Emulating Swift's “defer” in C, with Clang or GCC+Blocks

Re:Emulating Swift's “defer” in C, with Clang or GCC+Blocks by conistonwater on Saturday October 10, 2015 @02:52PM (#10366515)

Not touching on the rest of what you said, but what's so bad about min? Apart from some internal clang stuff, like odd names and macros, it looks okay - I can see what the function is doing.

    // min

    template <class _Tp, class _Compare>
    inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    const _Tp&
    min(const _Tp& __a, const _Tp& __b, _Compare __comp)
    {
        return __comp(__b, __a) ? __b : __a;
    }

    template <class _Tp>
    inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    const _Tp&
    min(const _Tp& __a, const _Tp& __b)
    {
        return _VSTD::min(__a, __b, __less<_Tp>());
    }

    #ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS

    template<class _Tp, class _Compare>
    inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    _Tp
    min(initializer_list<_Tp> __t, _Compare __comp)
    {
        return *__min_element(__t.begin(), __t.end(), __comp);
    }

    template<class _Tp>
    inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    _Tp
    min(initializer_list<_Tp> __t)
    {
        return *__min_element(__t.begin(), __t.end(), __less<_Tp>());
    }

    #endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS

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Re:Emulating Swift's “defer” in C, with Clang or GCC+Blocks by Animats on Saturday October 10, 2015 @03:08PM (#10366575)

It used to be

    #define min(x,y) ((x) < (y) ? (x) : (y))

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Re:Emulating Swift's “defer” in C, with Clang or GCC+Blocks by vbernat on Saturday October 10, 2015 @06:13PM (#10367194)

Better use:

    #define min(X, Y)                \
         ({ typeof (X) x_ = (X);          \
            typeof (Y) y_ = (Y);          \
            (x_ < y_) ? x_ : y_; })

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Re:Emulating Swift's “defer” in C, with Clang or GCC+Blocks by pjmlp on Saturday October 10, 2015 @04:13PM (#10366820)

Which is anything but safe.

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Re:Emulating Swift's “defer” in C, with Clang or GCC+Blocks by azinman2 on Saturday October 10, 2015 @05:52PM (#10367140)

Can you explain more please?

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Re:Emulating Swift's “defer” in C, with Clang or GCC+Blocks by copascetic on Saturday October 10, 2015 @06:08PM (#10367180)

Because a macro in C/C++ is just text expansion, the given implementation will evaluate its arguments more than once, which will not be obvious at the "call" site and could have unintended consequences if the expressions have side-effects.

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Re:Emulating Swift's “defer” in C, with Clang or GCC+Blocks by azinman2 on Tuesday October 13, 2015 @01:58AM (#10378760)

Is there another way to do it as a macro that avoids this? How do you have temporary variables potentially in the middle of a larger expression, e.g. if (min(a,b) == 3) {...}

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