RE: [Dev-C++] #DEFINE versus cont variables in array inicializations

[Per W. <pw...@ia...>]

See below

/Per W

On Sat, 31 May 2003, Ioannis Vranos wrote:

> > -----Original Message-----
> > From: Per Westermark [mailto:pw...@ia...]
> > Sent: Saturday, May 31, 2003 3:18 AM
> > To: Ioannis Vranos
> > Cc: Dev-C++ Mailing List
> > Subject: RE: [Dev-C++] #DEFINE versus cont variables in array
> > inicializations
> >
> >
> > Give a declaration:
> >
> >   const int SIZE = 7;
> >
> > If you don't take the address of it, the compiler will generate code
> > looking like:
>
>
> It is difficult for the compiler to know if I use its address in another
> file. Usually the linker notices the uses in other files.
>

If you know that you need to take the address in another file, then
declare it as:
    extern const int SIZE = 7;

>
>
> >
> >   pushl $7
> >
> > If you take the address of it, the compiler will notice and
> > generate code
> > like:
> >
> >   pushl $_SIZE
> >
> >   ...
> >
> >   _SIZE:
> >     .long 7
> >
> > where the second case will store _SIZE in .text and not in .data.
>
>
> I can't understand the above very much but I do not think the compiler cn
> check every file for this, only the linker. Also what if I make obj files
> and then add some code in a cpp file that uses the address, make a new obj
> annd then link all objs together?
>

It doesn't. Either make sure that the file that declares SIZE takes it's
address, or declare it as 'extern const int SIZE = 7;'

>
>
> > You will be able to take the address of SIZE from one object
> > file. If you
> > declare 'const int SIZE = 7;' in another file to and try to take the
> > address of it, you will correctly get a linker error. If you
> > in the other
> > file declares 'extern const int SIZE', that file will always
> > reference the
> > variable SIZE, since it can't do any inlining.
>
>
>
> This is a bit difficult. You know, extern const int SIZE; is a *definition*
> in the absense of another definition and takes the default value 0.
>

extern const int SIZE; will just tell the compiler that somewhere in some
other object file, there is a symbol SIZE. The compile unit that sees this
declaration will not allocate any variable, so no default value either.

>
>
>
> Ioannis Vranos
>
> * Programming pages: http://www.noicys.freeurl.com
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> * Alternative URL 2: http://www.noicys.cjb.net
>
>
>
>
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