Re: upgrading production ada programs years later

["Björn Lundin" <b.f.lundin@gmail.com>]

On 2018-02-01 20:25, polymorph self wrote:
> ez?
> hard?
> living hell here at work with oracle c++ and iis combo
> high hilarity in fact
> 


We produce Warehouse Management and Warehouse Control software
(WMS/WCS), that is we tell forklift drivers what and were to pick up and
deposit, we tell machines like conveyors/cranes/sorting
machines/autostores what and were to pick up and deposit.
In the other end we talk to ERP systems like SAP/Oracle/JD Edwards/Baan
and break down orders to pick lists.
small warehouse ~ 5 - 10 concurrent users
big warehouse ~ 250-400 concurrent users.

These systems live longer than we actually want ;-)
a lifetime of 20+ years is common.
During its lifetime we upgrade and enhance with bespoke functions
due to change in customers business. (or because OS/DB support exists)

Like e-commerce has put a large change in order structure.
20-25 years ago, it was fairly uncommon that a warehouse delivered
directly to customers. They almost always delivered to physical stores
or smaller warehouses. That means a large quantity was full pallets.
Now - most web-shops sell single units directly to the customer.
Most people would be (happily) surprised if they got a full pallet of
laptops when they order just 1 ... Picking has increased alot

But as I said - we maintain and upgrade systems from 1995 and forward.
It is _usually_ fairly simple.
It is more annoying when they want something in their 1997 system that
we started using in 2009 - like web services. Compiler generations
very quickly becomes an issue then.

BUT, we have never had any trouble in production due to upgraded
compilers. However we do get tonnes of new warnings compiling old code
with new compilers.

The most difficult parts has been switching from AlsysAda and ObjectAda
to gnat. Gnat is much pickier about elaboration circularities - or
the others where just plain wrong. Some parts of the code - usually
with heavy tasking - has been subject to elaboration circularities.
And they are no fun at all.

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Björn