I don't see a problem with reentrancy or recursion if the code follows the documented guidelines.
-- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Assembler List <ASSEMBLER-LIST@LISTSERV.UGA.EDU> on behalf of Thomas David Rivers <riv...@dignus.com> Sent: Wednesday, September 30, 2020 6:15 PM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: Register saving formats What if: a) your function is (directly or indirectly) recursive? b) your program needs to be RENT? Mix this problem with the problem of dynamically allocating save area and it gets to be quite an issue. The Dignus C runtime makes the same guarantee of the high-halves that the IBM Assembler Services do (when a 31-bit routine invokes a 64-bit one), as was mentioned before, only the high-halves of R2-R14 are guaranteed to be unchanged for a normal 64-bit function. The Dignus C compiler _can_ generate code that uses the high-halves of registers, and depending on different environment options, will save and restore those 64-bit registers in the caller... which is an even easier approach (the caller has allocated space for this in its DSA.) That way the invoked function can do whatever it needs to them. It's surprising how little saving/restoring winds up happening, as the full 64-bit registers are not frequently busy across a function call in a 31-bit environment. So - that could be another approach, and it would allow you to use standard linkage. - Dave R. - -- riv...@dignus.com Work: (919) 676-0847 Get your mainframe programming tools at http://secure-web.cisco.com/1kEaHjwuENl2Xn-yVtTTPAjmKO5dvKcgMh6_C2adAYlTfz_I4vHdu3qv1rD9o6R5HsChIieskI5B2eZQubh0W4OBDCjdmiJqG5YIAwEHDi1p-K0nmO4O8HAO6KFNJS_Up8irmbhL2vZBMVTo2-jbkrZAipE6HiSvBhQOjbBqkFcQqRIaesAweJnyvikAsGnfT5alYND9GlegzsEfnANbc_mS-npWlEI7l1p5Yn9WRA67beBHxuu6UaNGk_AqymXKw_KhhFxnDuUF4xCyJJKTWAMzFTRNVEnpwy-eoSkcKsiyRVeYnDLNY7ZAqGeZ1NP_PVvnXSrmscvVDPmzTWKbFIDC1swyJJtuxzmhSS3Fp6gzzuEM_UsowmcBG4JjLpRiR-Wz3i1MCW6RVQnZ4SZYREigYfU7mE9naGHs1VfmTZvHS3aKuyJaX-Pz77agn_C86/http%3A%2F%2Fwww.dignus.com
