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author | cor3ntin <corentinjabot@gmail.com> | 2024-12-18 10:44:42 +0100 |
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committer | GitHub <noreply@github.com> | 2024-12-18 10:44:42 +0100 |
commit | db93ef14aef9c572e02bc842762bc4d0278148f9 (patch) | |
tree | 079fa17b0bc8869f1e0613d179dbbef94e58edd7 /clang/lib/Sema/SemaExprMember.cpp | |
parent | 66bdbfbaa08fa3d8e64a7fe136a8fb717f5cdbb7 (diff) | |
download | llvm-db93ef14aef9c572e02bc842762bc4d0278148f9.zip llvm-db93ef14aef9c572e02bc842762bc4d0278148f9.tar.gz llvm-db93ef14aef9c572e02bc842762bc4d0278148f9.tar.bz2 |
[Clang] Implement CWG2813: Class member access with prvalues (#120223)
This is a rebase of #95112 with my own feedback apply as @MitalAshok has
been inactive for a while.
It's fairly important this makes clang 20 as it is a blocker for #107451
---
[CWG2813](https://cplusplus.github.io/CWG/issues/2813.html)
prvalue.member_fn(expression-list) now will not materialize a temporary
for prvalue if member_fn is an explicit object member function, and
prvalue will bind directly to the object parameter.
The E1 in E1.static_member is now a discarded-value expression, so if E1
was a call to a [[nodiscard]] function, there will now be a warning.
This also affects C++98 with [[gnu::warn_unused_result]] functions.
This should not affect C where TemporaryMaterializationConversion is a
no-op.
Closes #100314
Fixes #100341
---------
Co-authored-by: Mital Ashok <mital@mitalashok.co.uk>
Diffstat (limited to 'clang/lib/Sema/SemaExprMember.cpp')
-rw-r--r-- | clang/lib/Sema/SemaExprMember.cpp | 67 |
1 files changed, 55 insertions, 12 deletions
diff --git a/clang/lib/Sema/SemaExprMember.cpp b/clang/lib/Sema/SemaExprMember.cpp index 85d5dfcb..bcc1b92 100644 --- a/clang/lib/Sema/SemaExprMember.cpp +++ b/clang/lib/Sema/SemaExprMember.cpp @@ -1003,15 +1003,6 @@ Sema::BuildMemberReferenceExpr(Expr *BaseExpr, QualType BaseExprType, : !isDependentScopeSpecifier(SS) || computeDeclContext(SS)) && "dependent lookup context that isn't the current instantiation?"); - // C++1z [expr.ref]p2: - // For the first option (dot) the first expression shall be a glvalue [...] - if (!IsArrow && BaseExpr && BaseExpr->isPRValue()) { - ExprResult Converted = TemporaryMaterializationConversion(BaseExpr); - if (Converted.isInvalid()) - return ExprError(); - BaseExpr = Converted.get(); - } - const DeclarationNameInfo &MemberNameInfo = R.getLookupNameInfo(); DeclarationName MemberName = MemberNameInfo.getName(); SourceLocation MemberLoc = MemberNameInfo.getLoc(); @@ -1128,26 +1119,68 @@ Sema::BuildMemberReferenceExpr(Expr *BaseExpr, QualType BaseExprType, BaseExpr = BuildCXXThisExpr(Loc, BaseExprType, /*IsImplicit=*/true); } + // C++17 [expr.ref]p2, per CWG2813: + // For the first option (dot), if the id-expression names a static member or + // an enumerator, the first expression is a discarded-value expression; if + // the id-expression names a non-static data member, the first expression + // shall be a glvalue. + auto ConvertBaseExprToDiscardedValue = [&] { + assert(getLangOpts().CPlusPlus && + "Static member / member enumerator outside of C++"); + if (IsArrow) + return false; + ExprResult Converted = IgnoredValueConversions(BaseExpr); + if (Converted.isInvalid()) + return true; + BaseExpr = Converted.get(); + DiagnoseDiscardedExprMarkedNodiscard(BaseExpr); + return false; + }; + auto ConvertBaseExprToGLValue = [&] { + if (IsArrow || !BaseExpr->isPRValue()) + return false; + ExprResult Converted = TemporaryMaterializationConversion(BaseExpr); + if (Converted.isInvalid()) + return true; + BaseExpr = Converted.get(); + return false; + }; + // Check the use of this member. if (DiagnoseUseOfDecl(MemberDecl, MemberLoc)) return ExprError(); - if (FieldDecl *FD = dyn_cast<FieldDecl>(MemberDecl)) + if (FieldDecl *FD = dyn_cast<FieldDecl>(MemberDecl)) { + if (ConvertBaseExprToGLValue()) + return ExprError(); return BuildFieldReferenceExpr(BaseExpr, IsArrow, OpLoc, SS, FD, FoundDecl, MemberNameInfo); + } - if (MSPropertyDecl *PD = dyn_cast<MSPropertyDecl>(MemberDecl)) + if (MSPropertyDecl *PD = dyn_cast<MSPropertyDecl>(MemberDecl)) { + // No temporaries are materialized for property references yet. + // They might be materialized when this is transformed into a member call. + // Note that this is slightly different behaviour from MSVC which doesn't + // implement CWG2813 yet: MSVC might materialize an extra temporary if the + // getter or setter function is an explicit object member function. return BuildMSPropertyRefExpr(*this, BaseExpr, IsArrow, SS, PD, MemberNameInfo); + } - if (IndirectFieldDecl *FD = dyn_cast<IndirectFieldDecl>(MemberDecl)) + if (IndirectFieldDecl *FD = dyn_cast<IndirectFieldDecl>(MemberDecl)) { + if (ConvertBaseExprToGLValue()) + return ExprError(); // We may have found a field within an anonymous union or struct // (C++ [class.union]). return BuildAnonymousStructUnionMemberReference(SS, MemberLoc, FD, FoundDecl, BaseExpr, OpLoc); + } + // Static data member if (VarDecl *Var = dyn_cast<VarDecl>(MemberDecl)) { + if (ConvertBaseExprToDiscardedValue()) + return ExprError(); return BuildMemberExpr(BaseExpr, IsArrow, OpLoc, SS.getWithLocInContext(Context), TemplateKWLoc, Var, FoundDecl, /*HadMultipleCandidates=*/false, @@ -1161,7 +1194,13 @@ Sema::BuildMemberReferenceExpr(Expr *BaseExpr, QualType BaseExprType, if (MemberFn->isInstance()) { valueKind = VK_PRValue; type = Context.BoundMemberTy; + if (MemberFn->isImplicitObjectMemberFunction() && + ConvertBaseExprToGLValue()) + return ExprError(); } else { + // Static member function + if (ConvertBaseExprToDiscardedValue()) + return ExprError(); valueKind = VK_LValue; type = MemberFn->getType(); } @@ -1174,6 +1213,8 @@ Sema::BuildMemberReferenceExpr(Expr *BaseExpr, QualType BaseExprType, assert(!isa<FunctionDecl>(MemberDecl) && "member function not C++ method?"); if (EnumConstantDecl *Enum = dyn_cast<EnumConstantDecl>(MemberDecl)) { + if (ConvertBaseExprToDiscardedValue()) + return ExprError(); return BuildMemberExpr( BaseExpr, IsArrow, OpLoc, SS.getWithLocInContext(Context), TemplateKWLoc, Enum, FoundDecl, /*HadMultipleCandidates=*/false, @@ -1181,6 +1222,8 @@ Sema::BuildMemberReferenceExpr(Expr *BaseExpr, QualType BaseExprType, } if (VarTemplateDecl *VarTempl = dyn_cast<VarTemplateDecl>(MemberDecl)) { + if (ConvertBaseExprToDiscardedValue()) + return ExprError(); if (!TemplateArgs) { diagnoseMissingTemplateArguments( SS, /*TemplateKeyword=*/TemplateKWLoc.isValid(), VarTempl, MemberLoc); |