From 3376467ce090aa0966d59ca3aea35db4f17a4b47 Mon Sep 17 00:00:00 2001 From: Jonathan Wakely Date: Thu, 26 Jan 2023 10:55:28 +0000 Subject: libstdc++: Add returns_nonnull to non-inline std::map detail [PR108554] std::map uses a non-inline function to rebalance its tree and the compiler can't see that it always returns a valid pointer (assuming valid inputs, which is a precondition anyway). This can result in -Wnull-derefernce warnings for valid code, because the compiler thinks there is a path where the function returns null. Adding the returns_nonnull attribute tells the compiler that is can't happen. While we're doing that, we might as well also add a nonnull attribute to the rebalancing functions too. libstdc++-v3/ChangeLog: PR libstdc++/108554 * include/bits/stl_tree.h (_Rb_tree_insert_and_rebalance): Add nonnull attribute. (_Rb_tree_rebalance_for_erase): Add nonnull and returns_nonnull attributes. * testsuite/23_containers/map/modifiers/108554.cc: New test. --- libstdc++-v3/include/bits/stl_tree.h | 2 ++ .../testsuite/23_containers/map/modifiers/108554.cc | 19 +++++++++++++++++++ 2 files changed, 21 insertions(+) create mode 100644 libstdc++-v3/testsuite/23_containers/map/modifiers/108554.cc (limited to 'libstdc++-v3') diff --git a/libstdc++-v3/include/bits/stl_tree.h b/libstdc++-v3/include/bits/stl_tree.h index 5b7a586..3c331fb 100644 --- a/libstdc++-v3/include/bits/stl_tree.h +++ b/libstdc++-v3/include/bits/stl_tree.h @@ -405,12 +405,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION _Base_ptr _M_node; }; + __attribute__((__nonnull__)) void _Rb_tree_insert_and_rebalance(const bool __insert_left, _Rb_tree_node_base* __x, _Rb_tree_node_base* __p, _Rb_tree_node_base& __header) throw (); + __attribute__((__nonnull__,__returns_nonnull__)) _Rb_tree_node_base* _Rb_tree_rebalance_for_erase(_Rb_tree_node_base* const __z, _Rb_tree_node_base& __header) throw (); diff --git a/libstdc++-v3/testsuite/23_containers/map/modifiers/108554.cc b/libstdc++-v3/testsuite/23_containers/map/modifiers/108554.cc new file mode 100644 index 0000000..7076682 --- /dev/null +++ b/libstdc++-v3/testsuite/23_containers/map/modifiers/108554.cc @@ -0,0 +1,19 @@ +// { dg-do compile { target c++17 } } +// { dg-options "-Wnull-dereference -O2" } + +// PR libstdc++/108554 +// Warning from -Wnull-dereference when extracting a unique_ptr from a map. + +#include +#include +#include + +int pop(std::map>& m) +{ + if (auto it = m.find("key"); it != m.end()) + { + auto item = std::move(m.extract(it).mapped()); + return *item; + } + return 0; +} -- cgit v1.1