1 files changed, 25 insertions, 0 deletions
diff --git a/js/src/gdb/mozilla/CellHeader.py b/js/src/gdb/mozilla/CellHeader.py
new file mode 100644
index 0000000000..8163e57e1b
--- /dev/null
+++ b/js/src/gdb/mozilla/CellHeader.py
@@ -0,0 +1,25 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import gdb
+
+
+def get_header_ptr(value, ptr_t):
+    # Return the pointer stored in Cell::header_ for subclasses of
+    # TenuredCellWithNonGCPointer and CellWithTenuredGCPointer.
+    return value["header_"]["mValue"].cast(ptr_t)
+
+
+def get_header_length_and_flags(value, cache):
+    # Return the length and flags values for subclasses of
+    # CellWithLengthAndFlags.
+    flags = value["header_"]["mValue"].cast(cache.uintptr_t)
+    try:
+        length = value["length_"]
+    except gdb.error:
+        # If we couldn't fetch the length directly, it must be stored
+        # within `flags`.
+        length = flags >> 32
+        flags = flags % 2 ** 32
+    return length, flags