Fixed GCC elides lambdas

See
  http://code.google.com/p/android/issues/detail?id=35933
  http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54170

Backport of r194098 to both GCC 4.6 and 4.7

    /cp
    2012-12-03  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/54170
	* cvt.c (cp_convert_to_pointer): Don't discard side-effects from
	expressions of nullptr_t.
	* typeck.c (build_ptrmemfunc): Likewise.

    /testsuite
    2012-12-03  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/54170
	* g++.dg/cpp0x/lambda/lambda-nullptr.C: New.

Change-Id: I4c90f9e06262a54796302773b36eb5bac7b4f1fa

3 files changed, 56 insertions, 11 deletions

diff --git a/gcc-4.7/gcc/cp/cvt.c b/gcc-4.7/gcc/cp/cvt.c
index c411a47f0..f68ce9034 100644
--- a/gcc-4.7/gcc/cp/cvt.c
+++ b/gcc-4.7/gcc/cp/cvt.c
@@ -207,16 +207,14 @@ cp_convert_to_pointer (tree type, tree expr)
 	return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0,
 				 /*c_cast_p=*/false, tf_warning_or_error);
 
-      if (TYPE_PTRMEM_P (type))
-	{
-	  /* A NULL pointer-to-member is represented by -1, not by
-	     zero.  */
-	  expr = build_int_cst_type (type, -1);
-	}
-      else
-	expr = build_int_cst (type, 0);
-
-      return expr;
+      /* A NULL pointer-to-data-member is represented by -1, not by
+	 zero.  */
+      tree val = (TYPE_PTRMEM_P (type)
+		  ? build_int_cst_type (type, -1)
+		  : build_int_cst (type, 0));
+
+      return (TREE_SIDE_EFFECTS (expr)
+	      ? build2 (COMPOUND_EXPR, type, expr, val) : val);
     }
   else if (TYPE_PTR_TO_MEMBER_P (type) && INTEGRAL_CODE_P (form))
     {
diff --git a/gcc-4.7/gcc/cp/typeck.c b/gcc-4.7/gcc/cp/typeck.c
index 96b7d4e44..f41ef00df 100644
--- a/gcc-4.7/gcc/cp/typeck.c
+++ b/gcc-4.7/gcc/cp/typeck.c
@@ -7251,7 +7251,7 @@ build_ptrmemfunc (tree type, tree pfn, int force, bool c_cast_p,
   /* Handle null pointer to member function conversions.  */
   if (null_ptr_cst_p (pfn))
     {
-      pfn = build_c_cast (input_location, type, nullptr_node);
+      pfn = build_c_cast (input_location, type, pfn);
       return build_ptrmemfunc1 (to_type,
 				integer_zero_node,
 				pfn);
diff --git a/gcc-4.7/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-nullptr.C b/gcc-4.7/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-nullptr.C
new file mode 100644
index 000000000..1aadbb490
--- /dev/null
+++ b/gcc-4.7/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-nullptr.C
@@ -0,0 +1,47 @@
+// PR c++/54170
+// { dg-do run { target c++11 } }
+
+#include <cassert> 
+
+struct A;
+typedef A* ptr;
+typedef int (A::*pmf) (int);
+typedef int (A::*pdm);
+
+int total;
+
+void add(int n)
+{
+  total += n;
+}
+
+template <typename RType, typename Callable>
+RType Call(Callable native_func, int arg)
+{
+  return native_func(arg);
+}
+
+template <typename RType>
+RType do_test(int delta)
+{
+  return Call<RType>([=](int delta) { add(delta); return nullptr; }, delta);
+}
+
+template <typename RType>
+void test()
+{
+  total = 0;
+  assert (!do_test<RType>(5));
+  assert (total == 5);
+  assert (!do_test<RType>(20));
+  assert (total == 25);
+  assert (!do_test<RType>(-256));
+  assert (total == -231);
+}
+
+int main()
+{
+  test<ptr>();
+  test<pdm>();
+  test<pmf>();
+}