RFR: 8262368: wrong verifier message for bogus return type [v2]

[David Holmes]

On 3/03/2021 1:26 am, Harold Seigel wrote:
> On Tue, 2 Mar 2021 05:37:52 GMT, David Holmes <dholmes at openjdk.org> wrote:
> 
>>> Harold Seigel has updated the pull request incrementally with one additional commit since the last revision:
>>>
>>>    changed error message text
>>
>> src/hotspot/share/classfile/verifier.cpp line 3152:
>>
>>> 3150:     verify_error(ErrorContext::bad_type(bci,
>>> 3151:         current_frame->stack_top_ctx(), TypeOrigin::signature(return_type)),
>>> 3152:         "Method does not expect a return value");
>>
>> You've changed the wrong line. This one does expect a return value
> 
> Hi David,
> If a method's descriptor has a void return type, but the method contains a bytecode such as areturn, then I think the message "Method does not expect a return type" is correct.  Perhaps the word 'expect' is ambiguous?  If so, then I think a more explicit message, similar to my original suggestion, should be used.

First the bug report does not concern the line you changed! The bug 
report is about:

"There is a typo in an error message in verifier.cpp on line 1678"

1675: case Bytecodes::_return :
1676:      if (return_type != VerificationType::bogus_type()) {
1677:        verify_error(ErrorContext::bad_code(bci),
1678:                     "Method expects a return value");
1679:        return;
1680:      }

Here we have a plain _return bytecode, but the return-type is not void 
as expected. So we have a return value where we do not expect one. Hence 
the message on line 1678 is wrong, the method does not expect a return 
value.

Now looking at the code you changed:

  if (return_type == VerificationType::bogus_type()) {
     verify_error(ErrorContext::bad_type(bci,
         current_frame->stack_top_ctx(), 
TypeOrigin::signature(return_type)),
         "Method does not expect a return value");
     return;
   }

We have found a void return and this is an error. That means a void 
return was not expected i.e. the method DOES expect a return value. And 
the original message is correct.

Is there some weird double-negative logic being applied in all this that 
is somehow inverting the sense of everything ???

Cheers,
David
-----

> Harold
> 
> -------------
> 
> PR: https://git.openjdk.java.net/jdk/pull/2757
>