re PR c++/28523 (Throw of a derived class casted to its base class using a C-style cast)

	PR c++/28523
	* tree.c (stabilize_expr): Tweak documentation.  Add assertion.
	(stabilize_call): Tweak documentation.
	(stabilize_init): Only call stabilize_call for calls.
	PR c++/28523
	* g++.dg/eh/cast1.C: New test.

From-SVN: r115862

4 files changed, 70 insertions, 37 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index a93e420..1e327c2 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2006-07-31  Mark Mitchell  <mark@codesourcery.com>
+
+	PR c++/28523
+	* tree.c (stabilize_expr): Tweak documentation.  Add assertion.
+	(stabilize_call): Tweak documentation.
+	(stabilize_init): Only call stabilize_call for calls.
+
 2006-08-01  Steve Ellcey  <sje@cup.hp.com>
 
 	PR c++/28432
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index 0d42502..53d37be 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -2229,9 +2229,11 @@ decl_linkage (tree decl)
   return lk_internal;
 }
 
-/* EXP is an expression that we want to pre-evaluate.  Returns via INITP an
-   expression to perform the pre-evaluation, and returns directly an
-   expression to use the precalculated result.  */
+/* EXP is an expression that we want to pre-evaluate.  Returns (in
+   *INITP) an expression that will perform the pre-evaluation.  The
+   value returned by this function is a side-effect free expression
+   equivalent to the pre-evaluated expression.  Callers must ensure
+   that *INITP is evaluated before EXP.  */
 
 tree
 stabilize_expr (tree exp, tree* initp)
@@ -2239,9 +2241,7 @@ stabilize_expr (tree exp, tree* initp)
   tree init_expr;
 
   if (!TREE_SIDE_EFFECTS (exp))
-    {
-      init_expr = NULL_TREE;
-    }
+    init_expr = NULL_TREE;
   else if (!real_lvalue_p (exp)
 	   || !TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (exp)))
     {
@@ -2255,8 +2255,9 @@ stabilize_expr (tree exp, tree* initp)
       exp = TARGET_EXPR_SLOT (init_expr);
       exp = build_indirect_ref (exp, 0);
     }
-
   *initp = init_expr;
+
+  gcc_assert (!TREE_SIDE_EFFECTS (exp));
   return exp;
 }
 
@@ -2273,8 +2274,10 @@ add_stmt_to_compound (tree orig, tree new)
   return build2 (COMPOUND_EXPR, void_type_node, orig, new);
 }
 
-/* Like stabilize_expr, but for a call whose args we want to
-   pre-evaluate.  */
+/* Like stabilize_expr, but for a call whose arguments we want to
+   pre-evaluate.  CALL is modified in place to use the pre-evaluated
+   arguments, while, upon return, *INITP contains an expression to
+   compute the arguments.  */
 
 void
 stabilize_call (tree call, tree *initp)
@@ -2299,50 +2302,58 @@ stabilize_call (tree call, tree *initp)
   *initp = inits;
 }
 
-/* Like stabilize_expr, but for an initialization.  If we are initializing
-   an object of class type, we don't want to introduce an extra temporary,
-   so we look past the TARGET_EXPR and stabilize the arguments of the call
-   instead.  */
+/* Like stabilize_expr, but for an initialization.  
+
+   If the initialization is for an object of class type, this function
+   takes care not to introduce additional temporaries.
+
+   Returns TRUE iff the expression was successfully pre-evaluated,
+   i.e., if INIT is now side-effect free, except for, possible, a
+   single call to a constructor.  */
 
 bool
 stabilize_init (tree init, tree *initp)
 {
   tree t = init;
 
+  *initp = NULL_TREE;
+
   if (t == error_mark_node)
     return true;
 
   if (TREE_CODE (t) == INIT_EXPR
       && TREE_CODE (TREE_OPERAND (t, 1)) != TARGET_EXPR)
-    TREE_OPERAND (t, 1) = stabilize_expr (TREE_OPERAND (t, 1), initp);
-  else
     {
-      if (TREE_CODE (t) == INIT_EXPR)
-	t = TREE_OPERAND (t, 1);
-      if (TREE_CODE (t) == TARGET_EXPR)
-	t = TARGET_EXPR_INITIAL (t);
-      if (TREE_CODE (t) == COMPOUND_EXPR)
-	t = expr_last (t);
-      if (TREE_CODE (t) == CONSTRUCTOR
-	  && EMPTY_CONSTRUCTOR_P (t))
-	{
-	  /* Default-initialization.  */
-	  *initp = NULL_TREE;
-	  return true;
-	}
+      TREE_OPERAND (t, 1) = stabilize_expr (TREE_OPERAND (t, 1), initp);
+      return true;
+    }
 
-      /* If the initializer is a COND_EXPR, we can't preevaluate
-	 anything.  */
-      if (TREE_CODE (t) == COND_EXPR)
-	return false;
+  if (TREE_CODE (t) == INIT_EXPR)
+    t = TREE_OPERAND (t, 1);
+  if (TREE_CODE (t) == TARGET_EXPR)
+    t = TARGET_EXPR_INITIAL (t);
+  if (TREE_CODE (t) == COMPOUND_EXPR)
+    t = expr_last (t);
+  if (TREE_CODE (t) == CONSTRUCTOR
+      && EMPTY_CONSTRUCTOR_P (t))
+    /* Default-initialization.  */
+    return true;
+
+  /* If the initializer is a COND_EXPR, we can't preevaluate
+     anything.  */
+  if (TREE_CODE (t) == COND_EXPR)
+    return false;
 
-      /* The TARGET_EXPR might be initializing via bitwise copy from
-	 another variable; leave that alone.  */
-      if (TREE_SIDE_EFFECTS (t))
-	stabilize_call (t, initp);
+  if (TREE_CODE (t) == CALL_EXPR
+      || TREE_CODE (t) == AGGR_INIT_EXPR)
+    {
+      stabilize_call (t, initp);
+      return true;
     }
 
-  return true;
+  /* The initialization is being performed via a bitwise copy -- and
+     the item copied may have side effects.  */
+  return TREE_SIDE_EFFECTS (init);
 }
 
 /* Like "fold", but should be used whenever we might be processing the
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 4afaae1..1e1effc 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2006-07-31  Mark Mitchell  <mark@codesourcery.com>
+
+	PR c++/28523
+	* g++.dg/eh/cast1.C: New test.
+
 2006-08-01  Thomas Koenig  <Thomas.Koenig@online.de>
 
 	PR libfortran/28452
diff --git a/gcc/testsuite/g++.dg/eh/cast1.C b/gcc/testsuite/g++.dg/eh/cast1.C
new file mode 100644
index 0000000..964dd69
--- /dev/null
+++ b/gcc/testsuite/g++.dg/eh/cast1.C
@@ -0,0 +1,10 @@
+// PR c++/28523
+
+class A {};
+class B : public A {};
+
+int main()
+{
+  throw (A) B();
+  return 0;
+}