Poettering: The Biggest Myths

Sometimes I work on code that is assembling various things into buffers in order to generate a representation out-of-program, like on disk or on the wire. These things often work with fixed sized buffers into which they are assembling data, because the data representation has a fixed size.

In this case, changing codepaths to use strlcopy gives SIGNIFICANT improvements in safety. strncpy is not acceptable in these cases because it will incur large performance penalties with the null padding. Yes, we try to have sane and well placed logic to enforce the sizing, but putting the logic in each callsite is just begging for overruns which can be unacceptable in some use cases, so strlcpy gives us some safeguard, despite being careful in the logic.