Question

Alternatively: duplicate of Facing an error — glibc detected free invalid next size (fast).

When I compile and run this code, I get an error message:
“realloc(): invalid next size: 0x0000000002483010”

I’ve been trying to find a solution for this for the last 6 hours without any luck..

Here are the relevant parts of my code-

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

typedef struct vertex
{
    char* name;
    int id;
    int outDegree;
}vertex;

int main(){
    vertex *tmpVertice;
    vertex *vertices = (vertex*)calloc(1, sizeof(vertex));
    int p=1;
    while(p<20){
        vertex temp={"hi",p,0};
        vertices[p-1]=temp;
        tmpVertice=(vertex*)realloc(vertices,p);
        if(tmpVertice!=NULL) vertices=tmpVertice;
        p++;
    }
    return 0;
}

Answer 1

realloc frees any previous buffer if necessary so the lines free(vertices) and free(tmpVertice) in your loop are wrong and should be removed.

Edit: I’ve included an updated version of your program below with further fixes. You needed to realloc p*sizeof(vertex) rather than p bytes. You were writing beyond the end of the array then growing it. I’ve changed to realloc at the start of the loop

int main(){
    vertex *tmpVertice;
    vertex *vertices = NULL;
    int p=1;
    while(p<20){
        vertex temp={"hi",p,0};
        tmpVertice=realloc(vertices,p*sizeof(vertex));
        if(tmpVertice==NULL) {
            printf("ERROR: realloc failed\n");
            return -1;
        }
        vertices=tmpVertice;
        vertices[p-1]=temp;

        p++;
    }
    return 0;
}