Sorry, there is an error in the second paragraph which could lead to
severe misunderstandings: "code page" should be "code base".
Kind regards
Bernd
Am 20.01.2015 um 10:32 schrieb Bernd Oppolzer:
Am 19.01.2015 um 23:07 schrieb Tony Harminc:
On 18 January 2015 at 04:29, Bernd Oppolzer<bernd.oppol...@t-online.de> wrote:
What do you think about this? For the existing PL/1 code base, for example,
it would be a big change if all pointers would be 8 bytes long ... I don't
see this happen in the near future.
In the PL/I Checkout compiler, pointers were (iirc) 128 bits, and
carried various baggage not defined to the language, but useful in
debugging. Of course no one used the Checker in production, but
certainly in most cases the PL/I code should not be aware of the size
of a pointer.
The problem is:
if you are building linked lists etc,
then pointers are part of structures etc.,
and if you have this, if pointer size changes, then offsets of other
fields
inside structures change, too. And this was what caused us some problems,
when we migrated our (large) math package from Windows-32 to Linux-64.
Another szenario is: pointers, that are overlaid by 32-bit integers in
variants
of structures (so-called unions), because the application assumes,
that both
have the same size. This doesn't work any more with 64 bit ... but maybe
you don't want to enlarge your ints to 64 bit at the same time (we didn't
do that, because THIS would have a much bigger impact on our structure
definitions, see above).
So, unfortunately, in a large code base, you have to take care about
pointer size,
because there are some functions or places in this code page, that assume
a certain pointer size ... often subconsciously. You have to find
those places
and eliminate the problem. Of course, it can be done, but it is a
project.
Tony H.
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