Apply unconstify() in more places

Discussion: https://www.postgresql.org/message-id/08adbe4e-38f8-2c73-55f0-591392371687%402ndquadrant.com

src/backend/utils/adt/json.c

@@ -207,12 +207,12 @@ IsValidJsonNumber(const char *str, int len)
 	 */
 	if (*str == '-')
 	{
-		dummy_lex.input = (char *) str + 1;
+		dummy_lex.input = unconstify(char *, str) + 1;
 		dummy_lex.input_length = len - 1;
 	}
 	else
 	{
-		dummy_lex.input = (char *) str;
+		dummy_lex.input = unconstify(char *, str);
 		dummy_lex.input_length = len;
 	}
 

src/backend/utils/adt/misc.c

@@ -423,7 +423,7 @@ pg_get_keywords(PG_FUNCTION_ARGS)
 		HeapTuple	tuple;
 
 		/* cast-away-const is ugly but alternatives aren't much better */
-		values[0] = (char *) ScanKeywords[funcctx->call_cntr].name;
+		values[0] = unconstify(char *, ScanKeywords[funcctx->call_cntr].name);
 
 		switch (ScanKeywords[funcctx->call_cntr].category)
 		{

src/backend/utils/adt/varlena.c

@@ -182,7 +182,7 @@ char *
 text_to_cstring(const text *t)
 {
 	/* must cast away the const, unfortunately */
-	text	   *tunpacked = pg_detoast_datum_packed((struct varlena *) t);
+	text	   *tunpacked = pg_detoast_datum_packed(unconstify(text *, t));
 	int			len = VARSIZE_ANY_EXHDR(tunpacked);
 	char	   *result;
 
@@ -213,7 +213,7 @@ void
 text_to_cstring_buffer(const text *src, char *dst, size_t dst_len)
 {
 	/* must cast away the const, unfortunately */
-	text	   *srcunpacked = pg_detoast_datum_packed((struct varlena *) src);
+	text	   *srcunpacked = pg_detoast_datum_packed(unconstify(text *, src));
 	size_t		src_len = VARSIZE_ANY_EXHDR(srcunpacked);
 
 	if (dst_len > 0)

src/port/win32setlocale.c

@@ -183,7 +183,7 @@ pgwin32_setlocale(int category, const char *locale)
 	 * forbidden to modify, so casting away the "const" is innocuous.
 	 */
 	if (result)
-		result = (char *) map_locale(locale_map_result, result);
+		result = unconstify(char *, map_locale(locale_map_result, result));
 
 	return result;
 }