return'ing a struct and trap representations

[Ralf Wildenhues]

Hello Bruno, all,

GCC 4.0.3 and newer (with `-Wall -Werror -fno-builtin' on a GNU/Linux
x86_64 system) errors out at some of the list implementation
"constructor" functions:
| gl_array_list.c: In function ‘gl_array_iterator’:
| gl_array_list.c:398: warning: ‘result.j’ is used uninitialized in this 
function
| gl_array_list.c:398: warning: ‘result.i’ is used uninitialized in this 
function

Now I have a question here: the structures in question are created on
the stack, and then passed to the calling function with `return'.  Does
the return expression count as accessing the value of the automatic
object?  Because if it does, then I read C99 6.2.6.1(5) and footnote 41
such that the values have to be initialized, if we want to avoid
undefined behavior: the variables could otherwise contain trap
representations.

Am I reading this wrongly?  If not: ok to apply?

Cheers,
Ralf

        * gl_anylinked_list2.h (gl_linked_iterator)
        (gl_linked_iterator_from_to): Initialize struct completely.
        * gl_anytree_list2.h (gl_tree_iterator): Likewise.
        (gl_tree_iterator_from_to): Likewise
        * gl_anytree_oset.h (gl_tree_iterator): Likewise.
        * gl_array_list.c (gl_array_iterator)
        (gl_array_iterator_from_to) : Likewise.
        * gl_array_oset.c (gl_array_iterator): Likewise.
        * gl_carray_list.c (gl_carray_iterator)
        (gl_carray_iterator_from_to): Likewise.

Index: lib/gl_anylinked_list2.h
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/gl_anylinked_list2.h,v
retrieving revision 1.2
diff -u -r1.2 gl_anylinked_list2.h
--- lib/gl_anylinked_list2.h    24 Jul 2006 16:34:38 -0000      1.2
+++ lib/gl_anylinked_list2.h    22 Sep 2006 05:10:20 -0000
@@ -697,6 +697,9 @@
   result.list = list;
   result.p = list->root.next;
   result.q = &list->root;
+  result.i = 0;
+  result.j = 0;
+  result.count = 0;
 
   return result;
 }
@@ -763,6 +766,10 @@
       result.q = node;
     }
 
+  result.i = 0;
+  result.j = 0;
+  result.count = 0;
+
   return result;
 }
 
Index: lib/gl_anytree_list2.h
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/gl_anytree_list2.h,v
retrieving revision 1.1
diff -u -r1.1 gl_anytree_list2.h
--- lib/gl_anytree_list2.h      17 Jul 2006 11:27:18 -0000      1.1
+++ lib/gl_anytree_list2.h      22 Sep 2006 05:10:20 -0000
@@ -349,6 +349,9 @@
   result.p = node;
   /* End point is past the rightmost node.  */
   result.q = NULL;
+  result.i = 0;
+  result.j = 0;
+  result.count = 0;
 
   return result;
 }
@@ -368,6 +371,9 @@
   result.p = (start_index < count ? node_at (list->root, start_index) : NULL);
   /* End point is the node at position end_index.  */
   result.q = (end_index < count ? node_at (list->root, end_index) : NULL);
+  result.i = 0;
+  result.j = 0;
+  result.count = 0;
 
   return result;
 }
Index: lib/gl_anytree_oset.h
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/gl_anytree_oset.h,v
retrieving revision 1.1
diff -u -r1.1 gl_anytree_oset.h
--- lib/gl_anytree_oset.h       17 Jul 2006 11:27:35 -0000      1.1
+++ lib/gl_anytree_oset.h       22 Sep 2006 05:10:20 -0000
@@ -211,6 +211,9 @@
   result.p = node;
   /* End point is past the rightmost node.  */
   result.q = NULL;
+  result.i = 0;
+  result.j = 0;
+  result.count = 0;
 
   return result;
 }
Index: lib/gl_array_list.c
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/gl_array_list.c,v
retrieving revision 1.2
diff -u -r1.2 gl_array_list.c
--- lib/gl_array_list.c 14 Sep 2006 14:18:36 -0000      1.2
+++ lib/gl_array_list.c 22 Sep 2006 05:34:34 -0000
@@ -394,6 +394,8 @@
   result.count = list->count;
   result.p = list->elements + 0;
   result.q = list->elements + list->count;
+  result.i = 0;
+  result.j = 0;
 
   return result;
 }
@@ -411,6 +413,8 @@
   result.count = list->count;
   result.p = list->elements + start_index;
   result.q = list->elements + end_index;
+  result.i = 0;
+  result.j = 0;
 
   return result;
 }
Index: lib/gl_array_oset.c
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/gl_array_oset.c,v
retrieving revision 1.2
diff -u -r1.2 gl_array_oset.c
--- lib/gl_array_oset.c 14 Sep 2006 14:18:36 -0000      1.2
+++ lib/gl_array_oset.c 22 Sep 2006 05:10:20 -0000
@@ -229,6 +229,8 @@
   result.count = set->count;
   result.p = set->elements + 0;
   result.q = set->elements + set->count;
+  result.i = 0;
+  result.j = 0;
 
   return result;
 }
Index: lib/gl_carray_list.c
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/gl_carray_list.c,v
retrieving revision 1.2
diff -u -r1.2 gl_carray_list.c
--- lib/gl_carray_list.c        14 Sep 2006 14:18:36 -0000      1.2
+++ lib/gl_carray_list.c        22 Sep 2006 05:10:20 -0000
@@ -528,6 +528,8 @@
   result.count = list->count;
   result.i = 0;
   result.j = list->count;
+  result.p = 0;
+  result.q = 0;
 
   return result;
 }
@@ -545,6 +547,8 @@
   result.count = list->count;
   result.i = start_index;
   result.j = end_index;
+  result.p = 0;
+  result.q = 0;
 
   return result;
 }