slist.3: Add details

Add remaining details to complete the page.

Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man3/slist.3

@@ -48,6 +48,7 @@ SLIST_REMOVE,
 .\"SLIST_REMOVE_AFTER,
 SLIST_REMOVE_HEAD
 .\"SLIST_SWAP
+\- implementation of a singly-linked list
 .SH SYNOPSIS
 .nf
 .B #include <sys/queue.h>
@@ -87,6 +88,8 @@ SLIST_REMOVE_HEAD
 .\".BI "void SLIST_SWAP(SLIST_HEAD *" head1 ", SLIST_HEAD *" head2 ", SLIST_ENTRY " NAME ");"
 .fi
 .SH DESCRIPTION
+These macros define and operate on doubly-linked lists.
+.PP
 In the macro definitions,
 .I TYPE
 is the name of a user-defined structure,
@@ -259,11 +262,38 @@ from the list.
 .\" and
 .\" .IR head2 .
 .SH RETURN VALUE
+.BR SLIST_EMPTY ()
+returns non-zero if the list is empty,
+and zero if the list contains at least one entry.
+.PP
+.BR SLIST_FIRST (),
+and
+.BR SLIST_NEXT ()
+return a pointer to the first or next
+.I SLIST_ENTRY
+structure, respectively.
+.PP
+.BR SLIST_HEAD_INITIALIZER ()
+returns an initializer that can be assigned to the list
+.IR head .
 .SH CONFORMING TO
 Not in POSIX.1, POSIX.1-2001 or POSIX.1-2008.
 Present on the BSDs
 (SLIST macros first appeared in 4.4BSD).
 .SH BUGS
+The macro
+.BR SLIST_FOREACH ()
+doesn't allow
+.I var
+to be removed or freed within the loop,
+as it would interfere with the traversal.
+The macro
+.BR SLIST_FOREACH_SAFE (),
+which is present on the BSDs but is not present in glibc,
+fixes this limitation by allowing
+.I var
+to safely be removed from the list and freed from within the loop
+without interfering with the traversal.
 .SH EXAMPLES
 .EX
 #include <stddef.h>
@@ -321,3 +351,5 @@ main(void)
 }
 .EE
 .SH SEE ALSO
+.BR insque (3),
+.BR queue (3)