rZhBoYao created this revision.
rZhBoYao added a reviewer: clang-language-wg.
Herald added a project: All.
rZhBoYao requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.
Implemented the C++23 paper P2718R0
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D139586
Files:
clang/docs/ReleaseNotes.rst
clang/include/clang/AST/Decl.h
clang/lib/Sema/SemaInit.cpp
clang/lib/Sema/SemaStmt.cpp
clang/test/CXX/stmt.stmt/stmt.iter/stmt.ranged/p1.cpp
clang/www/cxx_status.html
Index: clang/www/cxx_status.html
===================================================================
--- clang/www/cxx_status.html
+++ clang/www/cxx_status.html
@@ -1533,7 +1533,7 @@
<tr>
<td>Lifetime extension in range-based for loops</td>
<td><a href="https://wg21.link/P2718R0";>P2718R0</a></td>
- <td class="none" align="center">No</td>
+ <td class="unreleased" align="center">Clang 16</td>
</tr>
</table>
</details>
Index: clang/test/CXX/stmt.stmt/stmt.iter/stmt.ranged/p1.cpp
===================================================================
--- clang/test/CXX/stmt.stmt/stmt.iter/stmt.ranged/p1.cpp
+++ clang/test/CXX/stmt.stmt/stmt.iter/stmt.ranged/p1.cpp
@@ -1,6 +1,7 @@
-// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s
-// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify %s
-// RUN: %clang_cc1 -std=c++17 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -std=c++11 -verify=expected,pre-cxx2b %s
+// RUN: %clang_cc1 -std=c++14 -verify=expected,pre-cxx2b %s
+// RUN: %clang_cc1 -std=c++17 -verify=expected,pre-cxx2b %s
+// RUN: %clang_cc1 -std=c++2b -verify %s
struct pr12960 {
int begin;
@@ -342,3 +343,19 @@
for (auto x : f) {} // expected-error {{invalid range expression of type 'NF::F'; no viable 'end' function available}}
}
}
+
+namespace p2718r0 {
+struct T {
+ const int *begin() const;
+ const int *end() const;
+ T &r() [[clang::lifetimebound]];
+};
+
+const T &f1(const T &t [[clang::lifetimebound]]) { return t; }
+T g();
+
+void foo() {
+ for (auto e : f1(g())) {} // pre-cxx2b-warning {{temporary implicitly bound to local reference will be destroyed at the end of the full-expression}}
+ for (auto e : g().r()) {} // pre-cxx2b-warning {{temporary implicitly bound to local reference will be destroyed at the end of the full-expression}}
+}
+}
Index: clang/lib/Sema/SemaStmt.cpp
===================================================================
--- clang/lib/Sema/SemaStmt.cpp
+++ clang/lib/Sema/SemaStmt.cpp
@@ -2529,6 +2529,7 @@
VarDecl *RangeVar = BuildForRangeVarDecl(*this, RangeLoc,
Context.getAutoRRefDeductType(),
std::string("__range") + DepthStr);
+ RangeVar->setCXXRangeVar(true);
if (FinishForRangeVarDecl(*this, RangeVar, Range, RangeLoc,
diag::err_for_range_deduction_failure)) {
ActOnInitializerError(LoopVar);
Index: clang/lib/Sema/SemaInit.cpp
===================================================================
--- clang/lib/Sema/SemaInit.cpp
+++ clang/lib/Sema/SemaInit.cpp
@@ -6851,6 +6851,7 @@
/// the initializer are included.
struct IndirectLocalPathEntry {
enum EntryKind {
+ CXX2bForRangeInit,
DefaultInit,
AddressOf,
VarInit,
@@ -7188,6 +7189,23 @@
{IndirectLocalPathEntry::DefaultInit, DIE, DIE->getField()});
Init = DIE->getExpr();
}
+
+ if (auto *CE = dyn_cast<CallExpr>(Init);
+ CE && !Path.empty() &&
+ Path.front().Kind == IndirectLocalPathEntry::CXX2bForRangeInit) {
+ if (EnableLifetimeWarnings)
+ handleGslAnnotatedTypes(Path, Init, Visit);
+ visitLifetimeBoundArguments(Path, Init, Visit);
+ if (auto *ME = dyn_cast<MemberExpr>(CE->getCallee())) {
+ Init = ME->getBase();
+ } else {
+ for (auto *RSE : CE->getRawSubExprs())
+ if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(RSE))
+ if (Visit(Path, Local(MTE), RK))
+ visitLocalsRetainedByInitializer(Path, MTE->getSubExpr(), Visit,
+ true, EnableLifetimeWarnings);
+ }
+ }
} while (Init != Old);
if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(Init)) {
@@ -7356,6 +7374,24 @@
Init = CE->getSubExpr();
}
+
+ if (auto *CE = dyn_cast<CallExpr>(Init);
+ CE && !Path.empty() &&
+ Path.front().Kind == IndirectLocalPathEntry::CXX2bForRangeInit) {
+ if (EnableLifetimeWarnings)
+ handleGslAnnotatedTypes(Path, Init, Visit);
+ visitLifetimeBoundArguments(Path, Init, Visit);
+ if (auto *ME = dyn_cast<MemberExpr>(CE->getCallee())) {
+ visitLocalsRetainedByReferenceBinding(Path, ME->getBase(),
+ RK_ReferenceBinding, Visit,
+ EnableLifetimeWarnings);
+ } else {
+ for (auto *RSE : CE->getRawSubExprs())
+ if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(RSE))
+ visitLocalsRetainedByReferenceBinding(
+ Path, MTE, RK_ReferenceBinding, Visit, EnableLifetimeWarnings);
+ }
+ }
} while (Old != Init);
// C++17 [dcl.init.list]p6:
@@ -7558,7 +7594,8 @@
for (auto Elem : Path) {
if (Elem.Kind == IndirectLocalPathEntry::DefaultInit)
Kind = PathLifetimeKind::ShouldExtend;
- else if (Elem.Kind != IndirectLocalPathEntry::LambdaCaptureInit)
+ else if (Elem.Kind != IndirectLocalPathEntry::LambdaCaptureInit &&
+ Path.front().Kind != IndirectLocalPathEntry::CXX2bForRangeInit)
return PathLifetimeKind::NoExtend;
}
return Kind;
@@ -7575,6 +7612,7 @@
case IndirectLocalPathEntry::TemporaryCopy:
case IndirectLocalPathEntry::GslReferenceInit:
case IndirectLocalPathEntry::GslPointerInit:
+ case IndirectLocalPathEntry::CXX2bForRangeInit:
// These exist primarily to mark the path as not permitting or
// supporting lifetime extension.
break;
@@ -7824,6 +7862,7 @@
switch (Elem.Kind) {
case IndirectLocalPathEntry::AddressOf:
case IndirectLocalPathEntry::LValToRVal:
+ case IndirectLocalPathEntry::CXX2bForRangeInit:
// These exist primarily to mark the path as not permitting or
// supporting lifetime extension.
break;
@@ -7873,6 +7912,9 @@
bool EnableLifetimeWarnings = !getDiagnostics().isIgnored(
diag::warn_dangling_lifetime_pointer, SourceLocation());
llvm::SmallVector<IndirectLocalPathEntry, 8> Path;
+ if (auto *VD = dyn_cast_or_null<VarDecl>(Entity.getDecl());
+ getLangOpts().CPlusPlus2b && VD && VD->isCXXRangeVar())
+ Path.push_back({IndirectLocalPathEntry::CXX2bForRangeInit, nullptr});
if (Init->isGLValue())
visitLocalsRetainedByReferenceBinding(Path, Init, RK_ReferenceBinding,
TemporaryVisitor,
Index: clang/include/clang/AST/Decl.h
===================================================================
--- clang/include/clang/AST/Decl.h
+++ clang/include/clang/AST/Decl.h
@@ -1033,6 +1033,10 @@
/// (NRVO).
unsigned NRVOVariable : 1;
+ /// Whether this variable is __range{depth} initialized by the
+ /// for-range-initializer in a C++0x for-range statement.
+ unsigned CXXRangeVar : 1;
+
/// Whether this variable is the for-range-declaration in a C++0x
/// for-range statement.
unsigned CXXForRangeDecl : 1;
@@ -1457,6 +1461,16 @@
NonParmVarDeclBits.NRVOVariable = NRVO;
}
+ /// Determine whether this variable is __range{depth} initialized by the
+ /// for-range-initializer in a C++0x for-range statement.
+ bool isCXXRangeVar() const {
+ return isa<ParmVarDecl>(this) ? false : NonParmVarDeclBits.CXXRangeVar;
+ }
+ void setCXXRangeVar(bool RV) {
+ assert(!isa<ParmVarDecl>(this));
+ NonParmVarDeclBits.CXXRangeVar = RV;
+ }
+
/// Determine whether this variable is the for-range-declaration in
/// a C++0x for-range statement.
bool isCXXForRangeDecl() const {
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -688,6 +688,7 @@
- Implemented "char8_t Compatibility and Portability Fix" (`P2513R3 <https://wg21.link/P2513R3>`_).
This change was applied to C++20 as a Defect Report.
- Implemented "Permitting static constexpr variables in constexpr functions" (`P2647R1 <https://wg21.link/P2647R1>_`).
+- Implemented "Lifetime extension in range-based for loops" (`P2718R0 <https://wg21.link/P2718R0>_`).
CUDA/HIP Language Changes in Clang
----------------------------------
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