That code seems needlessly arcane. You can get the same results without resorting to anonymous bitfields:

  #define BUILD_BUG_ON_ZERO(e) (sizeof(char[(e) ? -1 : 0]))

which, when it fails, results in

  error: size of unnamed array is negative

which is no worse than the provided code which results in

  error: negative width in bit-field '<anonymous>'

It's worth noting that declaring an array with 0 elements is not allowed in C99. However, using a struct with no named members has undefined behavior in C99 [1].

[1] http://stackoverflow.com/a/12918937/959866

Edit: You can get around having 0 elements by using

  #define BUILD_BUG_ON_ZERO(e) (sizeof(char[(e) ? -1 : 1]) - 1)

but you're starting to lose clarity again.