Mark array as "going to be modified" in `Array#reject!`

Before this patch, if `reject!` is called on a shared array it can
mutate the shared array rather than a copy.  This patch marks the array
as "going to be modified" so that the shared source array isn't
mutated.

[Bug #15479] [ruby-core:90781]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66756 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 1 insertions, 0 deletions

diff --git a/array.c b/array.c
index 5fef843455..7b92bfe5b1 100644
--- a/array.c
+++ b/array.c
@@ -3540,6 +3540,7 @@ static VALUE
 rb_ary_reject_bang(VALUE ary)
 {
     RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
+    rb_ary_modify(ary);
     return ary_reject_bang(ary);
 }