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

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

Oops, goofed a bit. See below.

/Per W

On Sat, 31 May 2003, Per Westermark wrote:

> If you check gcc, it will allocate a SIZE symbol in the text area, if
> someone tries to take the address of it. By storing it in the text area,
> you will get a GP if you try to write to it, since the text area is
> write-protected for most operating systems.
>
> Since you are not allowed to change it, you can't use it as a target for a
> memory copy. If you use it as the source for a memory copy, it doesn't
> matter where it is - or if there is multiple copies of the value - since
> the copy would still copy the value of the const symbol.
>
> If you try to compare the address of SIZE from two different modules, you
> will - I haven't tested for different compilers - probably get a linker
> error, since both object files will contain a _SIZE symbol. But then again
> - 'a const &int = <value>' is a complicated declaration just to get a

Should of course be 'const int SIZE = <value>'

> "magic" address to compare against.
>
> /Per W
>
> On Fri, 30 May 2003, Ioannis Vranos wrote:
>
> > > -----Original Message-----
> > > From: Per Westermark [mailto:pw...@ia...]
> > > Sent: Saturday, May 31, 2003 12:19 AM
> > > To: Ioannis Vranos
> > > Cc: Dev-C++ Mailing List
> > > Subject: RE: [Dev-C++] #DEFINE versus cont variables in array
> > > inicializations
> > >
> > >
> > > At least for scalar data types, it doesn't matter if a global const xx
> > > variable is used in other modules.
> >
> >
> > Why? Imagine in another unit:
> >
> >
> > extern const int SIZE;
> >
> > void f()
> > {
> >   cout<<&SIZE;
> > }
> >
> >
> >
> > > Since the compiler inlines the value of the const variable
> > > everytime it is
> > > used, there is no need to keep a global reference for use by
> > > other source
> > > files.
> >
> >
> > What if we use its address in another unit? What about this:
> >
> > #include <cstring>
> >
> > extern const int SIZE;
> >
> > // in a function ...
> >
> > using std::memcpy;
> >
> > // ...
> >
> > int *p=new int;
> >
> > memcpy(p, &SIZE, sizeof(*p));
> >
> >
> >
> >
> > Ioannis Vranos
> >
> > * Programming pages: http://www.noicys.freeurl.com
> > * Alternative URL 1: http://run.to/noicys
> > * Alternative URL 2: http://www.noicys.cjb.net
> >
> >
> >
> >
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