/in/foo.c: In function 'read_data':
/in/foo.c:29:26: warning: implicit declaration of function 'malloc' [-Wimplicit-function-declaration]
 if((R_data=(struct dot *)malloc((num+1)*sizeof(struct dot)))==NULL) return(-2);
                          ^~~~~~
/in/foo.c:29:26: warning: incompatible implicit declaration of built-in function 'malloc'
/in/foo.c:29:26: note: include '<stdlib.h>' or provide a declaration of 'malloc'
/in/foo.c: At top level:
/in/foo.c:124:1: warning: return type defaults to 'int' [-Wimplicit-int]
 main(void)
 ^~~~
/in/foo.c: In function 'main':
/in/foo.c:131:31: warning: incompatible implicit declaration of built-in function 'malloc'
  if((line_func=(struct line *)malloc(num*sizeof(struct line)))==NULL) return(-2);
                               ^~~~~~
/in/foo.c:131:31: note: include '<stdlib.h>' or provide a declaration of 'malloc'
/in/foo.c:145:2: warning: implicit declaration of function 'free' [-Wimplicit-function-declaration]
  free(R_data);
  ^~~~
/in/foo.c:145:2: warning: incompatible implicit declaration of built-in function 'free'
/in/foo.c:145:2: note: include '<stdlib.h>' or provide a declaration of 'free'