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author | Jonathan Wakely <jwakely@redhat.com> | 2023-01-26 10:55:28 +0000 |
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committer | Jonathan Wakely <jwakely@redhat.com> | 2023-01-26 13:38:22 +0000 |
commit | 3376467ce090aa0966d59ca3aea35db4f17a4b47 (patch) | |
tree | e1ef41d1f1965baf9e07254bf777027c6b357efd /libstdc++-v3 | |
parent | 93e2bf51dedd0870b78b770b72e34b15a7a0d14a (diff) | |
download | gcc-3376467ce090aa0966d59ca3aea35db4f17a4b47.zip gcc-3376467ce090aa0966d59ca3aea35db4f17a4b47.tar.gz gcc-3376467ce090aa0966d59ca3aea35db4f17a4b47.tar.bz2 |
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.
Diffstat (limited to 'libstdc++-v3')
-rw-r--r-- | libstdc++-v3/include/bits/stl_tree.h | 2 | ||||
-rw-r--r-- | libstdc++-v3/testsuite/23_containers/map/modifiers/108554.cc | 19 |
2 files changed, 21 insertions, 0 deletions
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 <map> +#include <memory> +#include <string> + +int pop(std::map<std::string, std::unique_ptr<int>>& m) +{ + if (auto it = m.find("key"); it != m.end()) + { + auto item = std::move(m.extract(it).mapped()); + return *item; + } + return 0; +} |