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Bug 963056 - Part 2: Make MOZ_ARRAY_LENGTH a typesafe compile-time constant on compilers without constexpr support. r=Waldo

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This commit is contained in:
Birunthan Mohanathas 2014-02-11 13:31:58 -05:00
parent d07d624561
commit 9b3486cdf4
1 changed files with 13 additions and 2 deletions
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15
mfbt/ArrayUtils.h
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@ -82,6 +82,17 @@ ArrayEnd(const Array<T, N>& arr)
return &arr[0] + ArrayLength(arr);
}
namespace detail {
/*
* Helper for the MOZ_ARRAY_LENGTH() macro to make the length a typesafe
* compile-time constant even on compilers lacking constexpr support.
*/
template <typename T, size_t N>
char (&ArrayLengthHelper(T (&array)[N]))[N];
} /* namespace detail */
} /* namespace mozilla */
#endif /* __cplusplus */
@ -91,8 +102,8 @@ ArrayEnd(const Array<T, N>& arr)
* that can't use C++ template functions and for static_assert() calls that
* can't call ArrayLength() when it is not a C++11 constexpr function.
*/
#ifdef MOZ_HAVE_CXX11_CONSTEXPR
# define MOZ_ARRAY_LENGTH(array) mozilla::ArrayLength(array)
#ifdef __cplusplus
# define MOZ_ARRAY_LENGTH(array) sizeof(mozilla::detail::ArrayLengthHelper(array))
#else
# define MOZ_ARRAY_LENGTH(array) (sizeof(array)/sizeof((array)[0]))
#endif