I don't know the answer to your question but I share your general consternation. This used to be so simple: program, task or subroutine, on entry STM and chain.
I've spent enough time on it to think there is no good general answer. I could be/hope I am wrong. Charles -----Original Message----- From: IBM Mainframe Assembler List [mailto:[email protected]] On Behalf Of John McKown Sent: Tuesday, May 30, 2017 6:39 AM To: [email protected] Subject: Save areas (not XPLINK). As best as I can tell, there are 5 different Save Area formats. There is the historic 72 byte format. This saves bits 32..63 of GPR 14-12. There is an F4SA which is 144 bytes and contains bits 0..63 of GPRs 14-12. There is a F5SA which holds bits 0..63 of the GPRs 14-12 and bits 0..31 of GPRs 0-15. There is F7SA which holds bits 0..63 of GPRs 14-12 and ARs 14-12 plus "alet of previous save area" (isn't this just AR13 at entry?). And finally, there is F8SA which is bits 0..63 of GPRs 14-12, ARs 14-12, "alet of previous savearea", bits 32..63 of GPRs 0-15. ref: https://www.ibm.com/support/knowledgecenter/SSLTBW_2.2.0/com.ibm.zos.v2r2.iead200/iead200571.htm First question: Why save the "high word" of regs 0-15 in addition to the entire double word of regs 14-12 (all but GPR15)? Second question: Why say "alet of previous savearea" rather than AR13? Is there a case where this is _not_ in AR13 at entry? If so, how would I know? Philosophy question: If I am writing a non-LE enabled HLASM subroutine, should I check the "save area type" to ensure that my routine is properly callable from any non-XPLINK routine? I know that the standard says that it is the _caller's_ responsibility to do this. But I'm paranoid. And I don't way to ASSuME that the caller is paying attention and by so doing possibly introduce a memory overlay in the caller. Also, if I get a "bad" type of savearea, should I "do something", such as using the linkage stack, or should I abend or maybe return a "failed" return code? -- Windows. A funny name for a operating system that doesn't let you see anything. Maranatha! <>< John McKown
