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Reply-To: thomas DOT wuillemin AT gmail DOT com
Date: Tue, 3 Feb 2015 16:50:30 -0300
Message-ID: <CANro4aOM=uVAxmB_wi6cWzyKYcpxeYT58Bso8w+DQdCaom2gvg@mail.gmail.com>
Subject: Problem with vprintf () in Clang 3.4.2
From: Thomas Wuillemin <thomas DOT wuillemin AT gmail DOT com>
To: cygwin AT cygwin DOT com
Content-Type: text/plain; charset=UTF-8

Dear all,

While running some simple tests with the C vprintf function, I
detected different results between Gcc and Clang , where Clang seems
to be badly wrong.

Here is the faulty code that leads to a reproducible error (at least
in my configuration):

----------------------------------------------------
#include <stdio.h>
#include <stdarg.h>

void my_print1(char *format, ...)
{
    va_list arguments;

    va_start ( arguments, format );
    vprintf ( format, arguments );
    va_end ( arguments );
}

void my_print2(char *format, ...)
{
    va_list arguments;
    int value;

    va_start ( arguments, format );
    value = va_arg ( arguments, int );
    printf ( format, value );
    va_end ( arguments );
}

int main (int argc, char* argv[])
{
    (void) argc;
    (void) argv;

    my_print1 ( "Variadic argument found (should be 1): %d\n", 1 );
    my_print2 ( "Variadic argument found (should be 1): %d\n", 1 );
    return 0;
}
----------------------------------------------------

Compiled with gcc, the results are good:
$ gcc -Wall -Wextra -pedantic -g -O0 dummy.c -o dummy.exe
$ ./dummy.exe
Variadic argument found (should be 1): 1
Variadic argument found (should be 1): 1

Compiled with Clang, the results show a little issue:
$ clang -Wall -Wextra -pedantic -g -O0 dummy.c -o dummy.exe
$ ./dummy.exe
Variadic argument found (should be 1): 2271896
Variadic argument found (should be 1): 1

Working with char*, leads equally to various corruptions.

Is anyone already experienced such issue (or could confirm it) ?

Best regards,

Thomas

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