1 files changed, 25 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/heap-analysis/byteSize-of-symbol.js b/js/src/jit-test/tests/heap-analysis/byteSize-of-symbol.js
new file mode 100644
index 000000000..4a98bd424
--- /dev/null
+++ b/js/src/jit-test/tests/heap-analysis/byteSize-of-symbol.js
@@ -0,0 +1,25 @@
+// Check JS::ubi::Node::size results for symbols.
+
+// We actually hard-code specific sizes into this test, even though they're
+// implementation details, because in practice there are only two architecture
+// variants to consider (32-bit and 64-bit), and if these sizes change, that's
+// something SpiderMonkey hackers really want to know; they're supposed to be
+// stable.
+
+// Run this test only if we're using jemalloc. Other malloc implementations
+// exhibit surprising behaviors. For example, 32-bit Fedora builds have
+// non-deterministic allocation sizes.
+var config = getBuildConfiguration();
+if (!config['moz-memory'])
+  quit(0);
+
+const SIZE_OF_SYMBOL = config['pointer-byte-size'] == 4 ? 16 : 24;
+
+// Without a description.
+assertEq(byteSize(Symbol()), SIZE_OF_SYMBOL);
+
+// With a description.
+assertEq(byteSize(Symbol("This is a relatively long description to be passed to "
+                         + "Symbol() but it doesn't matter because it just gets "
+                         + "interned as a JSAtom* anyways.")),
+         SIZE_OF_SYMBOL);