<snip>
SETRP RC=4,RETREGS=YES,RETADDR=(R4),FRESDWA=YES,DUMP=YES, X
RECORD=YES,RUB=(R3),DUMPOPX=SNAPL
SNAPL SNAPX DCB=*-*,PDATA=ALL,SDATA=LSQA,LIST=(R7),STRHDR=L1
</snip>
That is not going to work for at least two reasons. One is that, as Walt
pointed out, the "LIST" operand isn't going to get set.
The second is that "SNAPL" is not the address of the parameter list in
this expansion. It is the address of the first instruction of the
expansion which is a branch around the expansion. And relying on there
being exactly 4 bytes from SNAPL to the beginning of the parameter area
staying that way forever would be foolhardy.
If you want to play for now, with no reliance on this working at any time
in the future, you could consider invoking SNAPX but then having ORG *-2
after the invocation (and continuing your program from there). The last
instruction of the expansion happens to be "SVC 51" so you would end up
no-oping the actual invocation of the service. This too is something that
would be foolhardy to rely upon.
But if you wanted to try, it would be something like this, assuming a
reentrant module:
<in your module storage>
SNAPL_STATIC SNAPX MF=L
<in your dynamic storage>
SNAPL_AUTO SNAPX MF=L
SNAPL_LEN EQU *-SNAPL_AUTO
<in your module storage>
MVC SNAPL_AUTO(SNAPL_LEN),SNAPL_STATIC
SNAPX <all_your_options>,MF=(E,SNAPL_AUTO)
ORG *-2
SETRP <all_your_options>,DUMPOPX=SNAPL_AUTO
Or, use the list form of SNAPX, examine the expansion of an execute form
of SNAPX that does any piece that the list form that you can't do (such as
the processing of LIST=(R7) ), and code that yourself to update your list
form (and/or use the IHASNAPX macro from 'sys1.modgen' to help do that if
you want your code to be more readable). This approach, if you get it
right, will likely work forever, unclean as it might be, because you are
producing exactly the same parameter area that would have been passed to
the SNAP service. But only if you get every bit and byte correct.
You won't need to specify DCB for this SNAPX. That information is not used
for SETRP DUMPOPX.
Peter Relson
z/OS Core Technology Design
