Fix Ractor.make_shareable changing locals for Procs

env_copy() uses rb_ary_delete_at() with a loop counting up while
iterating through the list of read only locals. rb_ary_delete_at() can
shift elements in the array to an index lesser than the loop index,
causing locals to be missed and set to Qfalse in the returned
environment.

Iterate through the locals in reverse instead, this way the shifting
never happens for locals that are yet to be visited and we process all
the locals in the array.

[Bug #18023]

1 files changed, 1 insertions, 1 deletions

diff --git a/vm.c b/vm.c
index 5a1756e33a..d5e984ce61 100644
--- a/vm.c
+++ b/vm.c
@@ -1006,7 +1006,7 @@ env_copy(const VALUE *src_ep, VALUE read_only_variables)
     volatile VALUE prev_env = Qnil;
 
     if (read_only_variables) {
-        for (int i=0; i<RARRAY_LENINT(read_only_variables); i++) {
+        for (int i=RARRAY_LENINT(read_only_variables)-1; i>=0; i--) {
             ID id = SYM2ID(rb_str_intern(RARRAY_AREF(read_only_variables, i)));
 
             for (unsigned int j=0; j<src_env->iseq->body->local_table_size; j++) {