Column names should be frozen

CHANGELOG.md

@@ -23,6 +23,7 @@ This release drops support for Ruby 2.7. [#453] @flavorjones
 ### Changed
 
 - Raise `StandardError` in a few places where `Exception` was previously raised.
+- `Database#columns` returns a list of frozen strings now
 
 
 ### Removed

ext/sqlite3/sqlite3_ruby.h

@@ -18,8 +18,7 @@
 #define UTF8_P(_obj) (rb_enc_get_index(_obj) == rb_utf8_encindex())
 #define UTF16_LE_P(_obj) (rb_enc_get_index(_obj) == rb_enc_find_index("UTF-16LE"))
 #define UTF16_BE_P(_obj) (rb_enc_get_index(_obj) == rb_enc_find_index("UTF-16BE"))
-#define SQLITE3_UTF8_STR_NEW2(_obj) \
-    (rb_enc_associate_index(rb_str_new2(_obj), rb_utf8_encindex()))
+#define SQLITE3_UTF8_STR_NEW2(_obj) (rb_utf8_str_new_cstr(_obj))
 
 #ifdef USING_SQLCIPHER_INC_SUBDIR
 #  include <sqlcipher/sqlite3.h>

ext/sqlite3/statement.c

@@ -374,8 +374,13 @@ column_name(VALUE self, VALUE index)
 
     name = sqlite3_column_name(ctx->st, (int)NUM2INT(index));
 
-    if (name) { return SQLITE3_UTF8_STR_NEW2(name); }
-    return Qnil;
+    VALUE ret = Qnil;
+
+    if (name) {
+        ret = SQLITE3_UTF8_STR_NEW2(name);
+        rb_obj_freeze(ret);
+    }
+    return ret;
 }
 
 /* call-seq: stmt.column_decltype(index)

test/test_integration_resultset.rb

@@ -18,6 +18,10 @@ def teardown
     @db.close
   end
 
+  def test_column_names_should_be_frozen
+    assert @stmt.columns.all?(&:frozen?)
+  end
+
   def test_reset_unused
     assert_nothing_raised { @result.reset }
     assert_empty @result.to_a