すべての偶数インデックスで、構築された json を MQTT 経由で送信する必要があり、送信されたら json をクリアする必要があり、json を再度構築する必要があります。同じために、以下のスクリプトを使用しています。
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#include <jansson.h>
char *jsonString;
void sendMQTT(char *jsonString){
MQTTClient client;
MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
MQTTClient_message pubmsg = MQTTClient_message_initializer;
MQTTClient_deliveryToken token;
int rc;
MQTTClient_create(&client, "tcp://localhost:1883", "client-pub",
MQTTCLIENT_PERSISTENCE_NONE, NULL);
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
exit(EXIT_FAILURE);
}
printf("Inside MQTT :: %s\n", jsonString);
pubmsg.payload = jsonString;
pubmsg.payloadlen = (int)strlen(jsonString);
pubmsg.qos = 1;
pubmsg.retained = 0;
MQTTClient_publishMessage(client, "mqtt-ex", &pubmsg, &token);
rc = MQTTClient_waitForCompletion(client, token, 10000L);
MQTTClient_disconnect(client, 10000);
MQTTClient_destroy(&client);
}
int main() {
json_t *root = json_object();
char myNum[10] = {10, 20, 10, 40, 10, 60, 10, 80, 10, 100};
for(int i=0; i<10;i++)
{
int json_size = json_object_size(root);
printf("json_size %d\n", json_size);
if(i%2==0 && json_size !=0)
{
sendMQTT(jsonString);
free(jsonString);
json_decref(root);
json_t *root = json_object();
}
char *key= (char*)malloc(8);
snprintf(key, sizeof(key), "%d", myNum[i]);
json_object_set_new( root, key, json_integer(i));
char *jsonString= (char*)malloc(100);
jsonString = json_dumps(root, 0);
printf("json_string :!!: %s\n", jsonString);
free(key);
}
}
一方、同じものをコンパイルして実行すると、
gdb ./editing_file
GNU gdb (Ubuntu 8.2-0ubuntu1~18.04) 8.2
Copyright (C) 2018 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./editing_file...done.
(gdb) run
Starting program: /home/sam/workspace_folder/sample/editing_file
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
json_size 0
json_string :!!: {"10": 0}
json_size 1
json_string :!!: {"10": 0, "20": 1}
json_size 2
Inside MQTT :: (null)
Program received signal SIGSEGV, Segmentation fault.
__strlen_avx2 () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:62
62 ../sysdeps/x86_64/multiarch/strlen-avx2.S: No such file or directory.
(gdb) where
#0 __strlen_avx2 () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:62
#1 0x0000555555554f61 in sendMQTT (jsonString=0x0) at editing_file.c:29
#2 0x0000555555555093 in main () at editing_file.c:51
(gdb)
これを解決するには？この上記のプロセスの何が問題で、これを修正する方法は?
コメントからの提案
コメントからの提案の後、上記のコードは次のように変更されました。
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#include <jansson.h>
char *jsonString;
void sendMQTT(char *jsonString){
MQTTClient client;
MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
MQTTClient_message pubmsg = MQTTClient_message_initializer;
MQTTClient_deliveryToken token;
int rc;
MQTTClient_create(&client, "tcp://localhost:1883", "client-pub",
MQTTCLIENT_PERSISTENCE_NONE, NULL);
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
exit(EXIT_FAILURE);
}
printf("Inside MQTT :: %s\n", jsonString);
pubmsg.payload = jsonString;
pubmsg.payloadlen = (int)strlen(jsonString);
pubmsg.qos = 1;
pubmsg.retained = 0;
MQTTClient_publishMessage(client, "mqtt-ex", &pubmsg, &token);
rc = MQTTClient_waitForCompletion(client, token, 10000L);
MQTTClient_disconnect(client, 10000);
MQTTClient_destroy(&client);
}
int main() {
json_t *root = json_object();
char myNum[10] = {10, 20, 10, 40, 10, 60, 10, 80, 10, 100};
for(int i=0; i<10;i++)
{
int json_size = json_object_size(root);
if(i%2==0 && json_size !=0)
{
sendMQTT(jsonString);
json_object_clear(root);
jsonString = json_dumps(root, 0);
printf("Inside for ===%s\n", jsonString);
}
char *key= (char*)malloc(8);
snprintf(key, sizeof(key), "%d", myNum[i]);
json_object_set_new( root, key, json_integer(i));
jsonString = json_dumps(root, 0);
}
}
そして、望ましい結果を達成することができます。
gdb ./editing_file
GNU gdb (Ubuntu 8.2-0ubuntu1~18.04) 8.2
Copyright (C) 2018 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./editing_file...done.
(gdb) run
Starting program: /home/sam/workspace_folder/sample/editing_file [Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Inside MQTT :: {"10": 0, "20": 1}
Inside for ==={}
Inside MQTT :: {"10": 2, "40": 3}
Inside for ==={}
Inside MQTT :: {"10": 4, "60": 5}
Inside for ==={}
Inside MQTT :: {"10": 6, "80": 7}
Inside for ==={}
[Inferior 1 (process 20590) exited normally]