-----Original Message----- From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of Charles Mills Sent: Sunday, February 21, 2010 8:00 PM To: IBM-MAIN@bama.ua.edu Subject: Best practice for 24-bit storage in assembler called from C/C++
I'm writing a fairly large MVS batch application in C++. At several points it is necessary to call "library" type routines that I am writing in assembler. Several of the routines (unfortunately) need to use QSAM macros and so need below-the-line storage. Obviously I could do a GETMAIN or STORAGE OBTAIN LOC=24 on the way in and FREEMAIN or STORAGE RELEASE on the way out. But that's less than optimal for a routine that is called multiple times. (And it would not work at all if the routine had to save state across calls, but fortunately that is not the case, at least for my requirements so far.) I could make the calling C++ responsible for providing a "work area" obtained with _malloc24(). But I don't like that for "aesthetic" reasons - violates encapsulation, making the caller responsible for the inner workings of the called function. Is there a better way? Is there some sort of "anchor word" where a library of called assembler routines could save an address across calls? Is this what CEECAA_TCASRV_USERWORD in CEECAA is for? Does R12 reliably point to the CEECAA on entry? Can I count on CEECAA_TCASRV_USERWORD being initialized to zero? Where is this stuff documented? I don't see much in LE Programming, in LE ILC, or in the C/C++ Programming Guide. <SNIP> If you KNOW that you will be serialized, then you can either build your DCB info into a REUSE program that you can LOAD. You can then call it to do the I/O that you need done, not get into all the overhead of multiple OPEN/CLOSE, etc. You can then do an INIT call and a Terminate call for the OPEN and CLOSE issues. Otherwise, you can get the storage from your assembler routine, and then have it IDENTIFY that storage so that you can find it again using LOAD, or a run of the CDE chain(s). Just two options you might want to consider. Regards, Steve Thompson -- Opinions expressed by this poster may not reflect those of poster's employer -- ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
