linux-kernel - Re: [PATCH v2] tools lib traceevent: Take care of return value of asprintf

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Date:   Mon, 17 Feb 2020 12:53:23 -0300
From:   Arnaldo Carvalho de Melo <acme@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>, zhe.he@...driver.com
Cc:     rostedt@...dmis.org, tstoyanov@...are.com, hewenliang4@...wei.com,
        linux-kernel@...r.kernel.org, acme@...nel.org
Subject: Re: [PATCH v2] tools lib traceevent: Take care of return value of
 asprintf

Em Fri, Feb 14, 2020 at 09:21:21PM +0800, zhe.he@...driver.com escreveu:
> From: He Zhe <zhe.he@...driver.com>
> 
> According to the API, if memory allocation wasn't possible, or some other
> error occurs, asprintf will return -1, and the contents of strp below are
> undefined.

Rostedt, did I miss some ack from you?

- Arnaldo
 
> int asprintf(char **strp, const char *fmt, ...);
> 
> This patch takes care of return value of asprintf to make it less error
> prone and prevent the following build warning.
> 
> ignoring return value of ‘asprintf’, declared with attribute warn_unused_result [-Wunused-result]
> 
> Signed-off-by: He Zhe <zhe.he@...driver.com>
> ---
> v2: directly check the return value without saving to a variable
> 
>  tools/lib/traceevent/parse-filter.c | 35 +++++++++++++++++++++--------------
>  1 file changed, 21 insertions(+), 14 deletions(-)
> 
> diff --git a/tools/lib/traceevent/parse-filter.c b/tools/lib/traceevent/parse-filter.c
> index 20eed71..6cd0228 100644
> --- a/tools/lib/traceevent/parse-filter.c
> +++ b/tools/lib/traceevent/parse-filter.c
> @@ -274,8 +274,7 @@ find_event(struct tep_handle *tep, struct event_list **events,
>  		sys_name = NULL;
>  	}
>  
> -	ret = asprintf(&reg, "^%s$", event_name);
> -	if (ret < 0)
> +	if (asprintf(&reg, "^%s$", event_name) < 0)
>  		return TEP_ERRNO__MEM_ALLOC_FAILED;
>  
>  	ret = regcomp(&ereg, reg, REG_ICASE|REG_NOSUB);
> @@ -285,8 +284,7 @@ find_event(struct tep_handle *tep, struct event_list **events,
>  		return TEP_ERRNO__INVALID_EVENT_NAME;
>  
>  	if (sys_name) {
> -		ret = asprintf(&reg, "^%s$", sys_name);
> -		if (ret < 0) {
> +		if (asprintf(&reg, "^%s$", sys_name) < 0) {
>  			regfree(&ereg);
>  			return TEP_ERRNO__MEM_ALLOC_FAILED;
>  		}
> @@ -1958,7 +1956,8 @@ static char *op_to_str(struct tep_event_filter *filter, struct tep_filter_arg *a
>  				default:
>  					break;
>  				}
> -				asprintf(&str, val ? "TRUE" : "FALSE");
> +				if (asprintf(&str, val ? "TRUE" : "FALSE") < 0)
> +					str = NULL;
>  				break;
>  			}
>  		}
> @@ -1976,7 +1975,8 @@ static char *op_to_str(struct tep_event_filter *filter, struct tep_filter_arg *a
>  			break;
>  		}
>  
> -		asprintf(&str, "(%s) %s (%s)", left, op, right);
> +		if (asprintf(&str, "(%s) %s (%s)", left, op, right) < 0)
> +			str = NULL;
>  		break;
>  
>  	case TEP_FILTER_OP_NOT:
> @@ -1992,10 +1992,12 @@ static char *op_to_str(struct tep_event_filter *filter, struct tep_filter_arg *a
>  			right_val = 0;
>  		if (right_val >= 0) {
>  			/* just return the opposite */
> -			asprintf(&str, right_val ? "FALSE" : "TRUE");
> +			if (asprintf(&str, right_val ? "FALSE" : "TRUE") < 0)
> +				str = NULL;
>  			break;
>  		}
> -		asprintf(&str, "%s(%s)", op, right);
> +		if (asprintf(&str, "%s(%s)", op, right) < 0)
> +			str = NULL;
>  		break;
>  
>  	default:
> @@ -2011,7 +2013,8 @@ static char *val_to_str(struct tep_event_filter *filter, struct tep_filter_arg *
>  {
>  	char *str = NULL;
>  
> -	asprintf(&str, "%lld", arg->value.val);
> +	if (asprintf(&str, "%lld", arg->value.val) < 0)
> +		str = NULL;
>  
>  	return str;
>  }
> @@ -2069,7 +2072,8 @@ static char *exp_to_str(struct tep_event_filter *filter, struct tep_filter_arg *
>  		break;
>  	}
>  
> -	asprintf(&str, "%s %s %s", lstr, op, rstr);
> +	if (asprintf(&str, "%s %s %s", lstr, op, rstr) < 0)
> +		str = NULL;
>  out:
>  	free(lstr);
>  	free(rstr);
> @@ -2113,7 +2117,8 @@ static char *num_to_str(struct tep_event_filter *filter, struct tep_filter_arg *
>  		if (!op)
>  			op = "<=";
>  
> -		asprintf(&str, "%s %s %s", lstr, op, rstr);
> +		if (asprintf(&str, "%s %s %s", lstr, op, rstr) < 0)
> +			str = NULL;
>  		break;
>  
>  	default:
> @@ -2148,8 +2153,9 @@ static char *str_to_str(struct tep_event_filter *filter, struct tep_filter_arg *
>  		if (!op)
>  			op = "!~";
>  
> -		asprintf(&str, "%s %s \"%s\"",
> -			 arg->str.field->name, op, arg->str.val);
> +		if (asprintf(&str, "%s %s \"%s\"",
> +			 arg->str.field->name, op, arg->str.val) < 0)
> +			str = NULL;
>  		break;
>  
>  	default:
> @@ -2165,7 +2171,8 @@ static char *arg_to_str(struct tep_event_filter *filter, struct tep_filter_arg *
>  
>  	switch (arg->type) {
>  	case TEP_FILTER_ARG_BOOLEAN:
> -		asprintf(&str, arg->boolean.value ? "TRUE" : "FALSE");
> +		if (asprintf(&str, arg->boolean.value ? "TRUE" : "FALSE") < 0)
> +			str = NULL;
>  		return str;
>  
>  	case TEP_FILTER_ARG_OP:
> -- 
> 2.7.4