a confusing way to define C structure

Question

I am a newbie in C and I stumbled on this c-structure:

typedef struct
{
   int dog;
   int cat;
} FOO;

typedef struct
{
   int  id;
   FOO* pRow[0]
} BAR;

I know basic c and c++ but I have no idea the motivation of the following line: "FOO* pRow[0]".

If the author wants to define a pointer to an array of FOO, then he/she should just define it as "FOO* pROW", right? Why does pROW[0] stands for in this case then?

Please enlighten me. Thanks!

It's called a "flexible array member": https://en.wikipedia.org/wiki/Flexible_array_member — nobody, Sep 03 '15 at 02:28
@AndrewMedico: It isn't. It's a [zero-length array](https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html). — cremno, Sep 03 '15 at 02:31
@AndrewMedico a flex array is an actual language feature in C99, this is a hack. — Ryan Haining, Sep 03 '15 at 02:33

score -2 · Answer 1 · answered Sep 03 '15 at 02:30

-2

the pRow is an array of pointers. the first element ,pRow[0] is pointing to a FOO struct.

if you write FOO* pRow, then the pRow is simply one pointer

answered Sep 03 '15 at 02:30

Chrim

100
8

Not really, because you can allocate it to N sizeof(FOO), and then it would't be one pointer. – Ryan Sep 03 '15 at 02:38

a confusing way to define C structure

1 Answers1