Fix #588 and #591

- Apply @geoffmcl's patches and tested.

src/attrs.c

@@ -1517,15 +1517,16 @@ static void CheckLowerCaseAttrValue( TidyDocImpl* doc, Node *node, AttVal *attva
     }
 }
 
-/* methods for checking value of a specific attribute */
-#ifdef _WIN32
+/* Issue #588 - use simple macros only!
+   Seems 'isalnum(c)' is undefined and can
+   cause an assert or a SIGSEGV in some libraries
+   if 'c' is not EOF, or in the range 0 to 0xff,
+   so avoid using it.
+*/
 #define ISUPPER(a) ((a >= 'A') && (a <= 'Z'))
 #define ISLOWER(a) ((a >= 'a') && (a <= 'z'))
 #define ISNUMERIC(a) ((a >= '0') && (a <= '9'))
 #define ISALNUM(a) (ISUPPER(a) || ISLOWER(a) || ISNUMERIC(a))
-#else
-#define ISALNUM(a)  isalnum(a)
-#endif
 
 static Bool IsURLCodePoint( ctmbstr p, uint *increment )
 {

src/clean.c

@@ -1902,7 +1902,9 @@ void TY_(CleanWord2000)( TidyDocImpl* doc, Node *node)
             attval = node->attributes;
             while ( attval ) {
                 next_attr = attval->next;
-                if ( strcmp(attval->attribute, "xmlns") != 0 )
+
+                /* Issue #591 - take care of a NULL attribute, too. */
+                if ( !attval->attribute || ( strcmp(attval->attribute, "xmlns") != 0 ))
                     TY_(ReportAttrError)(doc, node, attval, PROPRIETARY_ATTRIBUTE);
                 attval = next_attr;
             }