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 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
