Date: Tue, 01 Sep 1998 18:49:49 -0700 From: John Polstra <jdp@polstra.com> To: Mike Smith <mike@smith.net.au> Cc: "Andrew Reilly" <reilly@zeta.org.au>, current@FreeBSD.ORG Subject: Re: ELF binaries size Message-ID: <199809020149.SAA16932@austin.polstra.com> In-Reply-To: Your message of "Tue, 01 Sep 1998 18:40:42 -0000." <199809011840.SAA02659@dingo.cdrom.com>
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> > I don't understand what you're getting at. A program has to be able
> > to write its data. That's where the variables are.
>
> dingo:/tmp>cat a.c
> char *foo = "test";
> int bar;
> void main(void)
> {
> foo[0] = 0;
> }
> dingo:/tmp>./a.out
> Bus error (core dumped)
...
> As you can see, 'foo' is in the data segment, and it's pretty
> clearly read-only.
No, foo is writable. What foo points to is read-only. Foo is in
the data segment, but what it points to is in the text segment.
There's read-only data (which goes into the text segment), and there's
writable data (which goes into the data segment). It doesn't have
anything to do with initialization. What foo points to is read-only
because it's a string constant.
A counter-example to your program above is:
int foo = 100;
int
main(int argc, char **argv)
{
foo = 200;
return 0;
}
Here foo is initialized, but it is writable.
John
--
John Polstra jdp@polstra.com
John D. Polstra & Co., Inc. Seattle, Washington USA
"Self-knowledge is always bad news." -- John Barth
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