问题描述

我正在尝试编写一个 C++ 模板函数，它将在整数溢出时引发运行时异常，该函数在不同整数类型、不同宽度和可能的有符号/无符号不匹配之间进行转换.出于这些目的，我不关心从浮点类型到整数类型的转换，也不关心其他对象到对象的转换.我想这样做而不必编写大量特殊情况代码.这是我目前拥有的:

I am trying to write a C++ template function that will throw a runtime exception on integer overflow in casts between different integral types, with different widths, and possible signed/unsigned mismatch. For these purposes I'm not concerned with casting from floating-point types to integral types, nor other object-to-object conversions. I'd like to do this without having to write lots of special case code. This is what I currently have:

template< typename T, typename R > void safe_cast( const T& source, R& result )
{
    // get the maximum safe value of type R
    R rMax = (R) ~0;
    if ( rMax < 0 ) // R is a signed type
    {
        // assume that we're on an 8-bit twos-compliment machine
        rMax = ~( 0x80 << ( ( sizeof( R ) - 1 ) * 8 ) );
    }

    if ( ( source & rMax  ) != source )
    {
        throw new IntegerOverflowException( source );
    }

    result = static_cast<R>( source );
}

这是否正确且有效?

由于各种原因 stl 不可用，所以我不能使用 std::numeric_limits，而 Boost 中的任何东西都是正确的.

For various reasons stl isn't available, so I can't use std::numeric_limits, and anything from Boost is right out.

推荐答案

您是否尝试过 SafeInt?它是一个跨平台模板，将对各种整数类型进行整数溢出检查.github上已经有

Have you tried SafeInt? It's a cross platform template that will do integer overflow checks for a variety of integer types. It's available on github

• https://github.com/dcleblanc/SafeInt

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