tree-wide: make format_ifname() or friends return negative errno on failure

Also,
- drop unnecessary +1 from buffer size, as IF_NAMESIZE or IFNAMSIZ
  includes the nul at the end.
- format_ifname() does not update buffer on failure,
- introduces format_ifname_alloc(), FORMAT_IFNAME(), and their friends.

1 files changed, 16 insertions, 3 deletions

diff --git a/src/basic/format-util.h b/src/basic/format-util.h
index 579f231897..7dd422b987 100644
--- a/src/basic/format-util.h
+++ b/src/basic/format-util.h
@@ -61,11 +61,24 @@ typedef enum {
         FORMAT_IFNAME_IFINDEX_WITH_PERCENT = (1 << 1) | FORMAT_IFNAME_IFINDEX,
 } FormatIfnameFlag;
 
-char *format_ifname_full(int ifindex, char buf[static IF_NAMESIZE + 1], FormatIfnameFlag flag);
-static inline char *format_ifname(int ifindex, char buf[static IF_NAMESIZE + 1]) {
-        return format_ifname_full(ifindex, buf, 0);
+int format_ifname_full(int ifindex, FormatIfnameFlag flag, char buf[static IF_NAMESIZE]);
+int format_ifname_full_alloc(int ifindex, FormatIfnameFlag flag, char **ret);
+
+static inline int format_ifname(int ifindex, char buf[static IF_NAMESIZE]) {
+        return format_ifname_full(ifindex, 0, buf);
+}
+static inline int format_ifname_alloc(int ifindex, char **ret) {
+        return format_ifname_full_alloc(ifindex, 0, ret);
 }
 
+static inline char *_format_ifname_full(int ifindex, FormatIfnameFlag flag, char buf[static IF_NAMESIZE]) {
+        (void) format_ifname_full(ifindex, flag, buf);
+        return buf;
+}
+
+#define FORMAT_IFNAME_FULL(index, flag) _format_ifname_full(index, flag, (char[IF_NAMESIZE]){})
+#define FORMAT_IFNAME(index) _format_ifname_full(index, 0, (char[IF_NAMESIZE]){})
+
 typedef enum {
         FORMAT_BYTES_USE_IEC     = 1 << 0,
         FORMAT_BYTES_BELOW_POINT = 1 << 1,