__await is still broken in Visual Studio 2015 RTM
The following simple code does not work:
#include "stdafx.h"
#include <experimental\generator>
#include <future>
using namespace std;
using namespace std::experimental;
future<int> get_int()
{
return async([] { return 0; });
}
future<int> wait_int()
{
return __await get_int();
}
int main()
{
auto const i = wait_int().get();
return 0;
}
App hits int 3 instruction (XXX.exe has triggered a breakpoint) and then hangs forever waiting for suspended coroutine to finish. Bravo!
My investigation shows that compiler generates invalid instructions within XXX.exe!wait_int$_ResumeCoro$2() function:
00007FF6166FB0F0 mov qword ptr [rsp+8],rcx 00007FF6166FB0F5 push rbp 00007FF6166FB0F6 sub rsp,30h 00007FF6166FB0FA mov qword ptr [rsp+20h],0FFFFFFFFFFFFFFFEh 00007FF6166FB103 mov rbp,qword ptr [$S2] 00007FF6166FB108 mov eax,dword ptr [rbp+20h] 00007FF6166FB10B mov dword ptr [rbp+78h],eax 00007FF6166FB10E cmp dword ptr [rbp+78h],5
rbp has the address of coroutine frame, frame has two consequent 64-bit values - address of resume method and some internal state flag, which is set to 2 initially.
dword ptr [rbp+20h] - this instruction obtains the flag, but the offset is completely wrong, it must be dword ptr [rbp+8h].
So all cases of state flag switch are bypassed. Default case makes the assert hit. Boom.
UPD: It doesn't support Debug Information Format == Program Database for Edit And Continue (/Zl). With this setting set to something else the code is generated properly: mov eax, [rbp+8].
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