How flexible is the array implemented in c?

Question

..
char arKey[1]; } Bucket;

Above said what flexible array, how?

Answer 1

Often the last member of the structure is assigned a size 0or 1(although it 0is against the standard pre-C99, it is allowed in some compilers, since it is of great importance as a marker). Since an array of size 0or is usually not created 1, this tells other colleagues that this field is used as the beginning of a variable-size array, starting from the end member and ending with any available memory.

, , , , .

• http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
• C ?
• http://msdn.microsoft.com/en-us/library/6zxfydcs(VS.71).aspx
• http://blogs.msdn.com/b/oldnewthing/archive/2004/08/26/220873.aspx

typedef struct {
    size_t len;
    char arr[];
} MyString;

size_t mystring_len(MyString const *ms) { return ms->len; }

MyString *mystring_new(char const *init)
{
    size_t len = strlen(init);
    MyString *rv = malloc(sizeof(MyString) + len + 1);
    rv->len = len;
    strncpy(rv->arr, init, len);
    return rv;
}

Answer 2

0 C99. 1 C90 .

, malloc sizeof(Bucket) + array_length, array_length - . arKey ( ) , .

. :

http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html