What is the cause of flexible array member not at end of struct error?

Question

I am wondering why I keep getting error: flexible array member not at end of struct error when I call malloc. I have a struct with a variable length array, and

Answer 1

typedef struct {
  size_t N;
  double data[];
  int label[];
} s_col; 

You can't have flexible array member (double data[]) in the middle. Consider hardcoded array size or double *data