utils: add must_concat helper

src/lxc/utils.c

@@ -2426,6 +2426,30 @@ int run_command(char *buf, size_t buf_size, int (*child_fn)(void *), void *args)
 	return fret;
 }
 
+char *must_concat(const char *first, ...)
+{
+	va_list args;
+	char *cur, *dest;
+	size_t cur_len, it_len;
+
+	dest = must_copy_string(first);
+	cur_len = it_len = strlen(first);
+
+	va_start(args, first);
+	while ((cur = va_arg(args, char *)) != NULL) {
+		it_len = strlen(cur);
+
+		dest = must_realloc(dest, cur_len + it_len + 1);
+
+		(void)memcpy(dest + cur_len, cur, it_len);
+		cur_len += it_len;
+	}
+	va_end(args);
+
+	dest[cur_len] = 0;
+	return dest;
+}
+
 char *must_make_path(const char *first, ...)
 {
 	va_list args;

src/lxc/utils.h

@@ -567,6 +567,7 @@ extern int run_command(char *buf, size_t buf_size, int (*child_fn)(void *),
 /* Concatenate all passed-in strings into one path. Do not fail. If any piece
  * is not prefixed with '/', add a '/'.
  */
+__attribute__((sentinel)) extern char *must_concat(const char *first, ...);
 __attribute__((sentinel)) extern char *must_make_path(const char *first, ...);
 __attribute__((sentinel)) extern char *must_append_path(char *first, ...);