From 7e99ae19bb8eff10d517b8677163610df829350f Mon Sep 17 00:00:00 2001
From: Walter Bright <walter@walterbright.com>
Date: Wed, 30 Dec 2015 03:48:56 -0800
Subject: [PATCH] Dwarf EH: add _d_eh_swapContextDwarf

---
 src/core/thread.d | 48 +++++++++++++++++++++++++++++++++++++++++++++--
 src/rt/dwarfeh.d  | 15 +++++++++++++++
 2 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/src/core/thread.d b/src/core/thread.d
index d596862b72d..c55540412e6 100644
--- a/src/core/thread.d
+++ b/src/core/thread.d
@@ -118,6 +118,50 @@ private
      *         is switched in for the first time.
      */
     extern(C) void* _d_eh_swapContext(void* newContext) nothrow;
+
+    version (DigitalMars)
+    {
+        version (Windows)
+            alias _d_eh_swapContext swapContext;
+        else
+        {
+            extern(C) void* _d_eh_swapContextDwarf(void* newContext) nothrow;
+
+            void* swapContext(void* newContext) nothrow
+            {
+                /* Detect at runtime which scheme is being used.
+                 * Eventually, determine it statically.
+                 */
+                static int which = 0;
+                final switch (which)
+                {
+                    case 0:
+                    {
+                        assert(newContext == null);
+                        auto p = _d_eh_swapContext(newContext);
+                        auto pdwarf = _d_eh_swapContextDwarf(newContext);
+                        if (p)
+                        {
+                            which = 1;
+                            return p;
+                        }
+                        else if (pdwarf)
+                        {
+                            which = 2;
+                            return pdwarf;
+                        }
+                        return null;
+                    }
+                    case 1:
+                        return _d_eh_swapContext(newContext);
+                    case 2:
+                        return _d_eh_swapContextDwarf(newContext);
+                }
+            }
+        }
+    }
+    else
+        alias _d_eh_swapContext swapContext;
 }
 
 
@@ -1461,7 +1505,7 @@ private:
     }
     body
     {
-        m_curr.ehContext = _d_eh_swapContext(c.ehContext);
+        m_curr.ehContext = swapContext(c.ehContext);
         c.within = m_curr;
         m_curr = c;
     }
@@ -1476,7 +1520,7 @@ private:
     {
         Context* c = m_curr;
         m_curr = c.within;
-        c.ehContext = _d_eh_swapContext(m_curr.ehContext);
+        c.ehContext = swapContext(m_curr.ehContext);
         c.within = null;
     }
 
diff --git a/src/rt/dwarfeh.d b/src/rt/dwarfeh.d
index c9b63275cac..c348fd56e13 100644
--- a/src/rt/dwarfeh.d
+++ b/src/rt/dwarfeh.d
@@ -150,6 +150,21 @@ extern(C) Throwable __dmd_begin_catch(_Unwind_Exception* exceptionObject)
     return o;
 }
 
+/****************************************
+ * Called when fibers switch contexts.
+ * Params:
+ *      newContext = stack to switch to
+ * Returns:
+ *      previous value of stack
+ */
+extern(C) void* _d_eh_swapContextDwarf(void* newContext) nothrow
+{
+    auto old = ExceptionHeader.stack;
+    ExceptionHeader.stack = cast(ExceptionHeader*)newContext;
+    return old;
+}
+
+
 /*********************
  * Called by D code to throw an exception via
  * ---