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

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Date:   Fri, 14 Feb 2020 21:21:21 +0800
From:   <zhe.he@...driver.com>
To:     <rostedt@...dmis.org>, <acme@...hat.com>, <tstoyanov@...are.com>,
        <hewenliang4@...wei.com>, <linux-kernel@...r.kernel.org>,
        <zhe.he@...driver.com>
Subject: [PATCH v2] tools lib traceevent: Take care of return value of asprintf

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]

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