On 21/09/2012 12:09 AM, Farley, Peter x23353 wrote:
*** Comments and questions marked below.
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf
Of David Crayford
Sent: Thursday, September 20, 2012 11:40 AM
To: [email protected]
Subject: Re: Metal C runtime safe for dynamic LINKing?
__cinit returns an environment token which is stored in R12.
*** I am aware of that, since there is source coding required to support the
use and reservation of R12 for the token.
AFAIK, all __cinit() does is create a storage heap, and __cterm()
destroys it. I'm not sure if any of the runtime actually uses the heap,
the manual eludes to this by documenting
the required stack sizes of the runtime functions. I've nested several
__cinit/__cterm calls in the same program because I wanted to create a
new heap that I could tear down in
one call and thus reduce the overhead of tens of thousands of free()
calls. This technique is similar to memory pools or user heaps. Metal/C
is pretty low-level, no anchored control blocks
or anything sophisticated to worry about.
It's not unusual to have environment pools in both metal/c and LE using PIPI.
*** I do not understand this part of your reply. I am well aware of the use of PIPI for
LE programs to prevent repeated startup and teardown of the LE environment. But what do
you mean by "environment pools"? And how do they relate to my question, please?
It doesn't really relate to your question, sorry about that! I was
talking about the technique of reusing PIPI environments from a free
pool. Only really interesting to PIPI heavy users who
probably already know about it.
Peter
On 20/09/2012, at 11:00 PM, "Farley, Peter x23353"
<[email protected]> wrote:
In thinking about a possible Metal C project, I realized I might have to LINK
to other Metal C main programs as part of the project. My concern in this OCO
environment is whether this scenario is safe to plan:
EXEC PGM=A
__cinit
(Program A logic)
LINK to program B
__cinit
(Program B logic)
__cterm
RETURN to program A
(Program A more logic)
__cterm
RETURN to z/OS
My first question is whether the Program B invocation of __cinit will succeed
since __cinit was already called by Program A.
If the answer to the first question is Yes, then my second question is whether
the (Program A more logic) section would succeed or fail using the Metal C
runtime routines after the LINKed-to program B calls __cterm.
TIA for any practical experience or advice you can provide.
Peter
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