C++ support for -Wunused-but-set-variable

gcc/cp/ChangeLog:
	PR 18624
	* cp-tree.h (mark_exp_read, mark_rvalue_use, mark_lvalue_use,
	mark_type_use): Declare ...
	* expr.c (mark_exp_read, mark_rvalue_use, mark_lvalue_use,
	mark_type_use): ... new fns.
	* typeck.c (cxx_sizeof_expr, cxx_alignof_expr): Call mark_type_use.
	(perform_integral_promotions): Call mark_rvalue_use.
	(cp_build_unary_op): Call mark_lvalue_use.
	(decay_conversion): Update comment. Call mark_lvalue.
	* decl.c (unused_but_set_errorcount): New variable.
	(poplevel): Issue -Wunused-but-set-variable diagnostics.
	(duplicate_decls): Merge DECL_READ_P flags.
	(start_cleanup_fn): Set DECL_READ_P flag.
	(finish_function): Issue -Wunused-but-set-parameter diagnostics.
	* tree.c (rvalue): Call mark_rvalue_use.
	* pt.c (convert_nontype_argument): Likewise.
	* semantics.c (finish_typeof, finish_decltype_type): Call
	mark_type_use.
	(finish_asm_stmt): Call mark_lvalue_use.
	(finish_expr_stmt): Call mark_exp_read.
	* call.c (convert_like_real) <ck_identity, ck_user>: Call
	mark_rvalue_use.
	(build_x_va_arg): Call mark_lvalue_use.
	(build_over_call): Call mark_type_use.
	* init.c (build_new, build_delete): Call mark_value_use.
	* rtti.c (build_typeid): Call mark_lvalue_use or mark_type_use.
	(build_dynamic_cast_1): call mark_lvalue_use or mark_rvalue_use.

gcc/testsuite/ChangeLog:
	PR 18624
	* g++.dg/warn/Wunused-7.C: Add dg-warning.
	* g++.dg/template/sfinae16.C: Likewise.
	* gcc.dg/Wunused-var-1.c: Moved to...
	* c-c++-common/Wunused-var-1.c: ...here. New test.
	* gcc.dg/Wunused-var-2.c: Moved to...
	* c-c++-common/Wunused-var-2.c: ...here. New test.
	* gcc.dg/Wunused-var-3.c: Moved to...
	* c-c++-common/Wunused-var-3.c: ...here. New test.
	* gcc.dg/Wunused-var-4.c: Moved to...
	* gcc.dg/Wunused-var-1.c: ... here.
	* gcc.dg/Wunused-var-5.c: Moved to...
	* c-c++-common/Wunused-var-4.c: ...here. New test.
	* gcc.dg/Wunused-var-7.c: Moved to...
	* c-c++-common/Wunused-var-5.c: ...here. New test.
	* gcc.dg/Wunused-var-6.c: Moved to...
	* gcc.dg/Wunused-var-2.c: ... here.
	* c-c++-common/Wunused-var-1.c: New test.
	* c-c++-common/Wunused-var-2.c: New test.
	* c-c++-common/Wunused-var-3.c: New test.
	* c-c++-common/Wunused-var-4.c: New test.
	* c-c++-common/Wunused-var-5.c: New test.
	* g++.dg/warn/Wunused-var-1.C: New test.
	* g++.dg/warn/Wunused-var-2.C: New test.
	* g++.dg/warn/Wunused-var-3.C: New test.
	* g++.dg/warn/Wunused-var-4.C: New test.
	* g++.dg/warn/Wunused-var-5.C: New test.
	* g++.dg/warn/Wunused-var-6.C: New test.
	* g++.dg/warn/Wunused-var-7.C: New test.
	* g++.dg/warn/Wunused-var-8.C: New test.
	* g++.dg/warn/Wunused-parm-1.C: New test.
	* g++.dg/warn/Wunused-parm-2.C: New test.
	* g++.dg/warn/Wunused-parm-3.C: New test.

Co-Authored-By: Dodji Seketeli <dodji@redhat.com>

From-SVN: r159096

1 files changed, 13 insertions, 0 deletions

diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index d4ce014..f47a758 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -610,6 +610,13 @@ finish_expr_stmt (tree expr)
 	{
 	  if (warn_sequence_point)
 	    verify_sequence_points (expr);
+	  if (TREE_CODE (expr) != MODIFY_EXPR)
+	    /* Expr is not being 'used' here, otherwise we whould have
+	       called mark_{rl}value_use use here, which would have in turn
+	       called mark_exp_read. Rather, we call mark_exp_read directly
+	       to avoid some warnings when
+	        -Wunused-but-set-{variable,parameter} is in effect.  */
+	    mark_exp_read (expr);
 	  expr = convert_to_void (expr, "statement", tf_warning_or_error);
 	}
       else if (!type_dependent_expression_p (expr))
@@ -1238,6 +1245,8 @@ finish_asm_stmt (int volatile_p, tree string, tree output_operands,
 	     otherwise we'll get an error.  Gross, but ...  */
 	  STRIP_NOPS (operand);
 
+	  operand = mark_lvalue_use (operand);
+
 	  if (!lvalue_or_else (operand, lv_asm, tf_warning_or_error))
 	    operand = error_mark_node;
 
@@ -3182,6 +3191,8 @@ finish_typeof (tree expr)
       return type;
     }
 
+  expr = mark_type_use (expr);
+
   type = unlowered_expr_type (expr);
 
   if (!type || type == unknown_type_node)
@@ -4859,6 +4870,7 @@ finish_decltype_type (tree expr, bool id_expression_or_member_access_p)
         case PARM_DECL:
         case RESULT_DECL:
         case TEMPLATE_PARM_INDEX:
+	  expr = mark_type_use (expr);
           type = TREE_TYPE (expr);
           break;
 
@@ -4867,6 +4879,7 @@ finish_decltype_type (tree expr, bool id_expression_or_member_access_p)
           break;
 
         case COMPONENT_REF:
+	  mark_type_use (expr);
           type = is_bitfield_expr_with_lowered_type (expr);
           if (!type)
             type = TREE_TYPE (TREE_OPERAND (expr, 1));