Re: [Libguestfs] [nbdkit] ARRAY_SIZE [was: vddk: Demote another "phone home" error message to debug]

I see that is now done as part of 0fa23df5c. While include/array-size.h looks okay, I personally have a tough time with include/compiler-macros.h BUILD_BUG_ON_ZERO(expr). Every time I encounter a similarly-named macro in other projects, I have to go re-read the docs, because (to at least me) the name is not self-describing.

I'm also worried that your code uses 'struct { int _array_size_failed[(expr)...]; }', which may end up causing VLA situations, where (mistakenly) passing in a non-constant expr could compile (as a VLA) rather than letting the compiler diagnose that expr wasn't consant. Hence, I like bitfields better than array sizes when trying to force a conditional compiler error, as it gets VLA out of the picture. If I were designing it from scratch, I might create: /* If EXPR is true, produce a non-zero struct size. Otherwise, fail the build */ #define BUILD_BUG_STRUCT_SIZE(expr) \ (sizeof (struct { int: (expr) ? 1 : -1; }))