[TUHS] two AIX items [was Re: History of symbol preemption

[Charles H Sauer]

On 1/13/2020 1:58 PM, Paul Winalski wrote:

> ...  LInux, AIX and probably other implementations of ELF have a
> feature in the runtime loader called symbol preemption.  When loading

As far as I know, AIX has never used ELF.

On the RT, AIX 1 & 2 used a.out enhanced for basic shared library 
support, designed by Larry Loucks with help from ISC, probably John 
Levine, if I recall correctly.

Starting with AIX 3, AIX used an extended COFF. See Auslander et al, 
"Dynamic Linking and Loading in the AIX System", SA23-2619 RISC 
System/6000 Technology p. 151. (I don't have/know of PDF of SA23-2619.) 
See, also, https://en.wikipedia.org/wiki/XCOFF.

It seems likely that AIX XCOFF supported symbol preemption, I haven't 
tried to determine one way or the other.

AIX on 386 & 370 probably used a.out. Clem probably knows.

An IBM retirees group on Facebook led me to IBM AIX Enhancements and 
Modernization at http://www.redbooks.ibm.com/abstracts/sg248453.html, 
just available yesterday. I tend to think of AIX as abandoned by IBM in 
favor of Linux, but, of course, that isn't really true. I've downloaded 
the PDF, but not looked inside.

Charlie

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