NE executable data segment size erroneously adjusted when stack is placed in separate segment

[lixovibe]

https://github.com/open-watcom/open-watcom-v2/blob/master/bld/wl/c/loados2.c#L1017-L1031

I am writing an experimental 80286 operating system along with a New Executable-linked kernel. When I try to allocate a separate stack segment/selector for the kernel, then the separate stack size is erroneously subtracted from the data segment size.

What is the proper way to fix this?

[jmalak]

Due to segmented architecture you need to define which memory layout/model will be used by your OS.
I don't know what compiler and linker options you use, that it is hard to say how you should fix.
I am afraid that you use some 16-bit Windows memory layout and single DGROUP (near) which contains stack (near) and therefore it is correct behavior. You need to define far stack by -zu compiler option, then stack is not part of DGROUP (near) and SS != DS.

[lixovibe]

I'm using the large memory model with wcc. I am using -zu and it appears to work fine, at least with respect to the compiler understanding where the stack is.

I believe the issue is with the cited code above, attempting to subtract the stack from the BSS. My NE loader is under-allocating the segment and my kernel is crashing because of it.

[jmalak]

It looks like you have defined near stack and it is part of DGROUP.
You need to remove any definition of stack from your code.
Far stack must be handled by your loader somehow.
If you create linker map file you will see where near stack is defined.