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author | bors[bot] <26634292+bors[bot]@users.noreply.github.com> | 2022-12-14 14:46:30 +0000 |
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committer | GitHub <noreply@github.com> | 2022-12-14 14:46:30 +0000 |
commit | 3b89428c0d5710c8093055b3d92c543888759f93 (patch) | |
tree | beec559689144dfe4f023924ae1dd3a37b19a580 | |
parent | 3d6dbb6fc5d1d14bf36a879b6f4a00ae91090a63 (diff) | |
parent | 5c2e6c93d919b939ba7eca2100fa35cc444f4b8d (diff) | |
download | gcc-3b89428c0d5710c8093055b3d92c543888759f93.zip gcc-3b89428c0d5710c8093055b3d92c543888759f93.tar.gz gcc-3b89428c0d5710c8093055b3d92c543888759f93.tar.bz2 |
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>
-rw-r--r-- | gcc/cp/call.cc | 12 | ||||
-rw-r--r-- | gcc/testsuite/g++.dg/warn/Wdangling-reference5.C | 22 |
2 files changed, 33 insertions, 1 deletions
diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc index c7c7a12..2c0fa37 100644 --- a/gcc/cp/call.cc +++ b/gcc/cp/call.cc @@ -13467,7 +13467,17 @@ do_warn_dangling_reference (tree expr) can be e.g. const int& z = std::min({1, 2, 3, 4, 5, 6, 7}); which doesn't dangle: std::min here returns an int. */ - || !TYPE_REF_OBJ_P (TREE_TYPE (TREE_TYPE (fndecl)))) + || !TYPE_REF_OBJ_P (TREE_TYPE (TREE_TYPE (fndecl))) + /* Don't emit a false positive for: + std::vector<int> v = ...; + std::vector<int>::const_iterator it = v.begin(); + const int &r = *it++; + because R refers to one of the int elements of V, not to + a temporary object. Member operator* may return a reference + but probably not to one of its arguments. */ + || (DECL_NONSTATIC_MEMBER_FUNCTION_P (fndecl) + && DECL_OVERLOADED_OPERATOR_P (fndecl) + && DECL_OVERLOADED_OPERATOR_IS (fndecl, INDIRECT_REF))) return NULL_TREE; /* Here we're looking to see if any of the arguments is a temporary diff --git a/gcc/testsuite/g++.dg/warn/Wdangling-reference5.C b/gcc/testsuite/g++.dg/warn/Wdangling-reference5.C new file mode 100644 index 0000000..59b5538 --- /dev/null +++ b/gcc/testsuite/g++.dg/warn/Wdangling-reference5.C @@ -0,0 +1,22 @@ +// PR c++/107488 +// { dg-do compile } +// { dg-options "-Wdangling-reference" } + +#include <vector> + +int +do_sum (std::vector<int>& v) +{ + int sum = 0; + + std::vector<int>::const_iterator it = v.begin(); + while (it != v.end()) + { + // R refers to one of the int elements of V, not to a temporary + // object, so no dangling reference here. + const int &r = *it++; // { dg-bogus "dangling reference" } + sum += r; + } + + return sum; +} |