Add a necessary cast, because ptrdiff_t isn't necessarily the same as int.
Add a necessary cast, because ptrdiff_t isn't necessarily the same as int.

Obtained from: OpenBSD

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase