Thanks for the investigation Andrej.
In any case, I'd prefer a comment noting the interned-ness (or mostly
interned-ness, etc.) of the name to let other readers of the code using
== rather than .equals is intentional and not a bug.
Thanks,
-Joe
On 06/09/2014 12:56 PM, Andrej Golovnin wrote:
Hi Joel,
IIRC name isn’t actually interned with String.intern() but in the VM:s Symbol
table as a name representing a (Java) method. Should be equivalent, as long as
we don’t start comparing it with == with interned Strings.
I think that's not true.
The following small test program prints true on the console:
public class Test {
public static void main(String... argv) throws Exception {
Method m = Test.class.getMethod("main", String[].class);
System.out.println(m.getName() == new String("main").intern());
}
}
And if you look into reflection.cpp at lines 787-789, you will see following
code:
Symbol* method_name = method->name();
oop name_oop = StringTable::intern(method_name, CHECK_NULL);
Handle name = Handle(THREAD, name_oop);
And later at the line 798 we have this code:
java_lang_reflect_Method::set_name(mh(), name());
Therefore I would say the name is actually interned in terms of String.intern().
And you can compare the name of a method with == with interned Strings.
The same applies to a name of a class and to a name of a field too.
Please feel free to correct me.
Best regards,
Andrej Golovnin
cheers
/Joel
On 07 Jun 2014, at 22:34, Andrej Golovnin <andrej.golov...@gmail.com> wrote:
Hi Joe,
Sorry for the belated review.
Generally the change looks good. One question, in
2803 private boolean matchesNameAndDescriptor(Method m1, Method m2) {
2804 return m1.getReturnType() == m2.getReturnType() &&
2805 m1.getName() == m2.getName() &&
2806 arrayContentsEq(m1.getParameterTypes(),
2807 m2.getParameterTypes());
2808 }
Should the equality check on 2805 be .equals rather than == ?
"==" can be used in this case as the method name is interned by JVM.
Here is the comment for the field "name" from java.lang.reflect.Method:
// This is guaranteed to be interned by the VM in the 1.4
// reflection implementation
private String name;
BTW, in the old version of Class in the line 2766 there was already a similar
check:
2764 if (m != null &&
2765 m.getReturnType() == toRemove.getReturnType() &&
2766 m.getName() == toRemove.getName() &&
2767 arrayContentsEq(m.getParameterTypes(),
2768 toRemove.getParameterTypes())) {
2769 methods[i] = null;
Best regards,
Andrej Golovnin
