bsdcpio: ignore ENOENT for get{grg,pwu}id()

Starting from glibc 2.25, those calls set errno to ENOENT
when the requested id is not found.  So let's stop throwing
warning in this expected case.

Also rework the api of lookup_* functions so it is guaranteed that
lookup_name never returns NULL (unless ENOMEM).

1 files changed, 22 insertions, 24 deletions

diff --git a/cpio/cpio.c b/cpio/cpio.c
index 6c20ee68..59619601 100644
--- a/cpio/cpio.c
+++ b/cpio/cpio.c
@@ -1344,23 +1344,23 @@ lookup_name(struct cpio *cpio, struct name_cache **name_cache_variable,
 		cache->cache[slot].name = NULL;
 	}
 
-	if (lookup_fn(cpio, &name, id) == 0) {
-		if (name == NULL || name[0] == '\0') {
-			/* If lookup failed, format it as a number. */
-			snprintf(asnum, sizeof(asnum), "%u", (unsigned)id);
-			name = asnum;
-		}
-		cache->cache[slot].name = strdup(name);
-		if (cache->cache[slot].name != NULL) {
-			cache->cache[slot].id = id;
-			return (cache->cache[slot].name);
-		}
-		/*
-		 * Conveniently, NULL marks an empty slot, so
-		 * if the strdup() fails, we've just failed to
-		 * cache it.  No recovery necessary.
-		 */
+	if (lookup_fn(cpio, &name, id)) {
+		/* If lookup failed, format it as a number. */
+		snprintf(asnum, sizeof(asnum), "%u", (unsigned)id);
+		name = asnum;
+	}
+
+	cache->cache[slot].name = strdup(name);
+	if (cache->cache[slot].name != NULL) {
+		cache->cache[slot].id = id;
+		return (cache->cache[slot].name);
 	}
+
+	/*
+	 * Conveniently, NULL marks an empty slot, so
+	 * if the strdup() fails, we've just failed to
+	 * cache it.  No recovery necessary.
+	 */
 	return (NULL);
 }
 
@@ -1381,15 +1381,14 @@ lookup_uname_helper(struct cpio *cpio, const char **name, id_t id)
 	errno = 0;
 	pwent = getpwuid((uid_t)id);
 	if (pwent == NULL) {
-		*name = NULL;
-		if (errno != 0 && errno != ENOENT)
+		if (errno && errno != ENOENT)
 			lafe_warnc(errno, "getpwuid(%s) failed",
 			    cpio_i64toa((int64_t)id));
-		return (errno);
+		return 1;
 	}
 
 	*name = pwent->pw_name;
-	return (0);
+	return 0;
 }
 
 static const char *
@@ -1409,15 +1408,14 @@ lookup_gname_helper(struct cpio *cpio, const char **name, id_t id)
 	errno = 0;
 	grent = getgrgid((gid_t)id);
 	if (grent == NULL) {
-		*name = NULL;
-		if (errno != 0)
+		if (errno && errno != ENOENT)
 			lafe_warnc(errno, "getgrgid(%s) failed",
 			    cpio_i64toa((int64_t)id));
-		return (errno);
+		return 1;
 	}
 
 	*name = grent->gr_name;
-	return (0);
+	return 0;
 }
 
 /*