1 files changed, 35 insertions, 0 deletions
diff --git a/ext/-test-/string/rb_str_dup.c b/ext/-test-/string/rb_str_dup.c
new file mode 100644
index 0000000000..a0bd65820f
--- /dev/null
+++ b/ext/-test-/string/rb_str_dup.c
@@ -0,0 +1,35 @@
+#include "ruby.h"
+
+VALUE rb_str_dup(VALUE str);
+
+static VALUE
+bug_rb_str_dup(VALUE self, VALUE str)
+{
+    rb_check_type(str, T_STRING);
+    return rb_str_dup(str);
+}
+
+static VALUE
+bug_shared_string_p(VALUE self, VALUE str)
+{
+    rb_check_type(str, T_STRING);
+    return RB_FL_TEST(str, RUBY_ELTS_SHARED) && RB_FL_TEST(str, RSTRING_NOEMBED) ? Qtrue : Qfalse;
+}
+
+static VALUE
+bug_sharing_with_shared_p(VALUE self, VALUE str)
+{
+    rb_check_type(str, T_STRING);
+    if (bug_shared_string_p(self, str)) {
+        return bug_shared_string_p(self, RSTRING(str)->as.heap.aux.shared);
+    }
+    return Qfalse;
+}
+
+void
+Init_string_rb_str_dup(VALUE klass)
+{
+    rb_define_singleton_method(klass, "rb_str_dup", bug_rb_str_dup, 1);
+    rb_define_singleton_method(klass, "shared_string?", bug_shared_string_p, 1);
+    rb_define_singleton_method(klass, "sharing_with_shared?", bug_sharing_with_shared_p, 1);
+}