[Bug libstdc++/97659] Invalid pointer subtraction in vector::insert() (reported by pointer-subtract AddressSanitizer)

[chfast at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97659

--- Comment #4 from Paweł Bylica <chfast at gmail dot com> ---
I'd like to explain some things here (to my best knowledge):

1. The "pointer-subtract" checks is ASan extension, not enabled by default.
When running with this check enabled in my application I have not detected any
issues in std::vector.

2. The "pointer-subtract" checks if you pointer subtraction operands are from
the same memory allocation. Allowed values are all pointers from the memory
region plus the "end" pointer one element outside of the region. Other
subtractions are UB in C to my information.

3. The issue shows up only when "pointer-subtract" is combined with
_GLIBCXX_SANITIZE_VECTOR. Moreover, the report looks like false positive
because the subtraction is between the "end" pointer and a pointer from inside
of a memory region.