ext/phar: mark _phar_archive_data.ext field as const

This char* is derived from the fname char* field.

Author: Girgias

ext/phar/phar_internal.h

@@ -245,9 +245,9 @@ typedef struct _phar_entry_info {
 struct _phar_archive_data {
 	char                     *fname;
 	uint32_t                 fname_len;
-	/* for phar_detect_fname_ext, this stores the location of the file extension within fname */
+	/* The ext field stores the location of the file extension from the fname field, and thus should never be freed. */
 	uint32_t                 ext_len;
-	char                     *ext;
+	const char               *ext;
 	char                     *alias;
 	uint32_t                 alias_len;
 	char                     version[12];

ext/phar/phar_object.c

@@ -2113,7 +2113,7 @@ static zend_object *phar_rename_archive(phar_archive_data **sphar, char *ext) /*
 		goto err_reused_oldpath;
 	}
 	if (!phar->is_data) {
-		if (SUCCESS != phar_detect_phar_fname_ext(newpath, phar->fname_len, (const char **) &(phar->ext), &ext_len, 1, 1, true)) {
+		if (SUCCESS != phar_detect_phar_fname_ext(newpath, phar->fname_len, &(phar->ext), &ext_len, 1, 1, true)) {
 			zend_throw_exception_ex(spl_ce_BadMethodCallException, 0, "phar \"%s\" has invalid extension %s", phar->fname, ext);
 			goto err_reused_oldpath;
 		}
@@ -2136,7 +2136,7 @@ static zend_object *phar_rename_archive(phar_archive_data **sphar, char *ext) /*
 
 	} else {
 
-		if (SUCCESS != phar_detect_phar_fname_ext(newpath, phar->fname_len, (const char **) &(phar->ext), &ext_len, 0, 1, true)) {
+		if (SUCCESS != phar_detect_phar_fname_ext(newpath, phar->fname_len, &(phar->ext), &ext_len, 0, 1, true)) {
 			zend_throw_exception_ex(spl_ce_BadMethodCallException, 0, "data phar \"%s\" has invalid extension %s", phar->fname, ext);
 			goto err_reused_oldpath;
 		}