linux-kernel - Re: [PATCH perf/core v2 7/8] perf help: Do not use ALLOC_GROW in add_cmd

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Date:	Thu, 5 May 2016 20:58:12 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Masami Hiramatsu <mhiramat@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH perf/core v2 7/8] perf help: Do not use ALLOC_GROW in
 add_cmd_list

Em Sat, Apr 30, 2016 at 12:10:51AM +0900, Masami Hiramatsu escreveu:
> Replace ALLOC_GROW with normal realloc code in add_cmd_list()
> so that it can handle errors directly.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
>  tools/perf/util/help-unknown-cmd.c |   30 ++++++++++++++++++++++--------
>  1 file changed, 22 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/perf/util/help-unknown-cmd.c b/tools/perf/util/help-unknown-cmd.c
> index 43a98a4..d62ccae 100644
> --- a/tools/perf/util/help-unknown-cmd.c
> +++ b/tools/perf/util/help-unknown-cmd.c
> @@ -27,16 +27,27 @@ static int levenshtein_compare(const void *p1, const void *p2)
>  	return l1 != l2 ? l1 - l2 : strcmp(s1, s2);
>  }
>  
> -static void add_cmd_list(struct cmdnames *cmds, struct cmdnames *old)
> +static int add_cmd_list(struct cmdnames *cmds, struct cmdnames *old)
>  {
> -	unsigned int i;
> -
> -	ALLOC_GROW(cmds->names, cmds->cnt + old->cnt, cmds->alloc);
> -
> +	unsigned int i, nr = cmds->cnt + old->cnt;
> +	void *tmp;
> +
> +	if (nr > cmds->alloc) {
> +		/* Choose bigger one to alloc */
> +		if (alloc_nr(cmds->alloc) < nr)
> +			cmds->alloc = nr;
> +		else
> +			cmds->alloc = alloc_nr(cmds->alloc);
> +		tmp = realloc(cmds->names, cmds->alloc * sizeof(*cmds->names));
> +		if (!tmp)
> +			return -1;

Cool, here you use replace that big realloc-that-fails (ALLOC_GROW) but
still uses realloc, checking its return, great.

Looks ok.

> +		cmds->names = tmp;
> +	}
>  	for (i = 0; i < old->cnt; i++)
>  		cmds->names[cmds->cnt++] = old->names[i];
>  	zfree(&old->names);
>  	old->cnt = 0;
> +	return 0;
>  }
>  
>  const char *help_unknown_cmd(const char *cmd)
> @@ -52,8 +63,11 @@ const char *help_unknown_cmd(const char *cmd)
>  
>  	load_command_list("perf-", &main_cmds, &other_cmds);
>  
> -	add_cmd_list(&main_cmds, &aliases);
> -	add_cmd_list(&main_cmds, &other_cmds);
> +	if (add_cmd_list(&main_cmds, &aliases) < 0 ||
> +	    add_cmd_list(&main_cmds, &other_cmds) < 0) {
> +		fprintf(stderr, "ERROR: Failed to allocate command list for unknown command.\n");
> +		goto end;
> +	}
>  	qsort(main_cmds.names, main_cmds.cnt,
>  	      sizeof(main_cmds.names), cmdname_compare);
>  	uniq(&main_cmds);
> @@ -99,6 +113,6 @@ const char *help_unknown_cmd(const char *cmd)
>  		for (i = 0; i < n; i++)
>  			fprintf(stderr, "\t%s\n", main_cmds.names[i]->name);
>  	}
> -
> +end:
>  	exit(1);
>  }