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: r146011

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 905b6e431dd16bb5d16dbcd21c3244546d14f0e7..d77634d32631661684c6187b911852b3258f3584 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2009-04-09  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.
+
 2009-04-13  Jason Merrill  <jason@redhat.com>
 
        PR c++/39750

diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 869146efe8eaa940c27d853ff86ba5207e50e5f4..ef7c045acab4af1629c4fbd27c16f4c457421a7b 100644 (file)
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -5396,14 +5396,28 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain)
             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 = cp_build_unary_op (ADDR_EXPR, to, 0, complain);
+
+         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 = cp_build_indirect_ref (t, 0, complain);
        }
 

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index d29496fb18b0b87a6dc4025deadd07744412e0a0..457aee66bb2bb8b99727e5d4279760eaa4c40253 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2009-04-09  Jason Merrill  <jason@redhat.com>
+
+       PR c++/39480
+       * g++.dg/init/copy7.C: New.
+
 2009-04-13  H.J. Lu  <hongjiu.lu@intel.com>
 
        PR testsuite/39733

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);
+}