https://github.com/bolshakov-a updated https://github.com/llvm/llvm-project/pull/71077
>From e5ad8f5b00a297ef745e1b9341df32b80a7c6b77 Mon Sep 17 00:00:00 2001 From: Bolshakov <bolsh.and...@yandex.ru> Date: Thu, 2 Nov 2023 19:20:27 +0300 Subject: [PATCH] [clang] Improve bit-field in ref NTTP diagnostic Prior to this, attempts to bind a bit-field to an NTTP of reference type produced an error because references to subobjects in NTTPs are disallowed. But C++20 allows references to subobjects in NTTPs generally (see P1907R1). Without this change, implementing P1907R1 would cause a bug allowing bit-fields to be bound to reference template arguments. Extracted from https://reviews.llvm.org/D140996 --- clang/docs/ReleaseNotes.rst | 2 ++ clang/include/clang/Basic/DiagnosticSemaKinds.td | 2 ++ clang/lib/Sema/SemaOverload.cpp | 10 ++++++++++ clang/test/CXX/drs/dr12xx.cpp | 2 +- clang/test/SemaTemplate/temp_arg_nontype_cxx20.cpp | 6 ++++++ 5 files changed, 21 insertions(+), 1 deletion(-) diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index c7a948fd3fae5..01a927b2bc17e 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -503,6 +503,8 @@ Improvements to Clang's diagnostics 48 | static_assert(1 << 4 == 15); | ~~~~~~~^~~~~ +- Clang now diagnoses attempts to bind a bitfield to an NTTP of a reference type as erroneous + converted constant expression and not as a reference to subobject. Improvements to Clang's time-trace ---------------------------------- diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td index 6dfb2d7195203..b95d2bea00a5e 100644 --- a/clang/include/clang/Basic/DiagnosticSemaKinds.td +++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td @@ -2251,6 +2251,8 @@ def warn_cxx17_compat_aggregate_init_paren_list : Warning< def err_reference_bind_to_bitfield : Error< "%select{non-const|volatile}0 reference cannot bind to " "bit-field%select{| %1}2">; +def err_reference_bind_to_bitfield_in_cce : Error< + "reference cannot bind to bit-field in converted constant expression">; def err_reference_bind_to_vector_element : Error< "%select{non-const|volatile}0 reference cannot bind to vector element">; def err_reference_bind_to_matrix_element : Error< diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp index 5026e1d603e5e..ebbd4f48b57f8 100644 --- a/clang/lib/Sema/SemaOverload.cpp +++ b/clang/lib/Sema/SemaOverload.cpp @@ -6056,6 +6056,16 @@ static ExprResult BuildConvertedConstantExpression(Sema &S, Expr *From, diag::err_typecheck_converted_constant_expression_indirect) << From->getType() << From->getSourceRange() << T; } + // 'TryCopyInitialization' returns incorrect info for attempts to bind + // a reference to a bit-field due to C++ [over.ics.ref]p4. Namely, + // 'SCS->DirectBinding' occurs to be set to 'true' despite it is not + // the direct binding according to C++ [dcl.init.ref]p5. Hence, check this + // case explicitly. + if (From->refersToBitField() && T.getTypePtr()->isReferenceType()) { + return S.Diag(From->getBeginLoc(), + diag::err_reference_bind_to_bitfield_in_cce) + << From->getSourceRange(); + } // Usually we can simply apply the ImplicitConversionSequence we formed // earlier, but that's not guaranteed to work when initializing an object of diff --git a/clang/test/CXX/drs/dr12xx.cpp b/clang/test/CXX/drs/dr12xx.cpp index c23a515ba56cb..81c113d4c1c5a 100644 --- a/clang/test/CXX/drs/dr12xx.cpp +++ b/clang/test/CXX/drs/dr12xx.cpp @@ -138,7 +138,7 @@ namespace dr1295 { // dr1295: 4 #if __cplusplus <= 201402L // expected-error@-2 {{does not refer to any declaration}} expected-note@-3 {{here}} #else - // expected-error@-4 {{refers to subobject}} + // expected-error@-4 {{reference cannot bind to bit-field in converted constant expression}} #endif #if __cplusplus >= 201103L diff --git a/clang/test/SemaTemplate/temp_arg_nontype_cxx20.cpp b/clang/test/SemaTemplate/temp_arg_nontype_cxx20.cpp index 792dc78464b2a..982f6ec221570 100644 --- a/clang/test/SemaTemplate/temp_arg_nontype_cxx20.cpp +++ b/clang/test/SemaTemplate/temp_arg_nontype_cxx20.cpp @@ -93,6 +93,12 @@ namespace ConvertedConstant { template <A> struct X {}; void f(X<1.0f>) {} void g(X<2>) {} + + struct { + int i : 2; + } b; + template <const int&> struct Y {}; + void f(Y<b.i>) {} // expected-error {{reference cannot bind to bit-field in converted constant expression}} } namespace CopyCounting { _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
