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, 10 insertions, 1 deletions

diff --git a/gcc/cp/rtti.c b/gcc/cp/rtti.c
index 0f7225f..6f40653 100644
--- a/gcc/cp/rtti.c
+++ b/gcc/cp/rtti.c
@@ -318,7 +318,7 @@ typeid_ok_p (void)
 tree
 build_typeid (tree exp)
 {
-  tree cond = NULL_TREE;
+  tree cond = NULL_TREE, initial_expr = exp;
   int nonnull = 0;
 
   if (exp == error_mark_node || !typeid_ok_p ())
@@ -333,6 +333,9 @@ build_typeid (tree exp)
       && ! resolves_to_fixed_type_p (exp, &nonnull)
       && ! nonnull)
     {
+      /* So we need to look into the vtable of the type of exp.
+         This is an lvalue use of expr then.  */
+      exp = mark_lvalue_use (exp);
       exp = stabilize_reference (exp);
       cond = cp_convert (boolean_type_node, TREE_OPERAND (exp, 0));
     }
@@ -348,6 +351,8 @@ build_typeid (tree exp)
 
       exp = build3 (COND_EXPR, TREE_TYPE (exp), cond, exp, bad);
     }
+  else
+    mark_type_use (initial_expr);
 
   return exp;
 }
@@ -546,6 +551,8 @@ build_dynamic_cast_1 (tree type, tree expr, tsubst_flags_t complain)
       /* If T is a pointer type, v shall be an rvalue of a pointer to
 	 complete class type, and the result is an rvalue of type T.  */
 
+      expr = mark_rvalue_use (expr);
+
       if (TREE_CODE (exprtype) != POINTER_TYPE)
 	{
 	  errstr = _("source is not a pointer");
@@ -564,6 +571,8 @@ build_dynamic_cast_1 (tree type, tree expr, tsubst_flags_t complain)
     }
   else
     {
+      expr = mark_lvalue_use (expr);
+
       exprtype = build_reference_type (exprtype);
 
       /* T is a reference type, v shall be an lvalue of a complete class