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| From: | Paul Eggert |
| Subject: | bug#36649: 27.0.50; pure space and pdumper |
| Date: | Thu, 4 Mar 2021 13:52:29 -0800 |
| User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 |
On 3/4/21 6:56 AM, Robert Pluim wrote:
Pip> - zero vector handling depends on Qnil being all zero in memory
I think Emacs already assumes Qnil == 0, since there are places that
use ! to check for Qnil rather than using NILP.
The convention is to put a "verify (NIL_IS_ZERO);" near the rare bits of code that assume Qnil is all-bits-zero. This is to help out any hypothetical future developer who wants to change Qnil to be some other value. Currently there are only two such locations. (There is one other location that uses NIL_IS_ZERO for an optimization.)
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