Make the threatened fts(3) ABI fix. FTSENT now avoids the use of the struct

hack, thereby allowing future extensions to the structure (e.g., for extended
attributes) without rebreaking the ABI.  FTSENT now contains a pointer to the
parent stream, which fts_compar() can then take advantage of, avoiding the
undefined behavior previously warned about.  As a consequence of this change,
the prototype of the comparison function passed to fts_open() has changed
to reflect the required amount of constness for its use.  All callers in the
tree are updated to use the correct prototype.

Comparison functions can now make use of the new parent pointer to access
the new stream-specific private data pointer, which is intended to assist
creation of reentrant library routines which use fts(3) internally.

Not objected to in spirit by: -arch

1 files changed, 67 insertions, 13 deletions

diff --git a/lib/libc/gen/fts.c b/lib/libc/gen/fts.c
index 6220dc6..7a0b068 100644
--- a/lib/libc/gen/fts.c
+++ b/lib/libc/gen/fts.c
@@ -81,7 +81,7 @@ FTS *
 fts_open(argv, options, compar)
 	char * const *argv;
 	int options;
-	int (*compar)(const FTSENT **, const FTSENT **);
+	int (*compar)(const FTSENT * const *, const FTSENT * const *);
 {
 	FTS *sp;
 	FTSENT *p, *root;
@@ -96,7 +96,7 @@ fts_open(argv, options, compar)
 	}
 
 	/* Allocate/initialize the stream */
-	if ((sp = malloc((u_int)sizeof(FTS))) == NULL)
+	if ((sp = malloc(sizeof(FTS))) == NULL)
 		return (NULL);
 	memset(sp, 0, sizeof(FTS));
 	sp->fts_compar = compar;
@@ -547,6 +547,34 @@ fts_children(sp, instr)
 	return (sp->fts_child);
 }
 
+#ifndef fts_get_clientptr
+#error "fts_get_clientptr not defined"
+#endif
+
+void *
+(fts_get_clientptr)(FTS *sp)
+{
+
+	return (fts_get_clientptr(sp));
+}
+
+#ifndef fts_get_stream
+#error "fts_get_stream not defined"
+#endif
+
+FTS *
+(fts_get_stream)(FTSENT *p)
+{
+	return (fts_get_stream(p));
+}
+
+void
+fts_set_clientptr(FTS *sp, void *clientptr)
+{
+
+	sp->fts_clientptr = clientptr;
+}
+
 /*
  * This is the tricky part -- do not casually change *anything* in here.  The
  * idea is to build the linked list of entries that are used by fts_children
@@ -907,6 +935,21 @@ err:		memset(sbp, 0, sizeof(struct stat));
 	return (FTS_DEFAULT);
 }
 
+/*
+ * The comparison function takes pointers to pointers to FTSENT structures.
+ * Qsort wants a comparison function that takes pointers to void.
+ * (Both with appropriate levels of const-poisoning, of course!)
+ * Use a trampoline function to deal with the difference.
+ */
+static int
+fts_compar(const void *a, const void *b)
+{
+	FTS *parent;
+
+	parent = (*(const FTSENT * const *)a)->fts_fts;
+	return (*parent->fts_compar)(a, b);
+}
+
 static FTSENT *
 fts_sort(sp, head, nitems)
 	FTS *sp;
@@ -932,7 +975,7 @@ fts_sort(sp, head, nitems)
 	}
 	for (ap = sp->fts_array, p = head; p; p = p->fts_link)
 		*ap++ = p;
-	qsort((void *)sp->fts_array, nitems, sizeof(FTSENT *), sp->fts_compar);
+	qsort(sp->fts_array, nitems, sizeof(FTSENT *), fts_compar);
 	for (head = *(ap = sp->fts_array); --nitems; ++ap)
 		ap[0]->fts_link = ap[1];
 	ap[0]->fts_link = NULL;
@@ -948,26 +991,36 @@ fts_alloc(sp, name, namelen)
 	FTSENT *p;
 	size_t len;
 
+	struct ftsent_withstat {
+		FTSENT	ent;
+		struct	stat statbuf;
+	};
+
 	/*
 	 * The file name is a variable length array and no stat structure is
 	 * necessary if the user has set the nostat bit.  Allocate the FTSENT
 	 * structure, the file name and the stat structure in one chunk, but
-	 * be careful that the stat structure is reasonably aligned.  Since the
-	 * fts_name field is declared to be of size 1, the fts_name pointer is
-	 * namelen + 2 before the first possible address of the stat structure.
+	 * be careful that the stat structure is reasonably aligned.
 	 */
-	len = sizeof(FTSENT) + namelen;
-	if (!ISSET(FTS_NOSTAT))
-		len += sizeof(struct stat) + ALIGNBYTES;
+	if (ISSET(FTS_NOSTAT))
+		len = sizeof(FTSENT) + namelen + 1;
+	else
+		len = sizeof(struct ftsent_withstat) + namelen + 1;
+
 	if ((p = malloc(len)) == NULL)
 		return (NULL);
 
+	if (ISSET(FTS_NOSTAT)) {
+		p->fts_name = (char *)(p + 1);
+		p->fts_statp = NULL;
+	} else {
+		p->fts_name = (char *)((struct ftsent_withstat *)p + 1);
+		p->fts_statp = &((struct ftsent_withstat *)p)->statbuf;
+	}
+
 	/* Copy the name and guarantee NUL termination. */
-	memmove(p->fts_name, name, namelen);
+	memcpy(p->fts_name, name, namelen);
 	p->fts_name[namelen] = '\0';
-
-	if (!ISSET(FTS_NOSTAT))
-		p->fts_statp = (struct stat *)ALIGN(p->fts_name + namelen + 2);
 	p->fts_namelen = namelen;
 	p->fts_path = sp->fts_path;
 	p->fts_errno = 0;
@@ -975,6 +1028,7 @@ fts_alloc(sp, name, namelen)
 	p->fts_instr = FTS_NOINSTR;
 	p->fts_number = 0;
 	p->fts_pointer = NULL;
+	p->fts_fts = sp;
 	return (p);
 }