In file https://git.gnome.org/browse/libxml2/tree/valid.c

At two places the there are conditions which are checked twice.
Hence, checking the same condition again, is logically dead code.


1. In function xmlRemoveID(xmlDocPtr doc, xmlAttrPtr attr)

line no 2735-2748
int
xmlRemoveID(xmlDocPtr doc, xmlAttrPtr attr) {
    ----- Some Code -------
    if (doc == NULL) return(-1);
    if (attr == NULL) return(-1);
    table = (xmlIDTablePtr) doc->ids;
    if (table == NULL)
        return(-1);

    if (attr == NULL)
	return(-1);
    ---- Some Code -----
}

Here after first check to (attr==NULL), value of attr will never be NULL(0). So checking the same condition again is logically dead code.

2. Similar thing is happening in function xmlRemoveRef(xmlDocPtr doc, xmlAttrPtr attr)

line no 3053-3067

int
xmlRemoveRef(xmlDocPtr doc, xmlAttrPtr attr) {
    ------Some Code -------
    if (doc == NULL) return(-1);
    if (attr == NULL) return(-1);
    table = (xmlRefTablePtr) doc->refs;
    if (table == NULL)
        return(-1);

    if (attr == NULL)
        return(-1);
    -----Some Code ------
}

The solution to this is not to check the same condition twice. Remove the re-occurence of same condition in both functions.