CODEWITHSUNDEEP
carraysstruct
John Titor
John Titor

Reputation: 21

memcpy() and memmove() not working as expected

I ran into this problem while working with a struct array within a struct. I'm trying to set the entry array in the dict using memcpy. I'm getting a mixture of the expected values and some seemingly random integers as output.

Oddly enough, I tried this code with some online compilers, and it worked fine. I thought that it might have to do with overlapping memory regions, so I tried memmove() but the result was the same.

I think I might be using malloc improperly for the dict, but I'm not sure. It seems I can't use malloc for the internal array, or for the individual elements. I'd appreciate any help.

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

typedef struct{
    int i;
} entry;

typedef struct{
    entry e[10];
    int i;
} dict;

dict* d;

void test(dict* di){
    printf("%d\n", di->i);
    int k;
    for (k = 0; k < 10; k ++){
        printf(("%d\n"),di->e[k].i);
    }
}

int main(){
    entry en[10];

    d = malloc(sizeof(d));

    int k;
    for (k = 0; k < 10; k++){
        en[k].i = k;
    }

    d->i = 50; 
    memcpy(d->e, en, 10*sizeof(entry));

    test(d);

    return 0;
}

Upvotes: 1

Views: 513

Answers (1)

Ry-
Ry-

Reputation: 224903

d = malloc(sizeof(d));

d is a dict*; sizeof d is sizeof(dict*). Looks like you meant sizeof *d.

Upvotes: 6

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