2 ms·

Ah okay, well what you said is simply untrue. It's the C++ standard that requires two's complement (S 6.8.1.3 mandates this) regardless of architecture. The rea

by Kranar 4y ago

Ah okay, well what you said is simply untrue. It's the C++ standard that requires two's complement (S 6.8.1.3 mandates this) regardless of architecture. The reason for the negative result has nothing to do with computer architecture and has to do with C++'s integer promotion rules which promote an unsigned 16-bit integer to a signed int. There is a reason that the author explicitly states that MSVC is the compiler that produces this output, because clang and GCC do not do so, even if they run on the same computer architecture. This is due to the fact that both those compilers can recognize that signed integer overflow is undefined behavior and leverage this fact. As others have said, to consider these details just basic things is absurd. Almost no one knows this stuff, including you.

tines 4y ago
> It's the C++ standard that requires two's complement I looked into this and you're totally right! But it actually didn't until relatively recently. Other representations were explicitly permitted by the standard at least until C++14 or so, what I said should be interpreted in that context. (And in fact, the standard requires it _because_ architecture was already universally designed that way, which I know you already know.) Thanks for the information though, this is good to know. > The reason for the negative result has nothing to do with computer architecture An existing conforming implementation will produce the bit patterns given in the article because of the architecture of the machine it's running on, so that's why I mentioned architecture. > and has to do with C++'s integer promotion rules which promote an unsigned 16-bit integer to a signed int. For sure, it also has to do with that, it just wasn't relevant to the "architecture" part of my comment which I was explaining, so I omitted it. I think we're saying the same thing from different points of view. > As others have said, to consider these details just basic things is absurd. I guess I'm inured to it, having worked at this level of abstraction for a long time haha. This is why progress is made one funeral at a time I suppose D: > Almost no one knows this stuff, including you. There are a lot of things I don't know, and this may be one of them! Thanks for your responses.

by Kranar 4y ago

tines 4y ago

> It's the C++ standard that requires two's complement I looked into this and you're totally right! But it actually didn't until relatively recently. Other representations were explicitly permitted by the standard at least until C++14 or so, what I said should be interpreted in that context. (And in fact, the standard requires it _because_ architecture was already universally designed that way, which I know you already know.) Thanks for the information though, this is good to know. > The reason for the negative result has nothing to do with computer architecture An existing conforming implementation will produce the bit patterns given in the article because of the architecture of the machine it's running on, so that's why I mentioned architecture. > and has to do with C++'s integer promotion rules which promote an unsigned 16-bit integer to a signed int. For sure, it also has to do with that, it just wasn't relevant to the "architecture" part of my comment which I was explaining, so I omitted it. I think we're saying the same thing from different points of view. > As others have said, to consider these details just basic things is absurd. I guess I'm inured to it, having worked at this level of abstraction for a long time haha. This is why progress is made one funeral at a time I suppose D: > Almost no one knows this stuff, including you. There are a lot of things I don't know, and this may be one of them! Thanks for your responses.