Parameter passing to function with void * as Argument Post: 302903260

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Top Forums Programming Parameter passing to function with void * as Argument Post 302903260 by Corona688 on Monday 26th of May 2014 12:33:06 PM

05-26-2014

Registered User

I repeat, unions do not work that way.

CS and DS were separate structure members originally. Putting them in a union like you suggest, means they will occupy the same memory! Alter CS and DS will change with it.

Furthermore, you say: "An unrequired additional member needlessly increases storage requirements." And then you suggest a structure that still has the "pointless" type element instead! Perhaps you didn't realize that elements in a union occupy the same place in memory... Meaning the "type" I put in the union wasn't an extra element, it was the same element.

The scheme I suggested is the one I see in use in practice in many libraries. I have never seen anyone use a scheme like yours (probably because it wouldn't work).

It comes down to this:

Code:

typedef struct mystr1 {
        int type;
        int payload;
} mystr;


typedef struct mystr2 {
        int type;
        char payload[64];
} mystr2;

typedef union mystr {
        int type;
        mystr1 t1;
        mystr2 t2;
} mystr;

The member labelled in red occupies the same area in memory always. It is not duplicated.

Last edited by Corona688; 05-26-2014 at 01:41 PM..

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grub-render-label

GRUB-RENDER-LABEL(1)                                               User Commands                                              GRUB-RENDER-LABEL(1)

NAME

       grub-render-label - generate a .disk_label for Apple Macs.

SYNOPSIS

       grub-render-label [OPTION...] [OPTIONS]

DESCRIPTION

       Render Apple .disk_label.

       -b, --bgcolor=COLOR
              use COLOR for background

       -c, --color=COLOR
              use COLOR for text

       -f, --font=FILE
              use FILE as font (PF2).

       -i, --input=FILE
              read text from FILE.

       -o, --output=FILE
              set output filename. Default is STDOUT

       -t, --text=STRING
              set the label to render

       -v, --verbose
              print verbose messages.

       -?, --help
              give this help list

       --usage
              give a short usage message

       -V, --version
              print program version

       Mandatory or optional arguments to long options are also mandatory or optional for any corresponding short options.

REPORTING BUGS

       Report bugs to <bug-grub@gnu.org>.

SEE ALSO

       The  full  documentation  for grub-render-label is maintained as a Texinfo manual.  If the info and grub-render-label programs are properly
       installed at your site, the command

              info grub-render-label

       should give you access to the complete manual.

grub-render-label (GRUB) 2.02-2ubuntu8.3                             July 2018                                                GRUB-RENDER-LABEL(1)