[gcc/devel/rust/master] Merge #1703

[gcc/devel/rust/master] Merge #1703

[Thomas Schwinge]

https://gcc.gnu.org/g:3b89428c0d5710c8093055b3d92c543888759f93

commit 3b89428c0d5710c8093055b3d92c543888759f93
Merge: 3d6dbb6fc5d 5c2e6c93d91
Author: bors[bot] <26634292+bors[bot]@users.noreply.github.com>
Date:   Wed Dec 14 14:46:30 2022 +0000

    Merge #1703
    
    1703: Backport "c++: Quash -Wdangling-reference for member operator* [PR107488]" r=tschwinge a=tschwinge
    
    As had also been reported in <https://gcc.gnu.org/PR107633> "Bootstrap failure due to -Werror=unused-parameter and -Werror=dangling-reference", GCC `--enable-bootstrap` build is currently broken:
    
        [...]/gcc/rust/backend/rust-compile-expr.cc: In member function ‘tree_node* Rust::Compile::CompileExpr::resolve_method_address(Rust::TyTy::FnType*, Rust::HirId, Rust::TyTy::BaseType*, Rust::HIR::PathIdentSegment&, Rust::Analysis::NodeMapping, Location)’:
        [...]/gcc/rust/backend/rust-compile-expr.cc:2019:13: error: possibly dangling reference to a temporary [-Werror=dangling-reference]
         2019 |       auto &candidate = *candidates.begin ();
              |             ^~~~~~~~~
        [...]/gcc/rust/backend/rust-compile-expr.cc:2019:44: note: the temporary was destroyed at the end of the full expression ‘candidates.std::set<Rust::Resolver::PathProbeCandidate>::begin().std::_Rb_tree_const_iterator<Rust::Resolver::PathProbeCandidate>::operator*()’
         2019 |       auto &candidate = *candidates.begin ();
              |                                            ^
        [...]/gcc/rust/backend/rust-compile-expr.cc: In member function ‘tree_node* Rust::Compile::CompileExpr::generate_closure_fntype(Rust::HIR::ClosureExpr&, const Rust::TyTy::ClosureType&, tree, Rust::TyTy::FnType**)’:
        [...]/gcc/rust/backend/rust-compile-expr.cc:3034:35: error: possibly dangling reference to a temporary [-Werror=dangling-reference]
         3034 |   const TyTy::TypeBoundPredicate &predicate
              |                                   ^~~~~~~~~
        [...]/gcc/rust/backend/rust-compile-expr.cc:3035:52: note: the temporary was destroyed at the end of the full expression ‘(&(& closure_tyty)->Rust::TyTy::ClosureType::<anonymous>.Rust::TyTy::BaseType::<anonymous>.Rust::TyTy::TypeBoundsMappings::get_specified_bounds())->std::vector<Rust::TyTy::TypeBoundPredicate>::begin().__gnu_cxx::__normal_iterator<const Rust::TyTy::TypeBoundPredicate*, std::vector<Rust::TyTy::TypeBoundPredicate> >::operator*()’
         3035 |     = *closure_tyty.get_specified_bounds ().begin ();
              |                                                    ^
    
        [...]/gcc/rust/typecheck/rust-hir-type-check-path.cc: In member function ‘void Rust::Resolver::TypeCheckExpr::resolve_segments(Rust::NodeId, std::vector<Rust::HIR::PathExprSegment>&, size_t, Rust::TyTy::BaseType*, const Rust::Analysis::NodeMapping&, Location)’:
        [...]/gcc/rust/typecheck/rust-hir-type-check-path.cc:340:13: error: possibly dangling reference to a temporary [-Werror=dangling-reference]
          340 |       auto &candidate = *candidates.begin ();
              |             ^~~~~~~~~
        [...]/gcc/rust/typecheck/rust-hir-type-check-path.cc:340:44: note: the temporary was destroyed at the end of the full expression ‘candidates.std::set<Rust::Resolver::PathProbeCandidate>::begin().std::_Rb_tree_const_iterator<Rust::Resolver::PathProbeCandidate>::operator*()’
          340 |       auto &candidate = *candidates.begin ();
              |                                            ^
    
        [...]/gcc/rust/typecheck/rust-hir-type-check-type.cc: In member function ‘Rust::TyTy::BaseType* Rust::Resolver::TypeCheckType::resolve_segments(Rust::NodeId, Rust::HirId, std::vector<std::unique_ptr<Rust::HIR::TypePathSegment> >&, size_t, Rust::TyTy::BaseType*, const Rust::Analysis::NodeMapping&, Location)’:
        [...]/gcc/rust/typecheck/rust-hir-type-check-type.cc:465:13: error: possibly dangling reference to a temporary [-Werror=dangling-reference]
          465 |       auto &candidate = *candidates.begin ();
              |             ^~~~~~~~~
        [...]/gcc/rust/typecheck/rust-hir-type-check-type.cc:465:44: note: the temporary was destroyed at the end of the full expression ‘candidates.std::set<Rust::Resolver::PathProbeCandidate>::begin().std::_Rb_tree_const_iterator<Rust::Resolver::PathProbeCandidate>::operator*()’
          465 |       auto &candidate = *candidates.begin ();
              |                                            ^
    
    I understand this code has been changed in the GCC/Rust upstream submission; but in order to make progress with #1700, I'd like to first individually backport "c++: Quash -Wdangling-reference for member operator* [PR107488]", to resolve this issue here.
    
    
    Co-authored-by: Marek Polacek <polacek@redhat.com>

Diff:

 gcc/cp/call.cc                                   | 12 +++++++++++-
 gcc/testsuite/g++.dg/warn/Wdangling-reference5.C | 22 ++++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)