From b0524a0b18eec9d5e5c3f6ce30b6cecdd02a6306 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Tue, 20 Jan 2015 17:18:09 +0200
Subject: Diagnostic infrastructure revamp

---
 build/utility | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 52 insertions(+), 1 deletion(-)

(limited to 'build/utility')

diff --git a/build/utility b/build/utility
index bcbf834..5523e8b 100644
--- a/build/utility
+++ b/build/utility
@@ -5,9 +5,12 @@
 #ifndef BUILD_UTILITY
 #define BUILD_UTILITY
 
+#include <tuple>
 #include <string>
-#include <unordered_set>
+#include <utility>
 #include <cstring> // strcmp
+#include <exception>
+#include <unordered_set>
 
 
 namespace build
@@ -26,6 +29,54 @@ namespace build
     bool operator() (const P& x, const P& y) const {return *x < *y;}
   };
 
+  // Call a function if there is an exception.
+  //
+
+  // Means we are in the body of a destructor that is being called
+  // as part of the exception stack unwindining. Used to compensate
+  // for the deficiencies of uncaught_exception() until C++17
+  // uncaught_exceptions() becomes available.
+  //
+  // @@ MT: will have to be TLS.
+  //
+  extern bool exception_unwinding_dtor;
+
+  template <typename F, typename T>
+  struct exception_guard;
+
+  template <typename F, typename... A>
+  inline exception_guard<F, std::tuple<A&&...>>
+  make_exception_guard (F f, A&&... a)
+  {
+    return exception_guard<F, std::tuple<A&&...>> (
+      std::move (f), std::forward_as_tuple (a...));
+  }
+
+  template <typename F, typename... A>
+  struct exception_guard<F, std::tuple<A...>>
+  {
+    typedef std::tuple<A...> T;
+
+    exception_guard (F f, T a): f_ (std::move (f)), a_ (std::move (a)) {}
+    ~exception_guard ()
+    {
+      if (std::uncaught_exception ())
+      {
+        exception_unwinding_dtor = true;
+        call (std::index_sequence_for<A...> ());
+        exception_unwinding_dtor = false;
+      }
+    }
+
+  private:
+    template <std::size_t... I>
+    void
+    call (std::index_sequence<I...>) {f_ (std::get<I> (a_)...);}
+
+    F f_;
+    T a_;
+  };
+
   // Pools (@@ perhaps move into a separate header).
   //
   struct string_pool: std::unordered_set<std::string>
-- 
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