re PR c/18624 (GCC does not detect local variable set but never used)

	PR c/18624
	* tree.h (DECL_READ_P): Define.
	(struct tree_decl_common): Add decl_read_flag.
	* c-decl.c (pop_scope): If TREE_USED but !DECL_READ_P, issue
	a set but not used warning.
	(merge_decls): Merge DECL_READ_P flag.
	(finish_decl, build_compound_literal): Set DECL_READ_P flag.
	(finish_function): Issue -Wunused-but-set-parameter diagnostics.
	* c-common.c (handle_used_attribute, handle_unused_attribute):
	Likewise.
	* c-tree.h (default_function_array_read_conversion, mark_exp_read):
	New prototypes.
	* c-typeck.c (default_function_array_read_conversion, mark_exp_read):
	New functions.
	(default_conversion, c_process_expr_stmt): Call mark_exp_read.
	* c-parser.c (c_parser_initializer, c_parser_expr_no_commas,
	c_parser_binary_expression, c_parser_cast_expression,
	c_parser_expr_list, c_parser_omp_atomic, c_parser_omp_for_loop):
	Call default_function_array_read_conversion instead of
	default_function_array_conversion where needed.
	(c_parser_unary_expression, c_parser_conditional_expression,
	c_parser_postfix_expression_after_primary, c_parser_initelt):
	Likewise.  Call mark_exp_read where needed.
	(c_parser_statement_after_labels, c_parser_asm_operands,
	c_parser_typeof_specifier, c_parser_sizeof_expression,
	c_parser_alignof_expression, c_parser_initval): Call mark_exp_read
	where needed.
	* common.opt (Wunused-but-set-variable, Wunused-but-set-parameter):
	New.
	* toplev.c (warn_unused_but_set_variable): Default to warn_unused.
	(warn_unused_but_set_parameter): Default to warn_unused
	&& extra_warnings.
	* doc/invoke.texi: Document -Wunused-but-set-variable and
	-Wunused-but-set-parameter.

	* objc-act.c (finish_var_decl, objc_begin_catch_clause,
	really_start_method, get_super_receiver, handle_class_ref): Set
	DECL_READ_P in addition to TREE_USED.

	* gcc.dg/Wunused-var-1.c: New test.
	* gcc.dg/Wunused-var-2.c: New test.
	* gcc.dg/Wunused-var-3.c: New test.
	* gcc.dg/Wunused-var-4.c: New test.
	* gcc.dg/Wunused-var-5.c: New test.
	* gcc.dg/Wunused-var-6.c: New test.
	* gcc.dg/Wunused-parm-1.c: New test.

From-SVN: r158086

2 files changed, 15 insertions, 1 deletions

diff --git a/gcc/objc/ChangeLog b/gcc/objc/ChangeLog
index 3063af9..4307001 100644
--- a/gcc/objc/ChangeLog
+++ b/gcc/objc/ChangeLog
@@ -1,3 +1,10 @@
+2010-04-07  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/18624
+	* objc-act.c (finish_var_decl, objc_begin_catch_clause,
+	really_start_method, get_super_receiver, handle_class_ref): Set
+	DECL_READ_P in addition to TREE_USED.
+
 2010-04-07  Iain Sandoe <iains@gcc.gnu.org>
 
 	PR objc/35996
diff --git a/gcc/objc/objc-act.c b/gcc/objc/objc-act.c
index f5b754b..9e5fdb5 100644
--- a/gcc/objc/objc-act.c
+++ b/gcc/objc/objc-act.c
@@ -1,6 +1,7 @@
 /* Implement classes and message passing for Objective C.
    Copyright (C) 1992, 1993, 1994, 1995, 1997, 1998, 1999, 2000, 2001,
-   2002, 2003, 2004, 2005, 2007, 2008, 2009 Free Software Foundation, Inc.
+   2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010
+   Free Software Foundation, Inc.
    Contributed by Steve Naroff.
 
 This file is part of GCC.
@@ -1531,6 +1532,7 @@ finish_var_decl (tree var, tree initializer)
   mark_decl_referenced (var);
   /* Mark the decl to avoid "defined but not used" warning.  */
   TREE_USED (var) = 1;
+  DECL_READ_P (var) = 1;
   /* We reserve the right for the runtime to use/modify these variables
      in ways that are opaque to us.  */
   DECL_PRESERVE_P (var) = 1;
@@ -3867,6 +3869,7 @@ objc_begin_catch_clause (tree decl)
   /* ??? As opposed to __attribute__((unused))?  Anyway, this appears to
      be what the previous objc implementation did.  */
   TREE_USED (decl) = 1;
+  DECL_READ_P (decl) = 1;
 
   /* Verify that the type of the catch is valid.  It must be a pointer
      to an Objective-C class, or "id" (which is catch-all).  */
@@ -8722,7 +8725,9 @@ really_start_method (tree method,
 
   /* Suppress unused warnings.  */
   TREE_USED (self_decl) = 1;
+  DECL_READ_P (self_decl) = 1;
   TREE_USED (TREE_CHAIN (self_decl)) = 1;
+  DECL_READ_P (TREE_CHAIN (self_decl)) = 1;
 #ifdef OBJCPLUS
   pop_lang_context ();
 #endif
@@ -8799,6 +8804,7 @@ get_super_receiver (void)
 				       objc_super_template);
 	/* This prevents `unused variable' warnings when compiling with -Wall.  */
 	TREE_USED (UOBJC_SUPER_decl) = 1;
+	DECL_READ_P (UOBJC_SUPER_decl) = 1;
 	lang_hooks.decls.pushdecl (UOBJC_SUPER_decl);
         finish_decl (UOBJC_SUPER_decl, input_location, NULL_TREE, NULL_TREE,
 	    	     NULL_TREE);
@@ -9422,6 +9428,7 @@ handle_class_ref (tree chain)
   DECL_INITIAL (decl) = exp;
   TREE_STATIC (decl) = 1;
   TREE_USED (decl) = 1;
+  DECL_READ_P (decl) = 1;
   /* Force the output of the decl as this forces the reference of the class.  */
   mark_decl_referenced (decl);