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https://github.com/mozilla/gecko-dev.git
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c1becb4a54
At the same time, remove the MOZ_STATIC_ASSERT_VALID_ARG_COUNT, which doesn't actually work for more than 50 arguments(*), and which is now not useful to detect 0 arguments. (*) the build fails, but not directly thanks to the static_assert it expands to. --HG-- extra : rebase_source : 8f0fe7b352c89b5a3ec87f42ef5464c370c362ef
85 lines
3.3 KiB
C
85 lines
3.3 KiB
C
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* 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
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/*
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* Implements various macros meant to ease the use of variadic macros.
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*/
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#ifndef mozilla_MacroArgs_h
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#define mozilla_MacroArgs_h
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// Concatenates pre-processor tokens in a way that can be used with __LINE__.
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#define MOZ_CONCAT2(x, y) x ## y
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#define MOZ_CONCAT(x, y) MOZ_CONCAT2(x, y)
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/*
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* MOZ_PASTE_PREFIX_AND_ARG_COUNT(aPrefix, ...) counts the number of variadic
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* arguments and prefixes it with |aPrefix|. For example:
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*
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* MOZ_PASTE_PREFIX_AND_ARG_COUNT(, foo, 42) expands to 2
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* MOZ_PASTE_PREFIX_AND_ARG_COUNT(A, foo, 42, bar) expands to A3
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* MOZ_PASTE_PREFIX_AND_ARG_COUNT(A) expands to A0
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* MOZ_PASTE_PREFIX_AND_ARG_COUNT() expands to 0, but MSVC warns there
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* aren't enough arguments given.
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*
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* You must pass in between 0 and 50 (inclusive) variadic arguments, past
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* |aPrefix|.
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*
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* The `##__VA_ARGS__` form is a GCC extension that removes the comma if
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* __VA_ARGS__ is empty. It is supported by Clang too. MSVC ignores ##,
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* and its default behavior is already to strip the comma when __VA_ARGS__
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* is empty.
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*
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* So MOZ_MACROARGS_ARG_COUNT_HELPER(prefix) expands to
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* (_, prefix50, prefix49, ...)
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* MOZ_MACROARGS_ARG_COUNT_HELPER(prefix, a) expands to
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* (_, a, prefix50, prefix49, ...)
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* etc.
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*/
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#define MOZ_PASTE_PREFIX_AND_ARG_COUNT(aPrefix, ...) \
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MOZ_MACROARGS_ARG_COUNT_HELPER2( \
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MOZ_MACROARGS_ARG_COUNT_HELPER(aPrefix, ##__VA_ARGS__))
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#define MOZ_MACROARGS_ARG_COUNT_HELPER(aPrefix, ...) (_, ##__VA_ARGS__, \
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aPrefix##50, aPrefix##49, aPrefix##48, aPrefix##47, aPrefix##46, \
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aPrefix##45, aPrefix##44, aPrefix##43, aPrefix##42, aPrefix##41, \
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aPrefix##40, aPrefix##39, aPrefix##38, aPrefix##37, aPrefix##36, \
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aPrefix##35, aPrefix##34, aPrefix##33, aPrefix##32, aPrefix##31, \
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aPrefix##30, aPrefix##29, aPrefix##28, aPrefix##27, aPrefix##26, \
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aPrefix##25, aPrefix##24, aPrefix##23, aPrefix##22, aPrefix##21, \
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aPrefix##20, aPrefix##19, aPrefix##18, aPrefix##17, aPrefix##16, \
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aPrefix##15, aPrefix##14, aPrefix##13, aPrefix##12, aPrefix##11, \
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aPrefix##10, aPrefix##9, aPrefix##8, aPrefix##7, aPrefix##6, \
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aPrefix##5, aPrefix##4, aPrefix##3, aPrefix##2, aPrefix##1, aPrefix##0)
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#define MOZ_MACROARGS_ARG_COUNT_HELPER2(aArgs) \
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MOZ_MACROARGS_ARG_COUNT_HELPER3 aArgs
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#define MOZ_MACROARGS_ARG_COUNT_HELPER3(a0, \
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a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, \
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a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, \
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a21, a22, a23, a24, a25, a26, a27, a28, a29, a30, \
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a31, a32, a33, a34, a35, a36, a37, a38, a39, a40, \
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a41, a42, a43, a44, a45, a46, a47, a48, a49, a50, \
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a51, ...) a51
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/*
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* MOZ_ARGS_AFTER_N expands to its arguments excluding the first |N|
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* arguments. For example:
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*
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* MOZ_ARGS_AFTER_2(a, b, c, d) expands to: c, d
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*/
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#define MOZ_ARGS_AFTER_1(a1, ...) __VA_ARGS__
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#define MOZ_ARGS_AFTER_2(a1, a2, ...) __VA_ARGS__
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/*
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* MOZ_ARG_N expands to its |N|th argument.
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*/
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#define MOZ_ARG_1(a1, ...) a1
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#define MOZ_ARG_2(a1, a2, ...) a2
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#endif /* mozilla_MacroArgs_h */
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