInheritance.h"
+#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclTemplate.h"
@@ -3867,6 +3868,105 @@ static void handleCallbackAttr(Sema &S, Decl *D, const
ParsedAttr &AL) {
S.Context, AL, EncodingIndices.data(), EncodingIndices.size()));
}
+LifetimeCaptureByAttr *Sema::ParseLifetimeCaptureByAttr(const ParsedAttr &AL,
+ StringRef ParamName) {
+ // Atleast one capture by is required.
+ if (AL.getNumArgs() == 0) {
+ Diag(AL.getLoc(), diag::err_capture_by_attribute_no_entity)
+ << AL.getRange();
+ return nullptr;
+ }
+ SmallVector<IdentifierInfo *, 1> ParamIdents;
+ SmallVector<SourceLocation, 1> ParamLocs;
+ for (unsigned I = 0; I < AL.getNumArgs(); ++I) {
+ if (AL.isArgExpr(I)) {
+ Expr *E = AL.getArgAsExpr(I);
+ Diag(E->getExprLoc(), diag::err_capture_by_attribute_argument_unknown)
+ << E << E->getExprLoc();
+ continue;
+ }
+ assert(AL.isArgIdent(I));
+ IdentifierLoc *IdLoc = AL.getArgAsIdent(I);
+ if (IdLoc->Ident->getName() == ParamName) {
+ Diag(IdLoc->Loc, diag::err_capture_by_references_itself) << IdLoc->Loc;
+ continue;
+ }
+ ParamIdents.push_back(IdLoc->Ident);
+ ParamLocs.push_back(IdLoc->Loc);
+ }
+ SmallVector<int, 1> FakeParamIndices(ParamIdents.size(),
+ LifetimeCaptureByAttr::INVALID);
+ LifetimeCaptureByAttr *CapturedBy = ::new (Context) LifetimeCaptureByAttr(
+ Context, AL, FakeParamIndices.data(), FakeParamIndices.size());
+ CapturedBy->setArgs(std::move(ParamIdents), std::move(ParamLocs));
+ return CapturedBy;
+}
+
+static void HandleLifetimeCaptureByAttr(Sema &S, Decl *D,
+ const ParsedAttr &AL) {
+ // Do not allow multiple attributes.
+ if (D->hasAttr<LifetimeCaptureByAttr>()) {
+ S.Diag(AL.getLoc(), diag::err_capture_by_attribute_multiple)
+ << AL.getRange();
+ return;
+ }
+ auto *PVD = dyn_cast<ParmVarDecl>(D);
+ assert(PVD);
+ auto *CaptureByAttr = S.ParseLifetimeCaptureByAttr(AL, PVD->getName());
+ if (CaptureByAttr)
+ D->addAttr(CaptureByAttr);
+}
+
+void Sema::LazyProcessLifetimeCaptureByParams(FunctionDecl *FD) {
+ bool HasImplicitThisParam = isInstanceMethod(FD);
+
+ llvm::StringMap<int> NameIdxMapping;
+ NameIdxMapping["global"] = LifetimeCaptureByAttr::GLOBAL;
+ NameIdxMapping["unknown"] = LifetimeCaptureByAttr::UNKNOWN;
+ int Idx = 0;
+ if (HasImplicitThisParam) {
+ NameIdxMapping["this"] = 0;
+ Idx++;
+ }
+ for (const ParmVarDecl *PVD : FD->parameters())
+ NameIdxMapping[PVD->getName()] = Idx++;
+ auto HandleCaptureBy = [&](LifetimeCaptureByAttr *CapturedBy) {
+ if (!CapturedBy)
+ return;
+ const auto &Entities = CapturedBy->getArgIdents();
+ for (size_t I = 0; I < Entities.size(); ++I) {
+ StringRef Name = Entities[I]->getName();
+ auto It = NameIdxMapping.find(Name);
+ if (It == NameIdxMapping.end()) {
+ auto Loc = CapturedBy->getArgLocs()[I];
+ if (!HasImplicitThisParam && Name == "this")
+ Diag(Loc, diag::err_capture_by_implicit_this_not_available) << Loc;
+ else
+ Diag(Loc, diag::err_capture_by_attribute_argument_unknown)
+ << Entities[I] << Loc;
+ continue;
+ }
+ CapturedBy->setParamIdx(I, It->second);
+ }
+ };
+ for (ParmVarDecl *PVD : FD->parameters())
+ HandleCaptureBy(PVD->getAttr<LifetimeCaptureByAttr>());
+ if (!HasImplicitThisParam)
+ return;
+ TypeSourceInfo *TSI = FD->getTypeSourceInfo();
+ if (!TSI)
+ return;
+ AttributedTypeLoc ATL;
+ for (TypeLoc TL = TSI->getTypeLoc();
+ (ATL = TL.getAsAdjusted<AttributedTypeLoc>());
+ TL = ATL.getModifiedLoc()) {
+ auto *A = ATL.getAttrAs<LifetimeCaptureByAttr>();
+ if (!A)
+ continue;
+ HandleCaptureBy(const_cast<LifetimeCaptureByAttr *>(A));
+ }
+}
+
static bool isFunctionLike(const Type &T) {
// Check for explicit function types.
// 'called_once' is only supported in Objective-C and it has
@@ -6644,6 +6744,9 @@ ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
const ParsedAttr &AL,
case ParsedAttr::AT_Callback:
handleCallbackAttr(S, D, AL);
break;
+ case ParsedAttr::AT_LifetimeCaptureBy:
+ HandleLifetimeCaptureByAttr(S, D, AL);
+ break;
case ParsedAttr::AT_CalledOnce:
handleCalledOnceAttr(S, D, AL);
break;
diff --git a/clang/test/SemaCXX/attr-lifetime-capture-by.cpp
b/clang/test/SemaCXX/attr-lifetime-capture-by.cpp
new file mode 100644
index 00000000000000..192ec9bec640a5
--- /dev/null
+++ b/clang/test/SemaCXX/attr-lifetime-capture-by.cpp
@@ -0,0 +1,40 @@
+// RUN: %clang_cc1 -std=c++23 -verify %s
+
+struct S {
+ const int *x;
+ void captureInt(const int&x [[clang::lifetime_capture_by(this)]]) { this->x
= &x; }
+};
+
+///////////////////////////
+// Test for valid usages.
+///////////////////////////
+[[clang::lifetime_capture_by(unknown)]] // expected-error
{{'lifetime_capture_by' attribute only applies to parameters and implicit
object parameters}}
+void nonMember(
+ const int &x1 [[clang::lifetime_capture_by(s, t)]],
+ S &s,
+ S &t,
+ const int &x2 [[clang::lifetime_capture_by(12345 + 12)]], //
expected-error {{'lifetime_capture_by' attribute argument 12345 + 12 is not a
known function parameter. Must be a function parameter of one of 'this',
'global' or 'unknown'}}
+ const int &x3 [[clang::lifetime_capture_by(abcdefgh)]], //
expected-error {{'lifetime_capture_by' attribute argument 'abcdefgh' is not a
known function parameter. Must be a function parameter of one of 'this',
'global' or 'unknown'}}
+ const int &x4 [[clang::lifetime_capture_by("abcdefgh")]], //
expected-error {{'lifetime_capture_by' attribute argument "abcdefgh" is not a
known function parameter. Must be a function parameter of one of 'this',
'global' or 'unknown'}}
+ const int &x5 [[clang::lifetime_capture_by(this)]], // expected-error
{{'lifetime_capture_by' argument references unavailable implicit 'this'}}
+ const int &x6 [[clang::lifetime_capture_by()]], // expected-error
{{'lifetime_capture_by' attribute specifies no capturing entity}}
+ const int& x7 [[clang::lifetime_capture_by(u,
+ x7)]], // expected-error
{{'lifetime_capture_by' argument references itself}}
+ const S& u
+ )
+{
+ s.captureInt(x1);
+}
+
+struct T {
+ void member(
+ const int &x [[clang::lifetime_capture_by(s)]],
+ S &s,
+ S &t,
+ const int &y [[clang::lifetime_capture_by(s)]],
+ const int &z [[clang::lifetime_capture_by(this, x, y)]],
+ const int &u [[clang::lifetime_capture_by(global, x, s)]])
+ {
+ s.captureInt(x);
+ }
+};
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