As others have commented, the Linux incident involved an actual dereferencing of the pointer. The way I read http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1

As others have commented, the Linux incident involved an actual dereferencing of the pointer. The way I read http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf top of page 89 and footnote 102 on that page is that this is NOT undefined behavior in C, and though I haven’t checked the corresponding language in the C++ standard, I would think it’s not undefined in C++ either.