RFR: 8022899: SunStudio compiler can not handle EXCEPTION_MARK and inlining

[Mikael Gerdin]

Erik,

I agree with Coleen, I think this change is a good work-around.

/Mikael


On 2013-08-13 19:34, Coleen Phillimore wrote:
>
> This change is fine.   The side effect of assigning THREAD from
> EXCEPTION_MARK is something the code uses a lot, so it probably
> shouldn't be changed.
>
> redefining the macro to be:
>
> #define EXCEPTION_MARK  Thread* THREAD = Thread::current();
> ExceptionMark em(THREAD);
>
> would enable removing the non-const reference to ExceptionMark
> constructor but it might draw in thread.inline.hpp dependencies to
> exceptions.hpp, which would be bad.
>
> So I think your change is fine.
>
> Coleen
>
> On 08/13/2013 10:45 AM, Erik Helin wrote:
>> Hi all,
>>
>> this change initializes the Thread* in the EXCEPTION_MARK macro in
>> utilities/exception.hpp to NULL to avoid incorrect warnings from the Sun
>> Studio 12u1 compiler.
>>
>> Background:
>> HotSpot's exception handling code make use of the EXCEPTION_MARK macro
>> defined in utilities/exception.hpp:
>>
>>    #define EXCEPTION_MARK Thread* THREAD; ExceptionMark __em(THREAD);
>>
>> where THREAD is defined in the same file as:
>>
>>    #define THREAD __the_thread__
>>
>> The constructor for the class ExceptionMark takes a reference to Thread
>> pointer and assigns it:
>>
>>    ExceptionMark::ExceptionMark(Thread*& thread) {
>>      thread = Thread::current();
>>      // see utilities/exceptions.cpp for the rest
>>    }
>>
>> This means that the Thread pointer __the_thread__ from the
>> EXCEPTION_MARK macro will be initialized by the ExceptionMark
>> constructor (since it takes a pointer reference as argument).
>>
>> However, the Sun Studio compiler sometimes gives a warning that the
>> Thread pointer __the_thread__ is uninitialized. The following code is an
>> example:
>>
>> memory/example.cpp:
>>    static void print_str(const char* s, TRAPS) { // TRAPS is defined as:
>>      tty->print_cr(s);                           // #define TRAPS
>> Thread* THREAD
>>    }                                             // in
>> utilities/exception.hpp
>>
>>    static inline void example(const char* s) {
>>      EXCEPTION_MARK;
>>
>>      print_str(s, THREAD); // line 36
>>    }
>>
>>    void run_example() {
>>      example("This will not compile");
>>    }
>>
>> memory/example.hpp:
>>    void run_example();
>>
>> memory/universe.cpp:
>>    // include "runtime/example.hpp"
>>    // add a call to run_example() in universe_post_init
>>
>> Compiling this with Sun Studio 12u1 will (incorrectly) result in the
>> warning:
>> src/share/vm/memory/example.cpp", line 36:
>> Warning: The variable __the_thread__ has not yet been assigned a value.
>>
>> Removing the "inline" keyword from "static inline void example" makes
>> the code compiler without warnings.
>>
>> Solution:
>> Change the EXCEPTION_MARK macro to:
>>
>>    #define EXCEPTION_MARK Thread* THREAD = NULL; ExceptionMark
>> __em(THREAD);
>>
>> Webrev:
>> http://cr.openjdk.java.net/~ehelin/8022899/webrev.00/
>>
>> Testing:
>> - JPRT
>> - Compiling the example described above successfully
>>
>> Bug:
>> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8022899
>>
>> Thanks,
>> Erik
>