Segmentation fault when using redisAsyncCommand() - c

Question

i have next simple code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include "hiredis.h"
#include "async.h"
#include "adapters/libevent.h"
void onMessage(redisAsyncContext *c, void *reply, void *privdata) {
redisReply *r = reply;
if (reply == NULL) return;
int j;
if (r->type == REDIS_REPLY_ARRAY) {
for (j = 0; j < r->elements; j++) {
printf("%u) %s\n", j, r->element[j]->str);
}
}*/
}
int main (int argc, char **argv) {
signal(SIGPIPE, SIG_IGN);
struct event_base *base = event_base_new();
redisAsyncContext *c = redisAsyncConnect("127.0.0.1", 6379);
if (c->err) {
printf("error: %s\n", c->errstr);
return 1;
}
redisLibeventAttach(c, base);
redisAsyncCommand(c, onMessage, NULL, "SUBSCRIBE messages");
event_base_dispatch(base);
return 0;
}
program compiles and runs well. but it returns error "Segmentation fault" when executes. if i comment redisAsyncCommand() function error disappears.
where is the error in my code?
added:
when i compile my code i have warnings:
make all
'Building file: ../src/redis.c'
'Invoking: Cross GCC Compiler'
arm-linux-gnueabihf-gcc -I"C:\SysGCC\Raspberry\include" -I"C:\SysGCC\Raspberry\include\hiredis" -I"C:\SysGCC\Raspberry\include\event2" -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"src/redis.d" -MT"src/redis.o" -o "src/redis.o" "../src/redis.c"
In file included from ../src/redis.c:7:0:
C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h: In function 'redisLibeventAddRead':
C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:56:15: warning: passing argument 1 of 'event_add' from incompatible pointer type
event_add(&e->rev,NULL);
^
In file included from C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:33:0,
from ../src/redis.c:7:
C:\SysGCC\Raspberry\include\event2/event.h:937:5: note: expected 'struct event *' but argument is of type 'struct event **'
int event_add(struct event *ev, const struct timeval *timeout);
^
In file included from ../src/redis.c:7:0:
C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h: In function 'redisLibeventDelRead':
C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:61:15: warning: passing argument 1 of 'event_del' from incompatible pointer type
event_del(&e->rev);
^
In file included from C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:33:0,
from ../src/redis.c:7:
C:\SysGCC\Raspberry\include\event2/event.h:950:5: note: expected 'struct event *' but argument is of type 'struct event **'
int event_del(struct event *);
^
In file included from ../src/redis.c:7:0:
C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h: In function 'redisLibeventAddWrite':
C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:66:15: warning: passing argument 1 of 'event_add' from incompatible pointer type
event_add(&e->wev,NULL);
^
In file included from C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:33:0,
from ../src/redis.c:7:
C:\SysGCC\Raspberry\include\event2/event.h:937:5: note: expected 'struct event *' but argument is of type 'struct event **'
int event_add(struct event *ev, const struct timeval *timeout);
^
In file included from ../src/redis.c:7:0:
C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h: In function 'redisLibeventDelWrite':
C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:71:15: warning: passing argument 1 of 'event_del' from incompatible pointer type
event_del(&e->wev);
^
In file included from C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:33:0,
from ../src/redis.c:7:
C:\SysGCC\Raspberry\include\event2/event.h:950:5: note: expected 'struct event *' but argument is of type 'struct event **'
int event_del(struct event *);
^
In file included from ../src/redis.c:7:0:
C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h: In function 'redisLibeventCleanup':
C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:76:15: warning: passing argument 1 of 'event_del' from incompatible pointer type
event_del(&e->rev);
^
In file included from C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:33:0,
from ../src/redis.c:7:
C:\SysGCC\Raspberry\include\event2/event.h:950:5: note: expected 'struct event *' but argument is of type 'struct event **'
int event_del(struct event *);
^
In file included from ../src/redis.c:7:0:
C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:77:15: warning: passing argument 1 of 'event_del' from incompatible pointer type
event_del(&e->wev);
^
In file included from C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:33:0,
from ../src/redis.c:7:
C:\SysGCC\Raspberry\include\event2/event.h:950:5: note: expected 'struct event *' but argument is of type 'struct event **'
int event_del(struct event *);
^
In file included from ../src/redis.c:7:0:
C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h: In function 'redisLibeventAttach':
C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:102:5: warning: implicit declaration of function 'event_set' [-Wimplicit-function-declaration]
event_set(&e->rev,c->fd,EV_READ,redisLibeventReadEvent,e);
^
C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:104:25: warning: passing argument 2 of 'event_base_set' from incompatible pointer type
event_base_set(base,&e->rev);
^
In file included from C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:33:0,
from ../src/redis.c:7:
C:\SysGCC\Raspberry\include\event2/event.h:627:5: note: expected 'struct event *' but argument is of type 'struct event **'
int event_base_set(struct event_base *, struct event *);
^
In file included from ../src/redis.c:7:0:
C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:105:25: warning: passing argument 2 of 'event_base_set' from incompatible pointer type
event_base_set(base,&e->wev);
^
In file included from C:\SysGCC\Raspberry\include\hiredis/adapters/libevent.h:33:0,
from ../src/redis.c:7:
C:\SysGCC\Raspberry\include\event2/event.h:627:5: note: expected 'struct event *' but argument is of type 'struct event **'
int event_base_set(struct event_base *, struct event *);
^
'Finished building: ../src/redis.c'
' '
'Building target: redis'
'Invoking: Cross GCC Linker'
arm-linux-gnueabihf-gcc -L"C:\SysGCC\Raspberry\arm-linux-gnueabihf\sysroot\usr\local\lib" -L"C:\SysGCC\Raspberry\arm-linux-gnueabihf\lib" -o "redis" ./src/redis.o -lhiredis -levent_core -lpthread
'Finished building target: redis'
' '
00:20:55 Build Finished (took 1s.130ms)

Answer 1

EDIT
It seems the main issue was in the included adapter file.
The issue I pointed towards was unrelated.
Here is just one quick issue I noticed:
if (r->type == REDIS_REPLY_ARRAY) {
for (j = 0; j < r->elements; j++) {
printf("%u) %s\n", j, r->element[j]->str);
}
}
Your code assumes that the reply is an array of Strings.
This is incorrect.
The Subscribe command also returns an Array response and the last member of that response is a NUMBER (not a string).
Hence, the assumption that it's an array of strings will fail.
I'm not sure if that's the cause, but it is likely to be an important issue.
Good Luck!
P.S.
I might be shamelessly promoting my own project here, but you might enjoy using facil.io's integrated Redis Pub/Sub engine. If you need Websocket or HTTP support, it might save you a lot of coding.