Problem with xstr

[Tony Luck]

In article <145 at taux02.UUCP> amos at taux02.UUCP (Amos Shapir) writes:
>Unless you use a pdp11 with separate  I/D space, the solution is to just
>throw out all  the xstr stuff from your makefiles,  and compile normally
>instead.
>
>Xstr is a hack for putting  strings, which are supposed to be read-only,
>into the executable's  text (code) space. This makes more  room for data
>on  machines  with  limited  address space.  On  32-bit  machines,  this
>approach is obsolete and causes more trouble than benefit.

I don't think that xstr is any use on a split I/D space machine as you'd
have to bodge the compiler to address modes that refer to I-space addresses
rather than D-space when fetching bytes from the strings. (But I could be
wrong about this ... I went straight from a pdp 11/34 (no split I/D space)
running version 6 to a VAX running 4.1bsd ... talk about culture shock!)

Xstr isn't a hack for ... making more room for data. It is a hack to allow
you to share the strings between executables - so if you have some word
processor package that is packed full of cute error messages you don't
have 50K of memory used for strings in each and every copy of the program
running.

It's probably still obsolete though as with demand paging you can probably
leave all those strings on disk ... and with silly amounts of memory (the
"little" machine on my desk has 16 Mbytes ... but please don't let this be
the start of a "mine is bigger than yours" waste of net bandwidth) perhaps
there are more important things to worry about than saving a few kilobytes.

-Tony Luck (UniSoft Ltd.) <aegl at root.co.uk>