Re: [PATCH 25/32] tools/nolibc: allow different write callbacks in printf

[Willy Tarreau <w@1wt.eu>]

On Tue, Mar 04, 2025 at 08:10:55AM +0100, Thomas Weißschuh wrote:
> Decouple the formatting logic from the writing logic to later enable
> writing straight to a buffer in sprintf().
> 
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> ---
>  tools/include/nolibc/stdio.h | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h
> index 262d0da4da9062e0c83b55661b2509f36548cf88..434fbaddae7a216159fecf618da85889d631dff7 100644
> --- a/tools/include/nolibc/stdio.h
> +++ b/tools/include/nolibc/stdio.h
> @@ -208,13 +208,15 @@ char *fgets(char *s, int size, FILE *stream)
>  }
>  
>  
> -/* minimal vfprintf(). It supports the following formats:
> +/* minimal printf(). It supports the following formats:
>   *  - %[l*]{d,u,c,x,p}
>   *  - %s
>   *  - unknown modifiers are ignored.
>   */
> -static __attribute__((unused, format(printf, 2, 0)))
> -int vfprintf(FILE *stream, const char *fmt, va_list args)
> +typedef int (*_printf_cb)(intptr_t state, const char *buf, size_t size);

Keep in mind these ones will appear in the application, so you'd rather
appropriate the type name by prefixing it with "nolibc" as we've done in
a few macros and internal structs.

> +static __attribute__((unused, format(printf, 3, 0)))
> +int _printf(_printf_cb cb, intptr_t state, const char *fmt, va_list args)
       ^^^^^^^
Here as well, since it's not meant to be exposed to the application.

> +static int _fprintf_cb(intptr_t state, const char *buf, size_t size)

Likewise here I think.

Willy