MFC r307227 and r307343:

  Improve typing of POSIX search tree functions.

  Back in 2015 when I reimplemented these functions to use an AVL tree, I
  was annoyed by the weakness of the typing of these functions. Both tree
  nodes and keys are represented by 'void *', meaning that things like the
  documentation for these functions are an absolute train wreck.

  To make things worse, users of these functions need to cast the return
  value of tfind()/tsearch() from 'void *' to 'type_of_key **' in order to
  access the key. Technically speaking such casts violate aliasing rules.
  I've observed actual breakages as a result of this by enabling features
  like LTO.

  I've filed a bug report at the Austin Group. Looking at the way the bug
  got resolved, they made a pretty good step in the right direction. A new
  type 'posix_tnode' has been added to correspond to tree nodes. It is
  still defined as 'void' for source-level compatibility, but in the very
  far future it could be replaced by a proper structure type containing a
  key pointer.

1 files changed, 2 insertions, 5 deletions

diff --git a/lib/libc/stdlib/tfind.c b/lib/libc/stdlib/tfind.c
index 0ad391e..afcbc16 100644
--- a/lib/libc/stdlib/tfind.c
+++ b/lib/libc/stdlib/tfind.c
@@ -4,8 +4,6 @@
  * Tree search generalized from Knuth (6.2.2) Algorithm T just like
  * the AT&T man page says.
  *
- * The node_t structure is for internal use only, lint doesn't grok it.
- *
  * Written by reading the System V Interface Definition, not the code.
  *
  * Totally public domain.
@@ -29,11 +27,10 @@ __FBSDID("$FreeBSD$");
  * vkey   - key to be found 
  * vrootp - address of the tree root 
  */
-void *
-tfind(const void *vkey, void * const *vrootp,
+posix_tnode *
+tfind(const void *vkey, posix_tnode * const *rootp,
     int (*compar)(const void *, const void *))
 {
-	node_t **rootp = (node_t **)vrootp;
 
 	if (rootp == NULL)
 		return NULL;