linux-kernel - Re: DEFINE_FREE/CLASS && code readability (Was: [PATCH v2 2/6] Provide __free(argv) for argv

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Message-ID: <20250106102647.GB20870@noisy.programming.kicks-ass.net>
Date: Mon, 6 Jan 2025 11:26:47 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Oleg Nesterov <oleg@...hat.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	"David S . Miller" <davem@...emloft.net>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Tzvetomir Stoyanov <tz.stoyanov@...il.com>,
	Naveen N Rao <naveen@...nel.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Jason Baron <jbaron@...mai.com>, Ard Biesheuvel <ardb@...nel.org>,
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: DEFINE_FREE/CLASS && code readability (Was: [PATCH v2 2/6]
 Provide __free(argv) for argv_split() users)

On Sun, Jan 05, 2025 at 03:14:22PM +0100, Oleg Nesterov wrote:

> OK, so it can be used as
> 
> 	void func(void)
> 	{
> 		char **argv __free(argv) = argv_split(...);
> 		do_something(argv);
> 		return;
> 	}
> 
> And I cry every time when I read the code like this ;)
> 
> Because, to understand this code, I need to do the "nontrivial" grep to find
> "DEFINE_FREE(argv,".
> 
> Perhaps we can establish a simple rule that every DEFINE_FREE() or DEFINE_CLASS()
> should add another #define? I mean something like
> 
> 
> 	DEFINE_FREE(argv, char **, if (!IS_ERR_OR_NULL(_T)) argv_free(_T))
> 	#define __FREE_ARGV	__free(argv)
> 	
> 	void func(void)
> 	{
> 		char **argv __FREE_ARGV = argv_split(...);
> 		do_something(argv);
> 		return;
> 	}
> 
> This way I can press Ctrl-] and see what the cleanup code actually does.
> Can save a second or two. Important when you try to read the code you are
> not familiar with.

Right, so I've been playing with neovim and clangd (lsp), and I'm very
disappointed to have to tell you that that also doesn't get it :-(

One thing we can and should do is something like:

diff --git a/scripts/tags.sh b/scripts/tags.sh
index b21236377998..f01d694abe65 100755
--- a/scripts/tags.sh
+++ b/scripts/tags.sh
@@ -212,6 +212,8 @@ regex_c=(
 	'/^SEQCOUNT_LOCKTYPE(\([^,]*\),[[:space:]]*\([^,]*\),[^)]*)/seqcount_\2_init/'
 	'/^\<DECLARE_IDTENTRY[[:alnum:]_]*([^,)]*,[[:space:]]*\([[:alnum:]_]\+\)/\1/'
 	'/^\<DEFINE_IDTENTRY[[:alnum:]_]*([[:space:]]*\([[:alnum:]_]\+\)/\1/'
+	'/^\<DEFINE_FREE(\([[:alnum:]_]\+\)/cleanup_\1/'
+	'/^\<DEFINE_CLASS(\([[:alnum:]_]\+\)/class_\1/'
 )
 regex_kconfig=(
 	'/^[[:blank:]]*\(menu\|\)config[[:blank:]]\+\([[:alnum:]_]\+\)/\2/'

That should be able to let you do: ':ts cleanup_argv'