Dave Korn wrote: > Dave Korn wrote: >> Dave Korn wrote: >>> I've read http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html about six >>> times and can't see anywhere it even hints that you can use this syntax >>> anywhere except as the trailing member of a struct. >> Andrew Haley wrote: >>> But zero-length arrays are a gcc extension. There's nothing that limits >>> them to the last member of a struct. zero-length arrays must be rejected >>> with -pedantic, but not otherwise. >>> Because it's a documented gcc extension. >> Obviously I can't see for looking; can you please point me to the precise >> chapter/page/paragraph/line that I should have found earlier?
"Zero-length arrays are allowed in GNU C. They are very useful as the last element of a structure ..." That doesn't in any way imply that the last element of a struct is the only circumstance in which you may use a zero-length array. > (I honestly mean that, no sarcasm intended; it was late at night and I was > tired, I could easily have misread or overlooked something.) I did find this > comment in varasm.c:assemble_noswitch_variable() that says we need to handle > this case: > > /* Don't allocate zero bytes of common, > since that means "undefined external" in the linker. */ > if (size == 0) > rounded = 1; > > ... so I guess it counts as a backend bug if the backend still emits a zero in > the .comm directive, and that the documentation of ASM_OUTPUT.*COMMON should > probably be improved to warn of the danger that size may be zero. Yes. That's what is usually done: all you have to do is fix the back end. Andrew.
