Comment by greysphere

Maybe I'm misunderstanding. Here is what I'm trying to say.

"Accessing an object which is not correctly aligned" - this is UB

"As an example of this, take this code: ..." - this (code) is not UB.

Is this incorrect somehow?

You could interpret the second sentence as 'under the assumption of an unaligned pointer, let's look at what this seemingly innocuous (and correct) code does.'

But that's not what they did. They presented that code as if it's incorrect (following the whole premise of the article 'Everything in c is UB'). That's what the whole article does, they take a topic with real concerns, then present 'normal' code, and then imply the code is the issue (and therefore the language), not the premise.

You know what would be better, show an example that clearly shows the complete path for the premise to the issue. Ie show some code that generates an unaligned pointer and then uses it. Why did the author not do that? Surprise, because it's actually pretty hard to write code that's 'guaranteed' unaligned behavior.

    int foo[10];
    int *bar = (int *)(((int)&foo) + 1);

Is this unaligned access? You don't know because you don't know the size of int. (Not to mention it looks ridiculous. By only showing 'reasonable' code as the example, the article suppresses the common 'uh just don't do that' criticism.)

And in fact the ambiguity of alignments and sizes is the whole point - they are given the privilege/footgun of being undefined in c so that compilers are easier to write. It's very debatable if this was/is a good idea, but that's where the debate should be, not illusorily ascribed to derefing pointers.

If I'm misunderstanding, please let me know. Specifically, if you're claiming (1) either the literal code in the first box of the article is UB, or (2) please write some literal code that is UB in the vein of the first claim of the article. I think that would help me bridge the gap that we seem to be having.