Re: Problem with setlocale (found in libecpg) [accessing a memory location after freeing it]

On Tue, Sep 25, 2001 at 08:15:06PM +0200, Michael Meskes wrote:
> >
> > Well at least on glibc-2.2 it seems that setlocale retuns a pointer to
> > malloced memory, and frees this pointer on subsequent calls to
>
> Doesn't look that way on my system. The following programs simply dumps core
> in free().
>
> #include <locale.h>
> #include <stdio.h>
>
> main()
> {
> const char *locale=setlocale(LC_NUMERIC, NULL);
>
> printf("%c\n", locale);
> free(locale);
> }

Because you bad use setlocale().

The setlocale(LC_NUMERIC, NULL) returns actual LC_NUMERIC setting, but
your program hasn't some setting, because you don't call:

setlocale(LC_NUMERIC, "") or setlocale(LC_NUMERIC, "some_locales")

before setlocale(LC_NUMERIC, NULL), try this program:

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

int
main()
{
char *locale;

/* create array with locales names */
setlocale(LC_NUMERIC, "");

/* returns data from actual setting */
locale = setlocale(LC_NUMERIC, NULL);

printf("%s\n", locale);
free((void *) locale);
exit(1);
}

and don't forget set LC_ALL before program runnig. With default locales "C"
it is same as with NULL.

Previous code:

$ export LC_ALL="cs_CZ"
$ ./loc
cs_CZ
$ export LC_ALL="C"
$ ./loc
C
Segmentation fault <-- in free()

.... and see locale/setlocale.c in glibc sources :-)

Karel

--
Karel Zak <zakkr(at)zf(dot)jcu(dot)cz>
http://home.zf.jcu.cz/~zakkr/

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