[Bug 279443] LIBCPP assertions are enabled in optimized builds when -DNDEBUG is given to clang

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=279443

            Bug ID: 279443
           Summary: LIBCPP assertions are enabled in optimized builds when
                    -DNDEBUG is given to clang
           Product: Base System
           Version: 14.0-STABLE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: misc
          Assignee: bugs@FreeBSD.org
          Reporter: yuri@freebsd.org
 Attachment #251126 text/plain
         mime type:

Created attachment 251126
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=251126&action=edit
get_executable_filename.cpp

The attached code crashes due to the LIBCPP assertion:

1390│ template <class _Tp, class _Allocator>
1391│ _LIBCPP_CONSTEXPR_SINCE_CXX20 inline _LIBCPP_HIDE_FROM_ABI typename
vector<_Tp, _Allocator>::reference
1392│ vector<_Tp, _Allocator>::operator[](size_type __n) _NOEXCEPT {
1393├─> _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__n < size(), "vector[] index out
of bounds");
1394│   return this->__begin_[__n];
1395│ }

It should be possible to get an address of the end of the std::vector object,
even though it doesn't point to an allocated byte.

Regular asserts are disabled, but LIBCPP asserts are enabled for some reason.
It is unclear to me when LIBCPP assertions should be enabled, but optimized
runs with -DNDEBUG should definitely have them disabled.

Enabled assertions also cause the performance degradation.

This assertion caused the discovery of a real bug in the devel/hpx port, where
the attached testcase comes from.


Clang-18.1.5

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