Messages in this thread | | | Date | Mon, 14 Feb 2022 11:52:37 +0100 | Subject | Re: [PATCH v4 12/20] vsprintf: add new `%pA` format specifier | From | Rasmus Villemoes <> |
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On 14/02/2022 11.18, Andy Shevchenko wrote: > On Sat, Feb 12, 2022 at 02:03:38PM +0100, Miguel Ojeda wrote: > >> From: Gary Guo <gary@garyguo.net> > > Not sure I understand this... > >> 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. >> >> Co-developed-by: Alex Gaynor <alex.gaynor@gmail.com> >> Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com> >> Co-developed-by: Wedson Almeida Filho <wedsonaf@google.com> >> Signed-off-by: Wedson Almeida Filho <wedsonaf@google.com> > >> Signed-off-by: Gary Guo <gary@garyguo.net> > > ...together with this in the current SoB chain. > >> Co-developed-by: Miguel Ojeda <ojeda@kernel.org> >> Signed-off-by: Miguel Ojeda <ojeda@kernel.org> > > I'm wondering if you considered to use %pV. >
I think the point is for vsnprintf() to call (back) into Rust code.
That said, I don't like the !CONFIG_RUST version to return NULL, that will surely crash moments later.
So I prefer something like
[rust.h] // no CONFIG_RUST conditional +char *rust_fmt_argument(char* buf, char* end, void *ptr);
[vsprintf.c] + case 'A': + if (IS_ENABLED(CONFIG_RUST)) + return rust_fmt_argument(buf, end, ptr); + else + return string_nocheck(buf, end, "[%pA in non-Rust code?!]", default_str_spec);
Rasmus
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