On 2/7/20 1:06 PM, Iain Sandoe wrote:
Hi,This is the first of the (small number of) anticipated changes to bring the implementation into line with the latest published C++20 draft (this is now expected to be very close to the final, although some wording might still be adjusted). The allocation for the coroutine state frame is quite flexible - which means in reality a number of permutations to cater for and to test for. Partial or complete adoption of p2014r0 would be additive to this, but it seems better to me to separate changes for that to a future patch. Because of the number of permutations, the error messages are somewhat long-winded in an effort to point the user to the specific problem. OK for trunk? thanks Iain ======== This updates the coroutine frame allocation and deallocation usage to match n4849. [dcl.fct.def.coroutine] /9, /10, /12. 9 An implementation may need to allocate additional storage for a coroutine. This storage is known as the coroutine state and is obtained by calling a non-array allocation function. The allocation function’s name is looked up in the scope of the promise type. If this lookup fails, the allocation function’s name is looked up in the global scope. If the lookup finds an allocation function in the scope of the promise type, overload resolution is performed on a function call created by assembling an argument list. The first argument is the amount of space requested, and has type std::size_t. The lvalues p1 . . . pn are the succeeding [user's function] arguments. If no viable function is found, overload resolution is performed again on a function call created by passing just the amount of space required as an argument of type std::size_t. 10 The unqualified-id get_return_object_on_allocation_failure is looked up in the scope of the promise type by class member access lookup. If any declarations are found, then the result of a call to an allocation function used to obtain storage for the coroutine state is assumed to return nullptr if it fails to obtain storage, and if a global allocation function is selected, the ::operator new(size_t, nothrow_t) form is used. The allocation function used in this case shall have a non-throwing noexcept-specification. If the allocation function returns nullptr, the coroutine returns control to the caller of the coroutine and the return value is obtained by a call to T::get_return_object_on_allocation_failure(), where T is the promise type. 12 The deallocation function’s name is looked up in the scope of the promise type. If this lookup fails, the deallocation function’s name is looked up in the global scope. If deallocation function lookup finds both a usual deallocation function with only a pointer parameter and a usual deallocation function with both a pointer parameter and a size parameter, then the selected deallocation function shall be the one with two parameters. Otherwise, the selected deallocation function shall be the function with one parameter. If no usual deallocation function is found, the program is ill- formed. The selected deallocation function shall be called with the address of the block of storage to be reclaimed as its first argument. If a deallocation function with a parameter of type std::size_t is used, the size of the block is passed as the corresponding argument. gcc/cp/ChangeLog: 2020-02-07 Iain Sandoe <i...@sandoe.co.uk> * coroutines.cc (build_actor_fn): Implement deallocation function selection per n4849, dcl.fct.def.coroutine bullet 12. (morph_fn_to_coro): Implement allocation function selection per n4849, dcl.fct.def.coroutine bullets 9 and 10. gcc/testsuite/ChangeLog:
This is ok. I was having a dumb wrt to the type_size thing we talked about. nathan -- Nathan Sidwell
