Add workaround for MSVC bad codegen bug.

lewissbaker · lewissbaker · commit d965af88363c · 2018-09-07T08:23:37.000-07:00
Mark task&lt;T&gt;'s final_awaitable::await_suspend() method as noinline.

This fixes a crash in the multi-threaded async_auto_reset_event
tests under x86 optimised builds under MSVC 2017.8.
diff --git a/include/cppcoro/task.hpp b/include/cppcoro/task.hpp
@@ -33,7 +33,13 @@ namespace cppcoro
 			{
 				bool await_ready() const noexcept { return false; }
 
+				// HACK: Need to add CPPCORO_NOINLINE to await_suspend() method
+				// to avoid MSVC 2017.8 from spilling some local variables in
+				// await_suspend() onto the coroutine frame in some cases.
+				// Without this, some tests in async_auto_reset_event_tests.cpp
+				// were crashing under x86 optimised builds.
 				template<typename PROMISE>
+				CPPCORO_NOINLINE
 				void await_suspend(std::experimental::coroutine_handle<PROMISE> coroutine)
 				{
 					task_promise_base& promise = coroutine.promise();

Original file line number	Diff line number	Diff line change
`@@ -33,7 +33,13 @@ namespace cppcoro`
`33`	`33`	`{`
`34`	`34`	`bool await_ready() const noexcept { return false; }`
`35`	`35`
	`36`	`+ // HACK: Need to add CPPCORO_NOINLINE to await_suspend() method`
	`37`	`+ // to avoid MSVC 2017.8 from spilling some local variables in`
	`38`	`+ // await_suspend() onto the coroutine frame in some cases.`
	`39`	`+ // Without this, some tests in async_auto_reset_event_tests.cpp`
	`40`	`+ // were crashing under x86 optimised builds.`
`36`	`41`	`template<typename PROMISE>`
	`42`	`+ CPPCORO_NOINLINE`
`37`	`43`	`void await_suspend(std::experimental::coroutine_handle<PROMISE> coroutine)`
`38`	`44`	`{`
`39`	`45`	`task_promise_base& promise = coroutine.promise();`