RFR: JDK-8221851: Use of THIS_FILE in hotspot invalidates precompiled header on Linux/GCC

[Ioi Lam]

#define THIS_FILE (__FILE__ + FILE_MACRO_OFFSET)

This make me a little uneasy, as it could potential point past the end 
of the string.

For safety, Is it possible to get some sort of assert to make sure that 
__FILE__ always has more than FILE_MACRO_OFFSET characters?

Maybe we can add a static object in macros.hpp with a constructor that 
puts __FILE__ into a list, and then we can walk the list when the VM 
starts up? E.g.

     ...

     #ifdef ASSERT
     static ThisFileChecker __this_file_checker(__FILE__);
     #endif

     #endif // SHARE_UTILITIES_MACROS_HPP


Thanks
- Ioi


On 4/4/19 9:04 PM, David Holmes wrote:
> Hi Erik,
>
> Build and hotspot changes seem okay.
>
> Thanks,
> David
>
> On 5/04/2019 8:03 am, Erik Joelsson wrote:
>>
>> On 2019-04-04 14:26, Kim Barrett wrote:
>>>
>>> OK, I can do that.
>>>
>>> ------------------------------------------------------------------------------ 
>>>
>>> src/hotspot/share/utilities/macros.hpp
>>>   645 #if FILE_MACRO_OFFSET
>>>   646 #define THIS_FILE (__FILE__ + FILE_MACRO_OFFSET)
>>>   647 #else
>>>   648 #define THIS_FILE __FILE__
>>>   649 #endif
>>>
>>> Is the "#if FILE_MACRO_OFFSET" an intentional test for 0, or is this
>>> an implicit test for "defined"?
>>>
>>> If the former, e.g. we're assuming it will always be defined but might
>>> have a 0 value, then I'd skip it and just unconditionally define
>>> THIS_FILE as (__FILE__ + FILE_MACRO_OFFSET).
>>
>> Right, that makes sense. I was sort of hedging for all possibilities 
>> here, but as the build logic is currently structured, it will always 
>> be defined, just sometimes 0.
>>
>> New webrev: http://cr.openjdk.java.net/~erikj/8221851/webrev.02/
>>
>> /Erik
>>
>>> If the latter, some compilers will (with some warning levels or
>>> options, such as gcc -Wundef) complain about the (specified by the
>>> standard) implicit conversion to 0 for an unrecognized identifier in
>>> an #if expression, and an #ifdef should be used to protect against
>>> that.
>>>
>>> ------------------------------------------------------------------------------ 
>>>
>>>
>>>