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Fri, 07 Nov 2025 04:52:29 -0800 (PST) Date: Fri, 7 Nov 2025 13:52:27 +0100 From: Petr Mladek To: Andy Shevchenko Cc: David Laight , Andrew Morton , Junrui Luo , linux-kernel@vger.kernel.org, rostedt@goodmis.org, tiwai@suse.com, perex@perex.cz, linux-sound@vger.kernel.org, mchehab@kernel.org, awalls@md.metrocast.net, linux-media@vger.kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org Subject: Re: [PATCH 1/4] lib/sprintf: add scnprintf_append() helper function Message-ID: References: <20251107051616.21606-1-moonafterrain@outlook.com> <20251106213833.546c8eaba8aec6aa6a5e30b6@linux-foundation.org> <20251107091246.4e5900f4@pumpkin> Precedence: bulk X-Mailing-List: linux-sound@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri 2025-11-07 11:35:35, Andy Shevchenko wrote: > On Fri, Nov 07, 2025 at 09:12:46AM +0000, David Laight wrote: > > On Thu, 6 Nov 2025 21:38:33 -0800 > > Andrew Morton wrote: > > > On Fri, 7 Nov 2025 13:16:13 +0800 Junrui Luo wrote: > > ... > > > That is true for all the snprintf() functions. > > > > > I wonder if we should instead implement a kasprintf() version of this > > > which reallocs each time and then switch all the callers over to that. > > > > That adds the cost of a malloc, and I, like kasprintf() probably ends up > > doing all the work of snprintf twice. > > > > I'd be tempted to avoid the strlen() by passing in the offset. > > So (say): > > #define scnprintf_at(buf, len, off, ...) \ > > scnprintf((buf) + off, (len) - off, __VA_ARGS__) It does not handle correctly the situation when len < off. Othersise, it looks good. > > Then you can chain calls, eg: > > off = scnprintf(buf, sizeof buf, ....); > > off += scnprintf_at(buf, sizeof buf, off, ....); > > I like this suggestion. Also note, that the original implementation works directly > on static buffers. I would prefer this as well. IMHO, it encourages people to write a better code. Best Regards, Petr