Shmuel Metz , Seymour J. <[email protected]> wrote: (snip, I wrote) >>As I understand it, Fortran variables, and DS in assembler, generate >>holes in the object program (no TXT record for that position), and >>are filled in either by the linkage editor or program fetch.
> Not quite. The exact processing depended on the region size, but in > general the Linkage Editor packaged program data into text records, > with gaps when going to new csects. There might or might not be a gap > for a DS, depending on the size of the text record being built. So the > area for a DS might have residual data in a text record, or it might > have residual data from the storage allocated by Fetch. Well, by 'filled in' I meant either explicitly or implicitly, the latter being whatever happened to be in the buffer. If a DS happens to be at a load module record boundary then it isn't filled in by the linkage editor, otherwise it is. >>I believe that early OS/360 versions left whatever happened to be >>there, either in the linkage editor buffer or, for program fetch, in >>that memory location. At some time later, possibly for security >>reasons, this was changed to initialize to zero, or maybe something >>else (such as X'81'). > I'm not aware of IBM making any such change. Perhaps you had a local > mod from, e.g., SLAC? The X'81' was, at least at one time, a SLAC feature. As I understand it, though, at least by now they are zero filled. There was even a story that someone linked two load modules in one execution of the linkage editor, and found data from one left in the other. That was reported to IBM as a security leak. (The two modules belonged to different clients, who should not see each others data.) So, backing up more, is it true that early OS/360 didn't zero the buffers, and later systems did? -- glen ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
