Thread: Assign struct member value to struct member value

When these kinds of problems happen, I like to write small programs to try and figure out why the issue is happening. For instance:

Code:

#include <stdio.h>
#include <string.h>

struct display{
        int *src[10];
}display;

int main(void) {
        int i = 0;
        int test = 5;

        for(i=0; i<10; i++){
                display.src[i] = malloc(sizeof(int));
                *display.src[i] = i;
                printf("%d\n", *display.src[i]);
        }

        *display.src[test] = 15;

        printf("\n");

        for(i=0; i<10; i++)
                printf("%d\n", *display.src[i]);

        return 0;
}

When I originally wrote this, I removed the astrix on the red line to see if I could reproduce your compiler error. When I did this, I received the same error. I then compiled the program with the astrix and everything worked properly.

P.S. I'm not checking the return value of malloc or free'ing my malloced memory at the end of the program for simplicity sake. You should always do these things as they are good practice.

Alright... what have we learned here.

1) malloc your memory...
2) dereference your pointers when assigning values

Changes in red.

Code:

for(i = 0; i < display.num; i++) {
    display.src[i] = malloc(sizeof(int));
    *display.src[i] = -1;
}

Code:

if((!ret) && (dragging == 1) && (check(samp.x, samp.y) == 3)) {
    if(src_selected > -1) {
        *display.src[0] = src_selected;
        activate_display(0, src_selected);
        clean_loop();
        return 0;
    }
...

Code:

drag_label(video_bg, source.label[*display.src[mon_selected]], samp.x, samp.y, oldx, oldy);

All works as expected now. Thanks for dose of enlightenment.

Glad I could help!

Again, I would recommend checking the return value of malloc() to make sure you don't run out of memory and also remember to free your malloc'ed memory when your done using it.