Comment by foresto

1 year ago

> Note that the “q” suffix refers to the size of the pointer *(*i.e in C it represents *sizeof(*src) == 8 on 64-bit systems, and x86asm is smart enough to use 32-bit on 32-bit systems) but the underlying load is 128-bit.

I find that sentence confusing.

I assume that i.e is supposed to be i.e., but What is *(* supposed to mean? Shouldn't that be just an open parenthesis?

In what context would *sizeof(*src) be considered valid? As far as I know, sizeof never yields a pointer.

I get the impression that someone sprinkled random asterisks in that sentence, or maybe tried to mix asterisks-denoting-italics with C syntax.

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foresto

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kevingadd  1 year ago

Yes, this looks like something went wrong with the markdown itself or the conversion of the source material to markdown.

sweeter  1 year ago

Wouldn't it return the size of the pointer? I would guess it's exclusively used to handle architecture differences

  • foresto  1 year ago

    Strictly speaking, or maybe just the way I personally think of it, sizeof doesn't return anything. It's not a function, so it doesn't return at all. (At least, not at run time.)

    Nitpicking aside, the result of sizeof(*src) would be the size of the object at which the pointer points. The type of that result is size_t. That's what makes this code from the lesson I quoted invalid:

    *sizeof(*src)

    That first asterisk tries to dereference the result of sizeof as though it were a pointer, but it's a size_t: an unsigned integer type. Not a pointer.