CODEWITHSUNDEEP
c
Cryptonic Shadow
Cryptonic Shadow

Reputation: 11

how to fix 'mremap chunk assertion error' in C

I am presently learning C and am trying to expand the amount of memory available to an array of structures. When I attempt to grow the array I receive the following error at runtime

malloc.c:2852: mremap_chunk: Assertion `((size + offset) & (GLRO (dl_pagesize) - 1)) == 0' failed. Aborted.

Here is the code that is causing the problem.

I have tried reading the realloc man page and online tutorials, but have been unable to find anything that addresses this specific case.

typedef struct _hash{
        int times;
        char word[250];
        struct _hash *n;
}Hash;

int main(){
        Hash* temp;
        int currentMax=10;
        Hash* ptr[currentMax];
        for(int i=0; i<10;i++){
                ptr[i]=malloc(sizeof(ptr));
                strcpy(ptr[i]->word, "hello world");
                ptr[i]->times=1;
                ptr[i]->n=NULL;
        }
        temp=realloc(ptr, 3*sizeof(Hash));
}

I am expecting the array to expand by a size of three so that I can add additional elements at a later time, but I keep getting the same error.

Upvotes: 1

Views: 764

Answers (1)

Jonathon Reinhart
Jonathon Reinhart

Reputation: 137448

ptr[i]=malloc(sizeof(ptr));

You're allocating the wrong size here. This should be

ptr[i]=malloc(sizeof(*ptr[i]));

Or

ptr[i]=malloc(sizeof(Hash));

Because of this, you're subsequently overrunning your buffer and invoking undefined behavior.

You should consider compiling your program with -g (to enable debug symbols), and running it under valgrind. Errors like this will be immediately identified.

Upvotes: 1

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