llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-clang Author: None (yronglin) <details> <summary>Changes</summary> Implement P2748R5 "Disallow Binding a Returned Glvalue to a Temporary" https://wg21.link/P2748R5 --- Full diff: https://github.com/llvm/llvm-project/pull/89942.diff 5 Files Affected: - (modified) clang/docs/ReleaseNotes.rst (+3-1) - (modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (+2) - (modified) clang/lib/Sema/SemaInit.cpp (+11-2) - (modified) clang/test/CXX/drs/cwg650.cpp (+1-1) - (added) clang/test/CXX/stmt.stmt/stmt.return/p6.cpp (+18) ``````````diff diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 64526ed6d06f55..5e07000198d63a 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -129,7 +129,9 @@ C++2c Feature Support - Implemented `P2662R3 Pack Indexing <https://wg21.link/P2662R3>`_. -- Implemented `P2573R2: = delete("should have a reason"); <https://wg21.link/P2573R2>`_ +- Implemented `P2573R2: = delete("should have a reason"); <https://wg21.link/P2573R2>`_. + +- Implemented `P2748R5 Disallow Binding a Returned Glvalue to a Temporary <https://wg21.link/P2748R5>`_. Resolutions to C++ Defect Reports diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td index 6732a1a98452ad..7342215db9cc3d 100644 --- a/clang/include/clang/Basic/DiagnosticSemaKinds.td +++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td @@ -9950,6 +9950,8 @@ def warn_ret_stack_addr_ref : Warning< def warn_ret_local_temp_addr_ref : Warning< "returning %select{address of|reference to}0 local temporary object">, InGroup<ReturnStackAddress>; +def err_ret_local_temp_addr_ref : Error< + "returning %select{address of|reference to}0 local temporary object">; def warn_ret_addr_label : Warning< "returning address of label, which is local">, InGroup<ReturnStackAddress>; diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp index 793e16df178914..003c4c34810e1f 100644 --- a/clang/lib/Sema/SemaInit.cpp +++ b/clang/lib/Sema/SemaInit.cpp @@ -8340,8 +8340,17 @@ void Sema::checkInitializerLifetime(const InitializedEntity &Entity, << Entity.getType()->isReferenceType() << CLE->getInitializer() << 2 << DiagRange; } else { - Diag(DiagLoc, diag::warn_ret_local_temp_addr_ref) - << Entity.getType()->isReferenceType() << DiagRange; + // P2748R5: Disallow Binding a Returned Glvalue to a Temporary. + // [stmt.return]/p6: In a function whose return type is a reference, + // other than an invented function for std::is_convertible ([meta.rel]), + // a return statement that binds the returned reference to a temporary + // expression ([class.temporary]) is ill-formed. + if (getLangOpts().CPlusPlus26) + Diag(DiagLoc, diag::err_ret_local_temp_addr_ref) + << Entity.getType()->isReferenceType() << DiagRange; + else + Diag(DiagLoc, diag::warn_ret_local_temp_addr_ref) + << Entity.getType()->isReferenceType() << DiagRange; } break; } diff --git a/clang/test/CXX/drs/cwg650.cpp b/clang/test/CXX/drs/cwg650.cpp index dcb844095b0598..01a841b04b42d3 100644 --- a/clang/test/CXX/drs/cwg650.cpp +++ b/clang/test/CXX/drs/cwg650.cpp @@ -4,7 +4,7 @@ // RUN: %clang_cc1 -std=c++17 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK // RUN: %clang_cc1 -std=c++20 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK // RUN: %clang_cc1 -std=c++23 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK -// RUN: %clang_cc1 -std=c++2c %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK +// Since C++26, P2748R5 "Disallow Binding a Returned Glvalue to a Temporary". Therefore we do not test this issue after C++26. #if __cplusplus == 199711L #define NOTHROW throw() diff --git a/clang/test/CXX/stmt.stmt/stmt.return/p6.cpp b/clang/test/CXX/stmt.stmt/stmt.return/p6.cpp new file mode 100644 index 00000000000000..682d3a8a075d4e --- /dev/null +++ b/clang/test/CXX/stmt.stmt/stmt.return/p6.cpp @@ -0,0 +1,18 @@ +// RUN: %clang_cc1 -std=c++26 -fsyntax-only -verify %s + +auto&& f1() { + return 42; // expected-error{{returning reference to local temporary object}} +} +const double& f2() { + static int x = 42; + return x; // expected-error{{returning reference to local temporary object}} +} +auto&& id(auto&& r) { + return static_cast<decltype(r)&&>(r); +} +auto&& f3() { + return id(42); // OK, but probably a bug +} + +static_assert(__is_convertible(int, const int &)); +static_assert(__is_nothrow_convertible(int, const int &)); `````````` </details> https://github.com/llvm/llvm-project/pull/89942 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
