/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ /* vim: set ts=8 sts=2 et sw=2 tw=80: */ /* 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/. */
/* A version of |operator new| that eschews mandatory null-checks. */
// Credit goes to WebKit for this implementation, cf. // https://bugs.webkit.org/show_bug.cgi?id=74676 namespace mozilla { enum NotNullTag {
KnownNotNull,
};
} // namespace mozilla
/* * The logic here is a little subtle. [expr.new] states that if the allocation * function being called returns null, then object initialization must not be * done, and the entirety of the new expression must return null. Non-throwing * (noexcept) functions are defined to return null to indicate failure. The * standard placement operator new is defined in such a way, and so it requires * a null check, even when that null check would be extraneous. Functions * declared without such a specification are defined to throw std::bad_alloc if * they fail, and return a non-null pointer otherwise. We compile without * exceptions, so any placement new overload we define that doesn't declare * itself as noexcept must therefore avoid generating a null check. Below is * just such an overload. * * You might think that MOZ_NONNULL might perform the same function, but * MOZ_NONNULL isn't supported on all of our compilers, and even when it is * supported, doesn't work on all the versions we support. And even keeping * those limitations in mind, we can't put MOZ_NONNULL on the global, * standardized placement new function in any event. * * We deliberately don't add MOZ_NONNULL(3) to tag |p| as non-null, to benefit * hypothetical static analyzers. Doing so makes |MOZ_ASSERT(p)|'s internal * test vacuous, and some compilers warn about such vacuous tests.
*/ inlinevoid* operatornew(size_t, mozilla::NotNullTag, void* p) {
MOZ_ASSERT(p); return p;
}
#endif// mozilla_OperatorNewExtensions_h
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