linux-kernel - Re: [PATCH v2 2/3] perf: convert: fix duplicate field names and avoid reserved keywords.

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Date:	Fri, 30 Jan 2015 17:00:38 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Wang Nan <wangnan0@...wei.com>, jeremie.galarneau@...icios.com,
	alexmonthy@...populi.im, bigeasy@...utronix.de, lizefan@...wei.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] perf: convert: fix duplicate field names and
 avoid reserved keywords.

On Fri, Jan 30, 2015 at 10:25:37AM -0500, Steven Rostedt wrote:
> On Mon, Jan 26, 2015 at 06:38:24PM +0800, Wang Nan wrote:
> > (If Steven Rostedt accept the previous patch which introduce a priv
> >  field to 'struct format_field', we can use a relative simple method
> >  for name conversion. If not , perf must track name conversion by
> >  itself.)
> 
> Sorry for coming in so late here.
> 
> > 
> > Some parameters of syscall tracepoints named as 'nr', 'event', etc.
> > When dealing with them, perf convert to ctf meets some problem:
> > 
> >  1. If a parameter with name 'nr', it will duplicate syscall's
> >     common field 'nr'. One such syscall is io_submit().
> > 
> >  2. If a parameter with name 'event', it is denied to be inserted
> >     because 'event' is a babeltrace keywork. One such syscall is
> >     epoll_ctl.
> > 
> > This patch appends '_dupl_X' suffix to avoid problem 1, prepend a '_'
> > prefix to avoid problem 2.
> 
> Actually, I don't like this approach. That is, to have this private
> data structure. Why not just add an "alias" to format_field. In other
> words, instead of hiding this interaction behind a void pointer and 
> needing to create a function pointer to free it, just add another
> field to format field and be done with it. I think it would make
> the code a hell of a lot simpler and easier to understand.
> 
>  struct format_field {
>  	struct format_field	*next;
> 	struct event_format	*event;
> 	char			*type;
> 	char			*name;
> +	char			*alias;
> 	int			offset;
> 	int			size;
> 	unsigned int		arraylen;
> 	unsigned int		elementsize;
> 	unsigned long		flags;
> };
> 
> And put the logic in event parse to free alias if need be.
> Heck, you could even add a pevent_*() func to assign the alias
> using strdup, or what not.

ok, sounds good

thanks,
jirka
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