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Date: Sat, 3 Nov 2001 14:35:15 +0000
From: Giorgos Keramidas <charon@labs.gr>
To: Peter Pentchev <roam@ringlet.net>
Cc: Dag-Erling Smorgrav <des@ofug.org>,
	Joe Abley <jabley@automagic.org>, arch@FreeBSD.ORG
Subject: Re: POSIX character class support for 1Tawk
Message-ID: <20011103143515.D4464@hades.hell.gr>
References: <xzpu1wca91d.fsf@flood.ping.uio.no> <20011102233831.L25226@buffoon.automagic.org> <xzphesca0xv.fsf@flood.ping.uio.no> <20011103012226.Q25226@buffoon.automagic.org> <xzpvggse5j4.fsf@flood.ping.uio.no> <20011103145608.B76275@straylight.oblivion.bg>
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On Sat, Nov 03, 2001 at 02:56:08PM +0200, Peter Pentchev wrote:
> On Sat, Nov 03, 2001 at 07:23:59AM +0100, Dag-Erling Smorgrav wrote:
> > Joe Abley <jabley@automagic.org> writes:
> > > Our isalpha() and friends are locale-sensitive, I think.
> > 
> > Only if the caller has previously called setlocale().
> 
> So what's the problem in calling setlocale(LC_ALL, "")
> early in main() or something, as so many other utilities in
> our base system already do?

Unfortunately enough, it's not that simple.  You'd have to check for
all the possible LC_xxx environment variables.  The small program
below shows what can happen if you use setlocale() with NULL instead
of the correct value.

    #include <ctype.h>
    #include <locale.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>

    #define GREEK_ALPHA 0xe1

    int main (void)
    {
	    char *lc;

	    setlocale(LC_ALL, NULL);
	    printf("Using NULL: %s\n", isalpha(GREEK_ALPHA) ? "true" : "false");

	    if ((lc = getenv("LC_ALL")) == NULL) {
		    fprintf(stderr, "LC_ALL is not defined\n");
		    exit(1);
	    }

	    setlocale(LC_ALL, lc);
	    printf("Using getenv(): %s\n", isalpha(GREEK_ALPHA) ? "true" : "false");

	    return 0;
    }

Which gives the output shown below:

    $ cc -Wall -o blah blah.c
    $ ./blah
    Using NULL: false
    LC_ALL is not defined
    $ env LC_LANG=el_GR LC_ALL=el_GR.ISO8859-7 ./blah
    Using NULL: false
    Using getenv(): true

In the second case, of having the proper locale setup in the
environment, only when getenv() is used to retrieve the proper value
for setlocale() the GREEK_ALPHA character is recognized from isalpha() :/


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