1 files changed, 52 insertions, 0 deletions
diff --git a/memory/mozalloc/mozalloc_oom.cpp b/memory/mozalloc/mozalloc_oom.cpp
new file mode 100644
index 0000000000..efe5dab4a2
--- /dev/null
+++ b/memory/mozalloc/mozalloc_oom.cpp
@@ -0,0 +1,52 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=4 et :
+ */
+/* 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/. */
+
+#include "mozilla/mozalloc_abort.h"
+#include "mozilla/mozalloc_oom.h"
+#include "mozilla/Assertions.h"
+
+#define OOM_MSG_LEADER "out of memory: 0x"
+#define OOM_MSG_DIGITS "0000000000000000"  // large enough for 2^64
+#define OOM_MSG_TRAILER " bytes requested"
+#define OOM_MSG_FIRST_DIGIT_OFFSET sizeof(OOM_MSG_LEADER) - 1
+#define OOM_MSG_LAST_DIGIT_OFFSET \
+  sizeof(OOM_MSG_LEADER) + sizeof(OOM_MSG_DIGITS) - 3
+
+MFBT_DATA size_t gOOMAllocationSize = 0;
+
+static const char* hex = "0123456789ABCDEF";
+
+void mozalloc_handle_oom(size_t size) {
+  char oomMsg[] = OOM_MSG_LEADER OOM_MSG_DIGITS OOM_MSG_TRAILER;
+  size_t i;
+
+  // NB: this is handle_oom() stage 1, which simply aborts on OOM.
+  // we might proceed to a stage 2 in which an attempt is made to
+  // reclaim memory
+  // Warning: when stage 2 is done by, for example, notifying
+  // "memory-pressure" synchronously, please audit all
+  // nsExpirationTrackers and ensure that the actions they take
+  // on memory-pressure notifications (via NotifyExpired) are safe.
+  // Note that Document::SelectorCache::NotifyExpired is _known_
+  // to not be safe: it will delete the selector it's caching,
+  // which might be in use at the time under querySelector or
+  // querySelectorAll.
+
+  gOOMAllocationSize = size;
+
+  static_assert(OOM_MSG_FIRST_DIGIT_OFFSET > 0,
+                "Loop below will never terminate (i can't go below 0)");
+
+  // Insert size into the diagnostic message using only primitive operations
+  for (i = OOM_MSG_LAST_DIGIT_OFFSET; size && i >= OOM_MSG_FIRST_DIGIT_OFFSET;
+       i--) {
+    oomMsg[i] = hex[size % 16];
+    size /= 16;
+  }
+
+  mozalloc_abort(oomMsg);
+}