[Bug libfortran/67535] write.c sanitizer detects null pointer passed to memcpy

[zeccav at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67535

--- Comment #3 from Vittorio Zecca <zeccav at gmail dot com> ---
(In reply to kargl from comment #1)

> What happens to performance?  Simply making changes to
> make sanitizer happy seems rather questionable.  It's clear
> from context that if base_name == NULL, then base_name_len
> == 0, and the memcpy should be a NOP.

How costly is that NOP compared to if(base_name_len)?

How costly is to let go an undefined behaviour?