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List:       kde-devel
Subject:    Re: Desperate in need of help: Very very weird problem with sscanf
From:       Thiago Macieira <thiago () kde ! org>
Date:       2009-08-20 15:04:41
Message-ID: 200908201704.42184.thiago () kde ! org
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Em Quinta-feira 20 Agosto 2009, às 10:06:19, você escreveu:
> For the interested parties: I added an issue to tesseract. I hope I did sta
> te  the matter correctly:
> 
> http://code.google.com/p/tesseract-ocr/issues/detail?id=236

Technically, this is not about resetting. It's just about using locale-
dependent functions with locale-independent data. They have to solve that 
problem: they should use functions not affected by the locale.

What's more, it's not just KDE. *Most* programs that have user-interaction 
call setlocale(3). The example below illustrates:

$ cat /tmp/sscanf.c
#include <stdio.h>
#include <locale.h>

void execute(const char *stage)
{
    static const char string[] = "-0.25000 0.75000";
    float f1, f2;

    sscanf(string, "%f %f", &f1, &f2);
    printf("%s: %f %f\n", stage, f1, f2);
}

int main()
{
    /* before we call setlocale(3), the C library defaults to "C" */
    execute("before");

    /* calling setlocale to initialise libc's locale subsystem.
     * This sets the locale to the user's environment.
     * In my case, that's pt_BR.UTF-8 */
    setlocale(LC_ALL, "");
    execute("user locale");

    /* We can force the "C" locale */
    setlocale(LC_ALL, "C");
    execute("\"C\" locale");
}

$ /tmp/sscanf
before: -0.250000 0.750000
user locale: -0,000000 0,000000
"C" locale: -0.250000 0.750000

The problem is that the C library has no such locale-independent function. 
Even strtod/strtof are dependent.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Senior Product Manager - Nokia, Qt Development Frameworks
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