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154fd9c9ad
In bug 1423803, mozilla::fallible was made an "alias" of std::nothrow. Except C++ doesn't allow compilers to be too smart, and in many cases, they would actually create data fields to hold a copy of std::nothrow, even creating a static initializer on non-optimized builds to do so. By turning it into a reference, we allow compilers to just use std::nothrow directly, as if it were passed directly, but they can still create unused data fields. Turning it into a static allows compilers to skip the data fields altogether. On a local linux64 build, this saves 242 bytes of .bss. Note this does change a `lea` (address calculation) into a `mov` (read), but it shouldn't matter too much. --HG-- extra : rebase_source : 9c08e8263aef267b8ad5962b0248c7effcb67796
65 lines
1.7 KiB
C++
65 lines
1.7 KiB
C++
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_fallible_h
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#define mozilla_fallible_h
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#if defined(__cplusplus)
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/* Explicit fallible allocation
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*
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* Memory allocation (normally) defaults to abort in case of failed
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* allocation. That is, it never returns NULL, and crashes instead.
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*
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* Code can explicitely request for fallible memory allocation thanks
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* to the declarations below.
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*
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* The typical use of the mozilla::fallible const is with placement new,
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* like the following:
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*
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* foo = new (mozilla::fallible) Foo();
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*
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* The following forms, or derivatives, are also possible but deprecated:
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*
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* foo = new ((mozilla::fallible_t())) Foo();
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*
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* const mozilla::fallible_t fallible = mozilla::fallible_t();
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* bar = new (f) Bar();
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*
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* It is also possible to declare method overloads with fallible allocation
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* alternatives, like so:
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*
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* class Foo {
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* public:
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* void Method(void *);
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* void Method(void *, const mozilla::fallible_t&);
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* };
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*
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* Foo foo;
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* foo.Method(nullptr, mozilla::fallible);
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*
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* If that last method call is in a method that itself takes a const
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* fallible_t& argument, it is recommended to propagate that argument
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* instead of using mozilla::fallible:
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*
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* void Func(Foo &foo, const mozilla::fallible_t& aFallible) {
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* foo.Method(nullptr, aFallible);
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* }
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*
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*/
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#include <new>
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namespace mozilla {
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using fallible_t = std::nothrow_t;
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static const fallible_t& fallible = std::nothrow;
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} // namespace mozilla
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#endif
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#endif // mozilla_fallible_h
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