diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
index eab0f17a..205cb04b 100644
--- a/expat/lib/xmlparse.c
+++ b/expat/lib/xmlparse.c
@@ -3046,7 +3046,7 @@ doContent(XML_Parser parser, int startTagLevel, const ENCODING *enc,
             /* don't need to check for space - already done in storeAtts() */
             while (*localPart)
               *uri++ = *localPart++;
-            prefix = (XML_Char *)tag->name.prefix;
+            prefix = tag->name.prefix;
             if (parser->m_ns_triplets && prefix) {
               *uri++ = parser->m_namespaceSeparator;
               while (*prefix)
@@ -3142,8 +3142,8 @@ doContent(XML_Parser parser, int startTagLevel, const ENCODING *enc,
               (int)(dataPtr - (ICHAR *)parser->m_dataBuf));
         } else
           parser->m_characterDataHandler(
-              parser->m_handlerArg, (XML_Char *)s,
-              (int)((XML_Char *)end - (XML_Char *)s));
+              parser->m_handlerArg, (const XML_Char *)s,
+              (int)((const XML_Char *)end - (const XML_Char *)s));
       } else if (parser->m_defaultHandler)
         reportDefault(parser, enc, s, end);
       /* We are at the end of the final buffer, should we check for
@@ -3176,8 +3176,8 @@ doContent(XML_Parser parser, int startTagLevel, const ENCODING *enc,
             *eventPP = s;
           }
         } else
-          charDataHandler(parser->m_handlerArg, (XML_Char *)s,
-                          (int)((XML_Char *)next - (XML_Char *)s));
+          charDataHandler(parser->m_handlerArg, (const XML_Char *)s,
+                          (int)((const XML_Char *)next - (const XML_Char *)s));
       } else if (parser->m_defaultHandler)
         reportDefault(parser, enc, s, next);
     } break;
@@ -4092,8 +4092,8 @@ doCdataSection(XML_Parser parser, const ENCODING *enc, const char **startPtr,
             *eventPP = s;
           }
         } else
-          charDataHandler(parser->m_handlerArg, (XML_Char *)s,
-                          (int)((XML_Char *)next - (XML_Char *)s));
+          charDataHandler(parser->m_handlerArg, (const XML_Char *)s,
+                          (int)((const XML_Char *)next - (const XML_Char *)s));
       } else if (parser->m_defaultHandler)
         reportDefault(parser, enc, s, next);
     } break;
@@ -6376,8 +6376,9 @@ reportDefault(XML_Parser parser, const ENCODING *enc, const char *s,
     } while ((convert_res != XML_CONVERT_COMPLETED)
              && (convert_res != XML_CONVERT_INPUT_INCOMPLETE));
   } else
-    parser->m_defaultHandler(parser->m_handlerArg, (XML_Char *)s,
-                             (int)((XML_Char *)end - (XML_Char *)s));
+    parser->m_defaultHandler(
+        parser->m_handlerArg, (const XML_Char *)s,
+        (int)((const XML_Char *)end - (const XML_Char *)s));
 }
 
 static int
@@ -7221,7 +7222,7 @@ poolAppend(STRING_POOL *pool, const ENCODING *enc, const char *ptr,
     return NULL;
   for (;;) {
     const enum XML_Convert_Result convert_res = XmlConvert(
-        enc, &ptr, end, (ICHAR **)&(pool->ptr), (ICHAR *)pool->end);
+        enc, &ptr, end, (ICHAR **)&(pool->ptr), (const ICHAR *)pool->end);
     if ((convert_res == XML_CONVERT_COMPLETED)
         || (convert_res == XML_CONVERT_INPUT_INCOMPLETE))
       break;
@@ -8394,7 +8395,7 @@ getDebugLevel(const char *variableName, unsigned long defaultDebugLevel) {
   const char *const value = valueOrNull;
 
   errno = 0;
-  char *afterValue = (char *)value;
+  char *afterValue = NULL;
   unsigned long debugLevel = strtoul(value, &afterValue, 10);
   if ((errno != 0) || (afterValue == value) || (afterValue[0] != '\0')) {
     errno = 0;
diff --git a/expat/lib/xmltok.c b/expat/lib/xmltok.c
index c4627935..22821cb8 100644
--- a/expat/lib/xmltok.c
+++ b/expat/lib/xmltok.c
@@ -243,7 +243,7 @@ static int FASTCALL checkCharRefNumber(int);
 #endif
 
 #define SB_BYTE_TYPE(enc, p)                                                   \
-  (((struct normal_encoding *)(enc))->type[(unsigned char)*(p)])
+  (((const struct normal_encoding *)(enc))->type[(unsigned char)*(p)])
 
 #ifdef XML_MIN_SIZE
 static int PTRFASTCALL
@@ -407,7 +407,7 @@ utf8_toUtf16(const ENCODING *enc, const char **fromP, const char *fromLim,
   unsigned short *to = *toP;
   const char *from = *fromP;
   while (from < fromLim && to < toLim) {
-    switch (((struct normal_encoding *)enc)->type[(unsigned char)*from]) {
+    switch (SB_BYTE_TYPE(enc, from)) {
     case BT_LEAD2:
       if (fromLim - from < 2) {
         res = XML_CONVERT_INPUT_INCOMPLETE;
@@ -734,8 +734,7 @@ DEFINE_UTF16_TO_UTF16(big2_)
 #undef GET_HI
 
 #define LITTLE2_BYTE_TYPE(enc, p)                                              \
-  ((p)[1] == 0 ? ((struct normal_encoding *)(enc))->type[(unsigned char)*(p)]  \
-               : unicode_byte_type((p)[1], (p)[0]))
+  ((p)[1] == 0 ? SB_BYTE_TYPE(enc, p) : unicode_byte_type((p)[1], (p)[0]))
 #define LITTLE2_BYTE_TO_ASCII(p) ((p)[1] == 0 ? (p)[0] : -1)
 #define LITTLE2_CHAR_MATCHES(p, c) ((p)[1] == 0 && (p)[0] == (c))
 #define LITTLE2_IS_NAME_CHAR_MINBPC(p)                                         \
@@ -868,9 +867,7 @@ static const struct normal_encoding internal_little2_encoding
 #endif
 
 #define BIG2_BYTE_TYPE(enc, p)                                                 \
-  ((p)[0] == 0                                                                 \
-       ? ((struct normal_encoding *)(enc))->type[(unsigned char)(p)[1]]        \
-       : unicode_byte_type((p)[0], (p)[1]))
+  ((p)[0] == 0 ? SB_BYTE_TYPE(enc, p + 1) : unicode_byte_type((p)[0], (p)[1]))
 #define BIG2_BYTE_TO_ASCII(p) ((p)[0] == 0 ? (p)[1] : -1)
 #define BIG2_CHAR_MATCHES(p, c) ((p)[0] == 0 && (p)[1] == (c))
 #define BIG2_IS_NAME_CHAR_MINBPC(p)                                            \
diff --git a/expat/tests/runtests.c b/expat/tests/runtests.c
index 66409f2d..99a09c5b 100644
--- a/expat/tests/runtests.c
+++ b/expat/tests/runtests.c
@@ -3616,7 +3616,7 @@ END_TEST
 
 /* Test user parameter settings */
 /* Variable holding the expected handler userData */
-static void *handler_data = NULL;
+static const void *handler_data = NULL;
 /* Count of the number of times the comment handler has been invoked */
 static int comment_count = 0;
 /* Count of the number of skipped entities */
@@ -3768,7 +3768,7 @@ START_TEST(test_ext_entity_ref_parameter) {
    * what NULL would cause to be passed.
    */
   XML_SetExternalEntityRefHandlerArg(g_parser, (void *)text);
-  handler_data = (void *)text;
+  handler_data = text;
   if (_XML_Parse_SINGLE_BYTES(g_parser, text, (int)strlen(text), XML_TRUE)
       == XML_STATUS_ERROR)
     xml_failure(g_parser);
@@ -3778,7 +3778,7 @@ START_TEST(test_ext_entity_ref_parameter) {
   XML_SetParamEntityParsing(g_parser, XML_PARAM_ENTITY_PARSING_ALWAYS);
   XML_SetExternalEntityRefHandler(g_parser, external_entity_ref_param_checker);
   XML_SetExternalEntityRefHandlerArg(g_parser, NULL);
-  handler_data = (void *)g_parser;
+  handler_data = g_parser;
   if (_XML_Parse_SINGLE_BYTES(g_parser, text, (int)strlen(text), XML_TRUE)
       == XML_STATUS_ERROR)
     xml_failure(g_parser);
diff --git a/expat/xmlwf/xmlwf.c b/expat/xmlwf/xmlwf.c
index 499825ed..7fba67d9 100644
--- a/expat/xmlwf/xmlwf.c
+++ b/expat/xmlwf/xmlwf.c
@@ -178,7 +178,7 @@ is equivalent to lexicographically comparing based on the character number. */
 
 static int
 attcmp(const void *att1, const void *att2) {
-  return tcscmp(*(const XML_Char **)att1, *(const XML_Char **)att2);
+  return tcscmp(*(const XML_Char *const *)att1, *(const XML_Char *const *)att2);
 }
 
 static void XMLCALL
@@ -215,8 +215,8 @@ endElement(void *userData, const XML_Char *name) {
 
 static int
 nsattcmp(const void *p1, const void *p2) {
-  const XML_Char *att1 = *(const XML_Char **)p1;
-  const XML_Char *att2 = *(const XML_Char **)p2;
+  const XML_Char *att1 = *(const XML_Char *const *)p1;
+  const XML_Char *att2 = *(const XML_Char *const *)p2;
   int sep1 = (tcsrchr(att1, NSSEP) != 0);
   int sep2 = (tcsrchr(att2, NSSEP) != 0);
   if (sep1 != sep2)
@@ -370,8 +370,8 @@ xcscmp(const XML_Char *xs, const XML_Char *xt) {
 
 static int
 notationCmp(const void *a, const void *b) {
-  const NotationList *const n1 = *(NotationList **)a;
-  const NotationList *const n2 = *(NotationList **)b;
+  const NotationList *const n1 = *(const NotationList *const *)a;
+  const NotationList *const n2 = *(const NotationList *const *)b;
 
   return xcscmp(n1->notationName, n2->notationName);
 }
@@ -1051,7 +1051,7 @@ tmain(int argc, XML_Char **argv) {
       XMLWF_SHIFT_ARG_INTO(valueText, argc, argv, i, j);
 
       errno = 0;
-      XML_Char *afterValueText = (XML_Char *)valueText;
+      XML_Char *afterValueText = NULL;
       attackMaximumAmplification = tcstof(valueText, &afterValueText);
       if ((errno != 0) || (afterValueText[0] != T('\0'))
           || isnan(attackMaximumAmplification)