Extending the data segment

[PEREIRA at SU-CSLI.ARPA]

From:  Fernando Pereira <PEREIRA at SU-CSLI.ARPA>

A system system I'm working on could be speeded up considerably if the
data segment could be extended automatically on overflow.  I've done a
simple test with code that does an sbrk(increment) on SIGSEGV signals,
and it seems to work on a VAX 4.1 running 4.1c. It seems that the Bourne
shell uses a similar trick. Clearly, this cannot work in general on
machines that do not have a means of restarting interrupted
instructions (I was somewhat involved in a long fight with the stack
extension code to get V7 to work on a PDP 11/24).

I would like to hear of experiences (positive or negative) with this
method of extending the data segment for various Unix implementations,
in particular 4.2 on VAXes and 68K machines. (Methodological flames
to the bit bucket.)

Thanks in advance

-- Fernando Pereira
   pereira at su-csli
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