Newer gcc swallow version control keywords

[Elazar Leibovich]

First, please see my last email to Nadav, which discuss a lot of the
details.

On Tue, Oct 18, 2011 at 12:41 PM, Oleg Goldshmidt <pub at goldshmidt.org>wrote:

> On Tue, Oct 18, 2011 at 11:16 AM, Elazar Leibovich <elazarl at gmail.com>
> wrote:
> > I guess that it doesn't apply to libraries, which must include this
> global
> > variable.
>
> The whole point is that the constants are not global but have file
> scope. Therefore the optimizer can figure out they are not really
> used.
>

But you shouldn't care that they're having a file scope, do you?
So I think it's an OK solution to allow them have application scope. Am I
correct? See my C++ implementation in the reply to Nadav.


>
> > Excuse the idiotic solution, but can't you just add an option to print it
> > out?
> > int main(int argc,char**argv) {if (argc == 2 && strcmp(argv[1],"--ident")
> > puts(ident);...}
>
> This is fine for the main() routine of a regular application. What
> about other files? Headers? What about daemons that have no I/O?
>

It doesn't matter. The daemon will still not have output unless invoked with
"--ident". You shouldn't care about that, should you?
In case of libraries (.o, .a, .so), I think that if you expose the const
char* variable, the optimizer can't eat it away. How would it knows no user
of the library uses it?


>
> > It seems like a good idea anyhow, to have a stable way of extracting this
> > ident string from the executable
>
> That's the function of ident(1) - and that's what is not working
> because the compiler eats the strings.
>

See my reply to Nadav. I meant unstable because of "$Id: %d, $Name: %s" will
also be printed.


>
> > (what happens for instance if by accident
> > you have rcsident and rcs_ident? How would you know from the stripped
> > executable which one to trust?).
>
> It's the version control system's function to expand the keywords with
> the right data - if I have multiple strings they will be consistent.
>

My bad, I thought it's supposed to be an application scope version string.
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