ArraySet.addAll Implementation Bug

[caoliqingstudio]

Describe the bug The implementation of addAll in ArraySet has a logical issue that almost certainly triggers the oops exception in the add method.

https://github.com/soot-oss/soot/blob/d4061dca597daa54b72ef093f027ceed5072178e/src/main/java/soot/util/ArraySet.java#L121

To reproduce

a = new ArraySet();
b = new ArraySet();
b.addAll(a);  // throw exception

a = new ArraySet(1);
a.add("x");
a.clear();
b = new ArraySet();
b.addAll(a);  // throw exception or  b = {"x"}

Additional context

The following logic is incorrect because the valid data for as needs to take into account the content of numElements. Thus, directly iterating through the entire elements will not only generate exceptions but also lead to incorrect additions.

for (E elem : as.elements) {
    ret |= add(elem);
}

=>

for (int i = 0; i < as.numElements; i++) {
    ret |= add(as.elements[i]);
}

[StevenArzt]

Thank you for the analysis and the fix. That's great work.