socket.c: unlimited size hostname

* ext/socket/socket.c (sock_gethostname): support unlimited size
  hostname.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53677 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

2 files changed, 25 insertions, 6 deletions

diff --git a/ChangeLog b/ChangeLog
index e5e337bf57..30998cd327 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Jan 28 17:31:43 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/socket/socket.c (sock_gethostname): support unlimited size
+	  hostname.
+
 Wed Jan 27 21:03:45 2016  SHIBATA Hiroshi  <hsbt@ruby-lang.org>
 
 	* test/-ext-/string/test_capacity.rb: Added missing library.
diff --git a/ext/socket/socket.c b/ext/socket/socket.c
index dcf2498daa..542cd02ed6 100644
--- a/ext/socket/socket.c
+++ b/ext/socket/socket.c
@@ -893,13 +893,27 @@ sock_gethostname(VALUE obj)
 #  define RUBY_MAX_HOST_NAME_LEN 1024
 #endif
 
-    char buf[RUBY_MAX_HOST_NAME_LEN+1];
+    long len = RUBY_MAX_HOST_NAME_LEN;
+    VALUE name;
 
-    if (gethostname(buf, (int)sizeof buf - 1) < 0)
-	rb_sys_fail("gethostname(3)");
-
-    buf[sizeof buf - 1] = '\0';
-    return rb_str_new2(buf);
+    name = rb_str_new(0, len);
+    while (gethostname(RSTRING_PTR(name), len) < 0) {
+	int e = errno;
+	switch (e) {
+	  case ENAMETOOLONG:
+#ifdef __linux__
+	  case EINVAL:
+	    /* glibc before version 2.1 uses EINVAL instead of ENAMETOOLONG */
+#endif
+	    break;
+	  default:
+	    rb_syserr_fail(e, "gethostname(3)");
+	}
+	rb_str_modify_expand(name, len);
+	len += len;
+    }
+    rb_str_resize(name, strlen(RSTRING_PTR(name)));
+    return name;
 }
 #else
 #ifdef HAVE_UNAME