realloc() invalid nxt size - c

Question

I use this code, with this structure, im trying to make function to add item into array of this structure
typedef struct goods{
char *name;
int num;
} goods;
void addWord(char *what, goods *where, int pnr, int *arrsize, int n){
if (pnr >= *arrsize){
where = (goods*)realloc(where,*arrsize*2*sizeof(goods*));
*arrsize*=2;
}
where[pnr].name = (char*)malloc(strlen(what)*sizeof(char));
strcpy(where[pnr].name,what);
where[pnr].num = n;
}
in main function i have this:
int extstore = 1;
goods *store = (goods*)malloc(1*sizeof(goods*));
addWord(line, store, nr, &extstore, n);
Why am I getting an "invalid next size" runtime-error on the line where = (goods*)realloc(where,*arrsize*2*sizeof(goods*)); in addWord()?
EDIT:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct goods{
char *name;
int r;
} goods;
int main()
{
int linelen, i, nr = 0, current_r;
char *line = NULL;
size_t len = 0;
int extstore = 1;
goods *store;
store = malloc(extstore*sizeof(goods*));
while (1){
while ((linelen = getline(&line, &len, stdin)) != -1){
if (line[linelen - 1] == '\n'){
line[linelen - 1] = '\0';
}
linelen = strlen(line);
if (line[0] == '#'){
if (sscanf(line,"#%d",&current_r) != 1){
printf("bad input.");
return 0;
} else continue;
}
if (nr >= extstore){
store = realloc(store,extstore * sizeof(goods*) * 2);
extstore*=2;
}
store[nr].name = malloc(strlen(line)*sizeof(char));
strcpy(store[nr].name,line);
store[nr].r = current_r;
nr++;
}
if (linelen == -1) break;
}
printf("\n");
for (i = 0;i < nr;i++){
printf("%s, [id:%d]\n", store[i].name, store[i].r);
}
return 0;
}

Answer 1

extstore * sizeof(goods*) * 2
should be extstore * sizeof(goods) * 2 because the space for structures should be allocated - not just for pointers.
There is a fundamental problem in your code. You are passing pointer by value, which means that any change made to a pointer (not the variable pointed to, but the pointer itself) will not be visible from outside the function. You should pass a pointer by pointer instead, and you should check the result returned from realloc. Secondly, don't assign result of realloc back to same pointer - in case of failure you will lost pointer to memory -> thus, memory leak will occur.
To pass pointer by pointer:
void addWord( char *what, goods **where, size, ...) {
if ( *where == NULL) return; // nothing to do
if ( size < 1) return; // it would result in realloc=free call
goods *res = NULL;
res = realloc( *where, size * sizeof( goods));
if ( res != NULL) {
*where = res;
}
else {
// Error (re)allocating memory
// If realloc() fails the original block is left untouched,
// it is not freed or moved, so here *where is unchanged
}
And there is no need in C to cast a result from malloc.
* Error in `path': realloc(): invalid next size: 0x0000000000ec8010 *
This failure must be because "where" is invalid due to a heap corruption earlier in the execution.

Answer 2

C is pass-by-value.
Which means changing an argument in the function does not change the expression it was initialized from.
Thus, the first time realloc moves the memory, the pointer in main will be bad.
To correct that, either use an extra level of indirection, or preferably return the new value as the result.
(Anyway, you should check for allocation failure (malloc and realloc),
and you should not cast from void* to any pointer-type in C.)