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Date: Fri, 14 Feb 2020 21:17:26 +0800
From: He Zhe <zhe.he@...driver.com>
To: Arnaldo Carvalho de Melo <acme@...hat.com>
CC: <rostedt@...dmis.org>, <tstoyanov@...are.com>,
<hewenliang4@...wei.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tools lib traceevent: Take care of return value of
asprintf
On 2/14/20 8:57 PM, Arnaldo Carvalho de Melo wrote:
> Em Fri, Feb 14, 2020 at 03:31:26PM +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.
>>
>> 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]
> Sure this fixes problems, but can you make it more compact, i.e. no need
> to add most if not all those 'int ret;' lines, just check the asprintf
> result directly, i.e.:
>
> if (asprintf(&str, val ? "TRUE" : "FALSE") < 0)
> str = NULL;
>
> saving the return value for that function is interesting when you need
> to know how many bytes it printed to do some extra calculation, but if
> all you need is to know if it failed, checking against < 0 is enough,
> no?
OK. Thanks. I'll send v2.
Zhe
>
> - Arnaldo
>
>
>> Signed-off-by: He Zhe <zhe.he@...driver.com>
>> ---
>> tools/lib/traceevent/parse-filter.c | 42 +++++++++++++++++++++++++++++--------
>> 1 file changed, 33 insertions(+), 9 deletions(-)
>>
>> diff --git a/tools/lib/traceevent/parse-filter.c b/tools/lib/traceevent/parse-filter.c
>> index 20eed71..279b572 100644
>> --- a/tools/lib/traceevent/parse-filter.c
>> +++ b/tools/lib/traceevent/parse-filter.c
>> @@ -1912,6 +1912,7 @@ static char *op_to_str(struct tep_event_filter *filter, struct tep_filter_arg *a
>> int left_val = -1;
>> int right_val = -1;
>> int val;
>> + int ret;
>>
>> switch (arg->op.type) {
>> case TEP_FILTER_OP_AND:
>> @@ -1958,7 +1959,9 @@ static char *op_to_str(struct tep_event_filter *filter, struct tep_filter_arg *a
>> default:
>> break;
>> }
>> - asprintf(&str, val ? "TRUE" : "FALSE");
>> + ret = asprintf(&str, val ? "TRUE" : "FALSE");
>> + if (ret < 0)
>> + str = NULL;
>> break;
>> }
>> }
>> @@ -1976,7 +1979,9 @@ static char *op_to_str(struct tep_event_filter *filter, struct tep_filter_arg *a
>> break;
>> }
>>
>> - asprintf(&str, "(%s) %s (%s)", left, op, right);
>> + ret = asprintf(&str, "(%s) %s (%s)", left, op, right);
>> + if (ret < 0)
>> + str = NULL;
>> break;
>>
>> case TEP_FILTER_OP_NOT:
>> @@ -1992,10 +1997,14 @@ 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");
>> + ret = asprintf(&str, right_val ? "FALSE" : "TRUE");
>> + if (ret < 0)
>> + str = NULL;
>> break;
>> }
>> - asprintf(&str, "%s(%s)", op, right);
>> + ret = asprintf(&str, "%s(%s)", op, right);
>> + if (ret < 0)
>> + str = NULL;
>> break;
>>
>> default:
>> @@ -2010,8 +2019,11 @@ static char *op_to_str(struct tep_event_filter *filter, struct tep_filter_arg *a
>> static char *val_to_str(struct tep_event_filter *filter, struct tep_filter_arg *arg)
>> {
>> char *str = NULL;
>> + int ret;
>>
>> - asprintf(&str, "%lld", arg->value.val);
>> + ret = asprintf(&str, "%lld", arg->value.val);
>> + if (ret < 0)
>> + str = NULL;
>>
>> return str;
>> }
>> @@ -2027,6 +2039,7 @@ static char *exp_to_str(struct tep_event_filter *filter, struct tep_filter_arg *
>> char *rstr;
>> char *op;
>> char *str = NULL;
>> + int ret;
>>
>> lstr = arg_to_str(filter, arg->exp.left);
>> rstr = arg_to_str(filter, arg->exp.right);
>> @@ -2069,7 +2082,9 @@ static char *exp_to_str(struct tep_event_filter *filter, struct tep_filter_arg *
>> break;
>> }
>>
>> - asprintf(&str, "%s %s %s", lstr, op, rstr);
>> + ret = asprintf(&str, "%s %s %s", lstr, op, rstr);
>> + if (ret < 0)
>> + str = NULL;
>> out:
>> free(lstr);
>> free(rstr);
>> @@ -2083,6 +2098,7 @@ static char *num_to_str(struct tep_event_filter *filter, struct tep_filter_arg *
>> char *rstr;
>> char *str = NULL;
>> char *op = NULL;
>> + int ret;
>>
>> lstr = arg_to_str(filter, arg->num.left);
>> rstr = arg_to_str(filter, arg->num.right);
>> @@ -2113,7 +2129,9 @@ 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);
>> + ret = asprintf(&str, "%s %s %s", lstr, op, rstr);
>> + if (ret < 0)
>> + str = NULL;
>> break;
>>
>> default:
>> @@ -2131,6 +2149,7 @@ static char *str_to_str(struct tep_event_filter *filter, struct tep_filter_arg *
>> {
>> char *str = NULL;
>> char *op = NULL;
>> + int ret;
>>
>> switch (arg->str.type) {
>> case TEP_FILTER_CMP_MATCH:
>> @@ -2148,8 +2167,10 @@ static char *str_to_str(struct tep_event_filter *filter, struct tep_filter_arg *
>> if (!op)
>> op = "!~";
>>
>> - asprintf(&str, "%s %s \"%s\"",
>> + ret = asprintf(&str, "%s %s \"%s\"",
>> arg->str.field->name, op, arg->str.val);
>> + if (ret < 0)
>> + str = NULL;
>> break;
>>
>> default:
>> @@ -2162,10 +2183,13 @@ static char *str_to_str(struct tep_event_filter *filter, struct tep_filter_arg *
>> static char *arg_to_str(struct tep_event_filter *filter, struct tep_filter_arg *arg)
>> {
>> char *str = NULL;
>> + int ret;
>>
>> switch (arg->type) {
>> case TEP_FILTER_ARG_BOOLEAN:
>> - asprintf(&str, arg->boolean.value ? "TRUE" : "FALSE");
>> + ret = asprintf(&str, arg->boolean.value ? "TRUE" : "FALSE");
>> + if (ret < 0)
>> + str = NULL;
>> return str;
>>
>> case TEP_FILTER_ARG_OP:
>> --
>> 2.7.4
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