Re: memccpy(3) and stpcpy(3) status in C2x (was: stpecpy(): A better string copy function)

[Steffen Nurpmeso]

Martin Sebor wrote in
 <dcd2227a-8e53-86d5-e6a4-7f192494d5d1@gmail.com>:
 |On 2/13/22 13:32, Alejandro Colomar (man-pages) wrote:
 |> On 2/13/22 19:29, Alejandro Colomar (man-pages) wrote:
 ..
 |>>> I expect/hope stpcpy to become the new norm for string copying, though
 |>>> it will require overcoming much inertia and many dusty old books.
 |>>>
 |>>> It was introduced to POSIX in Issue 7 (2018).
 |>>>
 |>>> https://pubs.opengroup.org/onlinepubs/9699919799/functions/strcpy.html
 |>>>
 |>>> Martin Sebor is sponsoring its inclusion in C2x.
 |>>>
 |>>> http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2352.htm
 |>>>
 |>>> (It may have been accepted, or not--I haven't checked the status.)
 |>>
 |>> No, stpcpy(3) was not accepted.  memccpy(3) was instead.  The problem
 |>> wasn't stpcpy(3) as it seems, but stpncpy(3) about which I'll rant a bit
 |>> below :).
 |> 
 |> I forgot to link to the C2x document, which contains very interesting
 |> information:
 |> 
 |> <http://www.open-std.org/JTC1/SC22/WG14/www/docs/n2349.htm>
 |> 
 |> TL;DR: That document considers strlcpy(3) to be "optimal", but not
 |> widely supported enough, and then selects memccpy(3) as "good enough"
 |> and way more widespread.
 |
 |I think that was also the sentiment in WG14 when the proposal was
 |discussed.  N2352 proposed stpcpy and stpncpy by themselves but it
 |didn't gain enough support.  More detail of the committee discussion
 |of both proposals (and others) is in the meeting minutes:
 |   http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2376.pdf

I personally like my

  /*! Copy \a{src} to \a{dst}, return pointer to NUL in \a{dst}.
   * Returns \NIL if \a{dst} is not large enough; \a{dst} will always be
   * terminated unless \a{n} was 0 on entry. */
  EXPORT char *su_cs_pcopy_n(char *dst, char const *src, uz n);

But mostly i either use memcpy if possible, or

  /*! Copy at most \a{n} bytes of \a{src} to \a{dst}, and return \a{dst} again.
   * Returns \NIL if \a{dst} is not large enough; \a{dst} will always be
   * terminated unless \a{n} was 0 on entry.
   * Also see \r{su_cs_pcopy_n()}. */
  EXPORT char *su_cs_copy_n(char *dst, char const *src, uz n);

They are C-only implementations yet.

--Steffen Schönbein