[Patch] Fix PR 5582 and 10538, missed uninitialized variable warning

[Andrew Pinski <pinskia at physics dot uc dot edu>]

This is a follow up with my pervious patch which did not compile at all 
in any non C language.
This fixes PR 5582 only when pedantic is on because it as a GCC 
extension to do int i = i; to turn
off the uninitialized warnings for that variable.
I also do not warn about int *x = &x; because x is initialized.

There is one case where I warn when we should not: int *x = &(x+2);.
I will add some testcases when approved.

Testing on i686-unknown-openbsd3.1.

Okay if the no regressions (or with a follow up to fix the testcases)?


ChangeLog:

	* langhooks-def.h (lhd_decl_uninit): Declare.
	(LANG_HOOKS_DECL_UNINIT): New macro.
	(LANG_HOOKS_INITIALIZER): Adjust.
	* langhooks.h (struct lang_hooks): Add new field
	decl_uninit.
	* langhooks.c (lhd_decl_uninit): Define.
	* c-common.c (c_decl_uninit_1): New function.
	(c_decl_uninit): New function.
	* c-common.h (c_decl_uninit): Declare.
	* c-lang.c (LANG_HOOKS_DECL_UNINIT): Define.
	* objc/objc-lang.c  (LANG_HOOKS_DECL_UNINIT): Define.
	* function.c (uninitialized_vars_warning): Call the language hook.

cp/ChangeLog:
	* cp/cp-lang.c (LANG_HOOKS_DECL_UNINIT): Define.


Patch:
Index: langhooks-def.h
===================================================================
RCS file: /cvs/gcc/gcc/gcc/langhooks-def.h,v
retrieving revision 1.60
diff -u -p -r1.60 langhooks-def.h
--- langhooks-def.h	4 Aug 2003 20:44:13 -0000	1.60
+++ langhooks-def.h	17 Aug 2003 04:20:05 -0000
@@ -63,6 +63,7 @@ extern void lhd_incomplete_type_error (t
 extern tree lhd_type_promotes_to (tree);
 extern bool lhd_decl_ok_for_sibcall (tree);
 extern tree lhd_expr_size (tree);
+extern bool lhd_decl_uninit (tree);
 extern size_t lhd_tree_size (enum tree_code);

 /* Declarations of default tree inlining hooks.  */
@@ -114,6 +115,7 @@ extern void lhd_initialize_diagnostics (
 #define LANG_HOOKS_PRINT_ERROR_FUNCTION lhd_print_error_function
 #define LANG_HOOKS_DECL_PRINTABLE_NAME	lhd_decl_printable_name
 #define LANG_HOOKS_EXPR_SIZE		lhd_expr_size
+#define LANG_HOOKS_DECL_UNINIT		lhd_decl_uninit
 #define LANG_HOOKS_TREE_SIZE		lhd_tree_size

 #define LANG_HOOKS_FUNCTION_INIT	lhd_do_nothing_f
@@ -278,6 +280,7 @@ extern int lhd_tree_dump_type_quals (tre
   LANG_HOOKS_DECL_PRINTABLE_NAME, \
   LANG_HOOKS_PRINT_ERROR_FUNCTION, \
   LANG_HOOKS_EXPR_SIZE, \
+  LANG_HOOKS_DECL_UNINIT, \
   LANG_HOOKS_ATTRIBUTE_TABLE, \
   LANG_HOOKS_COMMON_ATTRIBUTE_TABLE, \
   LANG_HOOKS_FORMAT_ATTRIBUTE_TABLE, \
Index: langhooks.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/langhooks.c,v
retrieving revision 1.48
diff -u -p -r1.48 langhooks.c
--- langhooks.c	3 Aug 2003 22:14:47 -0000	1.48
+++ langhooks.c	17 Aug 2003 04:20:05 -0000
@@ -430,6 +430,14 @@ lhd_expr_size (tree exp)
   else
     return size_in_bytes (TREE_TYPE (exp));
 }
+/* lang_hooks.decl_uninit: Find out if a variable is uninitialized 
based
+   on DECL_INITIAL.  */
+
+bool
+lhd_decl_uninit (tree t ATTRIBUTE_UNUSED)
+{
+  return false;
+}

 /* lang_hooks.tree_size: Determine the size of a tree with code C,
    which is a language-specific tree code in category 'x'.  The
Index: langhooks.h
===================================================================
RCS file: /cvs/gcc/gcc/gcc/langhooks.h,v
retrieving revision 1.69
diff -u -p -r1.69 langhooks.h
--- langhooks.h	4 Aug 2003 20:44:13 -0000	1.69
+++ langhooks.h	17 Aug 2003 04:20:05 -0000
@@ -361,6 +361,10 @@ struct lang_hooks
      semantics in cases that it doesn't want to handle specially.  */
   tree (*expr_size) (tree);

+  /* Called from uninitialized_vars_warning to find out if a variable 
is
+     uninitialized based on DECL_INITIAL. */
+  bool (*decl_uninit) (tree);
+
   /* Pointers to machine-independent attribute tables, for front ends
      using attribs.c.  If one is NULL, it is ignored.  Respectively, a
      table of attributes specific to the language, a table of
Index: c-common.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/c-common.c,v
retrieving revision 1.445
diff -u -p -r1.445 c-common.c
--- c-common.c	5 Aug 2003 21:15:52 -0000	1.445
+++ c-common.c	17 Aug 2003 04:20:06 -0000
@@ -5727,6 +5715,36 @@ c_estimate_num_insns (tree decl)
   int num = 0;
   walk_tree_without_duplicates (&DECL_SAVED_TREE (decl), 
c_estimate_num_insns_1, &num);
   return num;
+}
+
+/* Used by c_decl_uninit to find where expressions like x = x + 1; */
+static tree
+c_decl_uninit_1 (tree *t, int *walk_sub_trees, void *x)
+{
+  /* If x = EXP(&x)EXP, then do not warn about the use of x.
+     FIXME:  Should not warn about this: int *x = &(x+2);.  */
+  if (TREE_CODE (*t) == ADDR_EXPR && TREE_OPERAND (*t, 0) == x)
+    {
+      *walk_sub_trees = 0;
+      return NULL_TREE;
+    }
+  if (*t == x)
+    return *t;
+  return NULL_TREE;
+}
+
+/* Find out if a variable is uninitialized based on DECL_INITIAL.  */
+bool
+c_decl_uninit (tree t)
+{
+  /* int x = x; is GCC extension to turn off this warning, only if not 
pedantic. */
+  if (DECL_INITIAL (t) == t)
+    return pedantic ? true : false;
+
+  /* Walk the trees look for the variable it self. */
+  if (walk_tree_without_duplicates (&DECL_INITIAL (t), 
c_decl_uninit_1, t))
+    return true;
+  return false;
 }

 #include "gt-c-common.h"
Index: c-common.h
===================================================================
RCS file: /cvs/gcc/gcc/gcc/c-common.h,v
retrieving revision 1.202
diff -u -p -r1.202 c-common.h
--- c-common.h	5 Aug 2003 21:15:52 -0000	1.202
+++ c-common.h	17 Aug 2003 04:20:06 -0000
@@ -1289,6 +1288,7 @@ extern void builtin_define_with_value (c
 extern void c_stddef_cpp_builtins (void);
 extern void fe_file_change (const struct line_map *);
 extern int c_estimate_num_insns (tree decl);
+extern bool c_decl_uninit (tree t);

 /* In c-ppoutput.c  */
 extern void init_pp_output (FILE *);
Index: c-lang.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/c-lang.c,v
retrieving revision 1.113
diff -u -p -r1.113 c-lang.c
--- c-lang.c	10 Aug 2003 18:17:05 -0000	1.113
+++ c-lang.c	17 Aug 2003 04:20:06 -0000
@@ -87,6 +87,8 @@ enum c_language_kind c_language = clk_c;
 #define LANG_HOOKS_FUNCTION_LEAVE_NESTED c_pop_function_context
 #undef LANG_HOOKS_DUP_LANG_SPECIFIC_DECL
 #define LANG_HOOKS_DUP_LANG_SPECIFIC_DECL c_dup_lang_specific_decl
+#undef LANG_HOOKS_DECL_UNINIT
+#define LANG_HOOKS_DECL_UNINIT c_decl_uninit

 /* Attribute hooks.  */
 #undef LANG_HOOKS_COMMON_ATTRIBUTE_TABLE
Index: function.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/function.c,v
retrieving revision 1.449
diff -u -p -r1.449 function.c
--- function.c	25 Jul 2003 09:52:25 -0000	1.449
+++ function.c	17 Aug 2003 04:20:08 -0000
@@ -5564,9 +5564,9 @@ uninitialized_vars_warning (tree block)
 	     with a nonzero DECL_INITIAL had an initializer, so do not
 	     claim it is potentially uninitialized.

-	     We do not care about the actual value in DECL_INITIAL, so we do
-	     not worry that it may be a dangling pointer.  */
-	  && DECL_INITIAL (decl) == NULL_TREE
+	     When the DECL_INITIAL is NULL call the language hook to tell us
+	     if we want to warn.  */
+	  && (DECL_INITIAL (decl) == NULL_TREE || lang_hooks.decl_uninit 
(decl))
 	  && regno_uninitialized (REGNO (DECL_RTL (decl))))
 	warning ("%H'%D' might be used uninitialized in this function",
                  &DECL_SOURCE_LOCATION (decl), decl);
Index: objc/objc-lang.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/objc/objc-lang.c,v
retrieving revision 1.37
diff -u -p -r1.37 objc-lang.c
--- objc/objc-lang.c	4 Aug 2003 20:44:20 -0000	1.37
+++ objc/objc-lang.c	17 Aug 2003 04:20:09 -0000
@@ -79,6 +79,8 @@ enum c_language_kind c_language = clk_ob
 #define LANG_HOOKS_DECL_PRINTABLE_NAME objc_printable_name
 #undef LANG_HOOKS_WARN_UNUSED_GLOBAL_DECL
 #define LANG_HOOKS_WARN_UNUSED_GLOBAL_DECL c_warn_unused_global_decl
+#undef LANG_HOOKS_DECL_UNINIT
+#define LANG_HOOKS_DECL_UNINIT c_decl_uninit

 #undef LANG_HOOKS_FUNCTION_ENTER_NESTED
 #define LANG_HOOKS_FUNCTION_ENTER_NESTED c_push_function_context
Index: cp/cp-lang.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cp/cp-lang.c,v
retrieving revision 1.60
diff -u -p -r1.60 cp-lang.c
--- cp/cp-lang.c	5 Aug 2003 19:23:14 -0000	1.60
+++ cp/cp-lang.c	17 Aug 2003 04:20:09 -0000
@@ -106,6 +106,8 @@ static void cxx_initialize_diagnostics (
 #define LANG_HOOKS_WARN_UNUSED_GLOBAL_DECL cxx_warn_unused_global_decl
 #undef LANG_HOOKS_WRITE_GLOBALS
 #define LANG_HOOKS_WRITE_GLOBALS lhd_do_nothing
+#undef LANG_HOOKS_DECL_UNINIT
+#define LANG_HOOKS_DECL_UNINIT c_decl_uninit


 #undef LANG_HOOKS_FUNCTION_INIT