hamt: fix technically undefined behavior
authorMarc Nieper-Wißkirchen <marc@nieper-wisskirchen.de>
Fri, 12 Aug 2022 14:00:23 +0000 (16:00 +0200)
committerBruno Haible <bruno@clisp.org>
Wed, 31 Aug 2022 23:25:13 +0000 (01:25 +0200)
Bug reported by Bruno Haible in
<https://lists.gnu.org/r/bug-gnulib/2022-04/msg00023.html>.
* lib/hamt.c (entry_insert): Remove technically undefined
behavior when shifting an integer of N bits by N or more bits.

ChangeLog
lib/hamt.c

index d3fa2e0ddcc779290841fbfdedbba5bc6a56a147..8aa95ecfbab6776d776fffbb5f752843d308a1db 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2022-08-12  Marc Nieper-Wißkirchen  <marc@nieper-wisskirchen.de>
+
+       hamt: fix technically undefined behavior
+       Bug reported by Bruno Haible in
+       <https://lists.gnu.org/r/bug-gnulib/2022-04/msg00023.html>.
+       * lib/hamt.c (entry_insert): Remove technically undefined
+       behavior when shifting an integer of N bits by N or more bits.
+
 2022-08-09  Paul Eggert  <eggert@cs.ucla.edu>
 
        verify: port ‘assume’ to C23 non-GCC
index 8a12f216d1e7ddfe7d0fa691207c3f7a9cfbe388..7600433806f8124bdd0b52c61fd01fcaaaf12fb4 100644 (file)
@@ -680,6 +680,11 @@ entry_insert (const struct function_table *functions, Hamt_entry *entry,
       Hamt_entry *new_entry = copy_entry (*elt_ptr);
       if (replace)
         *elt_ptr = NULL;
+      /* We have to take this shortcut as shifting an integer of N
+        bits by N or more bits triggers undefined behavior.
+        See: https://lists.gnu.org/archive/html/bug-gnulib/2022-04/msg00023.html.  */
+      if (depth >= _GL_HAMT_MAX_DEPTH)
+       return (Hamt_entry *) create_populated_bucket (new_entry, copy_entry (entry));
       return create_populated_subtrie (new_entry, copy_entry (entry), hash,
                                        (hash_element (functions, entry)
                                         >> (5 * depth)), depth);