[Bug libstdc++/112314] Missing index assertions in basic_string_view

["redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112314

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-10-31
           Severity|normal                      |enhancement

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
For the first problem:

--- a/libstdc++-v3/include/std/string_view
+++ b/libstdc++-v3/include/std/string_view
@@ -301,7 +301,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION

       constexpr void
       remove_suffix(size_type __n) noexcept
-      { this->_M_len -= __n; }
+      {
+       __glibcxx_assert(this->_M_len >= __n);
+       this->_M_len -= __n;
+      }

       constexpr void
       swap(basic_string_view& __sv) noexcept


For the second one, I did start work on a patch that attempts to verify that
the provided length is not more than __builtin_object_size. I can't remember
why I stopped working on that. There's no way to make that check 100% reliable,
because __builtin_object_size depends on optimizations and whether the compiler
can see enough data.