From: Martin Ambuhl <mambuhl AT earthlink DOT net>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: scanf/gets bug?
Date: Mon, 09 Nov 1998 15:13:55 -0500
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To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

"Daniël Hörchner" wrote:
> 
> Hello fellow DJGPP-ers,
> I came across a weird problem with DJGPP (GCC 2.8.1). In the following
> program gets() should wait for input, but it doesn't. What's wrong? The
> strange thing is that if I insert a call to getch() between scanf() and
> gets(), getch() waits for input, but gets() still does not. With Turbo
> C++ 3.0 it works fine (i.e., gets() waits for input).

No.  You are relying on undefined behavior.  fflush() is defined only
for output streams, so there nothing that you can assume about the
effect of `fflush(stdin);'  

BTW, You should also never use gets().  Something like this will work
for you:

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

int main(void)
{
    int x;
    char string[128];
    if (!fgets(string, sizeof string, stdin) ||
         sscanf(string,"%d", &x) != 1) exit(EXIT_FAILURE);
    if (!fgets(string, sizeof string, stdin)) exit(EXIT_FAILURE);
    puts("hello\n");
    return 0;
}


> #include <stdio.h>
> 
> int main(void)
> {
>   int x;
>   char string[10];
> 
>   scanf("%d", &x);
> 
>   fflush(stdin);
>   gets(string);
>   puts("hello");
> 
>   return 0;
> }


-- 
Martin Ambuhl (mambuhl AT earthlink DOT net)
Note: mambuhl AT tiac DOT net will soon be inactive