Demand paged executables

[Guy Harris]

>In HP-UX 6.2 you cannot unlink an executing demand paged (or shared)
>program, regardless of how many other on-disk links there are.
>I have no idea why this change was made (HP-UX 6.0 did not have the
>restriction),

Amazingly enough, this stupid restriction is required by the SVID if you
support shared text.  (Check out UNLINK(BA_OS).)  Sometimes "SVID" stands
for "System V Implementation Description".... 

One way around this is to say you don't support shared text.  SunOS will
probably do so by Sun saying - quite correctly - that they don't support
shared text; instead, they support read-only copy-on-write mappings to
the file (yes, that really *is*, in effect, the way an "exec" of a 0413
executable is done; the net effect, of course, is that the pages are
*still* shared - unless you try to run a debugger on the program and set
breakpoints, in which case private copies are made of the pages in which
breakpoints are set).