The assembler and binder don't control how you use Q-cons, but it's clear that the intended use case is one large storage allocation for a bunch of elements that are not all defined in the same source module. The Binder assigns offsets and calculates CXD. As a practical matter, the compiler has to pick a size for the offsewts and stick to it so that you can link separately compiled modules.
Yes, the early PL/I compilers used signed halfwords for array extents. Bit and character strings also had halword lengths. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Assembler List [ASSEMBLER-LIST@LISTSERV.UGA.EDU] on behalf of Paul Gilmartin [00000014e0e4a59b-dmarc-requ...@listserv.uga.edu] Sent: Sunday, July 5, 2020 11:15 AM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: z390 RLD Entries ... Bug or Feature? On 2020-07-04, at 23:08:31, Keven wrote: > > 2-byte RLD entries are correctly handed by the link-editor/binder and > as far as I know they aren’t deprecated. Why would their use by Pl/I (to use > your example) perturb you? > My understanding is that Q-constants are offsets into an obtained storage area. PL/I places pointers to global objects in such an area. SAS/C chose to place the objects themselves in that area. CMS Loader supported only 2-byte Q-constants, severely limiting the total size of SAS/C global objects. Didn't PL/I also (previously?) limit subscripts to 16 bits? Storage was costly. > On Sat, Jul 4, 2020 at 7:57 PM -0500, "Seymour J Metz" wrote: > > The default length of a Q-type constant is 4, although early PL/I compilers > used QL2. I don't know whether Enterprise PL/I still uses QL2; I hope not. > It's not perturbing if the compiler allows the programmer the option of 4. Nowadays, 8 might be desirable. -- gil
