From: Andrew Schulman <schulman.andrew@epa.gov>
To: cygwin@cygwin.com
Subject: Re: libargp: argp_program_version does not work
Date: Thu, 11 Jul 2013 22:02:00 -0000 [thread overview]
Message-ID: <4q4ut8had25hqmo8b0752i8asuv6ism2qh@4ax.com> (raw)
In-Reply-To: <u4ett8due4p6h9ku1iumscvulp0g688tgk@4ax.com>
> > Hello!
> >
> > I have found a problem: argp_program_version string is ignored by libargp.
>
> Hi Pavel. Thanks for reporting this. I confirm your observation. For
> example, when I compile argp's example #2
> (http://www.gnu.org/software/libc/manual/html_node/Argp-Example-2.html#Argp-Example-2),
> the --version option doesn't work.
>
> > I guess the problem happens because of DLL's nature. DLLs cannot contain
> > unresolved symbols, so the DLL has own version of argp_program_version which
> > is always initialized to NULL. There's no way to override it.
>
> Also confirmed. argp.h declares argp_program_version as
>
> extern const char *argp_program_version;
>
> But gllib/argp-pv.c initializes it as
>
> const char *argp_program_version = (const char *) 0
>
> Whether there's a way to override that value by one declared in the user's
> code, I don't know. Maybe a linker switch?
OK, I remembered how this works. To override the initial values in your
program, you just have to reassign them at run time.
Here's how it's done with argp's example #2. Note the first two lines of
main(), which aren't present in the upstream example.
/*** Begin modified argp example #2 ***/
#include <argp.h>
const char version[] = "argp-ex2 1.0";
const char bug_address[] = "<bug-gnu-utils@gnu.org>";
/* Program documentation. */
static char doc[] = "Argp example #2 -- a pretty minimal program using
argp";
static struct argp argp = { 0, 0, 0, doc };
int main (int argc, char **argv)
{
argp_program_version = version;
argp_program_bug_address = bug_address;
argp_parse (&argp, argc, argv, 0, 0, 0);
}
/*** End modified argp example #2 ***/
If you compile the above version, you'll see that the --version option and
bug tracker text are available.
I'm sure this problem is familiar to developers and users of shared
libraries, but I had forgotten it. I'll add a note to the Cygwin README
file, to help all of us remember it next time.
Andrew
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next prev parent reply other threads:[~2013-07-11 20:28 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-11 10:17 Fedin Pavel
2013-07-11 16:35 ` Andrew Schulman
2013-07-11 22:02 ` Andrew Schulman [this message]
2013-07-12 14:52 ` Fedin Pavel
2013-07-12 15:36 ` Andrew Schulman
2013-07-17 9:57 ` [PATCH] Fix optional variables in libargp Fedin Pavel
2013-07-17 12:59 ` Eric Blake
2013-07-22 7:33 ` Andrew Schulman
2013-07-22 8:12 ` Pavel Fedin
2013-07-22 13:19 ` Pavel Fedin
2013-07-23 15:07 ` Andrew Schulman
2013-07-24 9:56 ` Pavel Fedin
2022-02-18 13:30 ` Andrew Schulman
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