[Bug tree-optimization/90264] [9/10 Regression] -Wnull-dereference false positive after r270574

[law at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90264

--- Comment #1 from Jeffrey A. Law <law at redhat dot com> ---
It doesn't look like a false positive to me.

We set *seq = 0.

Assume we do not return -1 from line A.

The for loop's initial test will be false because out = *seq = 0

out - *seq must also be zero and if that's <= len, then we'll *out = `\0' which
dereferences a NULL pointer.