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/* 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/. */
#ifndef mozilla_fallible_h
#define mozilla_fallible_h
#if defined(__cplusplus)
/* Explicit fallible allocation
*
* Memory allocation (normally) defaults to abort in case of failed
* allocation. That is, it never returns NULL, and crashes instead.
*
* Code can explicitely request for fallible memory allocation thanks
* to the declarations below.
*
* The typical use of the mozilla::fallible const is with placement new,
* like the following:
*
* foo = new (mozilla::fallible) Foo();
*
* The following forms, or derivatives, are also possible but deprecated:
*
* foo = new ((mozilla::fallible_t())) Foo();
*
* const mozilla::fallible_t fallible = mozilla::fallible_t();
* bar = new (f) Bar();
*
* It is also possible to declare method overloads with fallible allocation
* alternatives, like so:
*
* class Foo {
* public:
* void Method(void *);
* void Method(void *, const mozilla::fallible_t&);
* };
*
* Foo foo;
* foo.Method(nullptr, mozilla::fallible);
*
* If that last method call is in a method that itself takes a const
* fallible_t& argument, it is recommended to propagate that argument
* instead of using mozilla::fallible:
*
* void Func(Foo &foo, const mozilla::fallible_t& aFallible) {
* foo.Method(nullptr, aFallible);
* }
*
*/
namespace mozilla {
struct fallible_t { };
/* This symbol is kept unexported, such that in corner cases where the
* compiler can't remove its use (essentially, cross compilation-unit
* calls), the smallest machine code is used.
* Depending how the linker packs symbols, it will consume between 1 and
* 8 bytes of read-only data in each executable or shared library, but
* only in those where it's actually not optimized out by the compiler.
*/
extern const fallible_t fallible;
} // namespace mozilla
#endif
#endif // mozilla_fallible_h
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