AIX 5.2 unexec problem

AIX 5.2 unexec problem

[Joe Buehler]

Based on an examination of the file headers, the AIX unexec is simply moving
all of .bss into .data.  It does not attempt to move any part of .data to
.text.

I assume that no part of .data is moved to .text as a programming simplification.
Less memory will be shared between emacs instances, but everything will work fine.

My question regards treatment of .data/.bss.  Is all of the read/write data supposed
to be preserved across unexec?

If it is not, the AIX unexec is wrong, and further, the AIX link is incorrect:

Newer versions of the AIX linker reorder objects, so the manual placement of
lastfile.o on the link line doesn't cause the desired memory layout.  The
option -bnoobjreorder needs to be added to the link command line to turn off
object reordering.
-- 
Joe Buehler

Re: AIX 5.2 unexec problem

[Richard Stallman]

    My question regards treatment of .data/.bss.  Is all of the read/write data supposed
    to be preserved across unexec?

It is abslutely necessary to dump the bss as data because it is filled
with Lisp objects that must be preserved in the dumped Emacs.

    Newer versions of the AIX linker reorder objects, so the manual placement of
    lastfile.o on the link line doesn't cause the desired memory layout.  The
    option -bnoobjreorder needs to be added to the link command line to turn off
    object reordering.

Can you fix it using that method?

Re: AIX 5.2 unexec problem

[Joe Buehler]

Richard Stallman wrote:
>     My question regards treatment of .data/.bss.  Is all of the read/write data supposed
>     to be preserved across unexec?
>
> It is abslutely necessary to dump the bss as data because it is filled
> with Lisp objects that must be preserved in the dumped Emacs.
>   
Is all of bss supposed to be saved?  Even the parts that come after the
marker symbols in lastfile.c?

>     Newer versions of the AIX linker reorder objects, so the manual placement of
>     lastfile.o on the link line doesn't cause the desired memory layout.  The
>     option -bnoobjreorder needs to be added to the link command line to turn off
>     object reordering.
>
> Can you fix it using that method?
>   
I am currently building with -bnoobjreorder in LDFLAGS and that does
indeed preserve the proper
object ordering.

-- 
Joe Buehler



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Re: AIX 5.2 unexec problem

[Richard Stallman]

    I am currently building with -bnoobjreorder in LDFLAGS and that does
    indeed preserve the proper
    object ordering.

We can't add it to LDFLAGS directly, so please try using a file
aix5.h like this:

#include "aix4-2.h"

#define LD_SWITCH_SYSTEM -bnoobjreorder