Redo handling of unhandled exceptions in async execution

Here is the problem: noexcept looses the call stack. That is, unlike an
unhandled exception, if noexcept is tripped, then you won't see the place
where it was thrown.

In this new implementation we now have noexcept only on the task thunk. And
the task is called via a thunk only in case of async execution. This means
that if we are executing serially (-j 1), then this will be an unhandled
exception, not noexcept. Hopefully will be a bit easier to debug.

1 files changed, 1 insertions, 1 deletions

diff --git a/build2/scheduler b/build2/scheduler
index 86a48df..c6f4f7f 100644
--- a/build2/scheduler
+++ b/build2/scheduler
@@ -306,7 +306,7 @@ namespace build2
 
       template <size_t... i>
       void
-      thunk (std::index_sequence<i...>)
+      thunk (std::index_sequence<i...>) noexcept
       {
         move (func) (std::get<i> (move (args))...);
       }