windows: work around libxml2 xmlCleanupParser

Closes #2241

ext/nokogiri/nokogiri.c

@@ -196,7 +196,26 @@ Init_nokogiri()
   rb_const_set(mNokogiri, rb_intern("OTHER_LIBRARY_VERSIONS"), NOKOGIRI_STR_NEW2(NOKOGIRI_OTHER_LIBRARY_VERSIONS));
 #endif
 
+#if defined(_WIN32) && !defined(NOKOGIRI_PACKAGED_LIBRARIES)
+  /*
+   *  We choose *not* to do use Ruby's memory management functions with windows DLLs because of this
+   *  issue in libxml 2.9.12:
+   *
+   *    https://github.com/sparklemotion/nokogiri/issues/2241
+   *
+   *  If the atexit() issue gets fixed in a future version of libxml2, then we may be able to skip
+   *  this config only for the specific libxml2 versions 2.9.12.
+   *
+   *  Alternatively, now that Ruby has a generational GC, it might be OK to let libxml2 use its
+   *  default memory management functions (recall that this config was introduced to reduce memory
+   *  bloat and allow Ruby to GC more often); but we should *really* test with production workloads
+   *  before making that kind of a potentially-invasive change.
+   */
+  rb_const_set(mNokogiri, rb_intern("LIBXML_MEMORY_MANAGEMENT"), NOKOGIRI_STR_NEW2("default"));
+#else
+  rb_const_set(mNokogiri, rb_intern("LIBXML_MEMORY_MANAGEMENT"), NOKOGIRI_STR_NEW2("ruby"));
   xmlMemSetup((xmlFreeFunc)ruby_xfree, (xmlMallocFunc)ruby_xmalloc, (xmlReallocFunc)ruby_xrealloc, ruby_strdup);
+#endif
 
   xmlInitParser();
 

lib/nokogiri/version/info.rb

@@ -137,6 +137,7 @@ def to_hash
             else
               libxml["source"] = "system"
             end
+            libxml["memory_management"] = Nokogiri::LIBXML_MEMORY_MANAGEMENT
             libxml["iconv_enabled"] = libxml2_has_iconv?
             libxml["compiled"] = compiled_libxml_version.to_s
             libxml["loaded"] = loaded_libxml_version.to_s