strlcpy's flaw is its return value. In order to get the length of the string it has to walk the entire thing. If you are copying 20 character strings out of a 20TB mmaped file it will be outrageously slow and that's an unnecessary footgun.
It should have just returned the number of bytes copied to dst if the string was successfully copied and a -1 with an errno of E2BIG if the dst was too small for the src. It would still do the copy and termination of course, and the programmer will know the length in this case because they specified it in the function call. Of course this is what strscpy does.
If you aren't sure about the length of the src buffer strlcpy can be a ticking time bomb. If you aren't sure if the src string is NULL terminated it's also a problem, which is especially bad since one of the big reasons to use strlcpy is to avoid buffer overruns. GTA Online suffered from outrageous load times due to this very same API quirk. This would also make it easy for the function to return -1 and set errno to EINVAL if you specify NULL for the src or dst.
It should have just returned the number of bytes copied to dst if the string was successfully copied and a -1 with an errno of E2BIG if the dst was too small for the src. It would still do the copy and termination of course, and the programmer will know the length in this case because they specified it in the function call. Of course this is what strscpy does.
If you aren't sure about the length of the src buffer strlcpy can be a ticking time bomb. If you aren't sure if the src string is NULL terminated it's also a problem, which is especially bad since one of the big reasons to use strlcpy is to avoid buffer overruns. GTA Online suffered from outrageous load times due to this very same API quirk. This would also make it easy for the function to return -1 and set errno to EINVAL if you specify NULL for the src or dst.