[Redirected from gcc@] On 28 October 2014 09:33, Alex Markin wrote: > As far as I understand the main issue here is that class A has > external linkage and linker do not analyse the fields of class, it > just watches class A by name. And the example itself breaks `3.2 One > definition rule': That's correct. >> 5. >> ... >> — each definition of D shall consist of the same sequence of tokens > > > And now my questions: > > * am I right with the understanding of situation and the example is UB? Yes > * if two definitions had the same fields and the same constructors, > should the program be correct? It's not quite that simple. Every definition of the class must consist of the same sequence of tokens, and all the names and functions it refers to must resolve to the same entities in every translation unit. The full rules are described in 3.2 [basic.def.odr] and are too long to quote here. > * is correct gcc behaviour with `-O1' a coincidence, or it detects > another class anyway? The constructors get inlined into foo(void*) and bar(void*) > * does it make sense to give a warning in that case? The compiler cannot warn, it has no way to know when compiling t1.cpp that there's a different definition in t2.cpp, and vice versa. The linker can warn, and the Gold linker has a --detect-odr-violations option that warns about some cases. The linker is not part of GCC though.
