Date: Fri, 4 Jul 2014 18:20:24 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Dmitry Sivachenko <trtrmitya@gmail.com> Cc: freebsd-standards@freebsd.org Subject: Re: About sysconf(_SC_GETPW_R_SIZE_MAX) Message-ID: <20140704152024.GI93733@kib.kiev.ua> In-Reply-To: <5EA35BF7-3984-4FD4-B523-9767E142475A@gmail.com> References: <DDC4C361-1C27-4913-91BB-1974AD1163A7@gmail.com> <20140704130017.GG93733@kib.kiev.ua> <5EA35BF7-3984-4FD4-B523-9767E142475A@gmail.com>
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On Fri, Jul 04, 2014 at 06:17:18PM +0400, Dmitry Sivachenko wrote:
>=20
> On 04 =C9=C0=CC=D1 2014 =C7., at 17:00, Konstantin Belousov <kostikbel@gm=
ail.com> wrote:
>=20
> > On Fri, Jul 04, 2014 at 11:05:46AM +0400, Dmitry Sivachenko wrote:
> >> Hello!
> >>=20
> >> (FreeBSD-10/stable).
> >>=20
> >> According to sysconf(3), _SC_GETPW_R_SIZE_MAX is the valid argument to=
sysconf():
> >>=20
> >> _SC_GETPW_R_SIZE_MAX
> >> Suggested initial value for the size of the password entry
> >> buffer.
> >>=20
> >> But the following test program fails:
> >>=20
> >> #include <unistd.h>
> >> #include <err.h>
> >> #include <errno.h>
> >> #include <stdio.h>
> >>=20
> >> int main() {
> >> int buf_sz;
> >>=20
> >> errno=3D0;
> >> buf_sz =3D sysconf(_SC_GETPW_R_SIZE_MAX);
> >> printf("%d\n", buf_sz);
> >> warn("sysconf: ");
> >> return 0;
> >> }
> >>=20
> >> % ./a.out=20
> >> -1
> >> a.out: sysconf: : Invalid argument
> >>=20
> >>=20
> >> What is wrong?
> >=20
> > From lib/libc/gen/sysconf.c, around line 327:
> > #if _POSIX_THREAD_SAFE_FUNCTIONS > -1
> > case _SC_GETGR_R_SIZE_MAX:
> > case _SC_GETPW_R_SIZE_MAX:
> > #error "somebody needs to implement this"
> > #endif
>=20
>=20
> May be remove these two from man page?
I suppose it is better to implement them, trivially:
diff --git a/lib/libc/gen/sysconf.c b/lib/libc/gen/sysconf.c
index b7952b1..2b3acfb 100644
--- a/lib/libc/gen/sysconf.c
+++ b/lib/libc/gen/sysconf.c
@@ -367,11 +367,17 @@ yesno:
* _POSIX_FILE_LOCKING, so we can't answer this one.
*/
#endif
-#if _POSIX_THREAD_SAFE_FUNCTIONS > -1
+
+ /*
+ * SUSv4tc1 says the following about _SC_GETGR_R_SIZE_MAX and
+ * _SC_GETPW_R_SIZE_MAX:
+ * Note that sysconf(_SC_GETGR_R_SIZE_MAX) may return -1 if
+ * there is no hard limit on the size of the buffer needed to
+ * store all the groups returned.
+ */
case _SC_GETGR_R_SIZE_MAX:
case _SC_GETPW_R_SIZE_MAX:
-#error "somebody needs to implement this"
-#endif
+ return (-1);
case _SC_HOST_NAME_MAX:
return (MAXHOSTNAMELEN - 1); /* does not include \0 */
case _SC_LOGIN_NAME_MAX:
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