Am 18.01.2015 um 17:19 schrieb Peter Relson:
Storage for static variables, i.e. variables declared with
the STATIC keyword, is "allocated" in the so called static
CSECT that becomes part of the object module. Note that
this *is* read/write storage, so in PL/I STATIC does not
mean constant.
If it's truly part of a "CSECT" that is part of a load module, then this
statement is wrong (or needs to be fine-tuned). All z/OS storage is
read/write if you're in the right key (unless z/OS has page-protected it).
So if you're trying to say that a non-key-0 program can write into it, in
z/OS that will depend on the APF authorization of the load library
concatenation and the reentrancy of the module.
Even a non-authorized program which is linked RENT can write into its
STATIC CSECT.
We did this all the time in our PL/1 modules that are compiled using the
NORENT option
(or compiled with old releases of PL/1, before the RENT option was
available).
There are two use cases (at our site) to do that:
a) to store the entry point of modules that are dynamically loaded, so
that only at the
first call a LOAD macro is needed ... at the subsequent calls the entry
point is non-zero,
so it can be used immediately
b) to store results of expensive computations (and the arguments, that
leaded to this
results), in case that the following call is done with the same arguments
In the second case, you have to take care that there will be no damage
due to the
parallel use of the module from different tasks ... there are ways to do
this. In the
first case, you dont have such a problem ... the only damage that can
occur is
that you do the LOAD too often.
BTW: our PL/1 modules (no DLLs, simple LOAD modules) call each other using
ASSEMBLER interfaces, doing MVS LOAD ... we don't normally use LE services
for that (this is an old technique from the early 1980s). But it works
until today,
and the rest is all LE compliant. We use the new EP PL/1 compilers.
Same goes for C ... no difference at all.
Kind regards
Bernd
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