This is the mail archive of the gcc@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]

Re: Loop unrolling


> Is that from the C++ DWP? 

Yes. The concepts (sequence point, side effect) are borrowed from C++,
though.

> How does it define observable behavior?

>> The observable behavior of the abstract machine is its sequence of
>> reads and writes to volatile data and calls to library I/O
>> functions.6)

with footnote 6: 

>> An implementation can offer additional library I/O functions as an
>> extension. Implementations that do so should treat calls to those
>> functions as ''observable behavior'' as well.

The relation to sequence points is explained as

>> A conforming implementation executing a well­formed program shall
>> produce the same observable behavior as one of the possible
>> execution sequences of the corresponding instance of the abstract
>> machine with the same program and the same input.

> Who is the observer?

This standard does not deal with human-machine interaction. However,
the intent is clear: Observable behaviour really happens, and can be
observed by anyone using the conforming implementation.

Martin


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]