mozalloc_oom.cpp - mozsearch

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/* -*- 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);