GNU bug report logs - #48264
28.0.50; Changing the default for DEFVAR_PER_BUFFER variables takes O(#buffers) time

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From: Eli Zaretskii <eliz <at> gnu.org>
To: Spencer Baugh <sbaugh <at> catern.com>
Cc: 48264 <at> debbugs.gnu.org
Subject: bug#48264: [PATCH v3 07/15] Add BVAR_OR_DEFAULT macro as a stub
Date: Fri, 07 May 2021 13:54:15 +0300

> From: Spencer Baugh <sbaugh <at> catern.com>
> Date: Thu,  6 May 2021 17:33:38 -0400
> Cc: Spencer Baugh <sbaugh <at> catern.com>
> 
> For buffer variables without a default, we still use BVAR.  For any
> buffer variable with a default, we use BVAR_OR_DEFAULT.  A later
> commit will statically enforce this.

This part says they are the same:

> --- a/src/buffer.h
> +++ b/src/buffer.h
> @@ -284,6 +284,8 @@ struct buffer_text
>  
>  #define BVAR(buf, field) ((buf)->field ## _)
>  
> +#define BVAR_OR_DEFAULT(buf, field) BVAR (buf, field)

What am I missing here?

Also, I have a question: suppose we have a variable that is defined
with DEFVAR_LISP, and then some Lisp calls make-variable-buffer-local:
how will that work with these two macros when the C code needs to
access the buffer-local value?

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