x509name: refactor OpenSSL::X509::Name#to_s

Extract the body into a function in preparation for adding #to_utf8.

Also a potential memory leak is fixed: the GetX509Name() macro can
raise TypeError.

(cherry picked from commit 5896473)

ext/openssl/ossl_x509name.c

@@ -249,6 +249,23 @@ ossl_x509name_to_s_old(VALUE self)
     return str;
 }
 
+static VALUE
+x509name_print(VALUE self, unsigned long iflag)
+{
+    X509_NAME *name;
+    BIO *out;
+
+    GetX509Name(self, name);
+    out = BIO_new(BIO_s_mem());
+    if (!out)
+	ossl_raise(eX509NameError, NULL);
+    if (!X509_NAME_print_ex(out, name, 0, iflag)) {
+	BIO_free(out);
+	ossl_raise(eX509NameError, "X509_NAME_print_ex");
+    }
+    return ossl_membio2str(out);
+}
+
 /*
  * call-seq:
  *    name.to_s => string
@@ -264,25 +281,12 @@ ossl_x509name_to_s_old(VALUE self)
 static VALUE
 ossl_x509name_to_s(int argc, VALUE *argv, VALUE self)
 {
-    X509_NAME *name;
-    VALUE flag, str;
-    BIO *out;
-    unsigned long iflag;
-
-    rb_scan_args(argc, argv, "01", &flag);
-    if (NIL_P(flag))
+    rb_check_arity(argc, 0, 1);
+    /* name.to_s(nil) was allowed */
+    if (!argc || NIL_P(argv[0]))
 	return ossl_x509name_to_s_old(self);
-    else iflag = NUM2ULONG(flag);
-    if (!(out = BIO_new(BIO_s_mem())))
-	ossl_raise(eX509NameError, NULL);
-    GetX509Name(self, name);
-    if (!X509_NAME_print_ex(out, name, 0, iflag)){
-	BIO_free(out);
-	ossl_raise(eX509NameError, NULL);
-    }
-    str = ossl_membio2str(out);
-
-    return str;
+    else
+	return x509name_print(self, NUM2ULONG(argv[0]));
 }
 
 /*