Re: CALC expression

[Eric Norum <eric@norum.ca>]

On Sep 29, 2010, at 9:02 AM, Andrew Johnson wrote:

...

We *could* make RPCL into a char* pointer and allocate it dynamically
according to the particular _expression_, but that means making code changes to
the record and also opens up the possibility of free memory fragmentation on
vxWorks IOCs (none of the other standard record types allocate memory after
initialization to avoid that).  I think it's too late to make those kind of
changes at this point.

How long has it been since someone actually tested vxWorks to see if it still exhibit this fragmentation issue?

Sometimes urban legends are just that.

Alternatively we could add integer literal support to the code in libCom/calc,
which would reduce the incremental expansion factor from 21/4 to 10/3 or
better, but again that would be making code changes uncomfortably late in the
development cycle for 3.14.12.

Are the changes that extensive?

I would not worry /too/ much about wasted space.  After all, every record

has a 41-character DESC field, most of them are permanently empty, and I

don't recall hearing complaints about that.

Making CALC 80 translates to RPCL being 419 bytes instead of its current 209
bytes.  Lewis' suggestion of 64 bytes translates to RPCL being 335 bytes.

Do any small-IOC guys want to weigh in on these suggestions?

I'm about ready to admit defeat.

Plus, making the integer literal change could make the RPCL increase much less significant (or even non-existent)

-- 
Eric Norum
eric@norum.ca