On 06/17/2013 10:18 AM, Jan Hubicka wrote:
Does ODR hold also for extern "C" declarations in C++?
Yes.
In C, you can treat all structurally identical types as the same, right?
In next step we can sort out other reasons they
are not merged by Richard's merging code but stil equivalent in C++ sense.
There are easy cases to list - i.e. we will not merge class type from unit that
defines the keyed method with class type from other unit since the associated
binfo will differ in types of the declarations (DECL_EXTERNAL versus
TREE_PUBLIC+STATIC).
I'm surprised the code wouldn't handle that; don't you handle merging
extern function decls with definitions outside of classes?
OK, thanks! I naively assumed that checking DECL_NAME for NULL is enough
here. I will fix this.
Ah, yes, that ought to work. I was overlooking that bit.
The question is when will two types be "ODR equivalent" but not
"tree equivalent". Certainly there is no such thing as "ODR" for C,
so given C++ manually implemented in C you cannot expect same
"vtable" contents when the types have the same name.
yes, that is why I think we need flag specifying if type is ODR or not.
I'm not sure we do. A manual implementation wouldn't have the "vtable"
specially associated with the type, so that shouldn't be an issue.
Jason
