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Re: [RFC] an alternative to rebasing [recall]

Scratch my last message. 
I just did a re-build from clean, using default imagebases, and fork
still fails. So rebase is the only solution available right now. Sorry
for the false hopes.

On Tue, 6 Aug 2002 09:07:41 +0100
Steven O'Brien <> wrote:

> On Mon, Aug 05, 2002 at 12:41:44 -0400, Jason Tishler wrote:
> > I'm sorry to report that your patch does not fix the following
> > rebase problem:
> > 
> >
> > 
> > Specifically, I'm getting the following:
> > 
> >     $ make
> >     ...
> >     building 'gdbm' extension
> > gcc -DNDEBUG -g -O3 -Wall -Wstrict-prototypes -DUSE_DL_IMPORT -I.
> > -I/tmp/python-2.2.1-1/./Include -I/usr/local/include -IInclude/ -c
> > /tmp/python-2.2.1-1/Modules/gdbmmodule.c -o
> > build/temp.cygwin-1.3.13-i686-2.2/gdbmmodule.o
> > C:\cygwin\tmp\python-2.2.1-1\build\python.exe: *** unable to remap
> > C:\cygwin\bin\cygcrypto.dll to same address as parent -- 0x420000
> >       8 [main] python 1548 sync_with_child: child 2772(0x100) died
> >       before initialization with status code 0x1
> >    9652 [main] python 1548 sync_with_child: *** child state child
> >    loading dlls
> > error: Resource temporarily unavailable
> > make: *** [sharedmods] Error 1
> > 
> Jason,
> I've looked into this, and the problem now is with the imagebases of
> the python dlls. The makefile is linking them with
> "--enable-auto-image-base" and you will find that at least two of
> these values clash:
> _codecs.dll: 0x69400000
> libpython2.2.dll: 0x69340000
> Now that *should not* pose a problem if we had a rock-solid fork()
> implementation, but my patch is just a work-around, not a proper fix.
> However, --enable-auto-image-base is deprecated in cygwin anyway,
> because it may mean that a dll is given an image base that clashes
> with cygwin1.dll, which should never be relocated (IIRC according to
> the mailing list archives of last year).
> So, you should remove the --enable-auto-image-base flag, then your
> dlls will all get the default image base of 0x10000000, and cygwin
> with my patch is able to load and fork without problem!
> BTW I fully agree with Rob Collins that an effective rebase tool will
> give measurable performance improvements to cygwin apps and so this
> patch is not strictly an alternative to rebasing, but I think it is
> still a sensible change to the fork() implementation. This is because
> rebase should be an option to improve performance, not a necessity to
> permit function.
> Are there any cygwin regression tests that I can use to look for any
> undesirable side-effects of my patch?
> Steven

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