RFR (S): 8211394: CHECK_ must be used in the rhs of an assignment statement within a block

[David Holmes]

Hi Thomas,

On 8/10/2018 4:48 PM, Thomas Stüfe wrote:
> Looks good.

Thanks for looking at it.

> You missed:
> 
> classfile/verificationType.cpp line 113
> 
>        return comp_this.is_component_assignable_from(comp_from, context,
>                                            from_field_is_protected, CHECK_false);

Thank you - webrev updated in place with new file.

> and possibly more, did not check further. Difficult to grep for when multi line.

Yes. I don't know how to exhaustively detect this problem. :(

Cheers,
David

> Cheers, Thomas
> 
> 
> 
> On Mon, Oct 8, 2018 at 12:08 AM David Holmes <david.holmes at oracle.com> wrote:
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8211394
>> webrev: http://cr.openjdk.java.net/~dholmes/8211394/webrev/
>>
>> If a CHECK_ macro is used on a function call that is part of a return
>> statement i.e.
>>
>> return foo(CHECK_NULL);
>>
>> then it expands into an unreachable if-statement that checks the
>> exception state:
>>
>> return foo();
>> if (EXCEPTION_OCCURRED)
>>     return NULL;
>>
>> This is obviously a programming error, but unfortunately not something
>> our often pedantic compilers complain about.
>>
>> There are two ways to fix:
>>
>> 1. Convert to assignment:
>>
>> T* t = foo(CHECK_NULL);
>> return t;
>>
>> 2. If the method is local and its exception behaviour easily discernible
>> and matches the expected behaviour, then change CHECK_ to THREAD
>>
>> return foo(THREAD);
>>
>> Both fixes are applied as appropriate. As per the bug report I also
>> revisited an earlier fix in this area - JDK-8062808 - and made adjustments.
>>
>> Thanks,
>> David