[Bug sanitizer/112727] [11/12/13/14 Regression] UBSAN creates GIMPLE path with uninitialized variable

[jakub at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112727

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Actually
--- gcc/cp/cp-gimplify.cc.jj    2023-12-05 09:06:06.112878408 +0100
+++ gcc/cp/cp-gimplify.cc       2023-12-06 22:32:46.379370223 +0100
@@ -2906,7 +2906,14 @@ cp_fold (tree x, fold_flags_t flags)
     fold_cache = hash_map<tree, tree>::create_ggc (101);

   if (tree *cached = fold_cache->get (x))
-    return *cached;
+    {
+      /* unshare_expr doesn't recurse into SAVE_EXPRs.  If SAVE_EXPR's
+        argument has been folded into a tree invariant, make sure it is
+        unshared.  See PR112727.  */
+      if (TREE_CODE (x) == SAVE_EXPR && *cached != x)
+       return unshare_expr (*cached);
+      return *cached;
+    }

   uid_sensitive_constexpr_evaluation_checker c;

is what it really fixes.