Re: [PATCH v5 12/20] vsprintf: add new `%pA` format specifier

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Thu, Mar 17, 2022 at 07:10:00PM +0100, Miguel Ojeda wrote:
> From: Gary Guo <gary@garyguo.net>
> 
> This patch adds a format specifier `%pA` to `vsprintf` which formats
> a pointer as `core::fmt::Arguments`. Doing so allows us to directly
> format to the internal buffer of `printf`, so we do not have to use
> a temporary buffer on the stack to pre-assemble the message on
> the Rust side.
> 
> This specifier is intended only to be used from Rust and not for C, so
> `checkpatch.pl` is intentionally unchanged to catch any misuse.

...

> +	case 'A':
> +		if (!IS_ENABLED(CONFIG_RUST)) {
> +			WARN_ONCE(1, "Please remove %%pA from non-Rust code\n");
> +			return error_string(buf, end, "(%pA?)", spec);
> +		}

I'm wondering if the Big Scary Banner as trace_printk() does would be better
(in case we can tell that %pA is used in the code when RUST=n).

-- 
With Best Regards,
Andy Shevchenko