PX4 Autopilot: "initialization makes integer from pointer without a cast" - c

Question

I've currently started working on a PX4 autopilot and I was working throught one of the example applicaton and I tried to compile and upload the firmware to the Pixhawk.
The problem is that it failed to load giving me these errors:
make[2]: * [px4_simple_app.c.o] Error 1 make[1]: *
[/c/px4/Firmware/Build/px4fmu-v2_default.build//c/px4/Firmware/src/examples/px4_simple_app/module.pre.o]
Error 2 make[1]: Leaving directory
`/c/px4/Firmware/Build/px4fmu-v2_default.build' make: ***
[/c/px4/Firmware/Build/px4fmu-v2_default.build/firmware.px4] Error 2
I'm not sure what these mean, but inspecting the code it gave me this error in a certain line:
initialization makes integer from pointer without a cast
From this line:
int att_pub_fd = orb_advertise(ORB_ID(vehicle_attitude), &att);
and I'm not sure how I can fix this. Can someone give me some help?
This is the rest of the code:
/**
* #file px4_simple_app.c
* Minimal application example for PX4 autopilot
*/
#include <string.h>
#include <nuttx/config.h>
#include <unistd.h>
#include <stdio.h>
#include <poll.h>
#include <uORB/uORB.h>
#include <uORB/topics/sensor_combined.h>
#include <uORB/topics/vehicle_attitude.h>
__EXPORT int px4_simple_app_main(int argc, char *argv[]);
int px4_simple_app_main(int argc, char *argv[])
{
printf("Hello Sky!\n");
/* subscribe to sensor_combined topic */
int sensor_sub_fd = orb_subscribe(ORB_ID(sensor_combined));
orb_set_interval(sensor_sub_fd, 1000);
/* advertise attitude topic */
struct vehicle_attitude_s att;
memset(&att, 0, sizeof(att));
int att_pub_fd = orb_advertise(ORB_ID(vehicle_attitude), &att);
/* one could wait for multiple topics with this technique, just using one here */
struct pollfd fds[] = {
{ .fd = sensor_sub_fd, .events = POLLIN },
/* there could be more file descriptors here, in the form like:
* { .fd = other_sub_fd, .events = POLLIN },
*/
};
int error_counter = 0;
while (true) {
/* wait for sensor update of 1 file descriptor for 1000 ms (1 second) */
int poll_ret = poll(fds, 1, 1000);
/* handle the poll result */
if (poll_ret == 0) {
/* this means none of our providers is giving us data */
printf("[px4_simple_app] Got no data within a second\n");
} else if (poll_ret < 0) {
/* this is seriously bad - should be an emergency */
if (error_counter < 10 || error_counter % 50 == 0) {
/* use a counter to prevent flooding (and slowing us down) */
printf("[px4_simple_app] ERROR return value from poll(): %d\n"
, poll_ret);
}
error_counter++;
} else {
if (fds[0].revents & POLLIN) {
/* obtained data for the first file descriptor */
struct sensor_combined_s raw;
/* copy sensors raw data into local buffer */
orb_copy(ORB_ID(sensor_combined), sensor_sub_fd, &raw);
printf("[px4_simple_app] Accelerometer:\t%8.4f\t%8.4f\t%8.4f\n",
(double)raw.accelerometer_m_s2[0],
(double)raw.accelerometer_m_s2[1],
(double)raw.accelerometer_m_s2[2]);
/* set att and publish this information for other apps */
att.roll = raw.accelerometer_m_s2[0];
att.pitch = raw.accelerometer_m_s2[1];
att.yaw = raw.accelerometer_m_s2[2];
orb_publish(ORB_ID(vehicle_attitude), att_pub_fd, &att);
}
/* there could be more file descriptors here, in the form like:
* if (fds[1..n].revents & POLLIN) {}
*/
}
}
return 0;
}

Answer 1

the function
orb_advertise(ORB_ID(vehicle_attitude), &att)
returns a pointer and you are assigning it to an int.
Im not sure what you are trying to do but if its pointing to an integer than you need to dereference the pointer.