UBSAN warnings on calls to memcpy

Gary Lockyer gary at
Thu May 23 03:20:40 UTC 2019

One of the more common UBSAN errors is
"null pointer passed as argument 2, which is declared to never be null"

These are calls to memcpy where the source length is 0, and the data is
NULL. Adding an "if (length > 0) {" guard before the memcpy would fix
the warning.

I'm inclined to think we should do this, but also agree that it does
clutter the code. While the call to memcpy should be safe, removing the
warnings reduces the clutter and makes it less likely we'll miss a real

Thoughts and comments appreciated.

Ngā mihi

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