What's the size of "int" on your system? It's nearly always best to use types with defined sizes, like int32_t.

Also, i can' exactly make sense of what you are trying to do here. You are only allocating a single element. My "memory managment in C" is quite rusty, but if you want an array with N elements of type acme, i think it should be more in the line of this:

#define N 10

typedef struct _acme {
  int data;
} acme;

acme *gizmo;
gizmo* = (acme*)malloc(sizeof(acme) * N);
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But as i said, it's been a long time and i wrote this from memory.