The formatter for pointers was casting to uint64_t which sign extends a
32-bit pointer and produces a value that won't fit in the provided
buffer. Cast to uintptr_t instead.
There was also a bug in the __parse_integer helper when converting a
wide string to a narrow string in order to use std::from_chars on it.
The function would always try to read 32 characters, even if the format
string was shorter than that. Fix that bug, and remove the constexpr
implementation of __parse_integer by just using __from_chars_alnum
instead of from_chars, because that's usable in constexpr even in
C++20.
libstdc++-v3/ChangeLog:
PR libstdc++/110239
* include/std/format (__format::__parse_integer): Fix buffer
overflow for wide chars.
(formatter<const void*, C>::format): Cast to uintptr_t instead
of uint64_t.
* testsuite/std/format/string.cc: Test too-large widths.
(cherry picked from commit 3bb9f9329c378934541ae4cff9977b7487e97cf0)
Jonathan Wakely
2d40cd2f19