re PR c++/39480 (generated memcpy causes trouble in assignment)

        PR c++/39480
        * call.c (build_over_call): Don't call memcpy if the target is
        the same as the source.

From-SVN: r146020

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 0d2dbc63c91f5580f69f9453c0fc79292e1097d1..d363604a6d21a3c6af29e395b84ccb6fc9837382 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2009-04-13  Jason Merrill  <jason@redhat.com>
+
+       PR c++/39480
+       * call.c (build_over_call): Don't call memcpy if the target is
+       the same as the source.
+
 2009-04-10  H.J. Lu  <hongjiu.lu@intel.com>
 
        Backport from mainline:

diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 13560e218177cbf6fadb76276ad10ce0107b18f8..13713131d0b1a930979f62240d0697033781fa8d 100644 (file)
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -5118,17 +5118,33 @@ build_over_call (struct z_candidate *cand, int flags)
       else
        {
          /* We must only copy the non-tail padding parts.
-            Use __builtin_memcpy for the bitwise copy.  */
+            Use __builtin_memcpy for the bitwise copy.
+            FIXME fix 22488 so we can go back to using MODIFY_EXPR
+            instead of an explicit call to memcpy.  */
        
          tree arg0, arg1, arg2, t;
+         tree test = NULL_TREE;
 
          arg2 = TYPE_SIZE_UNIT (as_base);
          arg1 = arg;
          arg0 = build_unary_op (ADDR_EXPR, to, 0);
+
+         if (!(optimize && flag_tree_ter))
+           {
+             /* When TER is off get_pointer_alignment returns 0, so a call
+                to __builtin_memcpy is expanded as a call to memcpy, which
+                is invalid with identical args.  When TER is on it is
+                expanded as a block move, which should be safe.  */
+             arg0 = save_expr (arg0);
+             arg1 = save_expr (arg1);
+             test = build2 (EQ_EXPR, boolean_type_node, arg0, arg1);
+           }
          t = implicit_built_in_decls[BUILT_IN_MEMCPY];
          t = build_call_n (t, 3, arg0, arg1, arg2);
 
          t = convert (TREE_TYPE (arg0), t);
+         if (test)
+           t = build3 (COND_EXPR, TREE_TYPE (t), test, arg0, t);
          val = build_indirect_ref (t, 0);
        }
 

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 58fea4b5e1792f3d1ac2ea0fbf26864bf615e9b9..f791425ec862ebb093fa7c89a6a42b92cddceb11 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2009-04-13  Jason Merrill  <jason@redhat.com>
+
+       PR c++/39480
+       * g++.dg/init/copy7.C: New.
+
 2009-04-10  H.J. Lu  <hongjiu.lu@intel.com>
 
        Backport from mainline:

diff --git a/gcc/testsuite/g++.dg/init/copy7.C b/gcc/testsuite/g++.dg/init/copy7.C
new file mode 100644 (file)
index 0000000..f4364f3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/init/copy7.C
@@ -0,0 +1,32 @@
+// PR c++/39480
+// It isn't always safe to call memcpy with identical arguments.
+// { dg-do run }
+
+extern "C" void abort();
+extern "C" void *
+memcpy(void *dest, void *src, __SIZE_TYPE__ n)
+{
+  abort();
+}
+
+struct A
+{
+  double d[10];
+};
+
+struct B: public A
+{
+  char bc;
+};
+
+B b;
+
+void f(B *a1, B* a2)
+{
+  *a1 = *a2;
+}
+
+int main()
+{
+  f(&b,&b);
+}