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From: Eli Zaretskii <eliz@gnu.org>
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Subject: Re: MPS prstack
Date: Mon, 27 May 2024 14:34:31 +0300
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To: Helmut Eller <eller.helmut@gmail.com>
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> From: Helmut Eller <eller.helmut@gmail.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  Emacs Devel <emacs-devel@gnu.org>
> Date: Mon, 27 May 2024 09:27:31 +0200
> 
> Somewhat related: I wonder if this line in print_stack_push is safe:
> 
>   prstack.stack[prstack.sp++] = e;
> 
> This is not an atomic operation and prstack.sp gets updated before the
> new stack slot is initialized.

Are you sure?  I think the above assigns e to
prstack.stack[prstack.sp], and then increments prstack.sp.  What you
describe is this instead:

  prstack.stack[++prstack.sp] = e;

By analogy with the original code above, what does the following do?

  char *s;
  *s++ = 'a';

AFAIU, it stores 'a' in the address pointed by s and then increments
s.