implement druntime side of DIP1006

Author: WalterBright

mak/SRCS

@@ -269,6 +269,7 @@ SRCS=\
 	src\rt\deh_win64_posix.d \
 	src\rt\dmain2.d \
 	src\rt\dwarfeh.d \
+	src\rt\ehalloc.d \
 	src\rt\invariant.d \
 	src\rt\lifetime.d \
 	src\rt\llmath.d \

src/core/thread.d

@@ -223,6 +223,8 @@ version( Windows )
 
             void append( Throwable t )
             {
+                if (t.refcount())
+                    ++t.refcount();
                 if( obj.m_unhandled is null )
                     obj.m_unhandled = t;
                 else
@@ -377,6 +379,8 @@ else version( Posix )
 
             void append( Throwable t )
             {
+                if (t.refcount())
+                    ++t.refcount();
                 if( obj.m_unhandled is null )
                     obj.m_unhandled = t;
                 else

src/object.d

@@ -16,6 +16,8 @@ private
     extern (C) void rt_finalize(void *data, bool det=true);
 }
 
+public @trusted @nogc nothrow pure extern (C) void _d_delThrowable(scope Throwable);
+
 // NOTE: For some reason, this declaration method doesn't work
 //       in this particular file (and this file only).  It must
 //       be a DMD thing.
@@ -1666,6 +1668,11 @@ class Throwable : Object
      */
     Throwable   next;
 
+    private uint _refcount;     // 0 : allocated by GC
+                                // 1 : allocated by _d_newThrowable()
+                                // 2.. : reference count + 1
+    @system @nogc final pure nothrow ref uint refcount() return scope { return _refcount; }
+
     @nogc @safe pure nothrow this(string msg, Throwable next = null)
     {
         this.msg = msg;
@@ -1681,6 +1688,12 @@ class Throwable : Object
         //this.info = _d_traceContext();
     }
 
+    @trusted nothrow ~this()
+    {
+        if (next && next._refcount)
+            _d_delThrowable(next);
+    }
+
     /**
      * Overrides $(D Object.toString) and returns the error message.
      * Internally this forwards to the $(D toString) overload that

src/rt/deh_win32.d

@@ -611,21 +611,33 @@ int _d_exception_filter(EXCEPTION_POINTERS *eptrs,
 }
 
 /***********************************
- * Throw a D object.
+ * Throw a D instance of Throwable.
  */
 
-private void throwImpl(Object h)
+private void throwImpl(Throwable h)
 {
-    // @@@ TODO @@@ Signature should change: h will always be a Throwable.
     //printf("_d_throw(h = %p, &h = %p)\n", h, &h);
     //printf("\tvptr = %p\n", *(void **)h);
+
+    /* Increment reference count if `h` is a refcounted Throwable
+     */
+    auto refcount = h.refcount();
+    if (refcount)       // non-zero means it's refcounted
+        h.refcount() = refcount + 1;
+
     _d_createTrace(h, null);
     RaiseException(STATUS_DIGITAL_MARS_D_EXCEPTION,
                    EXCEPTION_NONCONTINUABLE,
                    1, cast(void *)&h);
 }
 
-extern(C) void _d_throwc(Object h)
+/***************************************
+ * The compiler converts:
+ *      throw h;
+ * into a call to:
+ *      _d_throwc(h);
+ */
+extern(C) void _d_throwc(Throwable h)
 {
     // set up a stack frame for trace unwinding
     version (AsmX86)

src/rt/deh_win64_posix.d

@@ -219,7 +219,7 @@ size_t __eh_find_caller(size_t regbp, size_t *pretaddr)
  * Throw a D object.
  */
 
-extern (C) void _d_throwc(Object h)
+extern (C) void _d_throwc(Throwable h)
 {
     size_t regebp;
 
@@ -242,6 +242,12 @@ extern (C) void _d_throwc(Object h)
     else
         static assert(0);
 
+    /* Increment reference count if `h` is a refcounted Throwable
+     */
+    auto refcount = h.refcount();
+    if (refcount)       // non-zero means it's refcounted
+        h.refcount() = refcount + 1;
+
     _d_createTrace(h, null);
 
 //static uint abc;

src/rt/dwarfeh.d

@@ -182,6 +182,12 @@ extern(C) void _d_throwdwarf(Throwable o)
     eh.push();  // add to thrown exception stack
     //printf("_d_throwdwarf: eh = %p, eh.next = %p\n", eh, eh.next);
 
+    /* Increment reference count if `o` is a refcounted Throwable
+     */
+    auto refcount = o.refcount();
+    if (refcount)       // non-zero means it's refcounted
+        o.refcount() = refcount + 1;
+
     /* Called by unwinder when exception object needs destruction by other than our code.
      */
     extern (C) static void exception_cleanup(_Unwind_Reason_Code reason, _Unwind_Exception* eo)

src/rt/ehalloc.d

@@ -0,0 +1,125 @@
+/**
+ * Exception allocation, cloning, and release compiler support routines.
+ *
+ * Copyright: Copyright (c) 2017 by D Language Foundation
+ * License: Distributed under the
+ *      $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost Software License 1.0).
+ *    (See accompanying file LICENSE)
+ * Authors: Walter Bright
+ * Source: $(DRUNTIMESRC src/rt/_dwarfeh.d)
+ */
+
+module rt.ehalloc;
+
+//debug = PRINTF;
+
+debug(PRINTF)
+{
+    import core.stdc.stdio;
+}
+
+/**********************************************
+ * Allocate an exception of type `ci` from the exception pool.
+ * It has the same interface as `rt.lifetime._d_newclass()`.
+ * The class type must be Throwable or derived from it,
+ * and cannot be a COM or C++ class. The compiler must enforce
+ * this.
+ * Returns:
+ *      default initialized instance of the type
+ */
+
+extern (C) Throwable _d_newThrowable(const TypeInfo_Class ci)
+{
+    debug(PRINTF) printf("_d_newThrowable(ci = %p, %s)\n", ci, cast(char *)ci.name);
+
+    assert(!(ci.m_flags & TypeInfo_Class.ClassFlags.isCOMclass));
+    assert(!(ci.m_flags & TypeInfo_Class.ClassFlags.isCPPclass));
+
+    import core.stdc.stdlib : malloc;
+    void* p = malloc(ci.initializer.length);
+    if (!p)
+    {
+        import core.exception : onOutOfMemoryError;
+        onOutOfMemoryError();
+    }
+
+    debug(PRINTF) printf(" p = %p\n", p);
+
+    // initialize it
+    p[0 .. ci.initializer.length] = ci.initializer[];
+
+    if (!(ci.m_flags & TypeInfo_Class.ClassFlags.noPointers))
+    {
+        // Inform the GC about the pointers in the object instance
+        import core.memory : GC;
+
+        GC.addRange(p, ci.initializer.length, ci);
+    }
+
+    debug(PRINTF) printf("initialization done\n");
+    Throwable t = cast(Throwable)p;
+    t.refcount() = 1;
+    return t;
+}
+
+
+/********************************************
+ * Delete exception instance `t` from the exception pool.
+ * Must have been allocated with `_d_newThrowable()`.
+ * This is meant to be called at the close of a catch block.
+ * It's nothrow because otherwise any function with a catch block could
+ * not be nothrow.
+ * Input:
+ *      t = Throwable
+ */
+
+nothrow extern (C) void _d_delThrowable(Throwable t)
+{
+    if (t)
+    {
+        debug(PRINTF) printf("_d_delThrowable(%p)\n", t);
+
+        /* If allocated by the GC, don't free it.
+         * Let the GC handle it.
+         * Supporting this is necessary while transitioning
+         * to this new scheme for allocating exceptions.
+         */
+        auto refcount = t.refcount();
+        if (refcount == 0)
+            return;     // it was allocated by the GC
+
+        if (refcount == 1)
+            assert(0);  // no zombie objects
+
+        t.refcount() = --refcount;
+        if (refcount > 1)
+            return;
+
+        TypeInfo_Class **pc = cast(TypeInfo_Class **)t;
+        if (*pc)
+        {
+            TypeInfo_Class ci = **pc;
+
+            if (!(ci.m_flags & TypeInfo_Class.ClassFlags.noPointers))
+            {
+                // Inform the GC about the pointers in the object instance
+                import core.memory : GC;
+                GC.removeRange(cast(void*) t);
+            }
+        }
+
+        try
+        {
+            import rt.lifetime : rt_finalize;
+            rt_finalize(cast(void*) t);
+        }
+        catch (Throwable t)
+        {
+            assert(0);  // should never happen since Throwable.~this() is nothrow
+        }
+        import core.stdc.stdlib : free;
+        debug(PRINTF) printf("free(%p)\n", t);
+        free(cast(void*) t);
+    }
+}
+