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Re: Structure packing & padding: what sizeof reports? Any caveats?

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On 08/ 8/16 07:15 PM, Test wrote:
> I am saving structures and variables to a string. For example:
>
> ...
> struct MixedData
> {
>      char Data1;
>      int num1;
>      short num2;
> };
>
> ....
> blah blah
> ...
>
> char mystr[256];
> int i;
> struct MixedData whatever;
>
> ....
> blah blah
> ...
>
> i=55;
> whatever.num1=60
> memcpy(&mystr[4],&whatever,sizeof(struct MixedData));
>
> ....
> blah blah
> ...
> memcpy(&whatever,&mystr[4],sizeof(struct MixedData));
> // i should be now 60
>
> Is above OK or should I worry about if my structed is padded or packed, ie. will
> sizeof() report correct value.

The value returned by sizeof includes any packing bytes.

-- 
Ian

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Structure packing & padding: what sizeof reports? Any caveats? Test <test@.nil.invalid.com> - 2016-08-08 10:15 +0300
  Re: Structure packing & padding: what sizeof reports? Any caveats? Ian Collins <ian-news@hotmail.com> - 2016-08-08 19:36 +1200
    Re: Structure packing & padding: what sizeof reports? Any caveats? Richard Heathfield <rjh@cpax.org.uk> - 2016-08-08 08:52 +0100
  Re: Structure packing & padding: what sizeof reports? Any caveats? Richard Heathfield <rjh@cpax.org.uk> - 2016-08-08 08:51 +0100
    Re: Structure packing & padding: what sizeof reports? Any caveats? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-08 11:29 +0100
    Re: Structure packing & padding: what sizeof reports? Any caveats? Keith Thompson <kst-u@mib.org> - 2016-08-08 08:56 -0700
  Re: Structure packing & padding: what sizeof reports? Any caveats? Barry Schwarz <schwarzb@dqel.com> - 2016-08-08 01:37 -0700
  Re: Structure packing & padding: what sizeof reports? Any caveats? James Kuyper <jameskuyper@verizon.net> - 2016-08-08 11:17 -0400

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