[PATCH] Fix PR debug/26754

[Eric Botcazou <ebotcazou at adacore dot com>]

Hi,

Debug info generated by the 4.x series of compilers are wrong for variables 
accessed from nested functions:

void foo(void)
{
  int a = 0;

  void bar(void)
  {
    a = 1;
  }

  bar ();
  a = a + 1;
}

int main(void)
{
  foo ();
}


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This GDB was configured as "i586-suse-linux"...Using host libthread_db library
"/lib/tls/libthread_db.so.1".

(gdb) b t.c:11
Breakpoint 1 at 0x8048389: file t.c, line 11.
(gdb) run
Starting program: /home/eric/gnat/bugs/F318-004/t

Breakpoint 1, foo () at t.c:11
11        a = a + 1;
(gdb) p a
$1 = -12412
(gdb) next
12      }
(gdb) p a
$2 = -12412

This is of course a regression from the 3.x series of compilers.  The culprit 
is the nested functions lowering pass that puts these variables into the 
"non-local frame structure" without telling anyone.  Surprisingly enough, 
there is already support code in mainline (get_nonlocal_debug_decl and 
get_local_debug_decl) but it is effectively disabled.

Bootstrapped/regtested on i586-suse-linux.  OK for mainline?


2006-05-13  Eric Botcazou  <ebotcazou@adacore.com>

	PR debug/26754
	* gimplify.c (declare_regular_vars): New function.
	* tree-gimple.h (declare_regular_vars): Declare it.
	* tree-nested.c (get_local_debug_decl): Set DECL_IGNORED_P
	on the original variable.
	(finalize_nesting_tree_1): Declare debug_var_chain as regular
	variables instead of temporary variables.


-- 
Eric Botcazou

Index: gimplify.c
===================================================================
--- gimplify.c	(revision 113625)
+++ gimplify.c	(working copy)
@@ -643,7 +643,7 @@ get_initialized_tmp_var (tree val, tree 
   return internal_get_tmp_var (val, pre_p, post_p, false);
 }
 
-/* Declares all the variables in VARS in SCOPE.  */
+/* Declares all nodes in VARS as temporary variables in SCOPE.  */
 
 void
 declare_tmp_vars (tree vars, tree scope)
@@ -666,6 +666,45 @@ declare_tmp_vars (tree vars, tree scope)
     }
 }
 
+/* Declares all nodes in VARS as regular variables in SCOPE.  */
+
+void
+declare_regular_vars (tree vars, tree scope)
+{
+  tree last = vars;
+  if (last)
+    {
+      tree temps, block;
+
+      /* C99 mode puts the default 'return 0;' for main outside the outer
+	 braces.  So drill down until we find an actual scope.  */
+      while (TREE_CODE (scope) == COMPOUND_EXPR)
+	scope = TREE_OPERAND (scope, 0);
+
+      gcc_assert (TREE_CODE (scope) == BIND_EXPR);
+
+      block = BIND_EXPR_BLOCK (scope);
+      if (!block)
+	{
+	  declare_tmp_vars (vars, scope);
+	  return;
+	}
+
+      /* We need to attach the nodes both to the BIND_EXPR and to its
+	 associated BLOCK for debugging purposes.  The key point here
+	 is that the BLOCK_VARS of the BIND_EXPR_BLOCK of a BIND_EXPR
+	 is a subchain of the BIND_EXPR_VARS of the BIND_EXPR.  */
+      temps = nreverse (last);
+      if (BLOCK_VARS (block))
+	BLOCK_VARS (block) = chainon (BLOCK_VARS (block), temps);
+      else
+	{
+	  BIND_EXPR_VARS (scope) = chainon (BIND_EXPR_VARS (scope), temps);
+	  BLOCK_VARS (block) = temps;
+	}
+    }
+}
+
 void
 gimple_add_tmp_var (tree tmp)
 {
Index: tree-gimple.h
===================================================================
--- tree-gimple.h	(revision 113625)
+++ tree-gimple.h	(working copy)
@@ -31,6 +31,7 @@ extern tree create_tmp_var (tree, const 
 extern tree get_initialized_tmp_var (tree, tree *, tree *);
 extern tree get_formal_tmp_var (tree, tree *);
 extern void declare_tmp_vars (tree, tree);
+extern void declare_regular_vars (tree, tree);
 
 extern void annotate_all_with_locus (tree *, location_t);
 
Index: tree-nested.c
===================================================================
--- tree-nested.c	(revision 113625)
+++ tree-nested.c	(working copy)
@@ -1186,6 +1186,9 @@ get_local_debug_decl (struct nesting_inf
   TREE_CHAIN (new_decl) = info->debug_var_chain;
   info->debug_var_chain = new_decl;
 
+  /* Do not emit debug info twice.  */
+  DECL_IGNORED_P (decl) = 1;
+
   return new_decl;
 }
 
@@ -1807,8 +1810,8 @@ finalize_nesting_tree_1 (struct nesting_
     declare_tmp_vars (root->new_local_var_chain,
 		      DECL_SAVED_TREE (root->context));
   if (root->debug_var_chain)
-    declare_tmp_vars (root->debug_var_chain,
-		      DECL_SAVED_TREE (root->context));
+    declare_regular_vars (root->debug_var_chain,
+			  DECL_SAVED_TREE (root->context));
 
   /* Dump the translated tree function.  */
   dump_function (TDI_nested, root->context);