avltree-list: avoid compiler warnings

* lib/gl_anytree_list2.h: Add _GL_ATTRIBUTE_PURE to avoid
-Werror=suggest-attribute=pure.
* lib/gl_array_list.c: Likewise.
* lib/gl_avltree_list.c (gl_avltree_list_check_invariants): Add extern
declaration to avoid -Werror=missing-prototypes.  This is not added
to a header as only exported for tests.  Add (void) to the
check_invariants() call to indicate we're discarding the result
in this context which avoids -Werror=unused-value.  Note we don't
use ignore_value here to avoid a dependency as we know we'll not
be adding __attribute__((warn_unused_result)) to check_invariants().
Add _GL_ATTRIBUTE_CONST to avoid -Werror=suggest-attribute=const.

1 files changed, 4 insertions, 4 deletions

diff --git a/lib/gl_array_list.c b/lib/gl_array_list.c
index b61b6cae26..3220dd83aa 100644
--- a/lib/gl_array_list.c
+++ b/lib/gl_array_list.c
@@ -120,7 +120,7 @@ gl_array_size (gl_list_t list)
   return list->count;
 }
 
-static const void *
+static const void * _GL_ATTRIBUTE_PURE
 gl_array_node_value (gl_list_t list, gl_list_node_t node)
 {
   uintptr_t index = NODE_TO_INDEX (node);
@@ -142,7 +142,7 @@ gl_array_node_nx_set_value (gl_list_t list, gl_list_node_t node,
   return 0;
 }
 
-static gl_list_node_t
+static gl_list_node_t _GL_ATTRIBUTE_PURE
 gl_array_next_node (gl_list_t list, gl_list_node_t node)
 {
   uintptr_t index = NODE_TO_INDEX (node);
@@ -156,7 +156,7 @@ gl_array_next_node (gl_list_t list, gl_list_node_t node)
     return NULL;
 }
 
-static gl_list_node_t
+static gl_list_node_t _GL_ATTRIBUTE_PURE
 gl_array_previous_node (gl_list_t list, gl_list_node_t node)
 {
   uintptr_t index = NODE_TO_INDEX (node);
@@ -169,7 +169,7 @@ gl_array_previous_node (gl_list_t list, gl_list_node_t node)
     return NULL;
 }
 
-static const void *
+static const void * _GL_ATTRIBUTE_PURE
 gl_array_get_at (gl_list_t list, size_t position)
 {
   size_t count = list->count;