Re: [patch/cygwin] Remove dependency on __COPY_CONTEXT_SIZE

[Pedro Alves <palves@redhat.com>]

On 03/31/2015 07:32 PM, Corinna Vinschen wrote:
> On Mar 31 17:30, Pedro Alves wrote:
>>>> That's not true.   GetThreadContext takes a size parameter,
>>>> and only writes to the bits that the caller requests with
>>>> context.ContextFlags.
>>>
>>> The ContextFlags member is not a size parameter,
>>
>> I didn't say it was.  The GetThreadContext function takes
>> an IN+OUT size parameter in _addition to the ContextFlags flag.
> 
> Uhm...no, it doesn't.  The prototype is
> 
>   BOOL WINAPI GetThreadContext(
>     _In_     HANDLE hThread,
>     _Inout_  LPCONTEXT lpContext
>   );

Eh, somehow I got confused.  Sorry about that.

>> I'm almost sure in the old days, the CONTEXT structure didn't have
>> the ExtendedRegisters field at all.
> 
> I don't know about that.  But the fact that CONTEXT is not a opaque
> structure but exposed to user space speaks against that.  Every time
> a Win32 datatype needs a change, MSFT kept the old datatype intact
> and added an "Ex" or "2" type instead, just as with the functions.

OK.

> 
>> I think it's bad to hard code
>> the size of the CONTEXT structure, but won't argue further.  Patch
>> is OK if you'd really like to apply it as is.
> 
> Thanks.  But incidentally I retract the patch.  It seems we made a
> mistake both, on 32 and 64 bit Cygwin as far as the definition of
> __COPY_CONTEXT_SIZE is concerned.  Changing that to sizeof(CONTEXT) now
> would potentially break backward compatibility with all Cygwin versions
> up to today.  Oh well.

Not sure I understand what you mean, but OK.

> Sorry for the longish discussion for nothing :(

Sounds like it wasn't for nothing then.

Thanks,
Pedro Alves