Re: problem with gnome_init

[George <jirka 5z com>]

On Sun, Sep 24, 2000 at 12:19:11AM +0200, Eric Laeuffer wrote:
> Hello,
> 
> I beggining to write a gnome software, but I have a strange problem.
> 
> I am doing exactly the same process before and after the gnome_init
> function and I don't obtain the same result.
> 
> It seems that the problem is coming from sscanf. The sscanf just parses
> a line and doesn't return the same things.
> 
> I attached to this email a small source which show this problem.
> 
> Have you got an idea about this issue ?

Well the problem is locale.  Since I suppose you are set up in french locale,
gnome_init will call setlocale.  This will change the behaviour of
scanf/printf functions.  Especially with respect to floating point numbers.
In french locale you are going to read/write floats in "1234,5678" format
while in C locale it's "1234.5678".  So if you try to read the bottom one
in french locale, you are likely gonna get screwed.

This can be quite a problem, especially since most people aren't aware of it
and happily read/write floats to files and expect then to read the same thing
using scanf/printf.

The "workaround" in various places in gnome is to do the following:

	char *old_locale;
	old_locale = g_strdup (setlocale (LC_NUMERIC, NULL));
        setlocale (LC_NUMERIC, "C");

	/* Do printf/scanf here */

        setlocale (LC_NUMERIC, old_locale);
	g_free (old_locale);

This will just set the numeric locale to C and force things to be done the
"C" locale way, and thus portably accross locales.

Note that other functions also have trouble.  Basically anything dealing with
string<->float conversions, such as strtod.

George

-- 
George <jirka 5z com>
   Personally, I'm always ready to learn, although I do not
   always like being taught.
                       -- Winston Churchill