strange array syntax

[pcr20]

I'm getting code like this generated:

struct s1 { uint32_t f0; signed char[4] pad8; uint32_t f8; unsigned char f12; signed char[3] pad16; int32_t f16; };

isn't this invalid C (use of [])? ie shouldn't the genenerated code have been: struct s1 { uint32_t f0; signed char pad8[4]; uint32_t f8; unsigned char f12; signed char pad16[3]; int32_t f16; }; ?

The code was generated from a linux 32bit ELF binary.

Thanks in advance, sorry if this is a dumb question

Paul