Programming

I have a pointer to a structure containing an integer pointer:

struct members {
int id;
int *neigh;
};

The number of members N and its neighbors M change as the code runs, so I allocate the memory dynamically:

members *grid = malloc(sizeof(members)*N);
for(i=0;i<N;i++) grid.neigh = malloc(sizeof(int)*M);

where M generally is a function of N.

This works well most of the time, but sometimes grid.neigh contains weird (and wrong) values. Is there anything fundamentally wrong in this way of allocating memory space?

Did you mean:

for(i=0;i<N;i++) grid[i].neigh = malloc(sizeof(int)*M);

If so, I don't see anything fundamentally wrong with it. The newly-allocated memory is not guaranteed to be blank, however:

Code:

for(i=0;i<N;i++)
{
  grid[i].neigh = malloc(sizeof(int)*M);
  memset(grid[i].neigh, 0, sizeof(int) * M);
}

Yes, that is of course what i meant. Thanks for the help.