foo.c: In function ‘main’:
foo.c:6:20: error: implicit declaration of function ‘malloc’ [-Wimplicit-function-declaration]
    6 |     int* A = (int*)malloc(sizeof(int) * m * n);
      |                    ^~~~~~
foo.c:2:1: note: include ‘<stdlib.h>’ or provide a declaration of ‘malloc’
    1 | #include<stdio.h>
  +++ |+#include <stdlib.h>
    2 | #define OFFFSET(i, j, n)((i) * (n) + j)
foo.c:6:20: warning: incompatible implicit declaration of built-in function ‘malloc’ [-Wbuiltin-declaration-mismatch]
    6 |     int* A = (int*)malloc(sizeof(int) * m * n);
      |                    ^~~~~~
foo.c:6:20: note: include ‘<stdlib.h>’ or provide a declaration of ‘malloc’
foo.c:18:27: error: implicit declaration of function ‘OFFSET’; did you mean ‘OFFFSET’? [-Wimplicit-function-declaration]
   18 |                 temp += A[OFFSET(i, k, n)] * B[OFFSET(k, j, p)];
      |                           ^~~~~~
      |                           OFFFSET