SysV.3 to SysV.4 binary compatibility.

[Dick Dunn]

geoffg at sigma21.oz.au (Geoffrey R Graham) writes:
> My understanding is that SysV.4 (on the 386) is fully binary compatible
> with SysV.3 on the same CPU.
> 
> Is this correct ?

No, it is not.

There is substantial compatibility (meaning a substantial number of V.3.2
programs will run on V.4) but it is by no means complete.

V.4 does support V.3.2 COFF binaries, even though it has its own yet-
another-object-file-format, ELF.

Areas where you may run into problems include V.3.2 X clients running on
V.4 (communicating with a server on the same machine), POSIX extensions,
signal extensions...

V.4 COFF compatibility covers everything in the original BCS (binary
compatibility specification), but there are several areas where BCS falls
short of what was needed.  There is work afoot to remedy these short-
comings.
-- 
Dick Dunn     rcd at ico.isc.com -or- ico!rcd       Boulder, CO   (303)449-2870
   ...Never offend with style when you can offend with substance.