Mail Archives: cygwin/1997/10/30/06:02:42
>> >At the time when cygwin_fork_helper1() returns isn't the
>> >child's state already a copy of the parent's state?
>>
>> No, actually, it isn't. The setjmp and longjmp are used to move the
>> current execution point into the appropriate point in the cygwin_fork_helper1
>> function to emulate a true UNIX fork().
>>
>> What happens is that to emulate a fork, the parent process starts the
>[...]
>> extends the stack to hopefully insure that the stack is large enough to
>> duplicate the parent, and longjmps to the child portion of the
>> cygwin_fork_helper1 routine. There it wakes up the parent and sleeps
>> itself.
>
>um.. this is a completely different setjmp/longjmp pair.
>The setjmp that is jumped to from crt0 is in the cygwin_fork_helper1()
>function. The __fork() function has its own setjmp/longjmp
>pair that seems to add no extra functionality. Perhaps some sort
>of legacy from fork implementations of past.
My sincere apologies. I've committed the usual Usenet sin of answering
the question that wasn't asked.
On inspection of the __fork code, I understand your confusion and share
it. I wonder if this is a holdover from a previous fork implementation
or if this assures stack synchronization in some arcane way.
--
http://www.bbc.com/ cgf AT bbc DOT com "Strange how unreal
VMS=>UNIX Solutions Boston Business Computing the real can be."
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