re PR c++/31246 (-Wunreachable-code warnings for compiler-generated code)

2009-07-08  Manuel López-Ibáñez  <manu@gcc.gnu.org>

	PR c++/31246
	* gimplify.c (gimplify_expr): Propagate no_warning flag when
	gimplifying.
	* gimple (gimple_build_call_from_tree): Likewise.
	* tree-cfg.c (remove_useless_stmts_warn_notreached): Check
	no_warning flag before warning.
cp/
	* init.c (build_new_1): Set TREE_NO_WARNING for compiler-generated
	code.
	* cp-gimplify.c (genericize_eh_spec_block): Likewise.
	
testsuite/	
	* g++.dg/warn/pr31246.C: New.
	* g++.dg/warn/pr31246-2.C: New.

From-SVN: r149354

gcc/ChangeLog

@@ -1,3 +1,12 @@
+2009-07-08  Manuel López-Ibáñez  <manu@gcc.gnu.org>
+
+	PR c++/31246
+	* gimplify.c (gimplify_expr): Propagate no_warning flag when
+	gimplifying.
+	* gimple (gimple_build_call_from_tree): Likewise.
+	* tree-cfg.c (remove_useless_stmts_warn_notreached): Check
+	no_warning flag before warning.
+	
 2009-07-07  Manuel López-Ibáñez  <manu@gcc.gnu.org>
 
 	* tree.c (set_expr_locus): Remove.

gcc/cp/ChangeLog

@@ -1,3 +1,11 @@
+2009-07-08  Manuel López-Ibáñez  <manu@gcc.gnu.org>
+
+	PR c++/31246
+	* init.c (build_new_1): Set TREE_NO_WARNING for compiler-generated
+	code.
+	* cp-gimplify.c (genericize_eh_spec_block): Likewise.
+	
+
 2009-07-07  Jason Merrill  <jason@redhat.com>
 
 	PR c++/35828

gcc/cp/cp-gimplify.c

@@ -153,6 +153,8 @@ genericize_eh_spec_block (tree *stmt_p)
   tree failure = build_call_n (call_unexpected_node, 1, build_exc_ptr ());
 
   *stmt_p = build_gimple_eh_filter_tree (body, allowed, failure);
+  TREE_NO_WARNING (*stmt_p) = true;
+  TREE_NO_WARNING (TREE_OPERAND (*stmt_p, 1)) = true;
 }
 
 /* Genericize an IF_STMT by turning it into a COND_EXPR.  */

gcc/cp/init.c

@@ -2185,8 +2185,14 @@ build_new_1 (VEC(tree,gc) **placement, tree type, tree nelts,
 	  else if (stable)
 	    /* This is much simpler if we were able to preevaluate all of
 	       the arguments to the constructor call.  */
-	    init_expr = build2 (TRY_CATCH_EXPR, void_type_node,
-				init_expr, cleanup);
+	    {
+	      /* CLEANUP is compiler-generated, so no diagnostics.  */
+	      TREE_NO_WARNING (cleanup) = true;
+	      init_expr = build2 (TRY_CATCH_EXPR, void_type_node,
+				  init_expr, cleanup);
+	      /* Likewise, this try-catch is compiler-generated.  */
+	      TREE_NO_WARNING (init_expr) = true;
+	    }
 	  else
 	    /* Ack!  First we allocate the memory.  Then we set our sentry
 	       variable to true, and expand a cleanup that deletes the
@@ -2206,6 +2212,9 @@ build_new_1 (VEC(tree,gc) **placement, tree type, tree nelts,
 
 	      sentry = TARGET_EXPR_SLOT (begin);
 
+	      /* CLEANUP is compiler-generated, so no diagnostics.  */
+	      TREE_NO_WARNING (cleanup) = true;
+
 	      TARGET_EXPR_CLEANUP (begin)
 		= build3 (COND_EXPR, void_type_node, sentry,
 			  cleanup, void_zero_node);
@@ -2217,8 +2226,9 @@ build_new_1 (VEC(tree,gc) **placement, tree type, tree nelts,
 		= build2 (COMPOUND_EXPR, void_type_node, begin,
 			  build2 (COMPOUND_EXPR, void_type_node, init_expr,
 				  end));
+	      /* Likewise, this is compiler-generated.  */
+	      TREE_NO_WARNING (init_expr) = true;
 	    }
-
 	}
     }
   else

gcc/gimple.c

@@ -357,6 +357,7 @@ gimple_build_call_from_tree (tree t)
   gimple_call_set_return_slot_opt (call, CALL_EXPR_RETURN_SLOT_OPT (t));
   gimple_call_set_from_thunk (call, CALL_FROM_THUNK_P (t));
   gimple_call_set_va_arg_pack (call, CALL_EXPR_VA_ARG_PACK (t));
+  gimple_set_no_warning (call, TREE_NO_WARNING (t));
 
   return call;
 }

gcc/gimplify.c

@@ -6787,6 +6787,7 @@ gimplify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
 
 	    gimplify_and_add (EH_FILTER_FAILURE (*expr_p), &failure);
 	    ehf = gimple_build_eh_filter (EH_FILTER_TYPES (*expr_p), failure);
+	    gimple_set_no_warning (ehf, TREE_NO_WARNING (*expr_p));
 	    gimple_eh_filter_set_must_not_throw
 	      (ehf, EH_FILTER_MUST_NOT_THROW (*expr_p));
 	    gimplify_seq_add_stmt (pre_p, ehf);

gcc/testsuite/ChangeLog

@@ -1,3 +1,9 @@
+2009-07-08  Manuel López-Ibáñez  <manu@gcc.gnu.org>
+	
+	PR c++/31246
+	* g++.dg/warn/pr31246.C: New.
+	* g++.dg/warn/pr31246-2.C: New.
+
 2009-07-07  Jason Merrill  <jason@redhat.com>
 
 	PR c++/35828

gcc/testsuite/g++.dg/warn/pr31246-2.C

@@ -0,0 +1,9 @@
+// PR 31246
+// { dg-do compile }
+// { dg-options "-Wunreachable-code" }
+#include <new>
+
+int* get_ptr(void* ptr)
+{
+  return new(ptr) int();
+}

gcc/testsuite/g++.dg/warn/pr31246.C

@@ -0,0 +1,9 @@
+// PR 31246
+// { dg-do compile }
+// { dg-options "-Wunreachable-code -D_GLIBCXX_DEBUG" }
+#include <vector>
+
+int main()
+{
+  std::vector<int>::iterator a;
+}

gcc/tree-cfg.c

@@ -1638,6 +1638,8 @@ remove_useless_stmts_warn_notreached (gimple_seq stmts)
     {
       gimple stmt = gsi_stmt (gsi);
 
+      if (gimple_no_warning_p (stmt)) return false;
+
       if (gimple_has_location (stmt))
         {
           location_t loc = gimple_location (stmt);