Thanks, Alexey.

I did try your suggestions -- unfortunately I still need the annoying line of 
nonsense code to avoid a crash... :-(
I suppose it could be the registers/build issue -- unfortunately I don't have 
time to dig in the next several days,
in the meantime, if you come up with a version of slp_switch for x86 that you 
believe is "build-option-proof" let me know and I'll be
glad to try it...

On Aug 18, 2011, at 2:17 PM, Alexey Borzenkov wrote:

> Jeff,
> 
> For what it's worth the situation with 32-bit is exactly the same as 64-bit. 
> Depending on configuration some registers are either cannot be clobbered, or 
> are not saved. You can see an example of compile switches in my fork's bug 
> report that can crash 32-bit greenlet on stock lion's Python.
> 
> Regarding cst I already mentioned that it needs to be marked volatile due to 
> double return semantics of stack switches. There was the exact same problem 
> with static globals in greenlet, where slight changes in code would make 
> corruptions go away.
> 
> On Aug 18, 2011 5:20 PM, "Jeff Senn" <[email protected]> wrote:
> > Anselm - can you have a look and see what you think of Alexey's version? 
> > Compare with your earlier proposal? What is you current best version for me 
> > to test on OS-X
> > (preferably w/o the darwin specific compile option which I can't tell if you
> > thought was necessary or not...)
> > 
> > FWIW: My problem with the 32-bit version does seem to have something to do
> > with the llvm version of gcc on Lion... putting a useless (but not 
> > optimize-away-able) 
> > statement directly after the call to slp_switch that refers to cst and 
> > cstprev
> > causes it to work again... so I suspect either some sort of "bug"
> > in code generation -- or an optimization that breaks the stack switching...
> > if this sounds familiar to anyone (before I have time to go rip apart and 
> > analyze
> > the object code -- which will be awhile), please let me know...
> > 
> > 
> > On Aug 17, 2011, at 6:09 PM, Alexey Borzenkov wrote:
> > 
> >> On Fri, May 6, 2011 at 7:27 PM, Estevo <[email protected]> wrote:
> >>> I got the following error trying to make release27-maint in a 64-bit
> >>> 
> >>> gcc -pthread -c -fno-strict-aliasing -DSTACKLESS_FRHACK=0 -g -O2 -DNDEBUG 
> >>> -g
> >>> -fwrapv -O3 -Wall -Wstrict-prototypes -I. -IInclude -I./Include 
> >>> -I./Stackless
> >>> -DPy_BUILD_CORE -fno-omit-frame-pointer -O2 -I. -o 
> >>> Stackless/core/slp_transfer.o
> >>> ./Stackless/core/slp_transfer.c
> >>> ./Stackless/core/slp_transfer.c: In function ‘slp_transfer’:
> >>> ./Stackless/core/slp_transfer.c:153:1: error: bp cannot be used in asm 
> >>> here
> >>> make: *** [Stackless/core/slp_transfer.o] Erro 1
> >> 
> >> While working on greenlet and fixing switch-related problems, I found
> >> that I cornered myself into the same issue with gcc (as opposed to
> >> llvm-gcc used on OS X Lion). It seems that for whatever reasons gcc
> >> doesn't allow clobbering rbp when it's using it for referencing stack
> >> frame.
> >> 
> >> Coincidentally I managed to find a way to correctly save rbp (as well
> >> as csr and cw), that works and compiles both with and without
> >> -fomit-frame-pointers. In anyone is interested you can find my
> >> slp_transfer for amd64 here:
> >> 
> >> https://bitbucket.org/snaury/greenlet/src/5d37cde9474c/platform/switch_amd64_unix.h
> >> 
> >> If anyone can verify it's 100% correct (though redundant), then you
> >> can maybe use it in stackless too.
> >> 
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> > 
> > 
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