forcing a static char string into libs and executables

forcing a static char string into libs and executables

[Bruce Allen]

I've searched the standard places, manuals and mailing lists and not found
the answer to this.

I use the 'ident' utility to parse CVS strings from libs and executables.  
It's a convenient tool for tracking version information: Typical output
looks like this (get file is an executable):

ident get_file
get_file:
     $Id: get_file.C,v 1.4 2004/12/08 00:39:22 ballen Exp $

The string are embedded typically with a declaration like this:
static volatile const char __attribute__((unused)) 
  *BOINCrcsid= $Id: get_file.C,v 1.4 2004/12/08 00:39:22 ballen Exp $";

The 'volatile' is a (perhaps misguided) attempt to force the
compiler-assembler-linker chain to preserve this quantity even under
agressive optimization. The __attribute((unused)) is to avoid compiler
warnings about BOINCrcsid, which is used nowhere in the code.

This worked with gcc 3.2.2 and earlier but fails with gcc 3.4.2. With gcc
3.4.3, I get:

ident get_file
get_file:
ident warning: no id keywords in get_file

If I change to __attribute__((used)) then my const char string comes back
and ident works correctly. So:

(1) Is there a better way? which will work with older and newer gcc
    versions?

(2) At which gcc version did __attribute__((used)) start being supported?
    I can't find it documented.  If someone can point me to the file or
    directory in gcc CVS I'll happily track this down.

I don't subscribe to this list: replies copied to ballen@uwm.edu would be
greatly appreciated.

Cheers,	
	Bruce