4 ms·

This gets me interested. Link [1] below shows their implementation of strlcpy(). This is a questionable implementation. With strncpy, the source string "src" ma

This gets me interested. Link [1] below shows their implementation of strlcpy(). This is a questionable implementation. With strncpy, the source string "src" may not be NULL terminated IIRC. The git implementation requires "src" to be NULL terminated. If not, an invalid read. EDIT: according to the strlcpy manpage [2], "src" is required to be NULL terminated, so strlcpy imposes more restrictions and is not a proper replacement of strncpy. Furthermore, imagine "src" has 1Mb characters but we only want to copy the first 3 chars. The git implementation would traverse the entire 1Mb to find the length first, but a proper implementation only needs to look at the first 3 chars. So, they banned strncpy and provided a worse solution to that. [1]: https://github.com/git/git/blob/master/compat/strlcpy.c https://github.com/git/git/blob/master/compat/strlcpy.c [2]: https://linux.die.net/man/3/strlcpy https://linux.die.net/man/3/strlcpy

kzrdude 6y ago
You have found the answer - strlcpy is not a replacement for strncpy at all (it's arguably a safer version of strcpy), and git people didn't invent this, it's the existing BSD strlcpy interface.
- attractivechaos 6y ago
  Thanks for the confirmation. But my concern remains: they banned strncpy without a proper replacement. In addition, I didn't know the extra restriction of strlcpy until today (I have never used it before because it is not conforming to C99/POSIX). I might have fallen into this trap.
  - notaplumber 6y ago
    The problem is the actually often the opposite, in the real world many treat strncpy as if it behaves like strlcpy. Note that strlcpy is equivalent to: snprintf(buf, sizeof(buf), "%s", string); strlcpy is on track for future standardization in POSIX, for Issue 8, but even as a de facto standard, it exists in libc on *BSD, macOS, Android, Solaris, QNX, and even Linux using musl. https://www.austingroupbugs.net/view.php?id=986#c5050 https://www.austingroupbugs.net/view.php?id=986#c5050 But you're correct in that it is not a replacement for strncpy because no code should be using strncpy.
tedunangst 6y ago
Take a step back and consider strlcpy isn't supposed to be a drop in replacement for strncpy (a function which already exists).
alcover 6y ago
Agreed. It's O(n) inefficient. I guess looping though chars up to `size` would perform better on average. I see this `strlcpy` recommanded everywhere.
- attractivechaos 6y ago
  A few days ago people here were discussing the quadratic sscanf() behavior. strlcpy() has the same problem.

kzrdude 6y ago

You have found the answer - strlcpy is not a replacement for strncpy at all (it's arguably a safer version of strcpy), and git people didn't invent this, it's the existing BSD strlcpy interface.

attractivechaos 6y ago
Thanks for the confirmation. But my concern remains: they banned strncpy without a proper replacement. In addition, I didn't know the extra restriction of strlcpy until today (I have never used it before because it is not conforming to C99/POSIX). I might have fallen into this trap.
- notaplumber 6y ago
  The problem is the actually often the opposite, in the real world many treat strncpy as if it behaves like strlcpy. Note that strlcpy is equivalent to: snprintf(buf, sizeof(buf), "%s", string); strlcpy is on track for future standardization in POSIX, for Issue 8, but even as a de facto standard, it exists in libc on *BSD, macOS, Android, Solaris, QNX, and even Linux using musl. https://www.austingroupbugs.net/view.php?id=986#c5050 https://www.austingroupbugs.net/view.php?id=986#c5050 But you're correct in that it is not a replacement for strncpy because no code should be using strncpy.

tedunangst 6y ago

Take a step back and consider strlcpy isn't supposed to be a drop in replacement for strncpy (a function which already exists).

alcover 6y ago

Agreed. It's O(n) inefficient. I guess looping though chars up to `size` would perform better on average. I see this `strlcpy` recommanded everywhere.

attractivechaos 6y ago
A few days ago people here were discussing the quadratic sscanf() behavior. strlcpy() has the same problem.