Consider two objects with static storage duration and equal, constant initializers:
static const int a = 50;
static const int b = 50;
Is it valid for a compiler to combine these such that &a == &b?
(For context, I was thinking of using static constant objects to get unique addresses to use as sentinel pointer values. If it is legal for a compiler to combine such objects and I use the same constant value for two such objects, then the addresses could be equal and I cannot use them as sentinel values.)
The pointers must compare not-equal. See C99 6.5.9 paragraph 6:
Two pointers compare equal if and only if both are null pointers, both are pointers to the same object (including a pointer to an object and a subobject at its beginning) or function, both are pointers to one past the last element of the same array object, or one is a pointer to one past the end of one array object and the other is a pointer to the start of a different array object that happens to immediately follow the first array object in the address space.