what does *for %es is 0000* mean?

[fangendou]

Hi,
When I read Wine Developer's Guide on http://www.winehq.org/docs/winedev-guide/wine-debugger, I can't understand this sentence *(In this case it is access to an invalid selector, for %es is 0000, as seen in the register dump).* in the page. Why *for %es is 0000* is an invalid selector?

[Chris-WF]

I don't read the Developer's Guide, so this situation of the empty ES Register could be in connection with a example for something context related. So i could be still wrong..

Take a look at this:

|Register dump:
| CS:01b7 SS:016f DS:0287 ES:0000
| IP:0c41 SP:878a BP:8796 FLAGS:0246
| AX:811e BX:0000 CX:0000 DX:0000 SI:0001 DI:ffff

The Register ES contains zero. ES stand for Extra Segment and is use for different things. What you describe should be a check if this Register is zero since this is a debug guide this should not be and i suppose the code is to handle an exception.

Oh the Developers Guide describe it, ES got zero because of an access to an invalid address.

[fangendou]

I don't read the Developer's Guide, so this situation of the empty ES Register could be in connection with a example for something context related. So i could be still wrong..
......
Oh the Developers Guide describe it, ES got zero because of an access to an invalid address.

thanks a lot！
I noticed that the es contains 0, but it should be the reason of *it is access to an invalid selector*. That's what I confused.
In addition, can the es register contain 0 or never.