re PR c++/67557 (Calling copy constructor of base class in constructor of…

re PR c++/67557 (Calling copy constructor of base class in constructor of derived class produces crashing code)

	PR c++/67557

	* expr.c (store_field): Call store_constructor directly when
	storing a CONSTRUCTOR into a target smaller than its type.
	Guard against unsafe bitwise copy.

From-SVN: r228704

gcc/ChangeLog

+2015-10-11  Jason Merrill  <jason@redhat.com>
+
+	PR c++/67557
+	* expr.c (store_field): Call store_constructor directly when
+	storing a CONSTRUCTOR into a target smaller than its type.
+	Guard against unsafe bitwise copy.
+
 2015-10-11  Jan Hubicka  <hubicka@ucw.cz>
 
 	* cgraphbuild.c (compute_call_stmt_bb_frequency): Use

gcc/expr.c

@@ -6616,7 +6616,11 @@ store_field (rtx target, HOST_WIDE_INT bitsize, HOST_WIDE_INT bitpos,
 	 operations.  */
       || (bitsize >= 0
 	  && TREE_CODE (TYPE_SIZE (TREE_TYPE (exp))) == INTEGER_CST
-	  && compare_tree_int (TYPE_SIZE (TREE_TYPE (exp)), bitsize) != 0)
+	  && compare_tree_int (TYPE_SIZE (TREE_TYPE (exp)), bitsize) != 0
+	  /* Except for initialization of full bytes from a CONSTRUCTOR, which
+	     we will handle specially below.  */
+	  && !(TREE_CODE (exp) == CONSTRUCTOR
+	       && bitsize % BITS_PER_UNIT == 0))
       /* If we are expanding a MEM_REF of a non-BLKmode non-addressable
          decl we must use bitfield operations.  */
       || (bitsize >= 0
@@ -6629,6 +6633,9 @@ store_field (rtx target, HOST_WIDE_INT bitsize, HOST_WIDE_INT bitpos,
       rtx temp;
       gimple *nop_def;
 
+      /* Using bitwise copy is not safe for TREE_ADDRESSABLE types.  */
+      gcc_assert (!TREE_ADDRESSABLE (TREE_TYPE (exp)));
+
       /* If EXP is a NOP_EXPR of precision less than its mode, then that
 	 implies a mask operation.  If the precision is the same size as
 	 the field we're storing into, that mask is redundant.  This is
@@ -6743,6 +6750,15 @@ store_field (rtx target, HOST_WIDE_INT bitsize, HOST_WIDE_INT bitpos,
       if (!MEM_KEEP_ALIAS_SET_P (to_rtx) && MEM_ALIAS_SET (to_rtx) != 0)
 	set_mem_alias_set (to_rtx, alias_set);
 
+      /* Above we avoided using bitfield operations for storing a CONSTRUCTOR
+	 into a target smaller than its type; handle that case now.  */
+      if (TREE_CODE (exp) == CONSTRUCTOR && bitsize >= 0)
+	{
+	  gcc_assert (bitsize % BITS_PER_UNIT == 0);
+	  store_constructor (exp, to_rtx, 0, bitsize/BITS_PER_UNIT);
+	  return to_rtx;
+	}
+
       return store_expr (exp, to_rtx, 0, nontemporal);
     }
 }

gcc/testsuite/g++.dg/init/vbase1.C

 // PR c++/50618
+// { dg-options "-fdump-rtl-expand" }
 // { dg-do run }
 
 struct Base
@@ -37,3 +38,8 @@ int main(int, char**)
     Diamond x(2);
     x.printText();
 }
+
+// Verify that the SubB() mem-initializer is storing 0 directly into
+// this->D.whatever rather than into a stack temp that is then copied into the
+// base field.
+// { dg-final { scan-rtl-dump "set \[^\n\]*\n\[^\n\]*this\[^\n\]*\n\[^\n\]*const_int 0" "expand" } }