Possible buffer overflow in compat_libevent.c?

Question

first of all let me say that I started to study the C three days ago. As exercise I'm reading source code as much as I can. I thought I'd start with Tor and, in this file src/common/compat_libevent.c, I found something that has puzzled me (n = strlcpy(buf, msg, sizeof(buf));):

STATIC void
libevent_logging_callback(int severity, const char *msg)
{
  char buf[1024]; //size of buf
  size_t n; //store the maximum size of n
  if (suppress_msg && strstr(msg, suppress_msg)) //if suppress_msg is not NULL and in suppress_msg there is msg...
    return;
  n = strlcpy(buf, msg, sizeof(buf)); //here I'm confused: msg, for example, of 2048 bytes will lead to a buffer overflow... or not?
  if (n && n < sizeof(buf) && buf[n-1] == '\n') {
    buf[n-1] = '\0';
  }
...

A msg, for example, of 2048 bytes will lead to a buffer overflow, right (or not)?

Answer 1

The manpage for strlcpy() says:

The strlcpy() function copies up to size - 1 characters from the NUL-terminated string src to dst, NUL-terminating the result.

So the size in your example is 1024 Bytes (sizeof(buf)). As far as I understand it it will copy 1023 from msg and terminate with NUL. Even if you enter a data block which is larger. So there is no buffer overflow possible. People in https://stackoverflow.com could possibly explain this in more detail.