[-] Workaround for mxml 2.10 memleak

2.10's mxmlDelete memleaks, and mxml is used in many parts of forked-daapd. So
to avoid that we ship upstream's fixed version of mxmlDelete and use that.

configure.ac

@@ -113,10 +113,16 @@ FORK_FUNC_REQUIRE([COMMON], [GNU libunistring], [LIBUNISTRING], [unistring],
 
 FORK_MODULES_CHECK([FORKED], [ZLIB], [zlib], [deflate], [zlib.h])
 FORK_MODULES_CHECK([FORKED], [CONFUSE], [libconfuse >= 3.0], [cfg_init], [confuse.h])
-FORK_MODULES_CHECK([FORKED], [MINIXML], [mxml], [mxmlNewElement], [mxml.h],
-	[AC_CHECK_FUNCS([mxmlGetOpaque] [mxmlGetText] [mxmlGetType] [mxmlGetFirstChild])])
 
-dnl SQLite3 requires extra checks
+FORK_MODULES_CHECK([FORKED], [MINIXML], [mxml],
+	[mxmlNewElement], [mxml.h],
+	[dnl check for old versions which have a serious memleak
+	 AC_CHECK_FUNCS([mxmlGetOpaque] [mxmlGetText] [mxmlGetType] [mxmlGetFirstChild])
+	 PKG_CHECK_EXISTS([libevent >= 2.11], [],
+		[AC_DEFINE([HAVE_MXML_OLD], 1,
+			[Define to 1 if you have libmxml < 2.11)])])
+	])
+
 FORK_MODULES_CHECK([COMMON], [SQLITE3], [sqlite3 >= 3.5.0],
 	[sqlite3_initialize], [sqlite3.h],
 	[dnl Check that SQLite3 has the unlock notify API built-in
@@ -137,7 +143,6 @@ FORK_MODULES_CHECK([COMMON], [SQLITE3], [sqlite3 >= 3.5.0],
 		[AC_MSG_RESULT([[runtime will tell]])])
 	])
 
-dnl libevent2 requires version checks
 FORK_MODULES_CHECK([FORKED], [LIBEVENT], [libevent >= 2],
 	[event_base_new], [event2/event.h],
 	[dnl check for old version
@@ -146,7 +151,6 @@ FORK_MODULES_CHECK([FORKED], [LIBEVENT], [libevent >= 2],
 			[Define to 1 if you have libevent 2 (<2.1.4)])])
 	])
 
-dnl json-c version checks
 FORK_MODULES_CHECK([FORKED], [JSON_C], [json-c],
 	[json_tokener_parse], [json.h],
 	[dnl check for old version
@@ -155,7 +159,6 @@ FORK_MODULES_CHECK([FORKED], [JSON_C], [json-c],
 			[Define to 1 if you have json-c < 0.11])])
 	])
 
-dnl antlr version checks
 FORK_FUNC_REQUIRE([FORKED], [ANTLR3 C runtime], [ANTLR3C], [antlr3c],
 	[antlr3BaseRecognizerNew], [antlr3.h],
 	[AC_CHECK_FUNC([[antlr3NewAsciiStringInPlaceStream]],

src/httpd_rsp.c

@@ -30,7 +30,7 @@
 #include <sys/types.h>
 #include <limits.h>
 
-#include <mxml.h>
+#include "mxml-compat.h"
 
 #include "httpd_rsp.h"
 #include "logger.h"

src/inputs/pipe.c

@@ -53,7 +53,8 @@
 
 #include <event2/event.h>
 #include <event2/buffer.h>
-#include <mxml.h>
+
+#include "mxml-compat.h"
 
 #include "input.h"
 #include "misc.h"
@@ -64,7 +65,6 @@
 #include "player.h"
 #include "worker.h"
 #include "commands.h"
-#include "mxml-compat.h"
 
 // Maximum number of pipes to watch for data
 #define PIPE_MAX_WATCH 4

src/lastfm.c

@@ -31,7 +31,6 @@
 #include <stdbool.h>
 
 #include <gcrypt.h>
-#include <mxml.h>
 #include <event2/buffer.h>
 #include <event2/http.h>
 

src/library/rssscanner.c

@@ -39,7 +39,7 @@
 #include <time.h>
 
 #include <event2/buffer.h>
-#include <mxml.h>
+
 #include "mxml-compat.h"
 
 #include "conffile.h"

src/mxml-compat.h

@@ -1,6 +1,96 @@
 #ifndef __MXML_COMPAT_H__
 #define __MXML_COMPAT_H__
 
+// mxml 2.10 has a memory leak in mxmlDelete, see https://github.com/michaelrsweet/mxml/issues/183
+// - and since this is the version in Ubuntu 18.04 LTS and Raspian Stretch, we
+// fix it by including a fixed mxmlDelete here. It should be removed once the
+// major distros no longer have 2.10. The below code is msweet's fixed mxml.
+#ifndef HAVE_MXML_OLD
+# include <mxml.h>
+#else
+// Trick to undefine mxml.h's mxmlDelete
+#define mxmlDelete mxmlDelete_memleak
+# include <mxml.h>
+#undef mxmlDelete
+
+static void
+compat_mxml_free(mxml_node_t *node)
+{
+  int i;
+
+  switch (node->type)
+  {
+    case MXML_ELEMENT :
+        if (node->value.element.name)
+	  free(node->value.element.name);
+
+	if (node->value.element.num_attrs)
+	{
+	  for (i = 0; i < node->value.element.num_attrs; i ++)
+	  {
+	    if (node->value.element.attrs[i].name)
+	      free(node->value.element.attrs[i].name);
+	    if (node->value.element.attrs[i].value)
+	      free(node->value.element.attrs[i].value);
+	  }
+
+          free(node->value.element.attrs);
+	}
+        break;
+    case MXML_INTEGER :
+        break;
+    case MXML_OPAQUE :
+        if (node->value.opaque)
+	  free(node->value.opaque);
+        break;
+    case MXML_REAL :
+        break;
+    case MXML_TEXT :
+        if (node->value.text.string)
+	  free(node->value.text.string);
+        break;
+    case MXML_CUSTOM :
+        if (node->value.custom.data &&
+	    node->value.custom.destroy)
+	  (*(node->value.custom.destroy))(node->value.custom.data);
+	break;
+    default :
+        break;
+  }
+
+  free(node);
+}
+
+static void
+mxmlDelete(mxml_node_t *node)
+{
+  mxml_node_t	*current,
+		*next;
+
+  if (!node)
+    return;
+
+  mxmlRemove(node);
+  for (current = node->child; current; current = next)
+  {
+    if ((next = current->child) != NULL)
+    {
+      current->child = NULL;
+      continue;
+    }
+
+    if ((next = current->next) == NULL)
+    {
+      if ((next = current->parent) == node)
+        next = NULL;
+    }
+    compat_mxml_free(current);
+  }
+
+  compat_mxml_free(node);
+}
+#endif
+
 /* For compability with mxml 2.6 */
 #ifndef HAVE_MXMLGETTEXT
 __attribute__((unused)) static const char *			/* O - Text string or NULL */