In article <CAAJSdjjjH6CZfpbbKdJCZbKnj0A9bjypHoOPqfAcfTyJ4_=u...@mail.gmail.com> you wrote: > On Tue, Jun 19, 2018 at 3:18 PM Farley, Peter x23353 < > peter.far...@broadridge.com> wrote: > > The recent discussion about the ability (or not) of setting R14 values in > > dbx at a break point while debugging brought me back to an old and (for me) > > somewhat sore subject. > > > > The z/Architecture hardware designers graced us with TRAP and TRAP4 and > > then with compare-and-trap instructions in the hardware. > > > > z/OS has yet to provide ordinary application-mode programmers (or for that > > matter compiler and debugger writers) with the tools to use these hardware > > features. Because updates to the DUCT are needed to properly utilize the > > TRAP features, only supervisor-state code (and therefore only > > APF-authorized code) can use these facilities in current z/OS versions, > > leaving ordinary application programmers with no way to use any of these > > hardware features.. > > > > When will z/OS provide application programmers (and others) the tools to > > utilize TRAP and friends? > > > > Inquiring minds would love to know. > > > ???I totally agree. This would make it easy to "trap" a C language style > "null pointer" dereferencing. A simple " CIT Rn,0,0" after doing a load of > the pointer. Or, after looking, a LAT or LGAT, which does an automatic > compare against 0, would make the C language much safer! All at "no cost" > to the compiler writers. However, this is assuming that the use of the TRAP > facility is relatively "cost free". I know that in the past, the SLIP IF > function was strongly discouraged because it use PER (Program Event > Recording?) which caused _significant_ CPU overhead. But that was back in > the 3090 days. I don't know as much about the z13+ internals. In fact, > perhaps CPU/performance impact is the reason that IBM doesn't make this > GUPI. Because GUPI implies "yes, feel free to use this anywhere you think > it makes sense" and if you get a 20% CPU hit, people will respond by > hitting back. > > > > Peter > > > -- > There is no such thing as the Cloud. It is just somebody else???s computer. > Maranatha! <>< > John McKown
You'd also want to have some language feature that _wouldn't_ trap if you _intend_ to do a "null pointer" dereference. After all, the first page of memory is where lots of good stuff lives. :) Also, I'm not sure how widely this is used, but we've gotten a lot of use out of it. "SLIP zero address detection (ZAD)" https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.3.0/com.ibm.zos.v2r3.ieag100/zaduse.htm -- Don Poitras - SAS Development - SAS Institute Inc. - SAS Campus Drive sas...@sas.com (919) 531-5637 Cary, NC 27513 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
