Hi Theo,
On 2/13/22 23:45, Theo de Raadt wrote:
> Your proposal isn't an improvement over the current situation with strl*
> functions, and I don't think this is helpful.
>
> Alejandro Colomar (man-pages) <[email protected]> wrote:
>> Compared to other string copy and concatenation functions
>> strlcat(3BSD)
>> *cat() functions have an inherent performance
>> problem: each *cat() call has to find again the
>> teminating null byte in the dest string. Read
>> about Shlemiel the painter’s algorithm
>> ⟨https://www.joelonsoftware.com/2001/12/11/back-
>> to-basics/⟩.
I agree that the improvement is tiny, and more theoretical than
practical (I have never seen strlcat(3) in a loop). Also, strlcat(3)
requires testing for truncation after every call, but it's also a minor
thing.
An equivalent usage of the example shown in strlcat(3):
Ignore truncation:
strlcat(3):
char *s, *p, buf[BUFSIZ];
...
(void)strlcpy(buf, s, sizeof(buf));
(void)strlcat(buf, p, sizeof(buf));
stpecpy():
char *s, *p, buf[BUFSIZ];
char *end = &buf[sizeof(buf) - 1];
...
(void)stpecpy(stpecpy(buf, s, end), p, end);
Detect truncation:
strlcat(3):
char *dir, *file, pname[MAXPATHLEN];
...
if (strlcpy(pname, dir, sizeof(pname)) >= sizeof(pname))
goto toolong;
if (strlcat(pname, file, sizeof(pname)) >= sizeof(pname))
goto toolong;
stpecpy():
char *dir, *file, pname[MAXPATHLEN];
char *end = &pname[sizeof(pname) - 1];
...
if (stpecpy(stpecpy(pname, dir, end), file, end) > end)
goto toolong;
I agree that they're quite similar, and for a system already providing
strl* functions, there's probably not enough improvement to add it.
However, considering some systems don't have strl* functions, and
explicitly don't want to add them (glibc rejected strl* functions),
there it might be useful to add this function.
Thanks for your opinion.
Regards,
Alex
--
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/
