linux-kernel - Re: [PATCH 1/3] perf probe: Remove length limitation for showing available variables

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Date:	Sat, 9 May 2015 15:16:45 +0800
From:	He Kuang <hekuang@...wei.com>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	<a.p.zijlstra@...llo.nl>, <acme@...nel.org>, <jolsa@...nel.org>,
	<mingo@...hat.com>
CC:	<wangnan0@...wei.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] perf probe: Remove length limitation for showing
 available variables


On 2015/5/8 22:17, Masami Hiramatsu wrote:
> On 2015/05/08 21:23, He Kuang wrote:
>> Use struct strbuf instead of bare char[] to remove the length limitation
>> of variables in variable_list, so they will not disappear due to
>> overlength, and make preparation for adding more description for
>> variables.
> Looks good to me, except one memory leak. please see below.

Oh yes, thanks!
>>  }
>>  
>> -#define MAX_VAR_LEN 64
>> -
>>  /* Collect available variables in this scope */
>>  static int collect_variables_cb(Dwarf_Die *die_mem, void *data)
>>  {
>>  	struct available_var_finder *af = data;
>>  	struct variable_list *vl;
>> -	char buf[MAX_VAR_LEN];
>> +	struct strbuf buf;
>>  	int tag, ret;
>>  
>>  	vl = &af->vls[af->nvls - 1];
>> +	strbuf_init(&buf, 64);
>>  
>>  	tag = dwarf_tag(die_mem);
>>  	if (tag == DW_TAG_formal_parameter ||
>> @@ -1257,10 +1256,13 @@ static int collect_variables_cb(Dwarf_Die *die_mem, void *data)
>>  						af->pf.fb_ops, &af->pf.sp_die,
>>  						NULL);
>>  		if (ret == 0) {

strbuf_init() should be called here to avoid useless malloc.

>> -			ret = die_get_varname(die_mem, buf, MAX_VAR_LEN);
>> -			pr_debug2("Add new var: %s\n", buf);
>> -			if (ret > 0)
>> -				strlist__add(vl->vars, buf);
>> +			ret = die_get_varname(die_mem, &buf);
>> +			pr_debug2("Add new var: %s\n", buf.buf);
>> +			if (ret == 0) {
>> +				strlist__add(vl->vars,
>> +					strbuf_detach(&buf, NULL));
>> +			}
>> +			strbuf_release(&buf);
> It seems that this strbuf_release() should be called in any case,
> since strbuf_init already allocated buffer.
>
>>  		}
>>  	}
> so here is the good place to call, isn't it?
>
> Thank you,
>
>>  
>>
>


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