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> on x86/amd4 sizeof(int) will always be equal to 4

Nothing is stopping your C compiler from making the guarantee sizeof(int)=4 on x86/amd64.

I think you are in agreement with the comment you are replying to.

The comment suggested the standard make it implementation defined rather than undefined. There's not a meaningful difference here.

Even today, an implementation may define unsigned overflow.

Oh, I see, I wonder if greenhouse_gas is suggesting a feature similar to sizeof() that can be used to portably adapt your program's design to the target's overflow capability.

C language lawyer in training: sizeof is not a function.

The parentheses are part of the operand and only needed for type names, to make them into cast expressions.

Yes, there is. Implementation defined means that a conforming implementation _must_ document its behavior.

That means that programmers don’t have to use trial and error to figure out how the compiler behaves and don’t have to _hope_ they found all the corner cases.

And that is how we get #if defined(_THIS_THING_SOME_COMPILER_DEFINES) && !defined(__BUT_NOT_THIS_ONE_THAT_COMPILER_X_DEFINES) soup ;)

Better than than silently ignoring an if guard preventing an overflow, and then overflowing anyways on addition.

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