etc.c: retry with allocated string buffer

* ext/etc/etc.c (etc_systmpdir): retry with allocated string
  buffer if static buffer size is not enough.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55262 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/etc/etc.c

@@ -664,9 +664,15 @@ etc_systmpdir(void)
     if (len > 0) {
 	tmpstr = path;
 	tmplen = len - 1;
+	if (len > sizeof(path)) tmpstr = 0;
     }
 # endif
     tmpdir = rb_filesystem_str_new(tmpstr, tmplen);
+# if defined _CS_DARWIN_USER_TEMP_DIR
+    if (!tmpstr) {
+	confstr(_CS_DARWIN_USER_TEMP_DIR, RSTRING_PTR(tmpdir), len);
+    }
+# endif
 #endif
     FL_UNSET(tmpdir, FL_TAINT);
     return tmpdir;