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September 04, 2023 Is sizeof() available in D language? | ||||
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 | I've seen everyone using datatype https://dlang.org/spec/property.html#sizeof It's great, but I wonder if it differ in any way from the standard C function https://www.geeksforgeeks.org/sizeof-operator-c/ I'm seeking for some speed/performance, so that's why the question. | |||
September 04, 2023 Re: Is sizeof() available in D language? | ||||
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 Posted in reply to BoQsc | On Monday, 4 September 2023 at 09:41:54 UTC, BoQsc wrote: >I've seen everyone using datatype https://dlang.org/spec/property.html#sizeof It's great, but I wonder if it differ in any way from the standard C function https://www.geeksforgeeks.org/sizeof-operator-c/ I'm seeking for some speed/performance, so that's why the question. In both case it's replaced at compile-time by an IntegerExpression (the ast node for an integer literal) I would not loose too much time comparing the "postfix" style (D) with the "intrinsic" style (C). Possibly there might a few micro ops difference... so only significant compile-time difference for 1 Billion | |||
September 04, 2023 Re: Is sizeof() available in D language? | ||||
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 Posted in reply to BoQsc | On Monday, 4 September 2023 at 09:41:54 UTC, BoQsc wrote: >I've seen everyone using datatype https://dlang.org/spec/property.html#sizeof It's great, but I wonder if it differ in any way from the standard C function Technically speaking, in C, sizeof is not a function, it is an operator. This is why it is not available in D (replaced by the .sizeof property). >https://www.geeksforgeeks.org/sizeof-operator-c/ I'm seeking for some speed/performance, so that's why the question. There is absolutely no difference in terms of runtime performance. In both cases, the compiler replaces it by the size of the type at compile-time. | |||
September 04, 2023 Re: Is sizeof() available in D language? | ||||
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 Posted in reply to Olivier Pisano | On Monday, September 4, 2023 2:34:08 PM MDT Olivier Pisano via Digitalmars-d- learn wrote:
> On Monday, 4 September 2023 at 09:41:54 UTC, BoQsc wrote:
> > I've seen everyone using **datatype**`.sizeof` property.
> >
> > https://dlang.org/spec/property.html#sizeof
> >
> > It's great, but I wonder if it differ in any way from the
> > standard C function `sizeof()`.
>
> Technically speaking, in C, sizeof is not a function, it is an operator. This is why it is not available in D (replaced by the .sizeof property).
>
> > https://www.geeksforgeeks.org/sizeof-operator-c/ https://en.cppreference.com/w/cpp/language/sizeof
> >
> > I'm seeking for some speed/performance, so that's why the
> > question.
> > Overall I'm alright with continuing using it.
>
> There is absolutely no difference in terms of runtime performance. In both cases, the compiler replaces it by the size of the type at compile-time.
Yeah. You can pretty much just think of C's sizeof and D's sizeof as being the same thing with different syntaxes. In both cases, it's a compile-time value that gives the size of a type in bytes. In neither case does how it is calculated have any impact on the performance of the program.
- Jonathan M Davis
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