On Thu, May 11, 2023 at 09:43:49PM +0000, Joseph Myers wrote: > On Thu, 11 May 2023, Kees Cook via Gcc wrote: > > > Why are zero-sized objects missing in Standard C? Or, perhaps, the better > > question is: what's needed to support the idea of a zero-sized object? > > Zero-sized objects break the principle that different objects have > different addresses, and the principle of being able to subtract pointers > to different elements of an array. There would also be serious C++ > compatibility concerns, since C++ allows a struct with no members but it > has nonzero size, unlike the GNU C extension where a struct with no > members has size zero.
Okay, understood. If this is a C-only thing, we can ignore the C++ impact. What depends on the "different objects have different addresses" principle? And why do unions not break this -- they could point to the same locations within the object? And don't flexible arrays already need special handling in this regard? -- Kees Cook
