v8: add cachedDataVersionTag

Adds `v8.cachedDataVersionTag()`, which returns an integer
representing the version tag for `cachedData` for the current V8
version & flags.

PR-URL: https://github.com/nodejs/node/pull/11515
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

1 files changed, 19 insertions, 0 deletions

diff --git a/test/parallel/test-v8-version-tag.js b/test/parallel/test-v8-version-tag.js
new file mode 100644
index 0000000000..22b0db0cd4
--- /dev/null
+++ b/test/parallel/test-v8-version-tag.js
@@ -0,0 +1,19 @@
+'use strict';
+require('../common');
+const assert = require('assert');
+const v8 = require('v8');
+
+const versionTag1 = v8.cachedDataVersionTag();
+assert.strictEqual(typeof versionTag1, 'number');
+assert.strictEqual(v8.cachedDataVersionTag(), versionTag1);
+
+// The value of cachedDataVersionTag is derived from the command line flags and
+// detected CPU features. Test that the value does indeed update when flags
+// are toggled.
+v8.setFlagsFromString('--allow_natives_syntax');
+
+const versionTag2 = v8.cachedDataVersionTag();
+assert.strictEqual(typeof versionTag2, 'number');
+assert.strictEqual(v8.cachedDataVersionTag(), versionTag2);
+
+assert.notStrictEqual(versionTag1, versionTag2);