Catch and dump unhandled exceptions in async task functions

The problem with relying on noexcept for this is that there is no stack.

5 files changed, 49 insertions, 15 deletions

diff --git a/build2/algorithm.cxx b/build2/algorithm.cxx
index 4e5ec78..9357632 100644
--- a/build2/algorithm.cxx
+++ b/build2/algorithm.cxx
@@ -485,6 +485,12 @@ namespace build2
       t.state_ = target_state::failed;
       l.offset = target::offset_applied;
     }
+    catch (const std::exception& e)
+    {
+      *diag_stream << "unhandled exception: " << e;
+      assert (false);
+      abort ();
+    }
 
     return t.state_;
   }
@@ -537,7 +543,9 @@ namespace build2
       //
       if (sched.async (start_count,
                        *task_count,
-                       [a] (target& t, size_t offset, const diag_frame* ds)
+                       [a] (target& t,
+                            size_t offset,
+                            const diag_frame* ds) noexcept
                        {
                          diag_frame df (ds);
                          phase_lock pl (run_phase::match);
@@ -779,6 +787,12 @@ namespace build2
     {
       ts = t.state_ = target_state::failed;
     }
+    catch (const std::exception& e)
+    {
+      *diag_stream << "unhandled exception: " << e;
+      assert (false);
+      abort ();
+    }
 
     // Decrement the task count (to count_executed) and wake up any threads
     // that might be waiting for this target.
@@ -864,10 +878,10 @@ namespace build2
           //
           if (sched.async (start_count,
                            *task_count,
-                           [a] (target& t, const diag_frame* ds)
+                           [a] (target& t, const diag_frame* ds) noexcept
                            {
                              diag_frame df (ds);
-                             execute_impl (a, t); // Note: noexcept.
+                             execute_impl (a, t);
                            },
                            ref (t),
                            diag_frame::stack))
diff --git a/build2/context b/build2/context
index bc73d5b..95030d8 100644
--- a/build2/context
+++ b/build2/context
@@ -138,7 +138,7 @@ namespace build2
   //   for (...)
   //   {
   //     sched.async (task_count,
-  //                  [] (...)
+  //                  [] (...) noexcept
   //                  {
   //                    phase_lock pl (run_phase::match);  // (2)
   //                    ...
diff --git a/build2/test/rule.cxx b/build2/test/rule.cxx
index 5cec891..0e1aff6 100644
--- a/build2/test/rule.cxx
+++ b/build2/test/rule.cxx
@@ -397,6 +397,12 @@ namespace build2
       {
         r = scope_state::failed;
       }
+      catch (const std::exception& e)
+      {
+        *diag_stream << "unhandled exception: " << e;
+        assert (false);
+        abort ();
+      }
 
       return r;
     }
diff --git a/build2/test/script/parser.cxx b/build2/test/script/parser.cxx
index d004223..0555f2f 100644
--- a/build2/test/script/parser.cxx
+++ b/build2/test/script/parser.cxx
@@ -2867,6 +2867,26 @@ namespace build2
         exec_scope_body ();
       }
 
+      static void
+      execute_impl (scope& s, script& scr, runner& r) noexcept
+      {
+        try
+        {
+          parser p;
+          p.execute (s, scr, r);
+        }
+        catch (const failed&)
+        {
+          s.state = scope_state::failed;
+        }
+        catch (const std::exception& e)
+        {
+          *diag_stream << "unhandled exception: " << e;
+          assert (false);
+          abort ();
+        }
+      }
+
       void parser::
       exec_scope_body ()
       {
@@ -2983,20 +3003,13 @@ namespace build2
               // bail out if we weren't asked to keep going.
               //
               if (!sched.async (task_count,
-                                [] (scope& s, script& scr, runner& r,
+                                [] (scope& s,
+                                    script& scr,
+                                    runner& r,
                                     const diag_frame* ds) noexcept
                                 {
                                   diag_frame df (ds);
-
-                                  try
-                                  {
-                                    parser p;
-                                    p.execute (s, scr, r);
-                                  }
-                                  catch (const failed&)
-                                  {
-                                    s.state = scope_state::failed;
-                                  }
+                                  execute_impl (s, scr, r);
                                 },
                                 ref (*chain),
                                 ref (*script_),
diff --git a/build2/utility b/build2/utility
index aec3806..0c129c4 100644
--- a/build2/utility
+++ b/build2/utility
@@ -10,6 +10,7 @@
 #include <string>     // to_string()
 #include <utility>    // move(), forward(), declval(), make_pair()
 #include <cassert>    // assert()
+#include <cstdlib>    // abort()
 #include <iterator>   // make_move_iterator()
 #include <algorithm>  // *
 #include <functional> // ref(), cref()