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Bug 989460 - Part 1: Add MacroArgs.h for macros related to implementing variadic macros. r=Waldo

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This also converts MOZ_RELEASE_ASSERT and MOZ_BEGIN_NESTED_ENUM_CLASS to use the new helper macros.
This commit is contained in:
Birunthan Mohanathas 2014-04-24 10:48:00 +02:00
parent a33ed136f3
commit accb4d62ef
6 changed files with 146 additions and 49 deletions
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30
mfbt/Assertions.h
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@ -12,6 +12,7 @@
#include "mozilla/Attributes.h"
#include "mozilla/Compiler.h"
#include "mozilla/Likely.h"
#include "mozilla/MacroArgs.h"
#include <stddef.h>
#include <stdio.h>
@ -295,30 +296,13 @@ __declspec(noreturn) __inline void MOZ_NoReturn() {}
MOZ_REALLY_CRASH(); \
} \
} while (0)
/* And now, helper macrology up the wazoo. */
/*
* Count the number of arguments passed to MOZ_ASSERT, very carefully
* tiptoeing around an MSVC bug where it improperly expands __VA_ARGS__ as a
* single token in argument lists. See these URLs for details:
*
* http://connect.microsoft.com/VisualStudio/feedback/details/380090/variadic-macro-replacement
* http://cplusplus.co.il/2010/07/17/variadic-macro-to-count-number-of-arguments/#comment-644
*/
#define MOZ_COUNT_ASSERT_ARGS_IMPL2(_1, _2, count, ...) \
count
#define MOZ_COUNT_ASSERT_ARGS_IMPL(args) \
MOZ_COUNT_ASSERT_ARGS_IMPL2 args
#define MOZ_COUNT_ASSERT_ARGS(...) \
MOZ_COUNT_ASSERT_ARGS_IMPL((__VA_ARGS__, 2, 1, 0))
/* Pick the right helper macro to invoke. */
#define MOZ_ASSERT_CHOOSE_HELPER2(count) MOZ_ASSERT_HELPER##count
#define MOZ_ASSERT_CHOOSE_HELPER1(count) MOZ_ASSERT_CHOOSE_HELPER2(count)
#define MOZ_ASSERT_CHOOSE_HELPER(count) MOZ_ASSERT_CHOOSE_HELPER1(count)
/* The actual macros. */
#define MOZ_ASSERT_GLUE(x, y) x y
#define MOZ_RELEASE_ASSERT_GLUE(a, b) a b
#define MOZ_RELEASE_ASSERT(...) \
MOZ_ASSERT_GLUE(MOZ_ASSERT_CHOOSE_HELPER(MOZ_COUNT_ASSERT_ARGS(__VA_ARGS__)), \
(__VA_ARGS__))
MOZ_RELEASE_ASSERT_GLUE( \
MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_ASSERT_HELPER, __VA_ARGS__), \
(__VA_ARGS__))
#ifdef DEBUG
# define MOZ_ASSERT(...) MOZ_RELEASE_ASSERT(__VA_ARGS__)
#else

105
mfbt/MacroArgs.h Normal file
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@ -0,0 +1,105 @@
/* -*- 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/. */
/*
* Implements various macros meant to ease the use of variadic macros.
*/
#ifndef mozilla_MacroArgs_h
#define mozilla_MacroArgs_h
/*
* MOZ_PASTE_PREFIX_AND_ARG_COUNT(aPrefix, ...) counts the number of variadic
* arguments and prefixes it with |aPrefix|. For example:
*
* MOZ_PASTE_PREFIX_AND_ARG_COUNT(, foo, 42) expands to 2
* MOZ_PASTE_PREFIX_AND_ARG_COUNT(A, foo, 42, bar) expands to A3
*
* You must pass in between 1 and 50 (inclusive) variadic arguments, past
* |aPrefix|. It is not legal to do
*
* MOZ_PASTE_PREFIX_AND_ARG_COUNT(prefix)
*
* (that is, pass in 0 variadic arguments). To ensure that a compile-time
* error occurs when these constraints are violated, use the
* MOZ_STATIC_ASSERT_VALID_ARG_COUNT macro with the same variaidc arguments
* wherever this macro is used.
*
* Passing (__VA_ARGS__, <rest of arguments>) rather than simply calling
* MOZ_MACROARGS_ARG_COUNT_HELPER2(__VA_ARGS__, <rest of arguments>) very
* carefully tiptoes around a MSVC bug where it improperly expands __VA_ARGS__
* as a single token in argument lists. For details, see:
*
* http://connect.microsoft.com/VisualStudio/feedback/details/380090/variadic-macro-replacement
* http://cplusplus.co.il/2010/07/17/variadic-macro-to-count-number-of-arguments/#comment-644
*/
#define MOZ_PASTE_PREFIX_AND_ARG_COUNT(aPrefix, ...) \
MOZ_MACROARGS_ARG_COUNT_HELPER((__VA_ARGS__, \
aPrefix##50, aPrefix##49, aPrefix##48, aPrefix##47, aPrefix##46, \
aPrefix##45, aPrefix##44, aPrefix##43, aPrefix##42, aPrefix##41, \
aPrefix##40, aPrefix##39, aPrefix##38, aPrefix##37, aPrefix##36, \
aPrefix##35, aPrefix##34, aPrefix##33, aPrefix##32, aPrefix##31, \
aPrefix##30, aPrefix##29, aPrefix##28, aPrefix##27, aPrefix##26, \
aPrefix##25, aPrefix##24, aPrefix##23, aPrefix##22, aPrefix##21, \
aPrefix##20, aPrefix##19, aPrefix##18, aPrefix##17, aPrefix##16, \
aPrefix##15, aPrefix##14, aPrefix##13, aPrefix##12, aPrefix##11, \
aPrefix##10, aPrefix##9, aPrefix##8, aPrefix##7, aPrefix##6, \
aPrefix##5, aPrefix##4, aPrefix##3, aPrefix##2, aPrefix##1, aPrefix##0))
#define MOZ_MACROARGS_ARG_COUNT_HELPER(aArgs) \
MOZ_MACROARGS_ARG_COUNT_HELPER2 aArgs
#define MOZ_MACROARGS_ARG_COUNT_HELPER2( \
a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, \
a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, \
a21, a22, a23, a24, a25, a26, a27, a28, a29, a30, \
a31, a32, a33, a34, a35, a36, a37, a38, a39, a40, \
a41, a42, a43, a44, a45, a46, a47, a48, a49, a50, \
a51, ...) a51
/*
* MOZ_STATIC_ASSERT_VALID_ARG_COUNT ensures that a compile-time error occurs
* when the argument count constraints of MOZ_PASTE_PREFIX_AND_ARG_COUNT are
* violated. Use this macro wherever MOZ_PASTE_PREFIX_AND_ARG_COUNT is used
* and pass it the same variadic arguments.
*
* This macro employs a few dirty tricks to function. To detect the zero
* argument case, |(__VA_ARGS__)| is stringified, sizeof-ed, and compared to
* what it should be in the absence of arguments.
*
* Detecting too many arguments is a little trickier. With a valid argument
* count and a prefix of 1, MOZ_PASTE_PREFIX_AND_ARG_COUNT expands to e.g. 14.
* With a prefix of 0.0, it expands to e.g. 0.04. If there are too many
* arguments, it expands to the first argument over the limit. If this
* exceeding argument is a number, the assertion will fail as there is no
* number than can simultaneously be both > 10 and < 0.1. If the exceeding
* argument is not a number, a compile-time error will still occur because the
* exceeding argument is compared to an int and a double.
*/
#define MOZ_MACROARGS_STRINGIFY_HELPER(x) #x
#define MOZ_STATIC_ASSERT_VALID_ARG_COUNT(...) \
static_assert( \
sizeof(MOZ_MACROARGS_STRINGIFY_HELPER((__VA_ARGS__))) != sizeof("()") && \
MOZ_PASTE_PREFIX_AND_ARG_COUNT(1, __VA_ARGS__) > 10 && \
MOZ_PASTE_PREFIX_AND_ARG_COUNT(0.0, __VA_ARGS__) < 0.1, \
"MOZ_STATIC_ASSERT_VALID_ARG_COUNT requires 1 to 50 arguments") /* ; */
/*
* MOZ_ARGS_AFTER_N expands to its arguments excluding the first |N|
* arguments. For example:
*
* MOZ_ARGS_AFTER_2(a, b, c, d) expands to: c, d
*/
#define MOZ_ARGS_AFTER_1(a1, ...) __VA_ARGS__
#define MOZ_ARGS_AFTER_2(a1, a2, ...) __VA_ARGS__
/*
* MOZ_ARG_N expands to its |N|th argument.
*/
#define MOZ_ARG_1(a1, ...) a1
#define MOZ_ARG_2(a1, a2, ...) a2
#endif /* mozilla_MacroArgs_h */

32
mfbt/TypedEnum.h
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@ -10,6 +10,7 @@
#define mozilla_TypedEnum_h
#include "mozilla/Attributes.h"
#include "mozilla/MacroArgs.h"
#if defined(__cplusplus)
@ -290,33 +291,12 @@
# define MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE(Name) typename Name::Enum
#endif
/*
* Count the number of arguments passed to MOZ_COUNT_BEGIN_ENUM_CLASS_ARGS,
* very carefully tiptoeing around an MSVC bug where it improperly expands
* __VA_ARGS__ as a single token in argument lists. See these URLs for
* details:
*
* http://connect.microsoft.com/VisualStudio/feedback/details/380090/variadic-macro-replacement
* http://cplusplus.co.il/2010/07/17/variadic-macro-to-count-number-of-arguments/#comment-644
*/
# define MOZ_COUNT_BEGIN_ENUM_CLASS_ARGS_IMPL2(_1, _2, count, ...) \
count
# define MOZ_COUNT_BEGIN_ENUM_CLASS_ARGS_IMPL(args) \
MOZ_COUNT_BEGIN_ENUM_CLASS_ARGS_IMPL2 args
# define MOZ_COUNT_BEGIN_ENUM_CLASS_ARGS(...) \
MOZ_COUNT_BEGIN_ENUM_CLASS_ARGS_IMPL((__VA_ARGS__, 2, 1, 0))
/* Pick the right helper macro to invoke. */
# define MOZ_BEGIN_NESTED_ENUM_CLASS_CHOOSE_HELPER2(count) \
MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER##count
# define MOZ_BEGIN_NESTED_ENUM_CLASS_CHOOSE_HELPER1(count) \
MOZ_BEGIN_NESTED_ENUM_CLASS_CHOOSE_HELPER2(count)
# define MOZ_BEGIN_NESTED_ENUM_CLASS_CHOOSE_HELPER(count) \
MOZ_BEGIN_NESTED_ENUM_CLASS_CHOOSE_HELPER1(count)
/* The actual macro. */
# define MOZ_BEGIN_NESTED_ENUM_CLASS_GLUE(x, y) x y
# define MOZ_BEGIN_NESTED_ENUM_CLASS_GLUE(a, b) a b
# define MOZ_BEGIN_NESTED_ENUM_CLASS(...) \
MOZ_BEGIN_NESTED_ENUM_CLASS_GLUE(MOZ_BEGIN_NESTED_ENUM_CLASS_CHOOSE_HELPER(MOZ_COUNT_BEGIN_ENUM_CLASS_ARGS(__VA_ARGS__)), \
(__VA_ARGS__))
MOZ_BEGIN_NESTED_ENUM_CLASS_GLUE( \
MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER, \
__VA_ARGS__), \
(__VA_ARGS__))
# define MOZ_BEGIN_ENUM_CLASS(...) MOZ_BEGIN_NESTED_ENUM_CLASS(__VA_ARGS__)
# define MOZ_END_ENUM_CLASS(Name) \

1
mfbt/moz.build
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@ -36,6 +36,7 @@ EXPORTS.mozilla = [
'IntegerTypeTraits.h',
'Likely.h',
'LinkedList.h',
'MacroArgs.h',
'MathAlgorithms.h',
'Maybe.h',
'MemoryChecking.h',

26
mfbt/tests/TestMacroArgs.cpp Normal file
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@ -0,0 +1,26 @@
/* -*- 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/. */
#include "mozilla/MacroArgs.h"
static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(100, a, b, c) == 1003, "");
static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(, a, b, c) == 3, "");
static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(, a) == 1, "");
static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(, !a) == 1, "");
static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(, (a, b)) == 1, "");
static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(, MOZ_ARGS_AFTER_1(a, b, c)) == 2,
"MOZ_ARGS_AFTER_1(a, b, c) should expand to 'b, c'");
static_assert(MOZ_ARGS_AFTER_2(a, b, 3) == 3,
"MOZ_ARGS_AFTER_2(a, b, 3) should expand to '3'");
static_assert(MOZ_ARG_1(10, 20, 30) == 10, "");
static_assert(MOZ_ARG_2(10, 20, 30) == 20, "");
int main()
{
}

1
mfbt/tests/moz.build
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@ -17,6 +17,7 @@ CPP_UNIT_TESTS += [
'TestEnumSet.cpp',
'TestFloatingPoint.cpp',
'TestIntegerPrintfMacros.cpp',
'TestMacroArgs.cpp',
'TestRollingMean.cpp',
'TestSHA1.cpp',
'TestTypedEnum.cpp',