Variable length array in C-language struct (flexible array member)

Variable length array in c_struct (flexible array member)

Flexible array member is a feature introduced in the C99 standard of the C programming language (in particular, in sections §6.7.2.1, item, page 103). It is a member of a struct, which was an array without a given dimension, and it must was the last member of such a struct, As in the following example:

struct vectord {    uint8_t  len;    double   // the flexible array member must be last};

• arr[]Does not occupy the storage space of the structure, sizeof (Strcut Vectord) has a value of 1
• Variable-length arrays must be the last member of a struct
• Contiguous storage space adjacent to a struct variable is the arr[] contents of an array
• A 0-length array is used in GCC arr[0] to represent a variable length array.

struct vectord *allocate_vectord (size_t len) {   struct vectord *vec = malloc(offsetof(structsizeof(vec->arr[0]));   if (!vec) {       perror("malloc vectord failed");       exit(EXIT_FAILURE);   }   vec->len = len;   for0; i < len; i++)       0;   return vec;}

Variable length array in C-language struct (flexible array member)