It is called "struct hack". You can search for it on SO or on the Net
http://www.google.com/search?q=struct+hack&sitesearch=stackoverflow.com/questions
Note that formally it is always illegal to declare arrays of size 0 in C. The code you provided formally is not even compilable. Most C compilers will accept 0-sized array declaration as an extension though, specifically because it is often used in "lazy" version of "struct hack" (it can rely on sizeof to determine how much memory to allocate, since 0-sized array supposedly does not affect the total size of the struct).
An arguably better implementation of struct hack uses an array of size 1
struct arr {
int cnt;
struct {
int size;
int *name;
} list[1];
};
It is "better" because it is formally compilable at least. In order to allocate memory for a struct with N elements in the list, standard offsetof macro is used
arr *a = malloc(offsetof(arr, list) + N * sizeof a->list);
In C99 version of the language specification the "struct hack" is supported through size-less array declaration (with empty []), since 0-sized array declarations are illegal in C99 as well.
