call printf using va_list

Instead of printf, I recommend you try vprintf instead, which was created for this specific purpose:

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

void errmsg( const char* format, ... )
{
    va_list arglist;

    printf( "Error: " );
    va_start( arglist, format );
    vprintf( format, arglist );
    va_end( arglist );
}

int main( void )
{
    errmsg( "%s %d %s", "Failed", 100, "times" );
    return EXIT_SUCCESS;
}

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Source

Use vprintf() instead.