Yeah, not only does this static union() method seem like dead code, it seems wrong
as well. Perhaps igraves should take a look at this.
The whole area seems suspicious. There doesn't seem to be any semantic difference
between BmpCharPredicate and CharPredicate. The and() & union() combinators
preserve class: combining BmpCharPredicates gives a BmpCharPredicate, otherwise a
CharPredicate. But evaluating one versus the other doesn't seem to make a
difference. However, there are a couple instanceof checks that change logic paths in
places where they're used... urghhh....
s'marks
On 8/27/21 8:37 AM, Pavel Rappo wrote:
Has that method been ever used? If nothing else its name seems strange. To me,
a union has OR semantics, not AND.
On 27 Aug 2021, at 15:37, Andrey Turbanov <turban...@gmail.com> wrote:
Hello.
I found suspicious code in the method
"java.util.regex.Pattern.BmpCharPredicate#union(java.util.regex.Pattern.CharPredicate...)"
https://github.com/openjdk/jdk/blob/master/src/java.base/share/classes/java/util/regex/Pattern.java#L5639
static CharPredicate union(CharPredicate... predicates) {
CharPredicate cp = ch -> {
for (CharPredicate p : predicates) {
if (!p.is(ch))
return false;
}
return true;
};
for (CharPredicate p : predicates) {
if (! (p instanceof BmpCharPredicate))
return cp;
}
return (BmpCharPredicate)cp;
}
Variable `cp` has type CharPredicate initially. And then it's casted
to BmpCharPredicate. This cast always fails with ClassCastException
when reached.
Can reproduced in small sample class:
public static void main(String[] args) {
CharPredicate result = BmpCharPredicate.union();
System.out.println(result);
}
interface CharPredicate {
boolean is(int ch);
}
interface BmpCharPredicate extends CharPredicate {
static CharPredicate union(CharPredicate... predicates) {
CharPredicate cp = ch -> true;
for (CharPredicate p : predicates) {
if (! (p instanceof BmpCharPredicate))
return cp;
}
return (BmpCharPredicate)cp;
}
}
Exception in thread "main" java.lang.ClassCastException: class
org.RegexpBug$BmpCharPredicate$$Lambda$14/0x0000000800c028f0 cannot be
cast to class org.RegexpBug$BmpCharPredicate
(org.RegexpBug$BmpCharPredicate$$Lambda$14/0x0000000800c028f0 and
org.RegexpBug$BmpCharPredicate are in unnamed module of loader 'app')
at org.RegexpBug$BmpCharPredicate.union(RegexpBug.java:20)
at org.RegexpBug.main(RegexpBug.java:5)
As I can see this method is never used. Perhaps it should be removed?
Andrey Turbanov
